مجله تحقیقات دام و طیور
سال دوم شماره 2 (1392)

In this research, a total number of 701212 (milk), 596331 (fat) and 505793 (protein) yields were used to estimate genetic parameters for persistency of lactation. The records were collected by the national animal breeding center of Karaj during 2006 and 2010. (Co) variance components were estimated using REML method and random regression models. Five persistency measures of lactation were evaluated using estimated breeding values. The estimated heritabilities of persistency for milk, fat, and protein yields ranged from 0.06 to 0.16, 0.03 to 0.17, and 0.06 to 0.20, respectively; the heritabilities for 305-d yield were 0.29, 0.28 and 0.28, respectively. Values of Spearman correlations between measures of persistency and EBVs of 305-d milk, fat, and protein yields ranged from 0.02 to 0.76, -0.24 to 0.58, and -0.50 to 0.80, respectively. Genetic correlations between persistency measures and EBVs of 305-d yield were varied; and were higher for milk and protein yields than for fat yield. For milk and protein yields, selection for EBVs of 305-d production identified sires or cows that are genetically superior in regards to persistency of lactation. But for fat yield, high breeding values for 305-d yield does not identify superior cows for yield persistency. Therefore, genetic evaluation for persistency of lactation is important for improving the milk production traits of Iranian Holstein cows and it is applicable in breeding programs for Iranian Holstein dairy cattle.

The sperm cell membrane is prone to oxidative stress and peroxidative damage due to an increase in reactive oxygen species (ROS) caused by the freezing process. The aim of present study was to determine the effect of different levels of reduced glutathione (GSH) and superoxide dismutase (SOD) antioxidants in freezing extender on the biochemical parameters of frozen–thawed bull semen. Thirty five ejaculates (5 ejaculate per bull) were collected from Holstein (n = 4) and Simmental (n = 3) breeds. Semen samples with appropriate conditions were pooled (separately for each replicate of each breed) and were diluted in Tris-egg yolk containing 5 and 7.5 mM GSH and 100 and 150 IU/ml SOD and an extender with no additives (control). Semen samples were cooled to 5°C during 2 h then they were filled and frozen in 0.5 ml French straws. Malonaldialdehyde (MDA) level, the intracellular activity of SOD and glutathione peroxides (GPx) enzymes were assayed after thawing samples. Results showed that, the addition of both levels of GSH to the semen freezing extender significantly decreased MDA level compared to the control group (P<0.05). However, the addition of 5 mM GSH improved GPx activity compared to the control group in Simmental breed (P <0.05). Generally, the results of this study showed that, the addition of 5 or 7.5 mM of GSH to the Tris-egg yolk extender has a positive effect on intracellular defense system and reduction of sperm membrane lipid peroxidation.

In this study, atriplex stem samples were irradiated with three doses (100, 200 and 300 KGy) to evaluate the effect of electron beam on the chemical composition, ruminal degradability parameters and ruminal-postruminal digestibility of dry matter (DM) and neutral detergent fiber (NDF). Initially, using nylon bag technique, an amount of 5 g of grounded sample (six replicates) was incubated for 0, 2, 4, 8, 16, 24, 48 and 72 hours in the rumen of two Holstein heifers and then parameters of ruminal degradability were estimated. Then ruminal digestibility and post ruminal digestibility of nutrients were determined by incubating of samples in rumen for 16 h and by Daisy digester apparatus, respectively. Statistical analysis was performed using SAS software. The results indicated that reduction of acid detergent fiber (ADF) in irradiated samples was numerically reduced, while NDF reduction was statistically significant (P<0.05). Quickly degradable fraction (a), potentially degradable fraction (b) and effective degradability of DM increased significantly (P<0.05) with increasing dose of irradiation. Quickly degradable fraction (a) of NDF at the doses of 100 and 200 KGy irradiation increased but this change was not statistically significant. Potentially degradable fraction (b) of NDF was significantly increased (P<0.01). Quickly degradable fraction (a) of ADF at the dose of 300 KGy increased that it was not statistically significant. Post-ruminal and total tract digestibility of DM increased significantly (P<0.05). Ruminal, post ruminal and total tract digestibility of NDF was not affected by irradiation. This experiment showed electron beam irradiation had an effective role in improving the nutritive value and digestibility of atriplex stem, but regarding the absence of a dose related effect, the dose of 100 KGy is recommended.

A data set belonging to Iranian Holsteins from 15 herds (1981 to 2005) were used to investigate the effect of milk production on fertility performance. The traits were: number of inseminations to conception (INS), calving interval (CI), days from calving to first service (DFS), interval between first and last insemination (IFL) days open (DO), and success to first insemination (SF). Cows were divided into three groups (low, medium and high producing) according to milk production. High milk producing group have low fertility performance (P<0.01). High producing group had more 0.37 INS, more 11 days DO, more 17 days CI, more 14 IFL than low producing group. DFS in low producing group was lower than medium and high producing group. SF in high producing cow was 10 % lower than low producing group. Undesirable genetic correlations (<0.37) were estimated between milk production and fertility performance traits. Among fertility traits DFS had lowest (0.17) and CI had highest (0.37) genetic correlation with milk production. Desirable genetic trend for milk production and undesirable genetic trend for fertility traits were observed. Milk production increased 198 kg per year, INS increased 0.048, IFL increased 1.51days per year and SF decreased 1.37 percent per year. Result of this study indicates that if breeding program only focuses on milk production, fertility performance will decrease.

This experiment was carried out to evaluate the effects of 1α-hydroxycholecalciferol as a replacement for cholecalciferol on broiler breeder hen performance. 288 Ross "308" broiler breeder hens at 57 weeks of age were allocated to a randomized complete block design with six treatments and four replications of twelve females and 1 male each. The treatments consisted of 3500Iu/kg vitamin D3(Control),combination of 3340IU D3+10 g/Ton 1α(OH)D3, 3300IU D3+12.5 g/Ton 1α(OH)D3, 3260IU D3+15gr/Ton 1α(OH)D3, 3180IU D3+20 g/Ton 1α(OH)D3 and one additional group was fed no supplemental D3. The results of this study indicated egg production, egg mass, feed conversion, egg specific gravity, early and late embryo mortality and hatchability of the broiler breeder hens fed the vitamin D3 deficient basal diet was significantly lower than all other treatments (P<0.05). In addition to egg production, egg mass and feed conversion between treatments were significantly differ, and egg production was significantly lower when added as 20 g/Ton 1α(OH)D3 as compared to lower levels of the same metabolites and also as compared with the hens fed D3(P<0.05), however no differences were observed in egg weight, egg specific gravity, hatchability, early, middle and late embryo mortality and pip egg between treatments supplemented combination of vitamin D¬3 and 1α(OH)D3 as compared with D3 (P>0.05).The result of this experiment indicated that replacement of 1α(OH)D3 with D3 in broiler breeder diets have no beneficial effect on egg production, egg shell quality and hatchability. It seems, that hens are able to metabolize sufficient 1,25(OH)2D3 from dietary vitamin D3 to meet requirement.

Genetic parameters for litter size trait in Makuie sheep were estimated using Bayesian method and different models. For this purpose, six threshold models were fitted. Different models with direct genetic effects, maternal and permanent environmental effects were implemented. Effects after significance test (P<0.05) by logistic procedure of SAS software were included in these models (herd and year of lambing). Variance components of litter size trait were estimated by Thrgibbs1f90 software. The most appropriate model was determined based on deviance information criterion (DIC). Model 4 was recognized as the best model for the genetic analysis of litter size trait in Makuie sheep. The meanof the posterior distribution of estimated additive and maternal heritability for best model (model 4) were 0.03% (0.004) and 0.109(0.017), respectively. Estimated genetic parameters of litter size in this studyshowed that for genetic gain in this trait more attention should be paid to maternal effect and improve environmental condition.

This experiment was conducted to evaluate the effects of using different levels of Chicory (Cichorium intybus L.) powder on performance, egg traits and blood metabolites of laying hens. The levels of Chicory were 0, 0.5, 1, 1.5, and 2 percent. In this experiment, 180 laying hens (Hy-line W36 strain) in five treatments and three replicates (with 12 hens in each replicate) from 65 until 76 weeks of age were used in a completely randomized design. The results showed that the using different levels of Chicory powder had significant effects on performance, egg traits, and immunity cells of blood in laying hens (P<0.05). The highest egg production percentage, highest amounts of egg mass, daily feed intake, the best feed conversion ratio, the lowest amount of feed price for production per kilogram of egg, the highest yolk color index and the highest albumin percentage were resulted by using 2% of Chicory powder. The lowest percentage of white blood cells, heterophil, and heterophil/lymphocyte and the highest percentage of lymphocyte were obtained by the use of 1.5% of Chicory powder. Different levels of Chicory powder did not have any significant effects on blood biochemical parameters of laying hens. It was concluded that in laying hens diets, using 1.5 of Chicory powder can improve their immunity cells status, performance, and egg traits.

The objective of this study was to determine the effects of different levels of prebiotic (A-MAX) included cell wall composition of Saccharomyces cervisiae yeast on performance, and rumenal fermentation parametersin west Azarbaijankids, with an average weight of 11.1 ± 1.8 kg and about five to six months of age, in a randomized complete block design with 4 treatments (5 kids per treatment). Treatments included 1) no prebiotic (control), 2) 2 gram, 3) 4 gram and 4) 6 gram prebiotic/day per animal which were fed with a basal diet. Daily weight gain significantly in treatments receiving prebiotic was higher than the control treatment (P<0.05). Moreover, feed conversation ratio in treatments receiving prebiotic significantly was better than control treatment (P<0.05). Dry matter intake was not affected by treatments. Rumenal pH and ammonia N were not affected by groups. Acetate, propionate and valerate concentrations were not affected by treatments. Butyrate increased in prebiotic groups compared with control group (P<0.05). The results indicated that the addition of prebiotic (A-MAX) to the diet of kids improved growth performance, and rumenal fermentation.