نشریه اصلاح و به نژادی دام
پیاپی 1 (پاییز 1400)

The aim of this research was estimation of genetic parameters for the fat: protein trait (FPR) in daily milk test records of Iranian dairy cow. From a total of 295,820 monthly daily milk test records, 29,582 first-parity cows in 622 herds were used which were calved from 1997 to 2012. The trait was analyzed using a covariance function. Orthogonal Legendre polynomials with a 3th order were implemented to take account of genetic and environmental aspects of milk production over the course of lactation. The data were analyzed with the help of DXMRR software. Maximum phenotypic and genetic correlations (0.209 and 0.988) was obtained between the ninth and tenth month Maximum permanent environment correlation (0.938) was observed between the seventh and eighth months. The lowest (0.029) and highest (0.064) heritability’s were obtained for the third and first months of the lactation, respectively. Low heritability magnitudes showed that there is a low genetic variation for FPR trait which is suggesting much more effects of environmental factors.

In order to study of polymorphism in exon 6 of CTSK gene and its association with carcass traits and blood parameters in Afshari×Booroola Merino sheep, blood samples were collected from 97 lambs of animal husbandry station of Zanjan University. DNA was extracted using phenol-chloroform method and a fragment of 500 bp from CTSK gene was amplified with polymerase chain reaction (PCR). The binding patterns for all animals were determined by single stranded conformation polymorphism (SSCP) and then sequenced. For this gene, two binding patterns of GG and GA were identified with the frequencies of 0.74 and 0.26, respectively. Chi-square test (χ2) showed that this population was not in the Hardy-Weinberg equilibrium. Results showed that genotype of GG was significantly associated with increased of tail weight, muscle thickness and muscle cross-sectional area and decreased of cholesterol and VLDL traits. However the more investigations with larger sample size are necessary in future for usage from this locus in breeding programs based on marker-assisted selection.

The objective of this study was estimate of the genetic and phenotypic trends of growth traits in Moghani sheep. In this study, a total of 21,423 records of growth traits belong to Moghani lambs that collected by raising and breeding of Moghani sheep station between 2003 and 2010, was used. The SAS 9.1 statistical software was used to evaluate the effect of environmental factors. Variance components and genetic parameters were estimated using restricted maximum procedure and univariate animal model and with wombat software. Animal breeding value of were estimated using the best univariate animal model. Environmental factors, like birth year, sex, herd, type of birth, and the age of mother are the significant factors as fixed effects. Estimation of direct genetic trend for birth weight, weaning weight, 6 month weight, 9 month weight and 12 month weight were as 6±1, 8±1.5, 8±6, 11±5 and 86±5 gr per year, respectively. The phenotypic trend for mentioned traits was estimated 30±1, 116±1, 37±6, -342±5 and -43±5 gr per year, respectively. The results showed that before designing any breeding program, optimum environmental condition must be prepared for appearance of maximum genetic potential, so phenotypic and genetic trends will be desirable in the herd.

In this study (Co) variance components and genetic parameters for growth traits in Zandi Sheeps estimated by various animal models. The data used in this study, related to birth weight, weaning weight, 6 month weight, 9 month weight and yearling weight. The data collected during 1991-2011 by Nakhjir station in Tehran. (Co) variance components and genetic parameters were estimated by restricted maximum likelihood (REML). Environmental factors such as birth season, birth year, sex of lamb, birth type and mother's age at birth were significant on all traits and were fixed effects in model. The fit model by lowest AIC for birth weight, weaning weight, 6 month weight, 9 month weight and yearling weight selected 6, 2, 6, 4 and 4, respectively. Direct heritability was estimated for these traits results fitted models, 0.13±0.03, 0.17±0.03, 0.17±0.04, 0.07±0.03 and 0.18±0.06, respectively. Maternal heritability for birth weight, 6 month weight, 9 month weight and yearling weight were estimated 0.09±0.02, 0.04 ±0.02, 0.03±0.02 and 0.05±0.02, respectively. The selected models for these traits showed that maternal genetic effects, have important role in the occurrence of these traits. Estimated low heritability for these traits indicating that genetic improvement was slow for these traits and will be mostly affected by the herd management.

Data used in this study related to growth traits in Lori sheep that were collected during 2001 - 2010 by Research Center for Agriculture and Natural Resources of Lorestan province. Growth traits were consist of different ags (brithy, 3 month, 6 month and 9 month). Avarage weight Lori sheep was in birth weight 3.49 kg and in 9 month weight 29.79 kg. The SAS statistical software was used to determine the effect of environmental factors and WOMBAT software was applied to estimate genetic parameters with 6 different models via animal model analysis one trait REML parameters. Environmental factors like birth year, sex, type of birth and age of mother on lambing time had significant effect on all traits (p<0.0001). Type of birth and sex had significant effect on all traits except the 9 month age (p<0.0001). The direct heritability using best chosen model for birth weight, weaning weight, 6 months weight, 9 months weight were respectively obtained as follows: 0.34, 0.01, 0.16 and 0.1 and mathernal heritability for these traits were estimated 0.16, 0.03, 0.05 and 0.06, respectively.