فصلنامه تحقیقات تولیدات دامی
سال یازدهم شماره 1 (بهار 1401)

The main purpose of a breeding program is to increase the genetic capacity of farm animals for important economic traits. Although the success of genetic selection to increase milk production in dairy cows is quite obvious, the fertility of herds has decreased. The heritability of lactation curve parameters has been reported to be low, indicating that the lactation curve is highly influenced by environmental factors. As a result, direct selection for these traits will not lead to effective genetic improvement, and selection based on correlated traits can be investigated. Studies on the lactation curve of Holstein cows in Iran have often been performed using three-parameter functions. The Rook function has recently been introduced as a suitable function to describe the lactation curve of Iranian Holstein cows. The purpose of this research was to estimate the correlation between the lactation curve parameters of the Rook function (initial production (a), the rate of reaching the production peak (b), maximum production (c), the curve changes after reaching the peak of production (d), the peak time (pt), amount of production at the peak (pm), and persistency (p)) with some production traits (305-d milk, fat and protein production), somatic cell score and age at first calving and also evaluating curve parameters in different phenotypic groups of the economic traits in Holstein cows. A total of 847129 test day records of milk production in the first lactation collected by the Animal Breeding Center and Promotion of Animal Products of Iran from 1983 until 2017, were used. The Rook function was fitted to the test day records and the function parameters were separately calculated for all animals. Estimation of variance components and genetic correlation between the parameters of the lactation curve with the production traits (305-d milk, fat, and protein), somatic cell score, and age at first calving was performed by bivariate analysis via the Gibbs sampling method. To investigate the relationship between economic traits and milk curve parameters, animals were divided into three phenotypic groups including high, medium, and low based on the phenotypes of economic trait, and then the value of curve parameters was evaluated between three groups. The highest genetic correlation was estimated between milk production and peak production (pm) (0.958). The genetic correlation between milk production and persistency was relatively high (0.725). Genetic correlation of somatic cell score with initial production (a), maximum production (c), and amount of production at the peak (pm) was undesirable and its correlation with parameter curve changes after maximum yield (d) was favorable. Therefore, it is expected that selection to reduce initial production and production at the peak and increase curve changes after maximum yield could decrease the somatic cell score. The correlation estimates between persistency with 305-d milk, fat, and protein production were positive, and a negative correlation was estimated between somatic cell score with age at first calving, so it can be expected that selection for persistency will increase the production traits, and udder health could be improved by reducing the number of somatic cell score and age at first calving. In most cases, the values of curve parameters among the three phenotypic groups of traits had significant differences, and in the high production group, age at first calving, the value of initial production, peak production, and persistency were higher compared to other groups; however, an inverse relation was observed for somatic cell score. The estimated correlations showed that the selection of animals for increased initial production (a) and production at the peak (pm) will improve milk production during 305 days. Increasing the somatic cell score reduces the peak time (pt), and persistency (p). A comparison of persistency between different phenotypic groups of economic traits suggested that persistency improves with increasing milk production and its components as well as decreasing somatic cell scores.

Organic acids are one of the alternatives to antibiotic growth promoters. They have beneficial effects on poultry performance and gastrointestinal microbial balance. In general, the addition of organic acids to the diet lowers the pH of the diet and gastrointestinal tract, stimulates growth, helps to overcome the population of beneficial bacteria over pathogenic bacteria, and reduces toxic metabolites produced by harmful bacteria. The purpose of this study was to determine the antibacterial effects of encapsulated versus non-encapsulated organic acids (OA) supplementation in drinking water on intestinal microbiota and broilers' growth performance.
A total of 360-day-old Ross 308 male broiler chicks were divided into six treatments, four replicates, and 15 chicks per replicate in a completely randomized design. The experimental treatments included: a negative control (without organic acids; OA, in drinking water), a positive control (200 mL of a commercial OA, acidifier 4+ in 1000 L drinking water), 500 and 1000 mL non-encapsulated blend of OA, and 500 and 1000 g encapsulated blend of OA in 1000 L drinking water. The blend of OA was composed of butyric, propionic, and acetic acids. Body weight and feed intake were measured weekly on a pen basis. From these data, average daily gain (ADG), average daily feed intake (ADFI), average daily water intake (ADWI) and feed conversion ratio (FCR) were calculated over the total rearing period. The European production efficiency factor (EPEF) was also calculated for the entire period of the trial. On day 42, gastrointestinal samples were collected from a total of 48 sacrificed birds (n = 12 birds from each experimental group) for pH and microflora analysis. Digesta from different sections of the gastrointestinal tract was collected and pH was measured using a digital pH meter. Total coliforms, lactobacilli, and Escherichia coli were counted in ileal digesta using a plate method with the use of a specific medium.
Broilers with an encapsulated blend of OA in drinking water had higher (P<0.05) body weight, ADG, and EPEF, and lower (P<0.05) FCR than the negative control. Broilers in the PC group and those with OA in their drinking water exhibited greater final BW, ADG, and FCR than those in the NC group (P<0.05) throughout the rearing period (0 to 21 d, 22 to 42 d, and 0 to 42 d). Organic acids can improve broilers' performance by inhibiting the growth of pathogenic bacteria in the intestine. In the current study, administration of encapsulated OA in the drinking water of broilers resulted in lower (P<0.05) pH in jejunum when compared to the negative control. Dietary organic acids reduced the pH of different sections of the gastrointestinal tract of broilers compared to those fed the control diet. The administration of 500 g encapsulated or 1000 mL non-encapsulated blend of OA in the current study resulted in a lower count of E. coli compared with the negative control (P<0.05). The count of E. coli was linearly decreased (P<0.05) in the ileum of broilers with graded levels of the non-encapsulated blend of OA. It seems that the gizzard and stomach of birds drink acidified water were more acidic and might decrease the bacteria that were present in the gastrointestinal tract, especially in the lower gastrointestinal tract. Organic acids provide acidic pH in the gut, which increases beneficial bacteria, and decreases harmful bacteria of broilers.
Growth performance and the European production efficiency factor were generally greater with encapsulated OA compared with non-encapsulated one. Results of the current study showed that administration of 500 mg encapsulated blend of OA was sufficient for achieving the desired results.

Increasing the growth rate has made broilers susceptible to environmental stresses and has reduced the bird's ability to confront oxidative stresses and has increased the incidence of metabolic diseases, especially ascites syndrome. Oxidative stress is caused by an imbalance between the production of free radicals in the body and antioxidant defense mechanisms and it is one of the effective factors in increased pulmonary blood pressure. Peppermint with the scientific name of Mentha piperita stimulates growth and immune response and in addition to antibacterial and antifungal effects, it has antioxidant properties. The most important constituents of this plant are menthol, menthone, and methyl acetate, which in low concentrations, dilate blood vessels and reduce the production of malondialdehyde. This experiment was performed to evaluate the effects of adding peppermint powder on the performance, immune response, and blood parameters of broilers under ascites induction conditions.

After preparing the dry powder of the peppermint plant, the amount of essential oils was extracted using a Clevenger apparatus, and the active substances, volatile and phenolic compounds were measured using a GC-Mass spectrometry. 600 male Ross broilers were used in a completely randomized design with six treatments, five replications, and 20 chicks per experimental unit from 10 to 42 days of age. Diets were adjusted based on the nutritional needs of the Ross strain. Experimental treatments were included: 1) positive control (without induction of ascites and without adding the antioxidant), 2) negative control (induction of ascites without adding the antioxidant), 3) vitamin C (induction of ascites with 400 mg/kg diet), 4) vitamin E (induction of ascites with 200 mg/kg diet), 5) and 6) levels of one and two percentages of peppermint powder with induction of ascites, respectively. To induce ascites, chickens were given water containing 1,200 mg/L sodium (3 g/L NaCl) from day 15 of the experiment. During the experimental period, performance traits (body weight and feed intake) were recorded and on day 38 of the experiment, two blood samples from each replication were taken to measure blood parameters (glucose, total protein, albumin, cholesterol, triglyceride, high-density lipoprotein (HDL) and low-density lipoprotein (LDL)). At the end of the experiment, two chicks of each replication were slaughtered to measure immune organs. The ratio of the right ventricle to the total ventricle (RV / TV) was also considered to be an anatomical indicator of ascites. To measure the humoral immune response, 10 % SRBC suspension solution was injected intravenously, and to measure the cellular immune response, 0.1 mL of phytohemagglutinin was injected between the toes of the bird's right toes.

Laboratory analysis of peppermint powder showed that the most active compounds and substances included menthol with 46.21 % and dihydrocarole acetate with 16.19 %. The total essential oil content of peppermint was measured as 1.1 %. Results showed that body weight gain and feed conversion ratio decreased significantly under the ascites induction (P<0.05). The use of antioxidant compounds of vitamin C and vitamin E, as well as peppermint powder at the level of one percent, led to their improvement (P<0.05). Feed intake was not affected by experimental treatments. The weight of the spleen and bursa of Fabricius as a percentage of live weight was not affected by experimental treatments. The ratio of the right ventricle to the total ventricle (ascites index) showed a significant tendency (P = 0.08) and the ascites index was relatively improved as a result of using antioxidant vitamins and peppermint powder. Blood parameters were not affected by experimental treatments. Induction of ascites decreased cellular immune response (PHA) (P<0.05), and antioxidant treatments, especially vitamin C, improved it. Humoral immune response was not affected by experimental treatments. The role of plant compounds as natural growth stimulants in broiler feed has been proven, although their growth stimulation mechanisms are still unclear. Medicinal plants have active aromatic compounds and they have beneficial effects on gastrointestinal health and bird performance. The effect of antioxidants on reducing the incidence of ascites is due to the elimination of free radicals, reduced blood density, and reduced resistance to pulmonary blood flow. Many of the active substances in medicinal plants prevent lipid peroxidation and improve bird performance by scavenging free radicals or by activating antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. The effectiveness of plant materials used in feeding broilers depends on factors such as the composition and level of plant material added to the diet, bird genetics, diet composition, and farm management.

‌ In general, the results of this study showed that the use of antioxidant compounds, especially vitamin C has a more effective role in improving performance, and the level of one percent peppermint powder in the diet can be used as an effective antioxidant compound in ascites syndrome.

Food additives are a group of different substances that are used for different purposes in poultry diets. Antibiotics are a group of food additives that have been used for many years in the poultry industry to improve performance. Numerous studies have shown that the use of antibiotics in poultry diets, although slightly improved performance; however, long-term use of antibiotics causes bacterial resistance and endangers human health. Therefore, today, due to the limitations of the use of antibiotics, the use of natural alternatives such as medicinal plants has been considered. Medicinal plants as a natural feed additive in poultry diets have been effective in improving performance, improving the immune response, maintaining bird health, and reducing the effects of oxidative spoilage. Turmeric is one of the medicinal plants used in poultry diets. Turmeric, due to its curcumin, can improve the antioxidant and immune status of poultry. Another medicinal plant is red pepper. Red pepper has been suggested as a beneficial factor due to its active ingredients such as capsaicin, vitamins A, E, C, and B, minerals, and carotenoids. Red pepper is effective on the immune system of poultry. Therefore, an experiment was conducted to investigate the effect of adding turmeric powder and red pepper in corn-based diets on the performance of growing quails.

The experiment was performed for 35 days using 512 day-old Japanese quails (as hatched), in a completely randomized design with eight treatments (three levels of turmeric (0.75, 1.5, and 2.25 %), three levels of red pepper powder (0.75, 1.5, and 2.25 %), an antibiotic treatment (500 ppm) and a control treatment without additive with four replicates and 16 birds in each replicate. Nutritional requirements of quails were extracted from NRC. Live weight and feed intake were measured weekly. To calculate the feed conversion ratio, first, the amounts of feed intake and daily weight gain during the experimental period were determined, and then the value of the feed conversion ratio was calculated by dividing the feed intake by weight gain. At 35 days of age, two male and two female birds from each treatment were numbered and slaughtered and carcass weight, thigh weight, and chest weight were measured. Carcass yield was then calculated by dividing carcass weight to live weight. Evaluation of the immune system of quails was assessed by measuring the weight of the thymus gland and bursa of Fabricius and blood immunoglobulin in terms of antibodies produced against Newcastle virus (HI test).

The results of this experiment showed that at the age of 35 days, quails receiving experimental diets had a higher live weight than the control group (P<0.05). The effect of treatments on feed intake was significant (P<0.05). Adding turmeric and red pepper throughout the experiment reduced feed intake compared with the control group. FCR was significantly affected by experimental diets during the whole experiment period (P<0.01), and quails received 0.75% turmeric powder (2.18) and quails received 1.50% turmeric powder (2.16) had a significantly lower FCR than the control treatment (2.69). Contrary to red pepper, adding turmeric powder improved the FCR of quails (P<0.01). Curcumin in turmeric has a positive effect on bile production, secretion of gastrointestinal enzymes (amylase and lipase), increases the length of intestinal villi, and increases digestion and absorption of nutrients in birds. Some studies have reported the effectiveness of red pepper on digestive enzymes, and performance has been improved in various species. Capsaicin (the main active ingredient in red pepper) has increased the activity of amylase, lipase, and trypsin enzymes in the duodenum. The levels of triglycerides, cholesterol, LDL and HDL, VLDL, and total serum antioxidants (TAC) significantly affected experimental diets (P<0.05). The triglycerides of quails received 2.25% red pepper powder (152 mg/dL) was lower than the control group (261 mg/dL). The reason for lowering blood triglycerides would be the presence of capsaicin in red pepper, which reduces the activity of glycerol 3-phosphate dehydrogenase and malate dehydrogenase, thereby reducing fat synthesis.

Based on the results of the present study, feeding 1.5 % turmeric powder or 2.25% chili pepper powder is recommended to improve the performance, blood parameters, and immune response of growing quails.

The importance of androgen-estrogen balance has been postulated to be more than complete levels of estrogen or androgen for an optimum reproductive function in males. In aged broiler breeder males, the low fertility is influenced by greater plasma and testicular estradiol as well as a low synthesis of plasma and testicular testosterone concentrations. Since aromatase is the main enzyme that converts the androgens into estrogens; therefore, it has been hypothesized that using the aromatase inhibitors could increase endogenous testosterone production without an associated increase in circulating estrogens. It is hypothesized that these steroid hormone changes that occur during post-peak fertility can affect the expression of several genes whose activity may be associated with steroid hormone changes, including Foxj1, PVRL3, and LPR2 genes. Estradiol plays a vital role in the proliferation and differentiation of the epithelial cells, which cause activation of the Foxj1 gene in these cells. The knocked-out mice for the Fox j1 gene (epithelium lacked ciliated cells) informing the importance of Foxj1 in estradiol-dependent epithelial cell differentiation. In this study, the effects of an aromatase inhibitor, letrozole, were evaluated on reproductive indices of broiler breeder roosters at short-term (three weeks) and during an interval (three days of use and two days of a stop).

Eighteen 55-weeks-old roosters were randomly divided into three groups receiving letrozole T0, T1, and T2 (0, 0.015, and 0.03 mg/kg of body weight, respectively). Deranged semen was collected via a syringe from the distal cauda of the vas deferens from each rooster as a single sample (n=6). Seminal traits, steroid hormone concentrations, the relative abundance of Pvrl3, Foxj1, and Lpr2 mRNA, and in vitro fertility were assessed at the end of the trial. Testes were carefully removed and the epididymal region was dissected free of extraneous tissues and weighed to determine the gonadal/somatic index [testis weight (g)/body weight (kg)]. Total RNA was extracted from the tissues using the TRI® reagent (Ambion, USA) according to the manufacturer’s protocol. The nucleotide sequences of all candidate genes of the roosters (Gallus gallus) were obtained from the GenBank database (https://www.ncbi.nlm.nih.gov/). The primer was designed using Primer3Plus online software and assessed using OligoCalc and PrimerBLAST. Beta-actin was considered an internal control. Quantification of all transcripts was performed using QuantiFast Eva Green PCR Kit (HOT FIRE Pol® EvaGreen ® qPCR Mix Plus) in a 20 μL reaction volume containing 3 μL single-strand cDNA, 7 μL of the master mix, 0.75 μL of either forward and reverse primers, and 8.5 μL of distilled H2O in 20 μL by a Rotor-Gene 6000 Real-Time PCR software (Corbett Research, Sydney, Australia). The data were tested for normality using the Shapiro-Wilk test. Single and repeated measurement data were analyzed with the GLM and Mixed procedures of SAS software. Rooster's testicular data and body weight were considered as covariates in the statistical models. Duncan’s multiple range test was used to compare means. Sperm quality characteristics and in vivo fertility were analyzed with the same models.

The results showed that gonadal somatic index (GSI), sperm total and forward motility, viability, membrane integrity, semen concentration, and fertility rate were improved for letrozole groups compared with the control group (P<0.001). Lipid peroxidation and sperm abnormalities measurements in the T1 and T2 groups were lower compared to the control group. The epithelium thickness and tubular diameter of seminiferous, and the epididymal and testes sperm count increased in the T1 and T2 groups. A concentration of testosterone was statistically increased in T2 group and testicular concentration testosterone was lower in both letrozole groups compared to the control group. FSH concentration was significantly influenced by letrozole (P<0.05). Plasma concentration of estrogen decreased in the T1 and T2 groups and the lowest one was in T2 group, also testicular concentration was lower compared with the control group. The ratio of estrogen to testosterone was significantly influenced by T1 group. An increase in relative mRNA levels was observed for a PVRL3 gene (related to spermiation) in testes, and a decrease of Foxj1 gene (related to ciliogenesis) and LPR2 in epididymal (related to endocytosis) in the T1 and T2 groups.

Based on the results of this study, using aromatase inhibitor improved reproductive indices in aged broiler breeder roosters. It is suggested that increasing testosterone alone cannot improve reproductive performance and a balance in the estradiol/testosterone ratio is necessary to achieve optimal fertility.

Harmful effect of antibiotics is evident in the feed industry. This industry needs an alternative instead of growth-promoting antibiotics. Medicinal plants can be the alternative due to their antimicrobial and nutritional effects. Coriander (Coriandrum sativum L.) is one of the medicinal plants used in animal and poultry nutrition. Coriander seeds’ essential oil is rich in oxygenated monoterpenes. In addition to camphor, granil acetate, alpha-pinene, graniol, and pisimin are other predominant constituents of coriander seed’s essential oil. Minerals including phosphorus, calcium, potassium, and essential amino acids including glutamine, asparagine, and arginine have also been identified as components of coriander seeds. The main component of coriander seeds is linalool. The effect of using coriander seeds and its positive effects on yield, rumen fermentation process, blood parameters, meat quality, and feed conversion ratio has been reported in sheep of different breeds. Therefore, this study aimed to investigate the effect of adding coriander seeds to the diet on yield, nutrient digestibility, and blood parameters of Sanjabi lambs. 16 male lambs with 90 days of age (weaning age) and an average weight of 27±1.5 kg were considered in this study. Fattening was done for 90 days. Lambs were also vaccinated against enterotoxemia. Diets contained the concentrate to forage ratio of 70 to 30. Diets included 0 (without medicinal plants), one, three, and five percentages of coriander seeds. During the fattening period, water and feed were ad libitum to the lambs and the feed was distributed three times a day. Lambs were weighed at the beginning of the period and then monthly after 14 hours of starvation. The dry matter intake was measured daily and the average daily weight gain and feed conversion ratio were calculated at the end of the fattening period. To prepare a stool sample for each head of lamb, five daily stool samples were mixed in equal value and thus a sample was prepared for each lamb. At the end of the rearing period, the fecal collection was performed directly from the rectum of the lamb for five consecutive days. Stool samples were collected from the rectum every three hours and immediately transferred to a refrigerator at 4 °C. The statistical analysis of data was conducted in a completely randomized design using the GLM procedure of the SAS program. Also, Duncan’s multiple range test was used for the comparison of treatment means. The digestibility of dry matter, crude protein, ether extract, and insoluble fibers in neutral detergent (percent) was the same in different treatments (P>0.05). Creatinine, albumin, total globulin, glucose, total protein, cholesterol, triglyceride, urea, beta-hydroxybutyrate, aspartate transaminase, and alanine transaminase were not affected by experimental treatments during feeding (P>0.05). None of the blood serum metabolites of lambs was affected by coriander seed ((P>0.05). The results showed that consumption of coriander seeds had a significant effect on dry matter intake and daily weight gain (P<0.05). The best feed conversion ratio was obtained in the treatment containing one percent of coriander seeds (P<0.05). Compared to the control diet, diets containing coriander seeds had a significant effect on the apparent digestibility of calcium and phosphorus (P<0.05). Using coriander seeds in the diet made a decrease in blood urea nitrogen and increased blood glucose during the fattening period, but did not affect other blood metabolites. Concentrations of liver enzymes including aspartate aminotransferase and alanine aminotransferase tended to be increased by five percent of coriander seed in the diet compared to the control treatment, indicating liver activity to remove toxic effects and anti-nutrients components. Coriander seeds have strong antioxidant properties due to compounds such as riboflavin, tocopherol, total polyphenols, gallic acid, caffeic acid, and quercin. In the present study, blood cholesterol decreased by increasing coriander seeds in the diet. This may be due to a decrease in the activity of the cholesterol-synthesizing enzyme in the liver, making a decrease in tissue cholesterol, and the ratio of unsaturated to saturated fatty acids by aging. According to the obtained results, it can be concluded the use of one to three percent of coriander seed in the diet of fattening lambs improved the performance, and apparent digestibility and has positive effects on blood metabolites including glucose and urea nitrogen in Sanjabi lambs.

Fodder beet is a valuable source of fodder in livestock diets due to favorable agronomic characteristics such as resistance to salinity and drought, less water requirement, and proper nutritional characteristics such as forage production and silage with high nutritional value, good taste, and good resistance to environmental changes. Despite the long history of using fodder beet in animal rations, its nutritional issues and physicochemical properties of it are not fully understood and further research is needed. Silage of fodder beet can be used well in the diet of all ruminants, but studying the proper ways of silage and controlling the physical and chemical properties of silage is one of the important issues that should be addressed. In addition to the stated benefits for fodder beet, such as low dry matter content, fiber, and fat, disruption of ion exchange and change in silo buffering capacity, as well as the difficulty of processing it for permanent consumption of livestock and also important restrictions such as high sugar and moisture in the roots and excess leachate and lack of production of quality silage are the most important obstacles to the consumption of this silage. Harvest time of fodder beet coincides with the heat of the summer season and the occurrence of numerous problems, so it is necessary to silo it to prevent spoilage with the correct method. Today with the introduction of new improved cultivars and the growth of processing technology, these limitations have been almost removed. This study aimed to evaluate some of the physicochemical parameters of ensiled fodder beet with and without Lactobacillus buchneri as a microbial additive.

Some physicochemical parameters of ensiled fodder beet with and without Lactobacillus buchneri as a microbial additive in combination with 10 and 15% dry beet pulp were investigated through a 3×2 factorial arrangement in four replicates. Different silages included: 1) 100% pure fodder beet without additive (control), 2) control + 10% dry beet pulp, and 3) control + 15% dry beet pulp. The microbial additive was added at the level of 6×1010 CFU/g of dry matter. 24 plastic bags containing 25 kg of different material were compacted, sealed, and stored at room temperature. After 75 days, four bags of each group were opened and pH, temperature, and quality were immediately determined. Also, a sample from each bag was used to measure the chemical compositions. Measurements of temperature and pH were performed. Two samples of silage, one for extraction and determination of ammonia nitrogen (using selective ion absorption electrode) by AFIA recommendations and the other sample for measurement of dry matter, crude protein, and ash according to the AOAC method were used. Measurement of NDF and ADF were done according to the Van Soest method. To evaluate the aerobic stability of silages when opening plastic bags, the characteristics of color, odor, and texture of silage in the range of 1 to 10 for high to poor quality were determined using the modified Konigsberg Scores method. Data were analyzed using a completely randomized design in a 3×2 factorial arrangement in four replicates using the mixed model procedure of the SAS program.

Experimental groups with 10 and 15% of dry beet pulp with microbial additive had a better quality (score: 6.5±0.16 vs. 9.4±0.21; pH: 4.04±0.06 vs. 4.59±0.08) than the control group (P<0.01). The type of ensiled materials had a significant effect on chemical compositions (DM, CP, NDF, and ADF) and the aerobic stability of silages at opening time (P<0.01). But microbial additives almost had no significant effect on the traits. Watery loss of silage for the control group was higher and its quality was lower than that in other groups (P<0.01). The best quality and more stability of silage were observed in the group with fodder beet+15% of dry beet pulp which is advisable.

According to the results of this study, adding 10 and 15% of dry beet pulp to fodder beet silage improved the appearance and aerobic stability of the resulting silages compared to the control group. Evaluation of appearance traits and pH of the samples showed that the treatments with dry pulp and the microbial additive had better quality than the control group. The type of mixture used had a significant effect on the chemical composition of silage and its aerobic stability when opened, but the microbial additive did not show a significant effect in most cases. The watery loss in the control group was higher than the other treatments and had a worse appearance quality than other silages. Overall, the most suitable silage composition in this experiment was a mixture of the control group+15% sugar beet pulp, which had better appearance quality, longer shelf life, higher dry matter level, and lower ammonia nitrogen than the other two groups.

Taking advantage of genetically modified queens that have desirable productive traits and behavior is an important factor in beekeeping. The current study aimed to evaluate the performance of the 14th-17th generations of breeding improved queens in the Iranian Honey Bee Breeding Program, and their comparison with control queens kept in private apiaries.
To evaluate the queens, specific questionnaires were designed and completed by beekeepers in their apiaries based on the performance of queens in the third layer. Means comparison showed that the improved queens had better performance than control queens in terms of swarming, honey production, aggressive behavior, and calmness behavior in comparison to queens kept in private apiaries. This evaluation and comparison were performed in private apiaries of 12 provinces in 2016, 11 provinces in 2017, 12 provinces in 2018, and 12 provinces in 2019. During the project, colonies with control and modified queens had the same management in each apiary in terms of nutritional conditions, migration management, and pest and disease management. To compare the improved queen and local queens (as control), a paired sample t-test was used. In each apiary, the minimum number of the improved queen was 10. The t-test was done for all of the recorded traits in the SPSS program. To investigate the effects of the year (2016 to 2019) and queen type (improved and local queens), a two-way analysis of variance was done using the GLM procedure of the SAS program.
The obtained results revealed that the bred queens in 2016 and 2017 are significantly superior to control queens in terms of swarming, and had fewer queen cells, which is desirable for beekeepers. Despite the superiority of the improved queens during 2018 and 2019, the difference between control and improved queens was not significant for swarming behavior. Totally, during generations 14 to 17, the bred queens were significantly better than control queens in terms of swarming behavior in private apiaries. Honey production evaluation of improved queens and comparison with control queens in private apiaries showed that improved queens in 2016-2019 had a significant advantage over control queens (P<0.05). A comparison of improved and control queens in terms of honey production during generations 14 to 17 showed the superiority of improved queens. Aggressiveness behavior comparison of control and bred colonies in 2016-2017 showed the superiority of Iranian bred colonies (P<0.01). A comparison of colony calmness in 2016-2017 also showed the superiority of Iranian improved colonies (P<0.01). Overwintering comparison of control and improved colonies showed that in 2016 and 2018, despite the low superiority of bred colonies, there is no significant difference between the modified and control colonies. However, there was a significant difference between the two groups and the Iranian improved colonies were better than the control colonies in terms of overwintering in 2017 and 2019 (P<0.05).  In other words, the bred colonies were significantly superior to the control colonies (P<0.05). According to the results of variance analysis, the effect of queen type (bred queen and control queen of beekeepers) on calmness, aggressive, swarming behavior and honey production was significant (P<0.01), but did not affect overwintering. The effect of year and generation on calmness, aggressive behavior, swarming, and honey was significant (P<0.01), and it was also significant on overwintering at the lower level (P<0.05). The interaction effect of queen type×year was significant for calmness (P<0.01) and for swarming and honey (P<0.05), but had no significant effect on other traits.
The obtained results revealed that to protect the Iranian honeybee as a valuable genetic resource while preserving the superiority of genetically improved queens and genetic stabilization of improved traits, prevention of sex alleles homozygosity which have a direct effect on decreasing colonies' performance, conducting more investigations against new problems of beekeeping industry are required.