فصلنامه تحقیقات تولیدات دامی
سال دهم شماره 3 (پاییز 1400)

This study aimed to compare different methods of genomic evaluation using the criteria of correlation (ρ), regression (β), mean square error (MSE), and selection effectiveness (SE). For this purpose, nine different scenarios were designed based on different levels of heritability (0.1, 0.3, and 0.5) and different numbers of QTLs (20, 200, and 1000). To simulate different scenarios, five generations with a size of 1000 animals were simulated, of which the first two generations were considered as the reference population and the next three generations as the validation population. For each animal, a genome of 500 centimorgans with a marker density of 10000 SNP consisting of five chromosomes was simulated. Genomic breeding values were predicted using three statistical methods GBLUP, Bayes A, and Bayes B. The results showed that with increasing generation interval from the reference population, the accuracy of genomic breeding values decreased for three statistical methods, although Bayesian methods performed better in terms of continuity of accuracy. Based on the criteria of correlation, regression, and selection effectiveness, with increasing the levels of heritability, improved accuracy was observed, but the criterion of mean squares error showed the opposite trend. Bayesian methods performed better in low QTLs, but differences in different genomic evaluation methods were minimized in high QTLs. The results of selection effectiveness in comparison with the accuracy of genomic breeding value showed that accuracy can’t always be a suitable criterion for determining the superior method of genomic evaluation.

The present study aimed to estimate the inbreeding coefficient and its impact on the economically important traits in West Azerbaijan native fowls. In this research, 61563 records collected from 1994 to 2018 (21 generations) from the breeding station of West Azerbaijan native fowls was used. The inbreeding coefficient of birds and the impacts of individual and maternal inbreeding on traits were estimated. Pedigree analysis showed that 54981 (89.31 %) of all chickens were inbred in the breeding station of West Azerbaijan native fowls and the averages of individual and maternal inbreeding coefficients were estimated to be 0.06 and 0.05, respectively. Inbreeding depression for body weight at hatch, at eight weeks and 12 weeks of age, age and weight at sexual maturity, egg number (the first 12 weeks of production), an average of egg production in 28th, 30th, and 32nd weeks of production, and weight at the first egg-laying due to one percent increase in individual inbreeding was as -0.04, -1.52, -2.49, 0.12, -1.22, -0.01, -0.01 and -0.02, respectively. The results showed despite close population in Azerbaijan native chicken station, the inbreeding rate was low because of implementing appropriate mating designs. Although, the absence of inbred birds is almost impossible in the closed population, it is possible to have a suitable mating design for reducing the probable undesirable effects of inbreeding.

Ascites syndrome is one of the most important causes of death in the poultry industry, in which various tissues of the body, including the kidneys, are involved. This syndrome occurs with different frequencies in males and females, and different mechanisms of ascites in the two sexes have not been studied to date. In this study, the gene expression profile of kidney tissue of male and female chickens with ascites syndrome from the paternal line (B) of the Arian commercial line was compared using RNA-Seq data. Due to severe cold stress applied, the mortality rate was high and about 59%, which was higher in males (63.4%) than females (54.1%). The results of transcriptome analysis showed that 240 genes were significantly different in comparison between ascites male and female birds. The annotation analysis of these genes showed that the metabolic pathways of antibiotic biosynthesis and amino acids, carbon metabolism, cell adhesion, receptor-extracellular matrix interaction (ECM) were involved in this process. The body's response to ascites-induced damage to kidney tissue is the development of renal fibrosis (to repair the damage) and reduced activity of the glycolysis pathways and increased gluconeogenesis to reduce energy and oxygen consumption in these pathways. Furthermore, an increase of the STAT-JAK2 signaling pathway activity (due to the high expression of JAK2 and STAT3 genes) was observed. This signal stimulates cell growth, angiogenesis, differentiation, migration, and apoptosis. It is expected that the results of the present study to provide new insights into understanding the molecular mechanism of ascites incidence and also differences in its occurrence in males compared to female broiler chickens.

The DMB2 gene is one of the MHC cluster genes that plays a role in the humoral immune response. This study was performed to identify the polymorphism of exon 2 of the MHC-DMB2 gene and its association with the humoral immune response in Japanese quail. For this purpose, on day 28, 0.2 mL of 5% saline suspension of sheep red blood cell (SRBC) was injected into 130 quail's breast muscle (65 males and 65 females). Seven days later, cervical vein blood sampling was performed on the 35th day. Afterward, the anti-SRBC titer antibody was determined using a micro hemagglutination technique. Also, genomic DNA was extracted from blood samples and a 333bp fragment of exon 2 was amplified using polymerase chain reaction and PCR products were digested by Hinf 1 restriction enzyme. The results showed that there were two types of C (333bp) and G (226, 107bp) alleles in this region with a frequency of 74.6% and 26.4% in the whole population, respectively. The results indicate high polymorphism and high homozygosity in the studied population. In addition, the results showed that genotype had a significant effect on antibody titers (P<0.01). The CC genotype showed the highest total antibody titer (2.13 mg/dL) and the GG genotype showed the lowest total antibody titer (0.33 mg/dL). It is suggested that the negative effects of this single nucleotide polymorphism be considered in breeding programs.

In this study, the relationship between the seven days old weight and the IGF-I gene expression in the breast and thigh muscles of 300 Manchuria quail was studied in a completely randomized design at 35 days of age. On the seventh day, quails were divided into three groups of light, medium, and heavy weight. The amount of IGF-I gene expression in the thigh and breast muscles of quails was evaluated using the Real-time PCR on day 35. At this age, the weight of the breasts, thighs, and live weight were measured in quails. The IGF-I gene expression was the lowest in the light weight group and the highest was in the heavy weight group. In the medium weight quails, the amount of gene expression was between the amounts in the other two groups (P<0.05). Also, all traits were higher in the heavy group than those in the light weight group (P<0.05). According to the results of this study, it can be concluded that low weight in the seven days of age will reduce IGF-I gene expression and weight at 35 days of age in the Manchuria quail. Increasing the expression of this gene in the present strain of quail can increase the growth rate. Reducing the IGF-I gene expression in the Manchuria quail reduced body weight and weight gain. Because this gene causes the rate of growth and the amount of expression of this gene was low in quail with low weight and low growth rate. Because of the role of the IGF-I gene in growth and development, an increase of the IGF-I gene expression can cause an increase in the growth in this quail strain.

The biological effects of aromatase inhibitors in humans and some animals have been studied in several types of research. This study was performed to investigate the effects of two aromatase inhibitors: Letrozole, a synthetic aromatase inhibitor, and Aphrodite, a blend of the medicinal plant containing natural aromatase inhibitor, on blood, reproductive parameters, and also testis and epididymis morphology in male quails. The experiment was conducted with 120 male quails from the age of three weeks in a completely randomized design with three treatments, five replicates, and eight birds in each replicate. Experimental birds in the treatments received distilled water, Aphrodite (100 μL) or letrozole (0.03 mg), via oral gavage. Administration of Aphrodite and letrozole significantly increased the body weight and feed conversion ratio (P<0.05). Feed intake was significantly increased in the Aphrodite received group (P<0.05). Elevated relative weight concurrent with a lowered number of sperm in the testis was also recorded in both Aphrodit and letrozole-treated birds. Serum levels of phosphorus, albumin, total protein, estrogen, and testosterone were not affected by the experimental treatments, but consumption of Aphrodite and letrozole improved sperm viability, acrosome, and membrane integrity (P<0.05). The result showed that application of Letrozole, and Aphrodite, improved production performance and reproductive parameters, such as body weight, feed conversion ratio, sperm viability, and acrosome and membrane integrity in experimental male quails. Letrozole did not reveal any negative effects on the examined parameters and organs and could be considered as a candidate to apply in the breeding programs.The result shows that application of Letrozole and Aphrodite improved productive performance and reproductive parameters, such as body weight, feed conversion ratio, sperm viability, and acrosome and membrane integrity in experimental male quails. Letrozole did not revealed any negative effects on the examined parameters and could be considered as a candidate to apply in the birds breeding programs

To investigate the effect of adding garlic and tomato pomace powder to the diet of Ross 308 broiler breeders on production performance, body weight, egg quality traits, and hatchability characteristics, a total of 375 chickens were randomly assigned to five iso-caloric and iso-nitrogenous diets, including four diets containing 0.2 and 0.4% of garlic and tomato pomace dried powder and a control diet with five replicates (15 hens and one rooster per pen). Chicken’s body weight through the trial period (47 to 56 weeks of age), daily egg production (%), average egg weight, and hatching traits were recorded daily. The chickens’ body weight was significantly affected in the first five weeks of the experiment (46 to 51 weeks of age) and during the second five-week period (52 to 56 weeks of age). Adding 0.4% tomato pomace to the diet significantly increased the chickens’ weight (P<0.05). For hatching traits, there were no significant differences between treatments (P>0.05). During the first five weeks of the experiment, the feed conversion ratio decreased in the control and the 0.4% garlic powder treatments compared with the other dietary groups. Also, in the second five weeks of the experiment, control, and garlic powder treatments had a lower feed conversion ratio compared with diets containing tomato powder (P<0.05). Based on the results of the present experiment, it can be concluded that adding garlic powder compared to tomato powder caused better results.

This study aimed to determine how delayed silo sealing at filling affects the chemical composition, fungal population, and dry matter recovery of maize silage. Whole crop maize silage was harvested and then ensiled using laboratory silos (n= 4) as 1) Control, ensiled immediately, 2) 24 hours later, and 3) 64 hours later. A 24 h aerobic exposure in fresh forage caused an increase (P<0.05) in NDF content, but 72 h aerobic exposure caused an increase (P<0.05) in dry matter and NDF content and a decrease (P<0.05) in CP content. A 72 h delay in sealing resulted in the lowest CP and the highest pH, yeast, and N-NH3 in silage. A delay in sealing caused an increase in yeast counts in silage (72 h; 3.90 vs. control; 3.05 CFU), and 72 h delayed sealing also resulted in lower (P<0.05) dry matter recovery rather than control silage (89.4% vs. 93.1% DM). Aerobic stability was adversely affected by 72 h delayed silo sealing (75.25 vs. 53.5 h). This study indicated that maize silage quality is affected by three days of delayed sealing and the fungal population and aerobic stability are affected particularly from aerobic exposure. This study indicated that maize silage quality is adversely affected by delayed sealing and aerobic exposure.