heat stress

Improving the ability of animals to deal with adverse environmental conditions is a challenge in the livestock industry. Adverse environmental conditions, especially heat stress, are important economic issues in animal husbandry because they negatively affect the production of dairy cows. Although animals can adapt to hot climates, their adaptation mechanisms may be detrimental to their productive performance. The genetic potential of an animal can play an important role in controlling reductions in milk production, reproductive performance, and herd udder health in stressful weather conditions. Therefore, this study aimed to investigate the effect of heat stress on milk production traits, reproduction, and somatic cell score (SCS) and to identify the best temperature-humidity index suitable for studying heat stress in Iranian Holstein dairy cows. Moreover, the superior genetic fathers for heat tolerance were identified and their genetic value in functional traits was investigated under the genetic evaluation for heat stress.

The estimated genetic parameters related to heat stress tolerance were milk production traits, udder health (SCS), and reproduction (open days and intervals from calving to first insemination). The data included 145,731 test day records of Holstein cows from the first lactation in 323 herds of the Iranian Breeding Center between 2008 and 2018. Test day records were merged with daily temperature-humidity index (THI) values based on weather records of weather stations. Each record included minimum, maximum, and average daily temperature, average daily relative humidity, and average daily rainfall. Genetic parameters were estimated using an animal model and random regression under the Bayesian method using GIBSF90 software. Variance components were estimated using multi-trait repeatable test day models with random regression on THI values. The models included herd test day classes and DIM as fixed effects, and normal weather, heat tolerance, and permanent environment as random effects.

The production and performance traits with increased THI (THI>72) showed a phenotypic and genetic decrease while the level of SCS increased with increasing THI. The average milk production in the THI index range of < 72 underwent a relatively stable trend with an average of 35.72 kg, but the average milk production decreased to 31.25 kg with the increase of the index from the threshold of 72. Thus, it can be claimed that the optimal THI point for milk production was between 72 and 70 THI (9-13 °C). The average open days was 114.47 ± 28.64 days, and the calving interval to the first insemination was estimated at 62.38 ± 16.42 days. The highest and the lowest lengths of open days and the interval from calving to the first insemination were respectively observed during summer (135.41 and 69.71, respectively) and in winter (100.07 and 54.64, respectively). In addition, the milk production and reproduction traits showed the highest genetic slope ratio, which indicates that they are more affected by heat stress at high levels of THI. Since this trait is known to reflect the mobilization of body reserves, using its changes in hot conditions can be a very cost-effective biomarker for heat stress in dairy cows that balances consumption and motility in hot conditions and highlights the need to include the additive genetic effect in the heat resistance evaluation model. Furthermore, the lactation stage in which cows experience heat stress intensifies the effect of heat stress on milk production. Mid-lactation and early-lactation cows are the most and, least affected, respectively, while late-lactation cows are moderately affected. High-producing cows were more affected by heat stress than low-producing ones. On the other hand, a positive genetic correlation was detected for SCS between neutral and heat stress, hence continued selection for lower SCS will result in a favorable selection response for SCS under heat stress.

Heat stress is one of the important factors that negatively affects the milk production, reproduction, and health of Holstein cows. The effect of heat stress can be reduced by modifying the environment (feeding and cooling) or by the genetic selection of animals that are less affected by heat stress. The results of this research show that productivity, reproductive performance, and SCS are significantly affected by the THI-. Since the genetic potential of animals is different under the influence of heat stress and considering the global temperature changes, it is recommended to consider the effect of the animal's resistance to heat stress as a factor in the evaluation indices of superior bulls and dams to produce and breed resistant animals in herds, especially in tropical areas. The optimal THI for Iranian Holstein cows was below 72 for productive, reproductive, and health traits. Disturbances in various reproductive functions due to heat stress can lead to low conception rates in the first insemination, thereby increasing the calving interval and open days, especially during the warm season.

Using genetic enhancement techniques has led to the development of poultry capable of fulfilling significant portions of human dietary requirements through meat and egg production. Maximizing genetic potential necessitates the provision of conducive environmental conditions. Heat stress poses a substantial challenge within the poultry sector, detrimentally impacting poultry production and growth, there by diminishing breeders' economic returns. Adaptation to heat stress is contingent upon a multitude of factors. The capacity to establish homeostasis through alterations in gene expression serves to mitigate extracellular damage and restore physiological equilibrium upon reversion to favorable temperature ranges. Domestic birds thrive within a temperature spectrum of 18-24 °C, with any deviation beyond this range precipitating elevated mortality rates. Elevated mortality is attributed to heat-induced suppression of the immune system and compromised resilience. Moreover, heat stress amplifies the secretion of the corticotropin-releasing hormone, subsequently elevating blood corticosterone levels, thereby instigating molecular alterations under stress conditions. Hence, a comprehensive examination of this challenge from diverse perspectives holds significant promise. Consequently, the present study endeavors to delineate protein complexes and pivotal signaling pathways regulated by distinct genes expressed in response to heat stress within the hypothalamus of broiler chickens.

The systemic response of chickens' hypothalamus transcripts to heat stress was comprehensively examined in this investigation. Transcript expression profiles from eight chicken hypothalamus tissues, including four subjected to thermal stress and four under non-stress conditions, were retrieved from the GEO database (accession number GSE37400). The raw microarray data underwent rigorous quality control measures and normalization using GEO2R software to ensure reliability and consistency. Genes with discernible expression changes were identified based on a stringent criterion of P-value > 0.05 and (LogFC < 0.5-0.5). Subsequently, a gene expression regulatory network was constructed to elucidate the interplay among genes implicated in broiler heat stress, employing Cytoscape software in conjunction with the STRING database. The network visualization facilitated the identification of protein clusters, representing areas of high density, which were further analyzed using the CytoCluster plugin renowned for its efficacy in detecting such densely interconnected regions. Following the delineation and characterization of genes within these clusters, the DAVID database was utilized to elucidate the relevant biological pathways associated with the identified genes. This comprehensive approach enabled a detailed exploration of the molecular mechanisms underlying the hypothalamic response to heat stress in chickens.

The analysis of microarray data unveiled a comprehensive portrait of the molecular response to heat stress in chickens. Among the 43,607 initially examined probes, 593 differentially expressed genes were identified after rigorous curation involving the elimination of duplicate genes and application of a significance threshold. A network encompassing 149 genes with a minimum interaction score of 0.4 was constructed utilizing the STRING software, shedding light on the intricate interplay among these genes. Subsequent investigations honed in on genes exerting significant regulatory effects in response to heat stress, elucidating their pivotal roles in orchestrating physiological processes. Functional assessment of the networked genes revealed their involvement in diverse biological activities, including the positive regulation of T cell-mediated immunity, WNT and MAPK signaling pathways, as well as phagocytosis and natural killer (NK) cell activity. Particularly noteworthy was the observation of suppressed NK cell activity in broilers under heat stress, likely influenced by heightened corticosterone levels and subsequent inhibition of thyroid hormone secretion, thereby impacting temperature regulation and metabolism. Moreover, the elevation in blood glucose levels observed in stressed chicks may contribute to their adaptive survival response. Importantly, heat stress was observed to disrupt cellular homeostasis and molecular pathways, manifesting in alterations in biological processes such as the cell cycle. This disruption in the cell cycle may signify a novel mechanism of stress resistance in vertebrates, further underscoring the complexity of the physiological response to thermal stress in chickens.

The analysis of gene functionality within the network underscores the intricate nature of the innate immune response and cellular demise elicited by heat stress. Notably, certain genes identified in this analysis participate in positively regulating T cell-mediated immunity, vascular endothelial growth factor (VEGF), WNT signaling, and mitogen-activated protein kinase (MAPK) pathways. Introducing a biomarker panel comprising genes, such as MAPK14, NT3, SOX2, YAP1, FGF2, LRRK1, LEF1, and TLE1, holds promise for advancing our understanding of the underlying molecular mechanisms governing stress responses in poultry. Furthermore, this approach may facilitate the discovery of novel genes whose modulation could mitigate the effects of thermal stress.

Rapid growth of broilers leads to insufficient cardiac output, cardiac hypertrophy, and finally sudden death. When livestock are exposed to hot environments, they often try to dissipate heat by increasing blood flow to the skin. This physiological response is a way for animals to adapt to long-term thermal conditions. However, this thermoregulatory mechanism has its limitations. While different animals have varying degrees of tolerance to heat stress, the cardiovascular system can only compensate within a certain range before it starts to impact food production. Domestic poultry, such as chickens, lack sweat glands, which is a key mechanism for body cooling in many other animals. This deficiency forces the cardiovascular system to work harder, sending more blood to the skin to help regulate body temperature. Broilers, in particular, have a narrow thermoneutral zone (the range of temperatures where an animal can maintain its body temperature without expending extra energy) and a high metabolic rate, which places an even greater burden on their cardiac function. Therefore, it is an appropriate model for studying cardiac disease. Heat stress is among the stressors affecting cardiac performance. In accordance with the cardiac system susceptibility of poultry to heat stress, especially broilers because of their fast growth rate, to enhance the ability of modern broiler chickens to withstand heat stress through selective breeding, we need to identify the crucial genes and biological processes that lead to unbalanced heart development and the high incidence of heat-induced heart problems. Thus, the aim was to consider the gene expression of cardiac contractility proteins under heat stress conditions during the growing period of broilers.

Ross 708 broilers were subjected to heat stress (HS) of 35–37 °C for 8 hours daily for 21 days post-hatch. Initially, male broilers had unrestricted access to feed and water in spacious colony houses maintained at 33 °C, with the temperature gradually decreasing by 3 °C per week until it reached 24 °C by the day 21 post-hatch. At the conclusion of the growth period, the broilers were euthanized, and their left ventricles were isolated for mRNA extraction. RNA-seq data were obtained from NCBI’s with the accession number SRP082125. All the expressions of deferentially expressed genes (DEGs) were determined and analyzed by DAVID online bioinformatics tools. Gene ontology qualification, including biological processes (BP), cellular component (CC), and molecular role (MF), were achieved from DAVID. Heat stress induction was from days 21-42 for 8 hours every day for 21 days until to end of the growing period.

Gene expression changes were related to 35 genes of the muscular cardiocyte of the left ventricle. From seven genes related to the protein of troponin, TNN and TNNI1 genes, declined significantly, with an increase in the TNNT3 gene expression (P< 0.05). Of five genes related to the tropomyosin protein, the TPM1 gene showed a significant increase in expression (P < 0.05). Of the two genes related to the ryanodine receptor, RYR3 had significant gene upregulation (P < 0.05). From the ten genes related to DHPR, only CACNA2D2 had significant downregulation (P < 0.05). Among four calmodulin-related genes, CAMKK1 and CAMK1D showed significant downregulation, and CAMSAP2 revealed upregulation (P< 0.05). Significant reductions occurred in the expression of five associated genes of heavy-chain myosin (P< 0.05).

Heat stress reduced gene expression of ryanodine, DHPR, and troponin, those related to calcium release into the cell cytosol. Furthermore, it prevents cardiac hypertrophy by decreasing the expression of genes related to the heavy chain of myosin. Thus, the vulnerability of modern broilers to heart problems, when exposed to high temperatures, may be linked to their heart's reduced capacity, which is likely due to their relatively smaller heart size. According to genetic analysis, the smaller heart size in broilers under heat stress than those in a comfortable temperature environment is likely caused by slower cell growth and division. This research identifies specific genes and biological pathways that could be targeted through breeding to develop broilers that are more resistant to heat stress and have healthier hearts. This study has identified specific genes and biological processes linked to the reduction in heart size observed in broiler chickens subjected to heat stress. These insights provide new opportunities for developing targeted breeding strategies to address this issue. The findings indicate that selective breeding, by focusing on the identified genes and pathways, may enable the development of broiler chickens that are more resistant to heat stress and have healthier hearts. By concentrating on these genetic factors, breeders can work toward creating broiler populations that are more resilient to high temperatures and less susceptible to heart problems.

The present study aims to investigate the effect of different forms of chromium (inorganic chromium, chromium-methionine and chromium nanoparticles) on blood parameters, antioxidant status and immunoglobin of Afshar ewes during the transition period and lambs. They were done under the influence of heat stress. 40 pregnant Afshar ewes from 42 ± 2 days before the expected parturition in a completely randomized design. Four experimental treatments were assigned with ten replications. Experimental treatments include basic diet without chromium supplement (control), basic diet containing 3 mg of chromium in mineral form per kg of dry matter, basic diet containing 3 mg of chromium in the form of chromium-methionine per kg of dry matter and The basic diet contained 3 mg of chromium in the form of chromium nanoparticles per kilogram of dry matter. The results showed that the addition of different forms of chromium to the ewes' diet caused a significant increase in the concentration of red blood cells, hemoglobin and blood hematocrit compared to the control group (P<0.05). Adding chromium to the diet of ewes caused a significant decrease in white blood cells (P<0.05). In experimental treatments, no significant difference was observed in terms of platelets, average volume of red blood cells, average concentration of red blood cells, neutrophils, lymphocytes, monocytes, and eosinophils. The concentration of superoxide desmutase, glutathione peroxidase, catalase, triiodothyronine and tetraiodothyronine in the blood in the treatments receiving different forms of chromium also increased compared to the control group (P<0.05). The results showed that the concentration of malondialdehyde and total antioxidant capacity in ewes and lambs receiving chromium supplementation was lower than the control treatment (P<0.05). However, there was no significant difference between different experimental treatments in terms of ceruloplasmin concentration and the ratio of T4 to T3 (P<0.05). The concentration of IgG and IgM in lambs receiving different forms of chromium also increased compared to the control group (P<0.05). In general, the use of chromium, especially in the form of chromium-methionine and chromium nanoparticles, is recommended during the transition period of ewes under the influence of heat stress.

During the time around parturition, animals make many metabolic adjustments to support the transition from pregnancy to lactation. In addition, dairy cattle produce milk more than their ability to consume energy, as a result, they are in a negative energy balance at the beginning of lactation, which may reduce the longevity of the cattle in the herd and increase the rate of elimination of dairy cattle. Heat stress in late pregnancy is aggravated by energy restriction. In such conditions, the use of management and nutritional methods will reduce the problems during the transfer period and heat stress. One of the ways to optimize the productive and reproductive conditions of livestock, through improving the metabolism of nutrients and eliminating or reducing stress conditions, is to use chromium as a metabolic improver. Scientific sources suggested the amount of chromium needed for sheep 3 to 5 mg per day and for dairy cows 15 to 50 mg per day. Inorganic chromium has a bioavailability of about 0.5 percent. While organic chromium has more than 25 percent intestinal absorption, and therefore, consumption of inorganic chromium is not recommended due to its low bioavailability and toxic effects. Among the sources of organic chromium, chromium-methionine has been recognized by important global food and drug organizations as a compound with high bioavailability, impressive metabolic responses and no toxicity complications.

This experiment was conducted to investigate the effect of using different forms of chromium around calving on feed consumption, nutrient digestibility, nutritional behavior of Afshar ewes and the performance of their lambs under the influence of heat stress. Forty pregnant Afshari ewes were assigned to four experimental treatments with ten replications from 42 ± 5 days before the expected birth in a completely randomized design. Experimental treatments include: 1) basic diet without chromium supplementation (control), 2) basic diet containing 3 mg of chromium in mineral form per kg of dry matter, 3) basic diet containing 3 mg of chromium in the form of chromium-methionine per kg Each kilogram of dry matter and 4) the basic diet contained 3 mg of chromium in the form of chromium nanoparticles per kilogram of dry matter. The length of the test period was 84 days. Weighing of ewes was done at the beginning, at the time of calving and at the end of the period. The rest of the feed is weighed every day and the daily feed consumption was calculated by deducting from the provided feed. In order to measure the digestibility of ewes, stool and feed samples were collected for 5 days from 10 to 6 days before possible calving and 31 to 35 days after calving. To determine the chemical composition of food and feces samples (dry matter, crude protein, crude fat, and organic matter), the methods of the official association of analytical chemists were used. The insoluble fiber in neutral detergent (NDF) and the insoluble fiber in acid detergent (ADF) were also determined by the Van Soest method. In relation to feed consumption behavior during 28 to 30 days after birth, it was measured as a 24-hour activity record. The time spent for the activities of eating, resting, standing and ruminating was recorded visually every 5 minutes and assuming that the activity continued in the last 5 minutes for all the animals during the day and night hours. After birth, the lambs were first dried and weighed after performing the necessary hygiene operations, and then they received the first portion of colostrum. Diarrhea status and duration of diarrhea and stool score were recorded daily. Stool scores were determined based on 1_ hard and consistent, 2_ soft and loose, 3_ loose and watery, 4_ watery with some blood and 5_ watery with blood and mucus. A digital thermometer was used to measure the rectal temperature. The thermometer was placed in the animal's rectum for 3 minutes and the temperature was recorded immediately. Respiration rate was measured by visual observation of the number of ups and downs of the animal's side in one minute. In order to measure the apparent digestibility of dry matter in lambs, feed and feces samples were sampled on the 35th day after birth using acid-insoluble ash (AIA) as an internal marker for six consecutive days.

The results showed that there was no significant difference in the weight of the ewes before calving. But from the beginning of ewes giving birth (P=0.0466) to 6 weeks after giving birth (P=0.0484), the treatments receiving different forms of chromium performed better than the control group of ewes. Dry matter consumption of ewes also had an upward trend from the third to the sixth week after giving birth in the ewes receiving chromium-methionine and chromium nanoparticles (P < 0.05). The digestibility of dry matter and insoluble fibers in neutral detergent increased during the period before and after the delivery of ewes under the influence of chromium intake (P=0.0001). Addition of chromium supplement to the diet of ewes did not cause a significant difference in the parameters of feed consumption behavior, but it caused a significant difference in the resting behavior of the ewes, so that the lowest and longest resting time was related to the treatment receiving chromium nanoparticles and the control, respectively (P=0.0411). Adding chromium supplement to the diet of ewes improves the birth weight, daily weight gain, digestibility and diarrhea condition of the born lambs (P<0.05).

In general, it is recommended to receive chromium, especially in the form of chromium-methionine and chromium nanoparticles, during the transition period of ewes under the influence of heat stress.

During the time around parturition, animals make many metabolic adjustments to support the transition from pregnancy to lactation. Before giving birth, animals are subjected to a lot of metabolic effects, to prepare the physiological conditions of the body in the time after giving birth and during lactation. In addition, dairy cattle produce milk more than their ability to consume energy, as a result, they are in a negative energy balance at the beginning of lactation, which may reduce the longevity of the cattle in the herd and increase the rate of elimination of dairy cattle. Heat stress in late pregnancy is aggravated by energy restriction. In such conditions, the use of management and nutritional methods will reduce the problems during the transfer period and heat stress. One of the ways to optimize the productive and reproductive conditions of livestock, through improving the metabolism of nutrients and eliminating or reducing stress conditions, is to use chromium as a metabolic improver. According to scientific sources, the chromium requirement for sheep is three to five mg per day, and for dairy cows is 15 to 50 mg per day. Inorganic chromium has a bioavailability of about 0.5%. Organic chromium has more than 25% intestinal absorption, and therefore, consumption of inorganic chromium is not recommended due to its low bioavailability and toxic effects. Among the sources of organic chromium, chromium-methionine has been recognized by important global food and drug organizations as a compound with high bioavailability, impressive metabolic responses, and no toxicity complications. This experiment was conducted to investigate the effect of using different forms of chromium around calving on feed consumption, nutrient digestibility, nutritional behavior of Afshari ewes, and the performance of their lambs under the influence of heat stress.
Forty pregnant Afshari ewes were assigned to four experimental treatments with 10 replicates from 42±5 days before the expected birth in a completely randomized design. Experimental treatments include 1) a basic diet without chromium supplementation (control), 2) a basic diet containing three mg of chromium in mineral form per kg of dry matter, 3) a basic diet containing three mg of chromium in the form of chromium-methionine per kg of dry matter, and 4) a basic diet contained three mg of chromium in the form of chromium nanoparticles per kilogram of dry matter. The length of the test period was 84 days. Weighing of ewes was done at the beginning, at the time of calving, and the end of the period. The rest of the feed is weighed every day and the daily feed consumption was calculated by deducting from the provided feed. Sampling of the rumen fluid was done on the 14th day after birth. The rumen fluid was taken before feeding in the morning (zero hour), and at three and six hours after feeding by esophageal tube, then the pH amount of rumen contents was measured and recorded immediately after extraction by a mobile digital pH meter (Metrohm laboratory pH meter-691) which was calibrated at the same place. To measure rumen liquid ammonia nitrogen, samples were used three hours after morning feeding. To measure the concentration of volatile fatty acids, five mL of rumen fluid samples were prepared and 1 mL of metaphosphoric acid 25% was added to them and kept at -20ºC until the experiment. On the 10th day after birth, blood samples were taken from the jugular vein of ewes and lambs three hours after morning feeding. To measure blood metabolites including glucose, insulin, cholesterol, triglyceride, urea, creatinine, total protein, albumin, and globulin, Pars Azmoun chemical kits and auto-analyzer (Spain BT 3500) were used.
The results showed that, from the third to the sixth weeks after birth, dry matter consumption in ewes receiving chromium-methionine and chromium nanoparticles had an upward trend compared to the other two treatments (P<0.05). The addition of chromium to the diet of ewes had no significant effect on rumen pH, volatile fatty acids, and rumen ammonia nitrogen concentration. The addition of chromium supplement to the diet of ewes caused a significant decrease in the rumen protozoa population compared to the control group (P<0.05). Adding different forms of chromium to the diet of sheep caused a decrease in glucose concentration, and an increase in chromium, insulin, total protein, albumin, and serum globulin compared to the control group (P<0.05). No significant difference was observed between experimental treatments on blood cholesterol, triglyceride, urea, and creatinine concentrations. Also, different forms of chromium did not have a significant effect on the blood parameters of the born lambs.
In general, the use of chromium, especially in the form of chromium-methionine and chromium nanoparticles, is recommended during the transfer phase of sheep under the influence of heat stress.

The transition period between late pregnancy and early lactation (also called the periparturient period) certainly is the most interesting stage of the lactation cycle and is the last 3 weeks before parturition to 3 weeks after parturition. Most infectious diseases and metabolic disorders occur during this period. Milk fever, ketosis, retained fetal membranes, metritis, and displaced abomasum primarily impact cows during the periparturient period (Drackley, 1999). Any nutritional limitation during this period has an important impact on cow efficiency and consequently, milk production decreases. Dairy cows encounter substantial metabolic and physiological adaptations during the transition period. The immune system during the periparturient period is impaired. At this time, the most important factor causing immune-suppression in highly productive cows is metabolic stress resulting from hormonal and metabolic fluctuations, a negative energy balance, shortage of proteins, minerals and vitamins which are required to meet the demands of the fetus as well as the onset of lactation (Sordillo, 2016). In the world, Cu deficiency is one of the most common problems in cattle with clinical and subclinical signs (Hill and Shannon, 2019). Even marginal Cu deficiency (6 to 7 ppm dietary Cu) depresses blood neutrophil function in dairy cattle (Torre et al., 1996). One strategy for improving immune system of transition dairy cows is mineral and vitamin supplementation. It has been reported that many minerals are enzymatic cofactors (Filappi et al., 2005). Studies showed that minerals injection would be a suitable method to improve mineral utilization, and this may be a promising alternative to improve animal performance (Collet et al., 2017). Furthermore, during this period, dairy cows need antioxidants to combat reactive oxygen species (ROS) which produce during oxidative stress. Vitamin C was identified as antioxidant and could help immune system to overcome ROS production. Hence, this experiment was aimed to study the effect of vitamin C and copper injection on the health status of transition dairy cows.

The study was carried out in a commercial farm located in Kermanshah province of Iran. Cows were enrolled from June 22, until September 22. Temperature and humidity index (THI) was calculated. It was between 72-78. The experiment was performed with 40 multiparous (twenty; second parity and twenty; third and fourth parity) Holstein lactating dairy cows which divided into four groups (10 animals/ group) in a 2×2 factorial arrangement. All cows were offered a TMR diet. Experimental treatments consisted of control (injection of 7 ml of NaCl % 0.9), Cu (injection of 75 mg Cu per cow) Vitamin C (injection of 25 mg vitamin C solution/kg BW), and Vitamin C-Cu (simultaneous injection of 25 mg vitamin C solution/kg BW and 75 mg Cu/ cow). Solutions were injected on d 20 and 40 days before expected parturition, parturition day and day 20 of postpartum. Serum concentrations of total protein, glucose, triglycerides, cholesterol, HDL-cholesterol, Ca, P and Mg were determined using autoanalyzer by Pars Azmoon Kits. Serum concentrations of Beta hydroxybutyrate (BHBA) and non-esterified fatty acids (NEFA) were measured using autoanalyzer by Randow Kits. Serum concentration of Cu was determined by atomic absorbtion. Serum concentrations of vitamin C and superoxide dismutase was measured by Elisa reader. Incidence of metabolic disorders and infection disease were recorded. Data of serum variables were analyzed based on a randomized block design with a 2×2 (Vitamin C and Cu, with or without injection) factorial arrangement using Proc Mix of SAS software. The differences among treatments were evaluated using Tukey adjustment when the overall F-test was P ≤ 0.05. Trends were declared when 0.05 < P < 0.10. In addition, percentages of metabolic disorders were reported.

Results showed that the interaction effect of vitamin C and Cu had no significant effect on serum concentration of vitamin C and superoxide dismutase activity. Cows received vitamin C had the greatest serum vitamin C concentration on d 20 prepartum, parturition day, d 10, 20 and 30 postpartum (P<0.05). Content of serum Cu were affected by the interaction of vitamin C and Cu on d 10 and d 20 postpartum (P<0.05). Copper injection increased serum Cu concentration and superoxide dismutase activity on d 20 prepartum, parturition day, d 10, 20 and 30 postpartum (P<0.05) in cows received Cu without vitamin C. Serum concentrations of P, Mg, glucose, BHBA, NEFA, triglycerides and HDL-cholesterol were not influenced by the interaction effect of vitamin C and Cu. Serum triglyceride concentration tended to decrease (P=0.06) in cows received vitamin C and on parturition day. Copper injection tended to increase (P=0.06) serum triglyceride concentration on d 20 postpartum. Serum protein concentration tended to decrease (P=0.07) in cows received vitamin C and in compared to other treatments on parturition day. Copper or vitamin C injections had no effect on serum concentrations of Ca, P, Mg, glucose, BHB and NEFA of experimental cows. Serum calcium concentration tended to increase (P=0.07) in cows received simultaneous injection of vitamin C and Cu in compared to the others on parturition day. Simultaneous injection of vitamin C and Cu tended to increase total cholesterol concentration (P=0.06) on d 10 and 30 of postpartum. Copper injection tended to increase total cholesterol concentration on d 20 prepartum, parturition day and d 10 postpartum (P=0.06). Control groups had the highest incidence rate of retained placenta and clinical mastitis.

It is concluded that vitamin C and Cu injection reduced incidence rate of retained placenta and clinical mastitis due to improving immunity system performance of transition dairy cows.

The Japanese quail is a species known for its short production period and high productivity. Due to their small size and low feed requirements, they are considered a cost-effective option for egg production compared to other poultry species. Additionally, quail eggs are recognized for their superior nutritional value compared to regular chicken eggs. However, there is a need for effective methods to enhance productivity, especially in stressful situations. Previous research has indicated that the use of certain dietary supplements can address this issue and improve the productive traits of birds. Therefore, there is considerable scientific interest in studying the effects of natural compounds such as black seed and L-carnitine on the productive performance of laying Japanese quails, both under normal conditions and during heat stress. Investigating these factors can provide valuable insights into the development of strategies to effectively manage and optimize egg production in laying Japanese quails. This, in turn, would contribute to the sustainability and profitability of the poultry industry. In this study, we aimed to examine the effects of black seed, L-carnitine, and vitamin E on the productive performance, carcass characteristics, blood biochemical parameters, and immune responses of Japanese laying quails.

A total of 500 Japanese laying quails were included in this study. They were divided into two temperature conditions: normal temperature and high temperature (36 degrees Celsius for 6 hours per day). Additionally, there were five experimental treatments: control diet (without any additives), black seed (1.5% black seed diet), L-carnitine (250 ppm + control diet), 1.5% black seed + 250 ppm L-carnitine diet, and Vitamin E diet (200 ppm + control diet). This resulted in a 5x2 factorial experiment with a total of 10 treatments, 5 replications, and 10 quails per replication. The study consisted of three phases: an adaptation period to the experimental diets lasting two weeks, exposure to the designated temperature conditions for five weeks, and a three-week recovery period. During these phases, various parameters were measured and recorded, including productive performance, carcass characteristics, and blood biochemical and immune indicators (such as triglyceride, cholesterol, LDL, HDL concentrations, heterophil, and lymphocyte percentages) under both heat stress and recovery periods in Japanese laying quails. Data analysis was performed using the Generalized Linear Model (GLM) method with the assistance of SAS software. Mean comparisons were conducted using Tukey's multiple range tests.

The results of this study revealed several important findings. During the initial two weeks of the experiment, the consumption of feed containing black seed + L-carnitine led to the highest feed intake, while diets containing black seed, black seed + L-carnitine, and vitamin E demonstrated the highest egg mass compared to the control group (P<0.05). During the heat stress period, high temperatures caused a decrease in feed intake, egg weight, egg production, and egg mass. However, the consumption of feed containing black seed + L-carnitine resulted in increased feed intake, and diets containing black seed, black seed + L-carnitine, and vitamin E showed increased egg production and mass compared to the control group. Furthermore, vitamin E exhibited a better conversion coefficient (P<0.05). During the recovery period, high temperatures led to a decrease in feed intake but an increase in bird body weight. The control group exhibited the lowest feed intake and body weight, whereas diets containing black seed, black seed + L-carnitine, and vitamin E demonstrated the highest egg production and egg mass compared to the control group. Birds fed diets with black seed and vitamin E exhibited a better conversion coefficient (P<0.05). Regarding carcass yield and relative liver weight, the effect of environmental temperature and experimental treatments during both heat stress and recovery periods was not significant. However, the consumption of black seed, L-carnitine, and vitamin E was found to increase carcass yield and relative heart weight. Additionally, high temperatures increased the relative liver weight (P<0.05). Moreover, birds fed control and black seed diets at normal and high temperatures exhibited higher blood cholesterol levels compared to other experimental treatments. In normal temperature conditions and diets containing vitamin E and L-carnitine, a higher percentage of lymphocytes was observed in the blood. In high temperature conditions and diets containing L-carnitine and vitamin E, the heterophil to lymphocyte ratio was also higher (P<0.05).

Finally, the findings of this study highlight the beneficial effects of incorporating black seed, L-carnitine, and vitamin E into the diet of Japanese laying quails, both under normal and high-temperature conditions. These dietary interventions have shown positive impacts on the performance of the quails. Consequently, these results can serve as valuable guidance for quail breeders and producers in selecting suitable feed regimens to manage heat stress in Japanese quail layers, thereby enhancing performance efficiency, carcass characteristics, and blood lipid and immune parameters.

During pregnancy, especially the period around birth, animals make many metabolic adjustments to support the transition from pregnancy to lactation. Since the last two months of pregnancy (late pregnancy) constitute 75% of fetal growth, therefore, enriching the sheep diet can have positive consequences on the health and general performance of the ewe and lamb. In such conditions, using of management and nutritional strategies will reduce the problems during the transition period and heat stress condition. Under stress condition, the mobilization of glycogen reserves and glucose production occur to produce energy to maintain stability in the body. Chromium is one of the scarce essential minerals that plays an important role in the metabolism of carbohydrates, lipids, proteins and nucleic acids. Chromium is part of the glucose tolerance factor that increases the affinity of insulin receptors to insulin hormone and increases the sensitivity of receptors to insulin.

This experiment was conducted to evaluate the effect of different forms of chromium in ewes during the transition period under the heat stress condition. Forty pregnant Afshari ewes from 42±5 days before the expected lambing were assigned to four treatments with 10 replications in a completely randomized design. Experimental treatments included: 1) basal diet without chromium supplementation (control), 2) basal diet containing three milligrams of inorganic chromium per kg of DM, 3) basal diet containing three milligrams of chromium in the form of chromium-methionine per kg of DM and 4) basal diet containing three milligrams of chromium in the form of chromium nanoparticles per kg of DM.

The results showed that ewes receiving chromium had less weight changes at two, four and six weeks after lambing (P≥0.05). Also, supplementation of different forms of chromium increased the body condition score of ewes at the time and six weeks after lambing (P≥0.05). Ewes receiving chromium-methionine and chromium nanoparticles had better body condition than control and inorganic chromium treatments. There was no significant difference in glucose concentration between the treatments 60 and 90 minutes after intravenous glucose injection. After 60, 90, 120 and 180 minutes after the intravenous injection of glucose, the insulin concentration of the ewes receiving different forms of chromium decreased compared to the control treatment (P≥0.05).

In general, the use of chromium, especially in the form of chromium-methionine and chromium nanoparticles, is recommended during the transition period of ewes under the influence of heat stress.

Heat stress as one of the most challenging environmental stresses can growth performance. Broilers are sensitive to heat stress due to the lack of sweat glands. The temperature range for most poultry species is between 16 and 26 degrees Celsius. Heat stress reduces welfare, growth performance, high mortality and large economic losses changes in carcass composition, lipid profile and lipolytic capacity are high under heat stress conditions because heat stress causes significant increases in catabolic and stress hormones (epinephrine, cortisol, and glucagon). Jestrbesk et al. (2017) reported that heat stress increases the activity of fatty acid synthetase (which converts malonyl-CoA to acyl-ACP and acyl-ACP to myristat or palmitate), acetyl cocarboxylase (which it converts acetyl-CoA to malonyl-CoA) and acyl-coasynthetase (which converts myristate to myristate-CoA and palmitate to palmitate-CoA). Liver and adipose tissue are rich in fatty acid synthase, but more than 90% of fatty acid is synthesized in the liver of broiler chickens, and adipose tissue is only responsible for storage (Ijiri et al. 2016). Heat stress, through the increase of lipoprotein lipase in adipose tissue of animals, increases the capacity to harvest and store intestinal and liver-derived triglyceride in adipose tissue (Lu et al. 2007).

The present study was performed to investigate the effect of mild and chronic heat stress on growth performance, carcass traits, blood parameters, meat quality and relative expression of broiler fatty acid synthase and lipoprotein lipase genes. For this purpose, 150 one-day-old male broilers of Ross 308 strain in a completely randomized design with 3 treatments (normal temperature (according to the recommendation of Ross 308 strain), mild stress (27 °C) and chronic stress (32 °C), 5 replicates and 10 birds were kept in each replication from 1 to 42 days. The diet was based on corn and soybean meal and formulated according Ross (308) requirements for three period of starter (1-10 d), growth (11-24 d) and finisher (25-42 d) days. Body weight gain and feed intake was measured periodically and calculated during the whole experiment on a pen basis, and the feed conversion ratio was calculated subsequently. At day 42 of age, two birds per pen were randomly selected, weighed, and slaughtered. After slaughter, percentage of carcass, breast, thigh, abdominal fat, pancreas, liver, heart, bursa of fabricius and spleen were calculated as a ratio of the live weight. To determine the meat quality, 50g of left breast muscle was collected in plastic bags and stored at a negative temperature of 20°C. Meat quality parameters including water holding capacity, moisture, ash, pH, fat, protein, malondialdehyde and total antioxidant activity were measured. Data were analyzed using the general Linear Model procedures of SAS 9.1. When the analysis of variance was significant, Duncan's multiple-range test was used to separate the means. Statements of statistical significance were based on P<0.05.

The results showed that the weight gain of chicks under chronic heat stress in the final period (25 to 42 days) and the whole period (1 to 42 days) was lower than chickens under normal temperature (P <0.05). Exposure to chronic heat stress significantly increased the relative weight of abdominal fat, plasma glucose and triglycerides, and malondialdehyde of broiler breast meat (P <0.05).In agreement with the present result, El-Husseiny and Krieger (1980) also reported that the abdominal fat of broiler chickens under 32 degrees Celsius temperature was more than that of chickens raised at 22 degrees Celsius. Mujahid et al. (2007) stated that heat stress increases plasma levels of fatty acids, triglycerides and cholesterol. The increase of these parameters is probably due to the release of glucocorticoids and the movement of fats, especially triglycerides from the tissues. In agreement with the present result, Lu et al. (2017) reported an increase in the level of malondialdehyde in the breast meat of broilers exposed to chronic heat stress. Heat stress leads to the creation of oxidative stress by increasing the production of free radicals, and the oxidative stress created during heat stress causes an increase in the level of malondialdehyde in skeletal muscles (Vosough-Ghanbari et al. 2010).Chronic heat stress also increased the relative expression of broiler lipoprotein lipase gene in broiler chickens (P <0.05). The relative expression of fatty acid synthase gene also increased significantly in the liver of birds exposed to mild and chronic heat stress (P <0.05). Fatty acid synthase is the limiting enzyme in last step of the synthesis of long-chain fatty acids in animals and the catalysis of acetyl-CoA and malonyll-CoA to fatty acids (Smith 2003). Fatty acid synthesized by liver are incorporated into triacyllglycerols and transported as very low- density lipoproteins (VLDL), which provide this key energy source for other tissues for immediate use or provides storage (Flees et al. 2017).Studies suggest that under stress conditions, high levels of corticosterone and plasma insulin can increase the expression level of LXRa mRNA, which in turn activates the expression of liver SREBp-LC mRNA (Janowski et al. 1999). Therefore, LXRa and SREBp-LC can activate the transfer of key genes required for fat synthesis, such as fatty acid synthase and acetyl cocarboxylase (Demeure et al. 2009). Lu et al. (2007) stated that chronic heat stress negatively affects fat storage and meat quality in broiler chickens, and through the increase of lipoprotein lipase in the adipose tissue of animals, it increases the capacity of harvesting and storing intestinal and liver-derived triglycerides in fat tissue.

In general, exposure to chronic heat stress further decreased yield and increased carcass fat and increased the relative expression of fatty acid synthase genes in the liver and lipoprotein lipase in the breast.

Selecting a breed with appropriate economic performance is one of the most challenging decisions that cattle farmers have to make. The Holstein breed has been imported to the country in the past few decades to increase milk production. This breed is scattered in different climates of Iran, including Golestan province, almost without previous study. Holstein is a breed with high milk production and sensitivity to heat stress. This breed in Golestan province did not have suitable reproductive and economic indicators. On the other hand, dual-purpose breeds, such as Montbéliarde, experience less thermal stress with less feed consumption. Therefore, the research was conducted to evaluate the performance of some reproductive traits and milk production of the Holstein breed, Montbéliarde breed, and hybrids to recommend a suitable breed in the region.

This study was carried out to evaluate the economic characteristics of some reproductive traits and milk production of Holstein cows with Montbéliarde cows and their crossbreeds in Golestan province in northern Iran. In this study, 395 cows were evaluated in the form of a completely randomized design. Indicators such as the age of first insemination and calving, open days, calving interval and the number of inseminations leading to fertility, length of pregnancy period, calf birth weight, and milk production Holstein, Montbéliarde, and 50:50 and 25 crosses: 75 Holstein x Montbéliarde were studied for 5 years in the same geographical point and same management. Meteorological data from 1390 to 1399 was analyzed with the approach of drawing the conditions of livestock breeding environment.

Investigating the results of long-term meteorological data showed that the temperature-humidity index has been above 68 for almost six months, and high-yielding dairy cows in this region are probably experiencing heat stress conditions. Based on the data of this research, Holstein cows showed more open days, so the number of inseminations leading to fertility in this breed increased, and the cost of maintenance, feed, as well as cost artificial insemination, and delay in pregnancy on the farm increased. The calving interval in the Montbéliarde breed, Holstein mixed with 75% Montbéliarde x 25% Holstein, 50% Holstein x 50% Montbéliarde was 398.31, 392.42, 387.59, and 421.72 days, respectively.

Conclusion:

The results of this research showed that the reproduction efficiency of Montbeliarde breeds cows in Golestan province was better than Holstein breed, moreover, heavier calves were produced. It seems that heat stress conditions in the region were more effective in Holstein cows with higher milk production. In an economic evaluation of milk production and herd longevity without considering meat production, the Montbéliarde breed was better than Holstein. It seems that breeding the Montbéliarde breed in the warm and semi-tropical conditions of the north of Golestan province is a more suitable option than the Holstein breed.

Heat stress in most parts of the world has a negative effect on the performance of dairy cows and reduces milk production in dairy cows. Supplementation of cows with micronutrients (minerals and vitamins), especially in the close up period, can have benefits in reducing the negative effects of heat stress and improve the yield of cows during the next lactation period. This study was conducted to investigate the effect of some nutrients on the physiological and performance processes of dairy cows in heat stress.

In this research, 24 multiparous dairy cows were used in the transition period. The cows were randomly divided into 2 groups of 12 and each group was assigned to a test treatment. Treatments include control group: only from the common diet and without nutritious additives and the second group, which in addition to the common diet, received a micronutrients for 21 days before parturition. After parturition, each of the control and treatment groups were again subdivided into two groups of 6, so that in each group, they were either fed with diets without micronutrients or enriched with micronutrients until 21 days after parturition.The supplement containing a micronutrient of the close up period, including micronutrients of selenium, copper, zinc, chromium, beta carotene, vitamin E, magnesium, ascorbic acid and niacin and the micronutrient supplementation of the freshly period in addition to the micronutrient above, contained sodium and potassium. The average temperature- humidity index was during the text period of 74 and cows were heat stress. The conditions of maintenance and management of nutrition and environment were the same for all the animals during the whole experiment period. Weight variations, feed intake and rectal temperature were determined each week 4 hours after feed intake in two consecutive days. The weight of the newborn calves, the weight of the placenta and the amount of colostrum produced during the first three milking was recorded.

The amount of dry matter intake during close up was higher in the micronutrient intake group than the control group, and in the last week of pregnancy there was a significant difference between them (P<0/05). Although weight gain during the close up was not affected by treatment, more weight gain was observed in the group receiving micronutrients. The numbers of pregnant days in cows receiving micronutrients were longer than the control group. The birth weight of calves in cows receiving micronutrients was higher than the control group. colostrum was also more produced in this group. Calves weaning weight was not affected by treatments. Feed intake during the lactating period was affected in the first week of lactation and receiving micronutrients transition period treatment in the third week had the highest feed intake, which in parallel with this week the milk production of this group was higher than other groups and its difference with other treatments was significant(P<0/05). Milk composition were not affected by treatments (P>0/05).

This experiment showed that heat stress can have a negative effect on the performance of dairy cows during the transition period and the use of micronutrients in this period can have beneficial effects on the repair of heat stress in dairy cows.

Oxidative stress plays a key role in sperm structure and function, semen quality and fertility. In poultry industries lipid peroxidation increases under chronic heat stress, particularly when the temperature exceeds 27 °C. In this situation, some practices are taken. One of important action is using pharmacological plant because of the lowest side effects. There is an increasing interest for applying natural antioxidants compare to synthetic because of the safety and low toxicity problems. The pharmacological plant generally used among foods. The use of natural antioxidant decreases sperm disorders and increases fertility. The rosemary has biological antioxidant mechanisms and belonging to thorny pharmacological plant, which is widely distributed in Europe and South-Eastern Asia. It has used in traditional medicine for its therapeutic properties. The Rosemarinus officinalis L. an evergreen perennial aromatic shrub belonging to the family Labiatae, commonly called rosemary. The rosemary is commonly used as a spice and flavoring agent in food processing. The rosemary contains some antioxidant phenolic that have been shown to provide a defense against oxidative stress from oxidizing agents and free radicals. The antioxidant capacity of rosemary is mainly related to the presence of components like carnosol, rosmanol, isorosmanol, epirosmanol, carnosic and rosmarinic acids. The antioxidant capacity of sperm is low, but enzymatic and non-enzymatic antioxidants in the seminal plasma protect sperm by scavenging the reactive oxygen species (ROS).

Heat stress is one of the serious issue in poultry industry which causes significant economic losses. Decreasing feed consumption, increasing excretion and decreasing the bioavailability of nutrients during heat stress reduces the performance and immune response. Selenium is an essential trace element for humans and animals that plays a role in improving the antioxidant status and the immune system and inflammatory response. The goal of this study was to investigate the effects of different selenium sources [2-hydroxy-4- methyl seleno butanoic acid, selenomethionine and sodium selenite) on performance, carcass characteristics, antioxidant and immune response and blood characteristics in broiler under heat stress condition.

This experiment was conducted in a completely random designs with 240 Arbor Acres (Male) broilers chicks. Chicks were randomly distributed in 4 treatments and 6 replicates (10 chicks in each replicate). The experimental treatments include that: (1) basal diet + 0.3 mg 2-hydroxy-4- methyl seleno butanoic acid; (2) basal diet + 0.3 mg selenomethionine per kilogram of diet; (3) basal diet + 0.3 mg sodium selenite per kilogram of diet; (4) The basal diet that did not have any additives. The birds were kept at 32-340C (10.00 to 16.00; for 6 hours) from 22 to 42 days.

The results of this experiment showed that feed intake, body weight gains and feed conservation ratio were not affected by the experimental diets. The use of different sources of selenium had no significant effect on blood biochemical factors in broiler chickens under heat stress. dding selenium source with 0.3 mg/kg 2-hydroxy-4- methyl seleno butanoic acid significantly affected immunoglobulin G in comparison to other treatments. Diets containing selenium sources significantly increased the relative weight of the spleen compared to the control treatment (P < 0.05). The treatments of 2-hydroxy-4- methyl seleno butanoic acid and selenomethionine significantly decreased liver weight percent. The concentration of glutathione peroxidase, superoxide dismutase and catalase enzymes in blood were significantly increased by selenium sources in different treatments.

The use of selenium source improved the immune system and blood antioxidant status in broiler chickens.

In the poultry industry, the heat stress caused by high environmental temperature has a negative influence on broiler chicken performance and has become a major challenge. Transcriptome profile analysis of the data and identification of patterns of differential gene expression in related tissues can be involved in the discovery of molecular mechanisms resistant to heat stress. The main purpose of this study was to use transcriptome profiles of three tissues brain, liver, and leg muscle of two groups of the control and heat stress broiler chickens to identify candidate genes associated with heat stress. By the analysis of microarray data to express the gene differences, 657 significant genes (P<0.05) were extracted, which a total of 94 genes showed significant expression differences (FDR < 0.05, Fold change > ± 2). Then, by studying the ontology of the relevant genes resulting from data analysis and literature mining as well as the reconstructed protein-protein interaction network, hub genes including NSDHL, DHCR24, LSS, FDPS, PCK1, ACTA1, HSP90AA1, HSPA2, HSPB1, HSF1, CRYAB, APOB, and IL6 were identified. Annotation results of these genes indicated that they have a role in the main process of metabolic and signaling pathways related to the ion transport system, steroid, antibodies, cholesterol biosynthesis, lipid metabolism, immune system function, and various signaling pathways such as MAP kinase, RET, and ERK. Overall, the present study can provide new insights into evidence of the pathways activated by these genes to identify effective genes and a better understanding of biological processes related to heat stress.