فصلنامه تحقیقات تولیدات دامی
سال نهم شماره 1 (بهار 1399)

The present study was aimed to assess the role of genotype× environment interaction (G×E) and generation interval on the genetic gain caused by importing the genetic materials of dairy cattle in a country without advanced breeding program. Changing allele substitution effects of quantitative trait loci (QTLs) underlying the trait was used to simulate G×E. To this end, three levels of 100 (control), 75 and 50% overlapping of QTL effects in imported sires at the heritability levels of 0.1, 0.3, and 0.5, as well as three scenarios of continuous replacing and discontinuous replacing with one and two generations of foreign genetic materials were considered. Moreover, the effect of decreasing the accuracy of genomic prediction in traits with the low level of heritability was investigated. Based on the performance of daughters of sires in the local population of control scenario, import-based strategies were better than on the strategies of local population. The genetic correlation created in 75% and 50% overlapping of QTL effects were as 0.7 and 0.5, respectively. Although the trend of genetic response increased by decreasing genetic correlation over the time, it was not equal to origin population. Maximum genetic gain (2.56) was observed with a heritability of 0.5 in continuous replacing and absence of G×E. A decrease in the accuracy of prediction resulted in exacerbation of G×E. In general, more genetic improvement is transmitted from origin population to local population only by importing the genetic materials related to populations with higher genetic mean and also by considering G×E in different traits.

The aim of this study was to compare three selection strategies and two properties of breeding value estimations using computer simulation. Simulated traits were weights at birth (BW1), eight weeks (BW8), twelve weeks (BW12), maturation (BWM) and also age at first laying (AFL), weight of first egg (EWM), average egg weight (EW) and egg number (EN). The first strategy was to select cockerels based on breeding value of BW12 and selection of hens based on a selection index with four traits including BW12, AFL, EW and EN. In the second strategy, cockerels and hens were selected using a selection index, as already said. But in the third strategy, cockerels were selected based on breeding value of BW12 and hens based on breeding value of EN. The individual's breeding values for three schemes were estimated by BLUP and ssGBLUP. Matings were performed based on the optimal genetic contribution. The results showed that the total economic values of the first and second programs using ssGBLUP estimations were 450, 460 and 421, and using BLUP were 434, 349 and 418, respectively. The rate of true inbreeding coefficient for ssGBLUP estimations were more than BLUP estimations (0.083, 0.287 and 0.046 vs. 0.072, 0.116 and 0.024, respectively). The results showed that the first strategy for a breeding flock of broiler production, the second strategy for a dual-purpose flock for producing egg and meat and the third strategy for a flock to achieve the highest total economic value with the lowest possible rate of true inbreeding were desirable.

Copy number variation (CNV), one of the most important structural changes in the genome, has been known as an important source of genetic and phenotypic variations. The purpose of this study was to compare the two different algorithms in CNV detection consisting PennCNV and QuantiSNP in Baluchi sheep.Data analysis was performed using the Illumina OvineSNP50k BeadChip on 96 Baluchi sheep.After CNV calling, the copy number variation regions (CNVRs) were determined using the CNVRuler program.91 CNVRs with a length range of 18.75 up to 511.7 kbp were identified by the PennCNV algorithm, covering 0.46% of whole sheep genome.Also, 316 CNVRs with the length range of 7.5 up to 1280 kbp were obtained using QuantiSNP algorithm, covering 1.33% of whole sheep genome. The number of loss events was about five and three times more than the number of gain events for QuantiSNP and PennCNV algorithms, respectively.Also, the number of CNVs detected by QuantiSNP was about four times higherthan PennCNV.Also, 86.6% of total CNVs (174 CNVs with average length of 12.62 kb) identified by PennCNV were common with CNVs detected by QuantiSNP. In general, the results showed that the use of several algorithms could improve the accuracy for detecting the structural variation in the genome and led to a better understanding of the sheep genome.

The objective of this study was to compare artificial neural network (ANN) with non-linear models including Brody, Gompertz, Logistic and von Bertalanffy for predicting the growth curve of Kurdish sheep. The database comprised of 17659 body weights from birth to yearling of 5074 lambs belonging to 162 rams and 1968 ewes during 1996-2013. The ANN model was developed according to three-multilayer perceptron with five nodes in each layer, Sigmoid-Axon function and Levenberg-Marquat learning rule by Neuro Solution software. Non-linear models were analyzed by the NLIN procedure of SAS program. The goodness of fit of models and their comparisons were conducted by using the coefficient of determination (R2), residual mean square (MSE), root of the residual mean square (RMSE), mean absolute deviation (MAD), Akaike’s information criterion (AIC) and Bayesian information criterion information criterion (BIC). The influences of fixed effect on model parameters were analyzed on the optimum model. The results revealed that the ANN had the highest accuracy (r= 0.9735) and the lowest error (MSE= 0.9170, RMSE= 3.452, MAD= 2.424) and described the growth curve better than the other models. Among all non-linear models, the Brody model had the highest coefficient of determination (R2= 0.966) and the lowest AIC, BIC, MAD and RMSE values indicating the best fit for both sexes. Male lambs, single lambs and those gave birth in winter had the highest mature weight and growth rate. The evaluation criteria indicated that the ANN had a suitable potential to predict growth curve of Kurdish sheep, after that the Brody model fitted the data better than the other non-linear models.

The present study evaluated the interaction of grain source (corn vs. barley) and ruminal undegradable protein: ruminal degradable protein ratios (RUP: RDP; 27:73 and 36:64) on growth performance and blood metabolites of Holstein calves. Forty three-day-old male calves with a body weight of 42.6 ± 2.9 kg were used in a completely randomized design with a 2 × 2 factorial arrangement of treatments. Treatments were: (1) corn grain with low RUP: RDP; (2) corn grain with high RUP: RDP; (3) barley grain with low RUP: RDP; (4) barley grain with high RUP: RDP. Calves were weaned on d 53 of age but remained in the study until d 63. The results showed that starter intake was similar among treatments. The average daily gain and feed efficiency were improved in calves fed barley grain (P = 0.04). Wither height was improved in high RUP: RDP fed calves. Hip height was improved in barely fed calves (P = 0.06). Blood concentration of beta hydroxyl butyric acid was 0.33 mmol and greater in barley fed calves (P = 0.02). The total protein level was greater in calves fed higher RUP: RDP. Barley fed calves had lower blood concentration of blood urea nitrogen (P = 0.01). The blood insulin concentration was increased in barley fed calves along with increase in RUP: RDP (P = 0.02). In conclusion, results indicated that feeding starter contained barley grain and high ratio RUP: RDP and also starter contained corn grain with low RUP: RDP is recommendable for starter diet of dairy calves.

In order to evaluate the effects of Thymbra spicata and Echinacea purpurea powders on quality of thigh muscle in broiler chickens orally challenged with Campylobacter jejuni, a total of 192 one day old broiler chickens (Ross 308) were randomly assigned to six dietary treatments in a completely randomized design with four replicates of eight birds for 42 days of age. The experimental dietary treatments included: 1) basal diet without additive (control group); 2, 3) basal diet supplemented with Thymbra spicata powder (2.5 and 5 g/kg); 4, 5) basal diet supplemented with Echinacea purpurea powder (2.5 and 5 g/kg) and 6) basal diet supplemented with Erythromycin (0.275 g/kg). All of the chicks were oral-gavaged with Campylobacter jejuni (4×1011 cfu/mL, one mL per bird) on d 21. In the finisher and entire periods, broiler chickens fed Echinacea purpurea (2.5 g/kg), Echinacea purpurea (5 g/kg), and Thymbra spicata (2.5 g/kg) had a higher feed efficiency than those on control diet (P<0.05). Moreover, feeding broiler chickens on diets supplemented with Echinacea purpurea (5 g/kg) and Thymbra spicata (2.5 g/kg) caused a decrease in malondialdehyde concentration of thigh muscle (P<0.05). Furthermore, broiler chickens fed diet containing Thymbra spicata (5 g/kg) had higher press loss (41/2%) and lower crude protein (22.7%) in thigh muscle (P<0.05). According to current results, Echinacea purpurea and Thymbra spicata powders at level of 2.5 g/kg could be recommended because of improving performance and reducing malondialdehyde.

The aim of this study was to investigate the effects of pomegranate seed pulp (PP) and its treated form with urea (PPTU) on performance, blood biochemical parameters and immune response of broiler chickens reared in heat stress condition. A total of 280 day-old Ross 308 chicks were used in a completely randomized design. The chicks were equally divided into seven treatments including 0, 3, 6 and 9 percent of PP and 3, 6 and 9 percent of PPTU with four replicates and 10 birds each. In heat stress period (25-42 days), the daily heat stress schedule was applied from 10:00 until 17:00 h for seven hours (35-37 oC). The PPTU increased the blood concentration of total protein (11 vs. 15.7 mg/dL). In heat-stressed chickens, PP increased body weight (1498 vs.1020 g) and decreased feed conversion ratio (1.82 vs. 2.56). The PP decreased the blood glucose concentration (611 vs. 1106 mg/dl) and also decreased the activity of the liver enzymes including alkaline phosphatase (1667 vs. 6483 U/L), aspartate aminotransferase (259.9 vs. 674.8 U/L) and lactate dehydrogenase (1506 vs. 3288 U/L). The immune response to SRBC in chickens fed PP with enzymes (9.25) or its urea-treated (8.5) were higher as compared to control (6.75). Therefore, these findings showed that the addition of pomegranate pulp with enzyme or its treated with urea up to 9% may improve performance, immune response and decreased the activity of liver enzymes in heat stressed broilers.

This experiment was conducted to compare the effect of natural mating (NM) and artificial insemination (AI) on reproductive performance in Chukar partridges. A total number of 96 female partridges were randomly assigned to two equal groups (four replicates of 12 birds each) to produce hatching eggs by either NM or AI. In addition to female partridges, one hundred forty-four male partridges were randomly selected where 48 and 96 numbers of those assigned to NM and AI treatment groups, respectively. The female partridges in both treatment groups were kept individually in cages for two weeks. Afterwards, one male partridge was randomly allotted to each female (a total of 48 male partridges) in the NM group. However, the female partridges in the AI group were inseminated by semen collected from 96 male partridges. During 10 days, 184 and 188 hatching eggs were collected for the NM and AI groups, respectively. The hatching eggs were then incubated. No significant differences were found between the NM and AI treatment groups in fertility rate (91.3 and 88.8%, respectively), hatchability of set eggs (58.1 and 53.2%, respectively) and hatchability of fertile eggs (63.7 and 59.9%, respectively). A high embryonic mortality rate was observed during the first 48 h of incubation (i.e. early mortality) in both NM (32.1%) and AI (31.7%) treatment groups; however, there were no significant differences between the treatment groups in embryonic mortality. In general, the efficiency of AI technique in Chukar partridges is comparable to that of natural mating.