فهرست مطالب alireza shahdadi

The purpose of dairy cattle breeding is improvement of productive and fertility performance. The breeding of dairy cows was done to increase milk production, longevity, disease resistance and fertility efficiency. In most countries, importation of bulls’ semen with highly breeding values was increased. Global sales of semen expose progeny of sires to climates and production systems vastly different from their original selection environment. This may cause sire re-ranking because the progeny of some sires are not expected to perform to their optimum in every different environment. The objective of this study was to investigate 305 d milk yield and 305 d fat percentage performance of Holstein dairy cows under different climates of Iran.
In this study, the records of 191910 first lactation Iranian Holstein (305 d milk yield and 305 d fat percentage) were used. These records were collected from 1368 herds during 2000 to 2011 by the Animal Breeding Center of Iran. Records from cows without pedigree information were excluded. Age at first calving was required to be between 20 and 40 month and calving interval between 300 and 600 d. According to weather conditions, geographical location of herds was classified to 5 climate groups (arid, semiarid, Mediterranean, semi humid and humid) via De Martonne method.
In this study, the models were developed based on data availability, literature evidence, genetic evaluation models that are used in other countries, and available computing facilities. Single-trait model for these traits was as follows: where yijk denoted 305 d milk yield and 305 d fat percentage, µ was overall mean, HYSi was a combination of fixed effect of herd by year of calving by season of calving, b1 and b2 were linear regression coefficients of Holstein percentage and age at first calving, respectively, HF was the effect of Holstein percentage, Age was effect of age at first calving, aj was a random animal genetic effect and eijk was a random error term. Variance and covariance components were estimated by restricted maximum likelihood method using DMU program. Genetic and phonotypic trends were computed as a linear regression of yearly means on year of birth using the REG procedure of SAS 9.1.
The average of 305 d milk yield was the highest in arid climate (7350.34±1558.29 kg) and was the lowest in humid climate (5578.66 ± 1024.2 kg). The higher 305 d milk yield in the arid climate can be due to better management conditions in these regions compared to other climates. It seems that high humidity in Mediterranean, semi humid and humid climates can intensify higher environmental temperature and thus management and control of diseases can be difficult that result in milk production depression in these climates. The estimated heritability ranged from 0.11 (Mediterranean climate) to 0.29 (arid climate) for 305 d milk yield. Logar et. al., (17) reported that additive genetic variance in environments with high milk production was higher than environments with low milk production. Thus, observed differences in additive genetic variance in the climates can be due to several factors including difference in level of herd yield, environmental variation, data size and management strategies in herds. In arid, semiarid, Mediterranean, semi humid and humid climates, genetic trends of 305 d milk yield was 22.20, 17.37, -0.074, 0.92 and -0.71, respectively. According to the results, it seems that genetic gain in herds of Mediterranean, semi humid and humid climates was very low.
Results showed that average 305 d fat percentage in Mediterranean climate was the highest and in semi humid was the lowest (3.44 ± 0.34% vs. 2.98 ± 0.56%). The estimated heritability for 305 d fat percentage was 0.11 (Mediterranean climate) to 0.29 (arid climate). It is concluded that small size of data in Mediterranean, semi humid and humid climates can lead to lower heritability. Also, differences in the estimated heritabilities in different climates can be due to difference in mean and coefficient of variations of 305 d fat percentage. Genetic trends of 305 d fat percentage was -0.0012, 1.23×10-5, 5×10-5, 0.0002 and -0.0004 for arid, semiarid, Mediterranean, semi humid and humid climates, respectively.
According to differences in genetic parameters of traits in different climates, it seems that performance of cows was different, that can be due to genotype by environment interaction.

Introduction Kurdish sheep breed is one of the most important native breeds of Iran. They are fat-tailed, large-sized, well adapted to the mountainous regions in northern Khorasan province and mainly raising for meat production under pastoral production system (28). Feed efficiency is a major component in the profitability of the small ruminant enterprise, because quality of range and pasture is low in poor environmental conditions in Iran. Growth rate and feed efficiency are two traits of great economic importance in sheep production and also Kleiber ratio has been suggested to be a useful indicator for these traits (2). There was no information regarding genetic parameters for growth traits in Kurdish sheep. Thus, the main objective of the present research was to estimate (co)variance components and genetic parameters for pre- and post-weaning growth traits and Kleiber ratio in Kurdish sheep.
Material and Methods In this study, the records of growth traits from 5144 lambs (from 161 rams and 1982 ewes) were used. The data were collected during a 17-year period (1996–2013) in Kurdish sheep Breeding Station located in Shirvan city of northern Khorasan province. Traits investigated were average daily gain from birth to weaning (ADG0-3), average daily gain from weaning to six months of age (ADG3-6), average daily gain from six to nine months of age (ADG6-9), average daily gain from nine to twelve months of age (ADG9-12) and Kleiber ratios (KR) defined as: KR1=ADG0-3/(BW3)0.75
KR2=ADG3-6/(BW6)0.75
KR3=ADG6-9/(BW9)0.75
KR4=ADG9-12/(BW12)0.75
Test of significance for the fixed effects to be included in the final functional model for each trait and calculation of least squares means was accomplished using GLM procedure of SAS software (24). The considered fixed effects were year of lambing (1996-2013), sex of lamb (male and female), type of birth (single and twin) and age of ewe (1–7 years old). (Co) variance components and genetic parameters were estimated applying restricted maximum likelihood (REML) method fitting six animal models using WOMBAT (18): y =Xb斦 Model 1
y=Xb斦빦鞩篧 Model 2
y =Xb斦빦榾 Cov(a,m)=0 Model 3
y =Xb斦빦榾 Cov(a,m)=Aσam Model 4
y =Xb斦빦榾暗ꥻ Cov(a,m)=0 Model 5
y =Xb斦빦榾暗ꥻ Cov(a,m)= Aσam Model 6
where y: is a vector of records, b: is a vector of fixed effects, a: is a vector of direct additive genetic effects, m: is a vector of maternal additive genetic effects, pe: is a vector of permanent environmental effects due to ewe, X, Za, Zm and Zpe are corresponding design matrices relating the fixed effects, direct additive genetic effects, maternal additive genetic effects and permanent environmental effects due to ewe to vector of y, respectively, e: is a vector of residual effects, and Cov(a,m): is the covariance between direct additive genetic and maternal additive genetic effects.
Akaike’s Information Criterion (AIC) was used for selecting the best model among the tested models (3): Where logLi: is the maximized log likelihood of model i at convergence and pi: is the number of the parameters in each model. Model with the lowest AIC was considered as the best model for each trait. Estimation of genetic and phenotypic correlations was accomplished using multi-trait analysis (with model 1). The fixed effects included in the multi-trait animal models were those in single-trait analyses.
Results and Discussion The pre-weaning average daily gain in Kurdish lambs was 215.33±0.96 g, while this trait in post-weaning periods had a decreased trend. These values (especially in pre-weaning period) indicated that Kurdish lambs have a good potential for growth. Results from the analysis of variance of ADG and KR in different ages showed that birth year and sex of the lambs significantly influenced studied traits (PConclusion It was observed that maternal genetic models could better explain the genetic variation observed in pre-weaning traits. Estimates of phenotypic and genetic correlations among ADG and KR traits were high in magnitude. These results suggest that selection for Kleiber ratio can result in genetic improvement of growth rate as well as feed effeciency.

The aim of this study was to evaluate the effects of feeding Pistachio Hull (PH) as a source of tannin and Polyethylene Glycol (PEG) supplementation on feed intake، nutrients digestibility، milk yield and compositions، blood lipid metabolits and milk fatty acids profile in Saanen dairy goats. Nine maltiparus Saanen dairy goats were used in a 3 × 3 replicated latin square design with 21-d periods، including 14 d of adaptation followed by 7 d of sampling. Three treatments were formulated: T1) Control، without PH، T2) 30% PH and T3) 30% PH + 1% PEG (DM basis). Results showed that DMI was not affected by the diets. DM، ADF and NDF digestibility were not significantly different between treatments (P)