s. zerehdaran

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 purpose of this experiment was to investigate the effect of one-week feeding of flaxseeds (rolled/extruded) on performance, n-3 fatty acids and oxidative stability of meat in broiler chickens. Seven pelleted diets (36-42d) were provided in a 3×2 factorial arrangement with three flaxseed levels (5, 10, and 15%) and two processing methods (rolled/extruded) and a zero flaxseed control diet. Before the main trial, a total collection method experiment showed that the replacement of 10 and 15% of rolled/extruded flaxseeds in broiler diets caused a marked reduction in the apparent metabolizable energy (AMEn) as compared to those fed basal or 5% flaxseed replaced diets. In the main trial; weight gain was significantly reduced when flaxseed was supplemented at the level of 15%. Lipid peroxidation in thigh meat of birds fed diets contained zero or 5% flaxseed were lower than those fed diet with 10 or 15% flaxseed. The inclusion of flaxseed in the last week of feeding finisher diet linearly reduced the concentrations of saturated fatty acids and monounsaturated fatty acids, in the thigh and breast meat, respectively, whereas, the n-3 and n-3:n-6 ratio linearly increased in both thigh and breast meat. Processing methods of flaxseed did not affect the bird’s performance and fatty acid profiles in meat. It is concluded that the replacement of diets with 5% flaxseed did not affect the AMEn of diet. Feeding diets containing flaxseed for one week before marketing can reduce saturated FA and increase n-3 and n-3: n-6 ratio in meat, but the adverse effect on performance appeared when diets contained 15% flaxseed.

Current experiment was conducted to investigate the effect of propylene glycol supplement (PG) and calcium salt long chain fatty acids (Ca-LCFA) on milk production and blood metabolites of dairy cows. A change over design with 2×2 factorial arrangement including 2 levels of PG (0 and 450 gram/day) and 2 levels of Ca-LCFA (0 and 2.5%) were applied. Treats were recorded on 8 Holstein dairy cows in 4 different periods. The results showed that there was no significant interaction between PG and Ca-LCFA on recorded treats. The concentration of blood glucose increased significantly after using PG in the diet (P<0.05). The blood betahydroxy butirate (BHBA) content decreased significantly after using PG in the diet. Using PG had no significant effect on blood concentration of triglyceride, urea nitrogen (BUN) and cholesterol. In addition PG supplement had no effect on dry matter intake, milk yield, protein, lactose and fat percentage of milk, milk dry matter content and milk solid not fat (SNF). Using Ca-LCFA had no significant effect on blood concentration of BUN, glucose, triglyceride and BHBA, but the blood cholesterol content were significantly increased when Ca-LCFA was used. Ca-LCFA has also no effect on milk yield, protein, lactose and fat percentage of milk, milk dry matter content and milk solid not fat (SNF). In addition Ca-LCFA reduced dry matter intake.

This experiment was conducted in order to compare the effect of feed form (pellet vs. mash), dietary nutrient density and metabolizable energy (min vs. max requirement) on performance of broiler chicks. For this purpose, growth response of eight hundred Ross 308 male broiler chicks was evaluated in a completely randomized design with a factorial 2×2 arrangement (2 factors including pelleted form and dietary nutrient density each at two levels), and eight replicates for each treatment. A number of 25 birds were allocated to each treatment. Results of this experiment showed that high level of nutrient and metabolizable energy density and also feed pelleting significantly increased weight gain (P<0.05). Feed dietary nutrient and metabolizable energy density affected feed intake in the first and third week of ages (P<0.05). Increasing of dietary nutrient density did not affect feed conversion ratio, but pelleted form of feed significantly improved feed conversion ratio during whole period of experiment (P<0.05). Birds fed with pelleted diet had higher mortality than those fed with mash diet. Dietary nutrient density had no effect on meat yield cost, but pelleted of feed resulted in decrease of meat yield cost. The result of experiment showed that feeding birds with pelleted diet and high level of nutrient and metabolizable energy would improve performance of broiler chickens.