Estimation of genetic trends is necessary to monitor and evaluate selection programs. The objective of this study was to estimate the genetic trends for milk yield in Iranian Holsteins cows using random regression test day model. Data set was consisted of 743205 test-day records from 1991 to 2008, which were collected by the Animal Breeding Centre of Iran. Breeding, environmental and phenotypic values were estimated using a random regression test-day model. The logarithmic form of Wood function was chosen to fit the additive genetic and permanent environmental effects of milk yield. Genetic, environmental, phenotypic trends were estimated by regressing the mean of breeding values, environmental values and phenotypic values on birth year. The genetic and phenotypic trends were positive and significant, whereas environmental trends were not significant. Genetic trends of sires and dams were estimated separately and it was positive and significant for dams, but it was not significant for sires. The phenotypic, environmental and genetic correlation between each days in milk and total 305 days were estimated. The correlations related to breeding values were weak and it showed that with the logarithmic transformation of milk yield, persistency can be improved independently from milk production. پرونده مقاله

Nowadays, the use of sex-sorted semen is more commonplace in industrial dairy farms. However, the reproductive efficiency of this kind of semen is controversial among dairy farmers. Reproductive efficiency can also be influenced by herd size as a result of different management practices. The current study compares the reproductive performance of Holstein heifers inseminated either with sex-sorted or conventional semen in Isfahan province of Iran. Data were included the reproductive performance of 64070 heifers collected during 2007-2017 from 10 industrial farms with various sizes. Evaluated reproductive traits were conception rate, dystocia, stillbirth, abortion as well as days open and days from calving to the first service in heifers inseminated with various semen types and various farm sizes. Conception rate in the first to the third insemination of sex-sorted semen, respectively decreased by 18, 16, and 12 percent compared to the conventional semen. The chance of abortion, still birth, and dystocia when using sex-sorted semen were 0.095, 0.43, and 0.81. The result illustrated that using sex-sorted semen dramatically decreases the proportion of reproductive disorders, yet it led to lower conception rate, and it is estimated that conception rate is going to be improved through more efficient reproductive management in larger farm sizes. Herd size did not show a consistent effect on reproductive performance however reproductive efficiency was somehow better in medium-sized farms. پرونده مقاله

A deterministic model based on the gene flow method, considering the features of Iranian Holstein cattle population, was implemented in this study to evaluate the effect of altering the number of age-classes in the dams of future sire (DS) path and the number of dams required for breeding a young bull (YB), to be evaluated as future sire, on genetic gain and resultant economic efficiency of a genomic selection program for milk production as a selection goal. Based on the simulation, changing the number of age-classes from 10 to 1 resulted in higher replacement rate of DS path (from 0.22 to 1) and shorter generation interval. Consequently, the economic efficiency of the program increased up to a maximum point and then a descending trend was observed. The maximum economic efficiency (25.68) was obtained when 7 age-classes in DS path was assumed. By chaining the number of dams required for breeding a YB from 7 to 1, the genetic gain in selection goal increased from 0.0232 to 0.0264 kg per dairy cattle and therefore, the economic efficiency rose from 25.42 to 28.52. The results revealed that a decrease in generation interval does not necessarily result in maximum economic efficiency and there is an optimum level for generation interval. Less number of required dams per YB could result in higher economic efficiency and therefore should be considered as an effective management strategy to improve the economic efficiency of a genomic selection program for milk production. پرونده مقاله

Acetyl-coenzyme A carboxylase α (ACC-alpha) is considered as the key regulatory enzyme in fatty acid biosynthesis. ACC-alpha gene is located on Caprine chromosome 11 and is polymorphic in many goat breeds. In the current study, we aimed to find possible single nucleotide polymorphisms (SNPs) in the exon 1 region of the ACC-alpha gene in Iranian Mahabadi goat breed. Genomic DNA was extracted from blood samples of 150 Mahabadi does. The exon 1 region of the ACC-alpha gene was amplified to produce a 390 bp fragment. The PCR products were analyzed by both polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) techniques. RFLP was performed utilizing HinfI endonuclease enzyme. No polymorphism was observed after digestion of the PCR products using HinfI. However, SSCP of the PCR products revealed two conformation patterns at the exon 1 region of goat ACC-alpha gene with frequencies of 86% and 14%, respectively. Sequencing the observed conformation patterns presented more than 10 SNPs compared with its reported squences in the exon 1 region of ovine ACC-alpha gene. Most observed polymorphic sites did not follow the Hardy-Weinberg equilibrium. Sequence results indicated more similarity in the exon 1 of the ACC-alpha gene among indigenous sheep and goat breeds. پرونده مقاله