فصلنامه تحقیقات تولیدات دامی
سال دوم شماره 1 (بهار 1392)

In this study the effects of zinc oxide (ZnO) and zinc oxide nano particles (nZnO) were investigated on some parameters of rumen with either in vitro or in vivo experiments based on a completely randomized design. The experimental treatments (5 treatments) were included levels of zero (control), 20 and 40 ppm zinc as ZnO and 20 and 40 ppm zinc as nZnO that were added to the basal diets. In in vitro experiments, rumen fermentation kinetics parameters during 144 h continuous incubation (GP144) and the volume of gas produced during the 24 h incubation (GP24) and the relevant fermentation parameters were analyzed separately. In in vivo experiments, 20 male Markhoz goat kids aged 7-8 months were fed for 14 days with experimental treatments and the pH, ammonia and total volatile fatty acids concentration and protozoa populations in rumen fluid were determined. Results showed, GP144 and GP24 and the relevant parameters (except for asymptotic gas production (A) and lag time (L)) and rumen parameters in in vivo experiment were not affected by zinc sources. No significant difference was observed between treatments for total number of protozoa. Highest number was seen for Entodinium spp. and lowest for Isotricha spp.. Overall, the levels of 20 and 40 ppm zinc as ZnO and nZnO had no effect on rumen parameters by either in vitro or in vivo methods.

This experiment was carried out to determine the bioefficacy of herbal methionine (H-Met)® versus to DLmethionine (DL-Met) on growth performance basisin broiler chickens. A total of 160 day-old male broiler chickens (Ross 308) were used in a completely randomized design and were randomly assigned to treatments, 4 replicates and 5 chicks in every experimental unit (cage).Treatments included basal diet supplemented increasingly with Herbal methionine and DL-methionine during three growth periods of chickens. Multiexponential regression was used to determined bioavailability of H-Met® relative to DL-Met on growth performance basis in broilers. Body weight gain and feed intake of the broilers fed H-Met or DL Met improved in the experiment, regardless of Met sources, relative to those broilers fed basal diet. The bioavailability of HMet ® relative to DL-Met with considering body weight gain, feed intake and feed conversion ratio in starter period were 45, 77 and 82% respectively, in grower period were 55, 69 and 75% respectively and in finisher period were 57, 71 and 75% respectively. Totally, the average bioavailability of H-Met® versus to DL-Met is 65% for broiler chickens.

In the study presented here, the scope of a reparameterized monomolecular model was extended in growing young male chicks to provide an estimate of their lysine and methionine requirements for maintenance and growth. The equation was used with the NLMixed procedure of SAS to estimate parameters and combine them to determine other biological indicators. A number of criteria were used to evaluate general goodness of fit of the model, including model behavior, biologically meaningful parameter estimates and statistical performance. The estimated maintenance requirements and the determined values of lysine and methionine requirements for protein accretion were in good agreement with values reported previously by other researchers. Average efficiency of recovering lysine and methionine were greatest at low intakes and decreased as intakes increased. In conclusion, results presented here showed the applicability of the monomolecular equation to predict the magnitude and direction of responses of growing young broilers to dietary lysine and methionine intake without making any initial assumptions.

This study was conducted to investigate, effects of diets supplemented with methionine and/or garlic powder on performance and carcass composition of broiler chickens. 540 day-old broiler chicks in a completely randomized design with 3 3 factorial arrangement (9 treatments and 4 replication) were fed with different levels of methionine including basal diet (without methionine addition), diet containing methionine recommended by NRC as well as 135% NRC, and different levels of antibiotic. Chicken in 52 days of age were slaughtered and their carcass were analyzed. Addition of methionine at 135% NRC level in diets increased breasts muscle weight(P<0.01). Diets supplemented with garlic powder resulted in significantly high breast muscle weight as compared with negative control(P<0.05). Diets supplemented with Garlic powder leads to significant decrease in abdominal fat pad.Methionine antibiotic interaction in BD+Met+GAR showed highest and BD+GAR appeared with lowest abdominal fat pad (P<0.05).Methionine antibiotic interaction resulted as lowest tight muscle weight (P<0.05). In conclusion results from present study demonstrated that beneficial effects of methionine and/or garlic powder for improvement of broiler carcass quality.

In this study, calving records of 4221 Iranian native buffaloes from 621 herds which were collected by the Animal Breeding and Livestock Products Improvement Center of Iran from 2003 to 2010 were used to estimate heritability, genetic and phenotypic correlations between milk production, milk fat production, age at first calving and first calving interval using univariate and bivariate animal models. The highest and the lowest heritabilities were estimated for milk production (0.46±0.01) and first calving interval (0.01±0.29), respectively. Heritability estimates for age at first calving and milk fat production in the studied population were 0.21±0.21 and 0.27±0.17, respectively. Positive and high genetic correlation between milk yield and milk fat production (0.55) in this study indicated that milk fat increased along with increasing in milk production. Negative and medium genetic correlation between milk production and age at first calving (-0.25) indicated that genetic selection for milk production cause decrease in age at first calving. Positive and high genetic correlation between age at first calving and first calving interval (0.96) indicated that selection based on lower age at first calving cause reduced first calving interval.

To study the effect of non-genetic factors on survival of Karakul lambs from birth to weaning age 6,426 records collected from year 1992 through 2009 were used. Traits under study were cumulative survival from birth to 14, 30, 60 and 90 days of age. For each trait a linear model fitted which included the factors of lamb's year and month of birth, type of birth, sex, age of dam and birth weight (as linear and quadratic covariates). The GLM procedure of SAS software was applied. All the factors except for age of dam had significant effects (P<0.001) on traits. Mortality to weaning age in total, single and twins were 8%, 5.87% and 17.79% respectively. Hazard ratio of death from birth to 30d of age had increasing trend and after that till weaning showed decreasing one. In males and twins hazard of death was higher compared to females and single lambs. Average birth weight in singles and twins were 5.32(0.67) and 4.25(0.65) kg respectively. Optimum birth weight in which survival would be maximum in 14, 30, 60 and 90 days of age in singles and twins were 5.78, 4.68; 5.88, 4.86; 5.93, 5.03 and 5, 5.93 kg respectively. Optimum birth weight in which survival would be maximum in 14, 30, 60 and 90 days of age in male and female lambs were 5.9, 5.4; 6.1, 5.6; 6.4, 5.6 and 5.9, 5 kg respectively. It can be suggested that in order to develop the survival of Karakul lambs we select lambs on the basis of the optimal birth weight instead of the higher one.

The reduction in milk yield on test day associated with somatic cell count up to 600 000 cells/ml using monthly cow’s-records collected for a 9-year period (2002-2010) on primiparous Iranian Holstein cows in 159 different herds was studied. The used dataset included 181226 records from 21469 cows. According to the results of this study, the increase in somatic cell score from 1 to 5 and above could resulted to reduction in average daily milk yield by 1.300 kg (0.04) and increasing of average daily fat and protein percentage by 0.14 and 0.08 %, respectively. Additionally in this study genetic parameters of production traits were estimated by a multi-trait random regression test-day model. Heritabilities of 305-d lactation for milk yield, fat and protein percentage 0.40, 0.39, and 0.69, respectively were estimated. Heritabilities of daily yields were lower than that for complete lactation (305-d) and varied from 0.08 to 0.297 for milk yield, 0.054 to 0.123 for fat percentage, and 0.044 to 0.286 for protein percentage. The highest value of genetic and permanent environmental correlations was observed between fat and protein percentage (0.60<).