فصلنامه تحقیقات تولیدات دامی
سال چهاردهم شماره 1 (بهار 1404)

Predicting quantitative traits is a fundamental aspect of plant and animal breeding. Genomic selection is a precise and efficient approach that estimates genetic merit using high-density single nucleotide polymorphisms (SNPs). However, most genomic selection procedures primarily focus on additive effects to calculate the genomic estimated breeding value (GEBV) for selection candidates. Nonetheless, incorporating non-additive effects offers several advantages: (i) it enhances the accuracy of GEBV predictions and subsequent selection responses, (ii) it facilitates optimized mate allocation among selection candidates, and (iii) it enables improved utilization of non-additive genetic variation through tailored crossbreeding or purebred breeding strategies. One of the most challenging factors affecting the accuracy of genomic evaluation is the selection of an appropriate statistical method to estimate marker effects with high accuracy. The most common parametric methods for genomic evaluation are the genomic best linear unbiased predictor (GBLUP) and Bayesian methods, which use the co-variance structure between individuals and regression of phenotype on markers to predict the genetic values ​​of individuals, respectively. However, in recent years, non-parametric methods of machine learning have been widely used for genomic evaluation in animal and plant breeding programs. This study aimed to evaluate and compare the accuracy of genomic predictions using GBLUP and support vector machine (SVM) methods. The SVM models employed various kernel functions, including linear (SVM-lin), Gaussian radial (SVM-rad), polynomial (SVM-pol), and cyclic (SVM-sig). Both purely additive and additive + dominance deviation gene action models were considered under varying levels of dominance variance.

A simulated genome comprising six chromosomes with a total length of 600 cM was used for this study. Each chromosome contained 1,000 evenly spaced SNPs and 100 randomly distributed quantitative trait loci (QTLs). Phenotypic variance ( ) and narrow-sense heritability ( ) were set to 1 and 0.4, respectively. Dominance variance ( ) levels were evaluated at 0.10, 0.15, 0.20, 0.25, 0.30, and 0.35. Prediction accuracy was calculated as the Pearson correlation coefficient between the true genetic value (TGV) or true breeding value (TBV) and their respective genomic estimates (GEGV or GEBV). The correlations were represented as  and , respectively. In addition, the practical significance of differences in prediction accuracy among the studied statistical methods was assessed using Cohen’s d effect size during 100 replicates.

The conventional GBLUP method consistently exhibited higher prediction accuracy for both GEBV and GEGV across all scenarios. Among the SVM approaches, the SVM-rad and SVM-sig kernels showed superior performance in predicting GEGV under both purely additive and additive + dominance deviation models. However, for GEBV prediction, their performance declined with increasing dominance variance. When dominance variance exceeded 0.30, SVM-lin and SVM-sig demonstrated prediction accuracy comparable to or slightly better than SVM-rad. The differences in prediction accuracy between GBLUP and SVM-rad were minimal (d=0.218) in the purely additive model but reached their peak (d=0.492 and d=0.404) in the additive + dominance deviation model at the highest dominance variance ( ). This disparity occurred because, as dominance variance increased, the GBLUP method exhibited slightly greater changes in accuracy compared to the SVM-rad method. Furthermore, with higher dominance variance, the difference in prediction accuracy for GEBV between the SVM methods and both GBLUP and SVM-rad substantially decreased. For example, in the purely additive model ( ), Cohen’s d was 2.608 and 2.336, respectively, while in the additive + dominance deviation model ( ), d dropped to 0.309 and 0.189, respectively. Using the additive + dominance deviation model significantly improved GEBV prediction accuracy, particularly when dominance variance contributed substantially to phenotypic variance. This improvement is due to dominance deviation, which arises from interactions between alleles at a locus. While additive effects are represented as breeding values, which partially incorporate dominance effects, genomic evaluations that explicitly consider dominance effects can further enhance GEBV accuracy.

The choice of kernel function in SVM models plays a pivotal role in the accuracy of GEBV and GEGV predictions. Overall, when applying the nonparametric SVM method to fit markers to phenotypes, the Gaussian radial kernel function is recommended for optimal performance. However, as the dominance variance increased, the performance of SVM-lin and SVM-sig methods improved significantly and the performance gap with GBLUP and SVM-rad decreased. This indicated the potential capacity of SVM in investigating non-additive effects, especially in situations where the contribution of dominance in explaining phenotypic variance increases.

The diacylglycerol acyltransferase (DGAT) gene family, particularly DGAT1 and DGAT2, is crucial in determining milk fat content, which affects both the nutritional quality and market value of dairy products. DGAT enzymes catalyze the final step of triglyceride synthesis, a key process in lipid metabolism. Understanding the genetic basis of milk fat synthesis is vital for improving dairy production efficiency and improving milk’s health benefits. However, gaps in cattle-specific gene expression data, especially regarding complex traits like milk fat synthesis and disease resistance, hinder genetic improvement efforts. Mastitis, a common and costly dairy cattle disease, may be genetically linked to milk fat synthesis pathways, though these interactions remain unclear. To address this, our study used a comparative genomics approach, analyzing gene expression data from both cattle and humans to explore the association between DGAT genes and mastitis. This research aimed to reveal genetic networks that could inform breeding strategies to boost milk quality, production efficiency, and animal health. To conduct this comparative analysis, two gene expression datasets were retrieved from the GEO/NCBI database: GSE24560 for cattle and GSE51874 for humans. These datasets were selected based on their relevance to mastitis and the availability of high-quality gene expression data. The datasets underwent rigorous preprocessing to ensure data quality and comparability. Differentially expressed genes (DEGs) were identified using the LIMMA package in the R environment, which employs linear models to assess differential expression. Clustering and principal component analysis (PCA) were performed to identify patterns and reduce dimensionality in the gene expression data, facilitating the identification of co-expressed gene modules. Co-expression networks were constructed and visualized using the WGCNA (Weighted Gene Co-expression Network Analysis) package, which is designed to identify modules of highly correlated genes and relate them to external traits. Functional enrichment analysis of the resulting networks was conducted using Enrichr, a comprehensive gene set enrichment analysis tool. This analysis helped identify biological processes and pathways associated with the DEGs, providing insights into the functional roles of the identified gene modules. In the human dataset, DGAT1, DGAT2L6, and MOGAT1 were identified as hub genes, indicating their central role in the co-expression networks. These genes are known to be involved in lipid metabolism and triglyceride synthesis, supporting their relevance to milk fat content. In the cattle dataset, IL1B and CXCL6 emerged as hub genes, highlighting their potential role in the inflammatory response associated with mastitis. Gene ontology (GO) analysis revealed a strong association with lipid metabolism, particularly in the synthesis and metabolic processes of acyl glycerols and triglycerides. The most significantly enriched biological processes included the biosynthetic process of acyl glycerol (GO:0046463), the biosynthetic process of monoacyl glycerol (GO:0006640), and the biosynthetic process of triglyceride (GO:0019432), all of which exhibited low P-values, indicating statistical significance. Despite these findings, the study did not establish a direct link between milk fat in humans and mastitis in cattle. This lack of a straightforward correlation highlights the complexity of genetic regulation across different species and biological contexts. While both datasets revealed hub genes and pathways associated with lipid metabolism and inflammation, the specific interactions and regulatory mechanisms appeared to be distinct. The number of modules created varied significantly between the cattle and human datasets. In the cattle dataset, the co-expression network analysis identified several modules that were enriched for genes involved in immune response and inflammation, reflecting the primary focus on mastitis. In contrast, the human dataset modules were more diverse, including pathways related to lipid metabolism, cell signaling, and general metabolic processes. This variability suggests that while there are shared genetic pathways, the organization and regulation of these pathways differ between species. The discussion of extracting conserved modules was inconclusive, further emphasizing the intricate nature of genetic networks. Conserved modules are groups of genes that maintain their co-expression patterns across different species or conditions, indicating fundamental biological processes. However, identifying such modules between cattle and humans proved challenging due to the differences in gene expression profiles and the specific biological contexts of milk fat synthesis and mastitis. This inconclusiveness underscores the need for more nuanced comparative analyses that account for species-specific adaptations and the multifaceted nature of genetic regulation. Moreover, the study's findings suggest that while there are shared genetic pathways involved in lipid metabolism and inflammation, the specific regulatory mechanisms governing these pathways may differ between cattle and humans. For instance, the hub genes identified in the cattle dataset, such as IL1B and CXCL6, are known for their roles in the inflammatory response, which is crucial in the context of mastitis. In contrast, the human dataset highlighted genes like DGAT1, DGAT2L6, and MOGAT1, which are more directly involved in lipid synthesis and metabolism. This difference indicates that the regulatory networks controlling milk fat synthesis and mastitis resistance in cattle may have evolved unique features that are not fully captured by human genetic data. From a systems biology standpoint, the identification of hub genes provides important insights into the regulatory genetic networks underlying milk production and its association with mastitis. These findings offer a foundation for the development of targeted breeding strategies aimed at improving milk quality and reducing mastitis incidence in cattle. Notably, hub genes such as DGAT1, DGAT2L6, and MOGAT1 in humans, and IL1B and CXCL6 in cattle, represent promising candidates for further functional validation through experimental approaches, including gene knockout and overexpression studies. The co-expression networks and gene modules identified herein establish a framework for future investigations into the broader genetic architecture governing these complex traits, particularly concerning immune response, metabolic regulation, and cell signaling pathways. Future research integrating multi-omics data, such as genomics, transcriptomics, proteomics, and metabolomics, as well as comparative genomics analyses across mammalian species, may uncover additional regulatory mechanisms and evolutionary adaptations relevant to milk production and disease resistance in cattle.

In recent years, the increasing demand for feed to increase livestock production and the climate problems have led to a significant increase in the price of feed, especially protein-based feed. The proper processing and use of alternative and cheap by-products therefore increases livestock production and contributes to the country's livestock feed shortage. Peanut waste is one of such by-products. Peanut, with the scientific name of Arachis hypogaea, belongs to the Legume family, which is also called groundnut or pistachio. Peanuts are classified as an oil seed because of their high oil content and are grown in much of the world and are rich in protein and fiber. The crude protein (CP) digestibility of peanuts is reported to be about 70%, but its fat digestibility varies based on the fatty acid structure. Peanuts contain anti-nutritional factors such as phenolic compounds (procyanidins) and phytic acid, which reduce the bioavailability of other nutrients, but this amount is lower in peanuts than in legumes such as soybeans. After oil extraction, peanut meal is produced, which is used as a source of protein in animal feed. By-products of peanut cultivation include almond husk, almond outer shell, thin skin on almond kernel, and peanut waste feed (PWF). Peanut shells are produced in large quantities annually and are discarded without any specific use or economic value. About 34 -35 grams of shells are produced per kg of peanut kernel. The annual production of peanut shells in the world is about 740 thousand tons as waste from the peanut processing industry. In a study, the CP, neutral detergent insoluble fiber (NDF), crude fat, total digestible nutrients, and condensed tannins of peanut shells were reported to be 22.7, 32.6, 19, 87.8, and 15.6% dry matter (DM), respectively. Phenolic compounds in peanut shells, such as tannins, may have positive effects on animal performance. In another study, the CP, crude fat, and total carbohydrate contents of peanut kernel shells were determined to be 12, 16, and 72% (DM basis), respectively, and the total phenolic content was determined to be 140-150 mg/g DM. In a study, supplementing goat diets with 25 and 50% peanut shells on a DM basis increased DM intake and daily weight gain, while also reducing fecal microbial load. In Iran's northern provinces, a significant area of land is devoted to peanut production. Peanuts are mostly consumed as nuts in Iran, so unfortunately, accurate amounts of peanut waste production are not available. The PWF is a new food waste produced in Iran and consists of the almond shell (hard shell), kernel waste, and the thin brown shell around the kernel. So far, few studies have been conducted to investigate the effects of feeding diets containing PWF on ruminant nutrition. Therefore, the purpose of this research was to investigate the effects of different levels of PWF on performance, apparent nutrient digestibility, rumen antioxidant activity, and nutritional behavior of Lori-Bakhtiari fattening lambs.
In this research, 28 fattening lambs with an average age of 120±6 days and an average live weight of 30±2.50 kg were used in a completely randomized design with four treatments and seven replications. The experimental diets were PWF included in the diet at levels 0 (control), 4, 8, and 12% DM and were fed to lambs for 60 days. Diet nutrient digestibility was measured using acid-insoluble ash as an internal marker on the 43rd day of the experiment. Determination of the total rumen antioxidant capacity was performed on the 45th day of the experiment and 3 hours after morning feeding. The feeding behavior of fattening lambs was determined visually on the 47th day of the experiment for 24 hours.
The contents of DM, crude protein, crude ash, crude fat, neutral detergent fiber, acid detergent fiber, non-fibrous carbohydrates, and total phenolic compounds of PWF were 92±2.22, 22.8±0.46, 16.5±0.26, 1.28±0.016, 25.7±0.53, 19.1±0.33, 34±0.57, and 21.5±0.35% DM, respectively, and metabolizable energy content was 2.4±0.075 Mcal/kg DM. Using different levels of PWF in the diet had no significant effect on nutrient intake, growth performance parameters, nutrient digestibility, and eating and rumination behavior (minutes per day) of fattening lambs (P>0.05). By increasing the level of PWF in the diet up to 12%, the total antioxidant capacity of the rumen increased, but the chewing behavior (minutes per day) in fattening lambs decreased compared to the control treatment (P<0.05).
The results generally indicated that the use of peanut waste up to 12% DM is recommended in the diet of fattening lambs.

Adding vegetable oils to broiler diets is common to supply energy and essential fatty acids and to increase diet palatability. Due to the high expense of vegetable oils, using restaurant oil in broiler diets has been increased. After the oxidation of these oils, certain compounds are formed, such as free radicals, peroxides, and secondary oxidation products such as malondialdehyde. These oxidation products have some negative effects on the growth performance and meat quality of broilers. One common method of inhibiting the oxidation process of oil is the use of antioxidants. The main active substance isolated from angelica and green tea, vanillin acid, is an oxidized vanillin compound consisting of phenols that inhibit lipid peroxidation in cells. In addition, vanillic acid has antioxidant, antimicrobial, anti-inflammatory, anticancer, and protective effects on the liver and may help improve broiler performance and meat quality. Therefore, this study was performed to investigate the effect of vanillic acid supplementation on growth performance, blood metabolites, and meat quality of broilers fed oxidized oil.
This experiment was conducted as a completely randomized design on 144 one-day-old Ross 308 male broilers using a 2×2 factorial design with four treatments, four replicates, and nine chicks per replication. Experimental treatments included: 1. A basal diet with soybean oil, 2. A diet with oxidized oil, 3. A diet with soybean oil+100 mg vanillic acid, and 4. A diet with oxidized oil+100 mg vanillic acid. Diets were formulated as isocaloric and isonitrogenous, and then a vanillic acid supplement was added to experimental diets. Restaurant oil was replaced completely with soybean oil in treatments containing this oil. The performance traits, such as feed intake and body weight gain, were recorded for three periods including starter (1-10 days), grower (11-24 days), and finisher (25-42 days), and then, feed conversion ratio was determined. Broilers were treated for 42 days and one bird from each replicate was selected and blood samples were collected from the brachial vein. The collected samples were centrifuged at 3000 rpm for 10 minutes to separate the serum and the metabolites of the blood, including glucose, total cholesterol, and triglyceride, were analyzed. After slaughter, carcass and internal organs were weighted for measuring carcass traits. The breast and thigh were separated from the carcass and transferred to the refrigerator. Meat quality parameters, including water holding capacity, cooking loss, dripping loss, and meat pH, were measured one day after slaughter. The data obtained from this experiment were statistically analyzed using the GLM procedure SAS software. The comparison of means was conducted using the Tukey test at P<0.05.
The results showed that in grower, finisher, and whole period, broilers fed by oxidized oil had the lowest feed intake (FI) and body weight gain (BWG), while the addition of vanillic acid improved FI, BWG, and feed conversion ratio (P<0.05). The interaction effect was significant for the growth performance and broilers fed with restaurant oil had the lowest BWG and FI, while vanillic acid-fed chicks had the highest BWG and FI (P<0.05). The relative weight of carcass, breast, and thigh was lower in broilers fed by oxidized oil, while vanillic acid supplementation caused a higher relative weight of these organs (P<0.05). The effect of treatments on the relative weight of internal organs was not significant. The effect of treatment on blood glucose was not significant. Vanillic acid decreased blood cholesterol, while oxidized oil treatment caused a decrease in blood triglyceride (P<0.05). The broilers fed by oxidized oil had lower meat pH and water holding capacity (WHC) and higher drip loss (DL) and cooking loss (CL), while vanillic supplementation decreased DL and CL, and increased pH and WHC (P<0.05). A negative impact of oxidized oil on growth performance has been reported due to the peroxidation products and their effect on the health of poultry and food. Vanillic acid is an effective compound with antioxidant and antimicrobial properties that can help in improving the negative effect of oxidized oil on performance and meat quality of broilers, by controlling the free radicals produced by oxidized oils.
Based on the results, the restaurant oil resulted in a decrease in feed intake, body weight, carcass, and breast relative to the broilers, as well as a decrease in the meat quality of the broiler, whereas the vanillic acid supplement increased BWG, FI, body weight and meat quality of the broiler fed with the oxidized oil. It can therefore be concluded that vanillic acid supplementation may be useful in improving the growth performance, carcass yield, and meat quality of broiler chickens when consumed in the form of restaurant oils.

Studies show that sodium chloride soluble in water can be used as a source of mineral supplementation to meet part of the mineral needs of birds and that sodium water can replace the dietary sodium supplement completely. Therefore, if it is possible to exploit this ability of poultry and to provide some of the water they consume from salt water, while preserving the country's fresh water resources, the problems caused by saltwater use will be largely resolved. This study examined the effect of high salt concentration in Caspian Sea water on the quality of the meat, intestinal morphology, and histopathology of the liver and kidney tissues of broiler chickens. As the permitted limit for total dissolved solids in broilers is 1000-3000 ppm, the amount of seawater used for broiler chickens was within this range. Based on the hardness of drinking water in poultry farms at 340 ppm and the annual mean hardness of seawater at 3,700 ppm, as well as the permissible NRC hardness limit for water consumption, the study was carried out in a completely randomized design with four experimental treatments including 1. Control, 2. A mixture of seawater and drinking water with TDS equal to 1000 ppm, 3. A mixture of seawater and drinking water with TDS equal to 2000 ppm, and 4. A mixture of seawater and drinking water with TDS equal to 3000 ppm in five replications. To check the quality of the meat at the end of the incubation period, five chickens of average weight were selected and slaughtered from each of the experimental groups. To measure the meat pH, we mixed 10 grams of minced chicken meat with 90 mL of distilled water and measured the meat pH with a calibrated pH meter. For the measurement of water retention, after centrifugation and weighing, the sample was placed at 70°C for 24 hours, and its weight was again recorded and finally calculated by the formula. To check the textural characteristics of meat, cube-shaped samples (2×2×2 cm) and rectangular cubes (4×2×2 cm) at a speed of 1 mm/s with a pressure of 50% and a penetration depth of 10 mm were prepared. They have been tested with the Texture Profile Analyzer (TPA). For the histopathological examination of the liver and kidneys, which included sampling, fixing, and molding of samples, tissue cutting, staining, and laminating of samples, the birds were completely dissected at the end of the incubation period, and after the birds had been killed and their histopathological changes recorded on slides for microscopic examination. To examine the intestinal morphology, a 3 cm long sample from the mid-joint of the small intestine was prepared and transferred to a 10% buffered formalin stability solution after washing with 0.9% saline. All the same procedures were then applied to liver and kidney tissue samples, and finally, 6-mm diameter cross-sections were prepared and stained with hematoxylin and eosin staining to investigate intestinal morphology. The length, width, depth, and the ratio of the length of the villus to the depth of the crypt of each tissue sample were then measured under a microscope and used for the study. There is no significant difference in the feed conversion rate of treatments by adding different percentages of seawater to drinking water, but water consumption and moisture content of the litter have increased. Comparing the average parameters of meat under the different TDS caused by the mixture of Caspian Sea and drinking water, no significant differences were observed in the pH, gumness, coagulation, chewing time, and chewing consistency of the examined treatments. It has shown that different TDS of water have no effect on these meat parameters and statistically they have almost the same average. The only significant difference observed was between the flexibility, water retention capacity, and hardness of the meat tissue, which indicates that meat tissue from treatment with a high TDS had a lower water retention capacity than control treatment. Concerning the length of the villus, which is one of the morphological parameters of the small intestine, it may be considered to be related to the increased capacity of the bird to absorb nutrients, as the length of the villus increases. Slow, longer villi prevent faster passage and increase conversion factor, and lower crypt depths indicate a decrease in the metabolic regeneration of the intestinal epithelium. Based on the results for the length of the blisters, the largest difference compared to the control treatment was related to the treatment with 75% Caspian Sea water, which resulted in a statistically significant difference. Based on the results concerning the width (depth) of the villa and the depth of the tomb, no significant difference was observed when using a mixture of water from the Caspian Sea and drinking water. Results from histopathological examination of the kidney and liver tissues of the treatment groups in this study showed that consumption of 1000 ppm seawater in these animals did not result in significant changes in liver and kidney tissue. There was significant tissue damage in these liver and kidney tissues, and the severity of these changes and damage was directly correlated to the increased seawater concentration in the diet. Based on the results of histopathological examination of kidney and liver tissues from the treatment animals, consumption of 1000 ppm seawater in these animals did not result in significant changes in liver and kidney tissue. When 50% of the water from the Caspian Sea was used and added to drinking water, no significant differences were observed in the ability to absorb and access nutrients from the intestinal villi and finally in the morphology of the small intestine.

Many variables must be considered in broiler production to achieve maximum profits. The selection of an appropriate broiler strain and optimal stocking density are among the key factors for maximizing economic returns. Today, several strains such as Ross, Arian, Cobb, and Arbor Acres are available in the Iranian market, each with specific rearing guidelines based on their genetic modifications. Maintaining an optimal stocking density throughout the production cycle is economically important. The study therefore compared the Iranian Arian strain and the Ross strain with different stocking densities (12 and 16 birds per square metre, respectively). Higher density can lead to stress, and arginine plays a critical role in the urea cycle and protein synthesis. It serves as a precursor for the production of polyamines, creatine, and especially nitric oxide (NO). In conditions of environmental stress, such as heat or oxidative stress, the role of arginine is even more important because of its role in the formation of NO. Therefore, in addition to broiler strain and stocking density, the study included the use of arginine.

A total of 448 one-day-old chicks (224 Arian and 224 Ross) of both sexes were used in a 42-day feeding trial. The experiment was conducted in a completely randomized design in a 2×2×2 factorial arrangement with two broiler strains (Arian and Ross), two stocking densities (12 and 16 birds/ square metre), and two levels of dietary arginine (100 and 130% of the Arian catalog recommendation). There were eight treatments with five replicates. Experimental diets were formulated for four phases: starter, grower, finisher 1, and finisher 2. Feed intake and body weight gain were recorded during the starter, grower, finisher 1, and finisher 2 periods. The feed conversion ratio (FCR) was calculated. At the end of the experiment (42 days), two birds were randomly selected from each replicate for blood sampling from the wing vein to measure blood parameters. To evaluate intestinal morphology, two birds from each pen were slaughtered at 42 days. A 4-cm section was taken from the jejunum (10 cm before Meckel's diverticulum) and fixed in 10% formalin after washing with physiological saline. To measure meat quality traits including water holding capacity (WHC), pH, drip loss (DL), and cooking loss (CL), two birds were randomly selected from each replicate at 42 days, and the left thigh muscle was collected. Data were analyzed using MiniTab 16 software. Data were analyzed using the general linear model (GLM), and treatment means were compared using Tukey's test at P<0.05.

The results showed that the Ross strain had a higher feed intake than the Arian strain (P<0.05). High stocking density significantly reduced feed intake throughout the entire period (P<0.05). In the starter phase, the use of 130% of the recommended arginine level increased feed intake compared to the 100% level (P<0.05). Ross strain chicks receiving 130% arginine also had a higher feed intake. The average daily weight gain of the Ross strain was significantly higher than that of the Arian strain during the grower phase and over the entire period (P<0.05). Stocking density reduced the average daily weight gain in the finisher 1, finisher 2, and entire periods (P<0.05). The use of 130% arginine improved daily weight gain in these phases (P<0.05). Ross broilers reared at a density of 12 birds per square meter exhibited the highest daily weight gain during the finisher 2 phase compared to the Ross and Arian strains at 16 birds per square meter (P<0.05). Ross chicks receiving 130% arginine had higher daily weight gains than those receiving 100% arginine (P<0.05). In the finisher 2 and overall periods, broilers raised at a density of 16 birds per square meter and fed 100% arginine had the lowest daily weight gain compared to other treatments (P<0.05). Both Ross and Arian broilers reared at high stocking density and fed 100% arginine had the lowest daily weight gain. The FCR of the Arian strain in the starter phase was lower than that of the Ross strain. High stocking density improved FCR in the starter phase, but it increased FCR in the finisher 2 and overall periods (P<0.05). The use of 130% arginine significantly improved FCR in broilers (P<0.05). In the finisher 1 and overall periods, Arian broilers reared at low stocking density had better FCR than those at high density. In the finisher 2 phase, Ross broilers reared at low stocking density had better FCR than those at high density. The results indicated that rearing both Ross and Arian strains at low stocking density improved FCR. In the finisher 1 phase, the lowest FCR was observed in the Ross strain fed 100% arginine and the Arian strain fed 130% arginine. Over the entire period, Arian broilers fed 100% arginine had the highest FCR compared to other levels. The interaction of stocking density × arginine showed that the highest FCR was observed in birds reared at 16 birds per square meter and fed 100% arginine. The interaction of strain × stocking density × arginine had a significant effect on FCR in the finisher 1 phase (P<0.05), with the lowest FCR observed in the Arian strain, reared at 12 birds per square meter, and fed 130% arginine. Increased stocking density reduced albumin and total protein concentrations and increased blood glucose concentration (P<0.05). Higher stocking density significantly reduced albumin concentration in both Ross and Arian strains compared to Arian birds reared at lower density. The interaction of strain × stocking density × arginine significantly affected total protein concentration (P<0.05), with the highest level observed in the Ross strain reared at 12 birds per square meter and fed 130% arginine. High stocking density increased cholesterol concentration (P<0.05). The 130% arginine level reduced cholesterol concentration compared to 100% arginine (P<0.05). Increased stocking density also raised AST concentration (P<0.05). Ross broilers had greater villus width and absorption surface area (P<0.05). High stocking density reduced villus length, width, and absorption surface area (P<0.05). The highest absorption surface area was observed in the Ross strain reared at 12 birds per square meter and fed 100% arginine, while the lowest was in the Arian strain reared at 16 birds per square meter and fed 100% arginine (P<0.05). Higher stocking density reduced water-holding capacity and increased cooking loss (P<0.05). Increased arginine levels improved water-holding capacity and reduced cooking loss (P<0.05).

Overall, the results of this study indicated that the Ross strain had higher feed intake and daily weight gain compared to the Arian strain, though their feed conversion ratios did not significantly differ. Stocking density harmed performance indices during the late and overall phases of the trial. The Ross strain showed a better response to arginine supplementation at high stocking densities than the Arian strain. The use of arginine supplementation can mitigate the negative effects of high stocking density and improve broiler performance.

Honey bees are vital to the economy of the people of Kurdistan Province, Iran. They produce honey and other hive products like royal jelly, wax, venom, and collect pollen and propolis. They also provide food security, create jobs in secondary industries, and prevent rural migration to cities. In addition to their significant role in pollination, they also increase the quantity and quality of agricultural products, develop and expand forests and pastures, preserve biodiversity, and increase income. Despite all these economic and social benefits, honeybee colonies and the beekeeping profession in Iran have been adversely affected by several adverse factors, one of the most important of which is the lack of access for beekeepers to improved, highly productive, and economical queens. The use of improved queens with desirable functional and behavioral traits is one of the most important factors of success in beekeeping. The current study was conducted to evaluate the performance of improved Iranian honey bee queens, "Aram", with native queens and their hybrids in three apiaries located in different climates of Kurdistan province during 2022-2023.

The present study was conducted in the form of a factorial experiment (3×3) and based on a completely randomized design with nine treatments and five replications. The treatments included improved and mated queens (improved and mated queens in the central core of the Iranian honey bee breeding plan), hybrid queens (improved and mated queens in the apiaries of Kurdistan province), and native queens (as control). In total, the current study was carried out on 45 honey bee colonies. After the preparation of colonies in each apiary and the successful introduction of queens, the colonies were homogenized in terms of population (adults and brood) and honey storage according to standard instructions. In the present study, the traits of calmness behavior, swarming, homozygosity of sex alleles, population (adults and brood), and honey production were evaluated in the studied bee colonies in each apiary. Data analysis was conducted by SAS 9.4 software.

Variance analysis results of calmness trait showed that the effect of treatment (P<0.01), queen (P<0.01), and the apiary (P<0.05) were significant on the calmness trait of the studied honey bee colonies. Based on the mean comparison results, the highest amount of this trait, with an average of 0.4 ± 0.12 related to the improved queens in the apiary located in the Saral region, and the lowest with an average of 1.7 ± 0.19 related to the native queens in the apiary located in the Genghis Ghalea village. Variance analysis results of swarming trait showed that the effect of treatment, apiary, queen, and the interaction effect of apiary × queen were significant on the swarming trait of the studied honey bee colonies (P<0.01). Based on the mean comparison results, the highest rate of swarming trait with an average of 20 queen cells is related to the native queens of apiary 2 (an apiary located in the Qazalali village), and the lowest rate of this trait with an average of 0.2 queen cells is related to the improved queens of apiary 2 (an apiary located in the Qazalali village). Variance analysis results of homozygosity of sex alleles showed that the effect of treatment and the interaction effect of apiary × queen (P<0.01) and the effect of apiary and queen (P<0.05) were significant on homozygosity of sex alleles of honey bee colonies in the studied apiaries. Based on the mean comparison results, the highest and lowest homozygosity of sex alleles was related to the improved queens of the third apiary (the apiary located in the Saral area) and the hybrid queens of the second apiary (the apiary located in the Qazalali village), respectively. Variance analysis results of the adult population trait showed that the effect of treatment and queen (P<0.01), and the apiary and the interaction effects of queen × apiary (P<0.05) were significant on the adult population trait of the studied honey bee colonies. Based on the mean comparison results, the highest amount of adult population was observed in improved queens of apiary 3, and the lowest in native queens of apiary 3 (apiary located in the Saral region). Variance analysis results of brood population trait showed that the effect of treatment, apiary, queen, and the interaction effects of apiary × queen were significant on the brood population of the studied honey bee colonies (P<0.01). Based on the mean comparison results, the highest average of this trait was related to the improved queens in apiary 3 (the apiary located in the Saral area), and the lowest was related to the native queens of apiary 1 (the apiary located in the Genghis Ghalea village). Variance analysis results of the honey production trait showed that the effect of treatment, apiary, and queen was significant on the honey production trait of honey bee colonies of the studied apiaries (P<0.01). Based on the mean comparison results, the highest production of honey, with an average of 8.2 kg, is related to the improved queens of the second apiary (the apiary located in the Qazalali village), and the lowest, with an average of 3.4 kg, is related to the native queens of the third apiary (the apiary located in the Saral region).

Considering the superiority and significant improvements of the improved queens of the Iranian honey bee breeding plan in the majority of the traits studied in the current research, it can be concluded that breeding has been effective in improving the target traits. Also, it can be suggested to use improved queens of Iranian honey bees to increase the performance of honey bee colonies in the country.