نشریه اصلاح و به نژادی دام
سال دوم شماره 1 (پیاپی 3، بهار 1401)

Normal distribution and DNA structure-based data, have paramount role in constructing and extending animal and plant breeding models. Nowadays, it has been proven that epigenetics plays an essential role in the appearance of different traits. Epigenetics examines acceptable changes in the expression of genes those are independent of changes in the nucleotide DNA. Thus, the epigenetics with the spirit of the development of genetic models can be contrasted, because it is not based on genetic assumptions used in animal breeding. For the first time, attempts have been made to divide and explain the epigenetic mechanisms and tools in a succession and to return to the comprehension of its application in animal breeding. Through the mechanism and tools of epigenetics, DNA methylation and genomic imprinting have been identified in a relatively large range of domestic animal species. Genomic imprinting is considered to be practical in genetic modeling. But histone corrections, which affect the way the nucleosomes are located, have a relatively small contribution to researches. It seems that the future of breeding research depends to a large extent on the epigenetic understanding of traits. epigenetics is expected to have perhaps the greatest effect in elucidating the interaction between environment and genetics. Since the transgenic is the level of environmental information transmission to the available genome, there will be a possibility in the future that, by examining this epigenetic level, undesirable traits,  such as the great tail fat in some Iranian sheep breeds, can be managed. This management will require a full understanding of the transgenic.

In order to determine of optimum Holstein inheritance on traits performance of dairy cattle, 305-days milk production records were used 20000 Holstein cows from Markazi province. Data were collected during 1999 to 2013 by Animal Breeding Center of Iran. Generalized linear model (GLM) procedure of SAS 9.1 software was used to analyze of fixed effects (herd, month of calving, year of calving and sperm type, inheritance) and calving age as covariate on production traits. Study on Holstein cow with different ratio of inheritance was done that includes: 12, 25, 50, 62, 68, 75, and 84,87,90,92 percent. Phenotypic and genetic (co) variance components for production traits with Wombat software were estimated. Then, a selection index was constructed for combine these traits. Optimum Holstein inheritance based on this index was determined by least squares mean comparisons of the index for different Holstein inheritance and simple linear regression. Results indicated 84-92 percent Holstein inheritance was the optimum level. Optimum inheritance on milk production, amount fat and protein has positive effected and it is increased the average production.

Ross and Cobb are two strains of broiler chickens that desirable Conversion Ratio makes them the most appropriate broiler chickens. In this experiment to evaluate morphometric carcass characteristics (live weight, featherless carcass weight, breast weight, thigh weight, back + neck, wing, liver, heart, bursa, spleen, pancreas, proventriculus + gizzard, abdominal fat) sampling of 134 broiler chickens were taken in South Khorasan. The results showed that 12 characteristics (live weight, featherless carcass weight, breast weight, thigh weight, back + neck, wing, heart, bursa, spleen, pancreas, proventriculus + gizzard, abdominal fat) between strains (P<0.01) were significantly different. The liver weight was not significantly different. Edible organs weight mean indicated that meat production efficiency and utility in Ross strain is higher compared to Cobb strain.

The aim of the current study was to estimate inbreeding coefficient and Annual changes in Moghani sheep. In this research, records of 7278 lambs born from 387 rams and 2433 ewes were used. Data was collected from Jafarabad sheep breeding station in Moghan during 1995-2011. Estimating of inbreeding coefficient was done by CFC program. In total pedigree, 1019 animals were inbred. Averages of inbreeding coefficient for total and inbred population were estimated at 0.6 and 4.4 respectively. The highest inbreeding coefficient was 6.1 % and most inbred animals had inbreeding coefficients lower than 5 %. These results confirmed the low level of inbreeding in the population. Annual trend in inbreeding coefficient for total population were 0.0014±0.0006 and statistically significant (P<0.01). Annual trend in inbreeding coefficient for inbred population were -0.0047±0.0026 and not statistically significant. The regression of inbreeding for birth weight, weaning weight, 6 month weight, 9 month weight and 12 month weight traits were calculated +0.046, 5.16, 1.04, 0.07 and -6.95 gr respectively. Applying a designed mating system like crossbreeding and supervised using of elite rams could be a suitable method to avoid inbreeding depression via keeping the level of inbreeding under control.

The objectives of this study were to summarize the effect of sexed semen on conception rate of Esfahan province Holsteins dairy herds based on breeding year, Season, service number and age group of heifers in the time of conception. For conducting this research, the data from 59 herds which was collected by Vahdat cooperation of Esfahan province was used. The data consists of 73115 of heifers inseminated with 3529 sexed semen and 69431 with conventional semen from spring 1991 to spring 2014. Binary distribiution of conception rate was analysed by logistic regression. The results indicated that for all sub-levels of the studied factors, except for the third and fourth service number, and for the unknown used sperms, the conception rate was higher, or, in other words, the ratio of pregnant heifers were significantly higher (P<0.05) than non-pregnants. Only in the fifth and higher service numbers, this ratio was reverse and non-pregnant rate of heifers significantly (P<0.05) were higher than pregnants. The average likelihood of conception rate of spring and summer season (53%) was significantly less (P<0.05) than autumn and winter season with a probability of 55%. The probability of conception rate of service numbers from first to fifth and higher had a descending trend, so that the probability of first service number was 63% significantly higher than others (P<0.05). The average likelihood conception rate of heifers for conventional sperm and sexed sperms was significantly different (P<0.05) and was 58% and 41%, respectively. The highest proportion of pregnant/ non-pregnant animals (75%) was obtained for naturally inseminated service. In conclusion, it seems that when using sexed sperm, different factors affecting conception rate should be take into consideration. So, the results of this research can be useful in the reproduction management of heifers during the use of sexed sperm and also taking into consideration of proper breeding and environmental factors.

In this study, it was aimed at estimating of the growth curve in Raeini Cashmere goats. For drawing growth curve, records of weight-age data of 6765 female and male goats were individually fitted to Brody, Von Bertalanffy, Verhulst, Logistic and Gompertz growth models. The growth models were compared using the coefficient of determination (R2), residual mean square error (MSE), Akaike’s information criterion (AIC) and a number of interations. Among all nonlinear models, the highest R2 and the smallest AIC, MSE values and number of interations were calculated by Brody function for both sexes. Moreover, males have higher A (weight at maturity) and B parameters than females and have a lower K parameter (rate of maturity) than females. As the Brody growth curve, female adult live weight was lower than males, because sex factor significantly influences on live weight. The range of inflection point 4.80 and 7.89 for females, 5.86 and 9.55 for males, respectively. The lowest of an inflection point in both sexes estimated for Von Bertalanffy model, and highest inflection point estimated for logistic in both sexes. The lowest and highest of inflection age in both sexes estimated for Von Bertalanffy and Verhulst models, respectively. In conclusion according to the results of this study, the nonlinear Brody growth model seems to be the most appropriate to adjust the growth curve of the Raeini Cashmere goats.