فصلنامه تحقیقات تولیدات دامی
سال دهم شماره 2 (تابستان 1400)

This study aimed to investigate the interaction effects between marker effect estimation methods, population structure, and genetic architecture of the trait on the accuracy of genomic evaluations. A reference population with two different effective population sizes (100 and 500) was simulated using the QMSim software. 500 markers and two different numbers of quantitative trait loci or QTLs (50 and 200) were distributed randomly through the genome including a 100 cM chromosome. In this study, three traits with different heritabilities (0.1, 0.3, and 0.5) were simulated. The genomic breeding values were predicted using Bayesian ridge regression, Bayes A, Bayes B, Bayes C, Bayesian LASSO, Reproducing kernel Hilbert space, and neural networks methods. Through the three heritabilities, as the effective population size increased, the accuracy of genomic evaluation decreased with different trends. As the number of QTLs increased, the accuracy of low heritability trait increased, but the accuracy of medium and high heritability traits decreased. Similarly, as the number of QTLs increased, the accuracy of the trait with normal distributed QTLs increased, but the accuracy of traits with gamma and univariate distributed QTLs decreased. For all types of QTL distributions, the increment of effective population size decreased the accuracy of genomic evaluations. The results of this study clearly showed the interaction effects between markers effect estimation methods, population structure, and genetic architecture of the trait on the accuracy of genomic evaluations.

Uneven distribution of recessive alleles among founder animals genomes leads to the heterogeneity of inbreeding depression among their descendants. In this study, pedigree information, birth weight, and weaning weight records of 4032 Baluchi sheep collected between 1989 to 2017 at the Baluchi sheep breeding station were used to assess the heterogeneity of inbreeding depression between founders of the population. The Wright inbreeding coefficient of the inbred animals was decomposed to the partial inbreeding of the four founder animals with the greatest contribution to the inbreeding of the population. Wright inbreeding coefficients and partial inbreeding coefficients of the founder animals were included as a covariate in the animal model, in two separate analyses. The regression coefficients of birth weight and weaning weight from Wright inbreeding were estimated to be -6.4 and -61.9 g, respectively. The effect of partial inbreeding from different founders on the studied traits was heterogeneous. The regression coefficient of birth weight on partial inbreeding of founder B was -79 g, while partial inbreeding from founder D caused an increase of 121 g in this trait. In weaning weight, partial inbreeding of founder D caused an increase of 83 g in this trait, while partial inbreeding of other founders did not affect this trait. The observed heterogeneity in the effects of partial inbreeding of the different animals can confirm the hypothesis that a few recessive alleles with major effects are contributing to the inbreeding depression of these traits. According to the results of this study, the heterogeneity of the effect of inbreeding of the founder animals should be considered in the genetic evaluation model of this breed.

Considering the importance of studying the performance of commercial silkworm hybrids at the level of silkworm rearing units in different rural areas, in the spring of 2019, the 14 hatched silkworm egg boxes per hybrids (12 imported and two Iranian boxes) were delivered to skilled sericulturists in 35 eastern and 32 western villages of Guilan province and then monitored till the end of the rearing period. The random samples including 200 cocoons were purchased from each farmer to record data. The performance of each silkworm box, the percentage of good cocoons, pupal mortality percentage, number and weight of cocoons in a liter, cocoon weight, cocoon shell weight, and cocoon shell percentage were measured. The interaction between areas and hybrids was not significant for all traits (P>0.05). The highest and the lowest performance per silkworm box were for 872× 871 and 103×104 hybrids, respectively (P<0.05). The heaviest and the biggest cocoons were for 153×154 and 872×871 hybrids, respectively; and the lowest was for Baiyu×Qiufeng (P<0.01). The highest and the lowest good cocoon percentages were obtained from 103×104 and HaoyuB×JingsongA, respectively (P<0.05). The highest and the lowest cocoon shell percentages were for 103×104 and BaiyuB×QiufengA, respectively (P<0.05). Among the four studied areas, the lowest average for all studied traits belonged to the plain areas of eastern Guilan. Among the six pairs of examined reciprocal crosses (imported hybrids), the performance of 872×871 and 871×872 and Suju×Minghu and Minghu×Suju can serve the interests of both cocoon producers and silk thread producers.

This research aimed to investigate the effect of different dietary methionine levels on performance, carcass characteristics, energy and protein efficiencies, breast muscle nutrients, and some blood indices in Japanese quails during 11-24 days of age. This experiment was conducted in a completely randomized design during 14 days with 490 quail chicks in seven treatments and five replicates each (14 chicks in each replicate). The experimental diets were the NRC requirement of methionine for quail (0.5 percent), three methionine levels of 7.5, 15, and 22.5 percent lower than that of NRC requirement level (0.4625, 0.425, and 0.3875%, respectively), and three levels higher than that of NRC requirement level (0.5375, 0.575 and 0.6125%, respectively). The results showed that consumption of 0.575% methionine level caused the highest weight gain and lowest feed conversion ratio (linear and quadratic responses). The breast protein content was linearly increased by increasing the methionine level to 0.5%. Consumption of 0.6125% methionine (the highest methionine level) caused the highest relative thigh weight (linear and quadratic responses). The best energy and protein efficiencies were indicated by consumption of 0.575% methionine (linear and quadratic responses). The methionine requirement for optimal weight gain, feed conversion ratio, and energy and protein efficiencies were 0.569, 0.578, 0.54, and 0.35% according to the quadratic broken line. In total, the level of 0.569% was determined for methionine requirement based on the cumulative response of weight gain, feed conversion ratio, and energy and protein efficiencies.

The present experiment was conducted to investigate the effect of the electron beam (beam) and low-pressure steam (steam) treatments on the nutritional value of date kernel powder for ruminants. At first, date kernel powders were irradiated with the beam at doses of 0, 25, 50, 75, 100, and 125 KGy. A part of the irradiated date kernels was then treated with steam (134 ᵒC, 40 min.). Digestion and fermentation of date kernel powder were measured using gas production and two-step digestion techniques. Compared to the control, beam or steam resulted in a decrease in NDF and ADF percentages (P<0.05), a significant increase in potential and rate of gas production, partitioning factor, truly degradable organic matter, and in vitro digestibility of dry matter, NDF, and ADF of date kernel (P<0.05), and the 100 KGy had the best performance (P<0.05). Overall, the treatment with steam or electron beam alone improved the nutritional value of the date kernel, but treatment with steam after beam did not have a positive additive effect. Therefore, the results of the present experiment indicate that beam alone has a great capacity for improving the nutritional value of the date kernel, and the use of steam after the beam has failed to make more improvement.

The objective of this study was to evaluate the effect of the replacement of different levels of wheat straw with cottonseed plant on performance, digestibility, blood parameters, and rumination behavior of Dalagh ewes. Therefore, 15 ewes with three treatments and five replications were used in a completely randomized design. The treatments consisted of 0, 50, and 100% replacement of wheat straw with cottonseed plant. The whole period of the experiment was carried out in 35 days, consisting of seven days for the adaptation period. Ewe body weight was recorded weekly. Fecal and feed samples were collected on days 31 to 35 for five consecutive days from each treatment to determine digestibility. Blood sampling was done on day 35 and 4 hours after morning feeding. On days 29 and 30, the rumination behavior of ewes was estimated for 24 hours. Results indicated that dry matter intake and weight gain in the second treatment (50% cottonseed plant) increased and feed conversion rate was decreased, but generally performance and digestibility were not affected by treatments. Also, there was no significant difference between experimental treatments in digestibility. Results of the present experiment showed, by increasing the amount of whole cottonseed plant in ewe diets, the concentration of triglyceride increased (p < /em><0.05). The most and the least concentrations of glucose were observed in the first (contained 0% cottonseed plant) and second treatment (contained 50% cottonseed plant), respectively. With the reduction of wheat straw levels in the diet, chewing time and rumination behavior were increased. The difference was not significant in eating, rumination, and chewing behavior. Based on the results of this experiment it could be possible to replace the cottonseed plant in the diet of ewes.

This study aimed to investigate the effect of different levels of yeast and monensin in high concentrate diets on the ruminal fermentation parameters by in vitro gas production method and protein degradability by in situ nylon bag technique. Experimental treatments included control diet (75% concentrate and 25% alfalfa) and supplemented control with three levels of yeast (2.5, 5, and 7.5 g per kg dry matter of diet) and three levels of monensin (15, 30, and 45 mg per kg dry matter of diet). The results showed that the addition of yeast in contrast to monensin resulted in a significant increase in cumulative gas production and the potential of gas production (b) (P<0.05). Ammonia nitrogen content was significantly decreased by adding different levels of monensin compared with the control treatment (P<0.05). Also, the average of short-chain fatty acids was significantly increased by adding yeast compared with the control treatment and different levels of monensin (P<0.05). The rumen degradable protein and its fractional degradation rate were significantly reduced by monensin supplementation (P<0.05). Based on the results of this study it can be suggested that the addition of 5 g yeast and 30 mg monensin (per kg DM) in high concentrate diets can improve ruminal fermentability and organic matter digestibility of feed and increase the accessibility of animal to diet energy.

To study the reaction of udder mRNA abundance of genes related to nuclear erythroid 2-related factor 2 (Nrf2) to an intramammary lipopolysaccharide (LPS) challenge with changes in blood insulin and metabolites levels, 24 dairy cows were used. Treatments included insulin infusion (HypoG, n=5), insulin and glucose (EuG, n=6), β-hydroxybutyrate (HyperB, n= 5), and saline (Control, n=8) for 56 h. At 48 h of infusions, two quarters were treated with 200µg LPS, and two control quarters were treated with physiological serum. Mammary tissue biopsies were obtained before and after the LPS challenge. The mRNA abundance of the genes was measured by the qPCR approach. In the LPS quarters, the mRNA abundance of MT1A, MT2A, and MT1E increased in all treatments. The mRNA abundance of GPX3 increased in HyperB and Control. The mRNA abundance of MGST3 and SOD1 decreased in all groups lacking EuG. Decreased mRNA abundance of NQO1 observed in HypoG. In the control quarters, the mRNA abundance of MT1A and MT2A was raised in all groups. Similarly, MT1E is up-regulated in all groups except for the HypoG. The increase of mRNA abundance of GPX3 was observed in the Control and EuG groups, and UGT1A1 in EuG. LPS decreased the mRNA abundance of MGT3, NQO1, and SOD1 in HypoG. In conclusion, LPS influenced the mRNA quantity of the investigated genes in both quarters, which indicate local and systemic reactions to endotoxin. Applying appropriate management strategies will reduce oxidative stress and susceptibility to diseases and will lead to better welfare and performance of the animal.