in this research, 272977 test day records collected from 659 herds during years 2001 to 2011 by the iranian animal breeding center were used. in the first section the ability of different models to predict daily milk yield from alternative milk recording was tested. the result showed that a complex model including noon milking time plus the effect of lactation curve of ali and schaeffer functio...

abstract             (co) variance components of milk, fat and protein yield of 11368 first lactation iranian holstein dairy cow were estimated by single trait random regression test-day models and restricted maximum likelihood (reml) method. in this study the homogeneous residual variance was assumed throughout lactation. estimated heritability for 305-day production traits ranged from 0.25 to...

In this research, 272977 test day records collected from 659 herds during years 2001 to 2011 by the Iranian animal breeding center were used. In the first section the ability of different models to predict daily milk yield from alternative milk recording was tested. The result showed that a complex model including noon milking time plus the effect of lactation curve of Ali and Schaeffer functio...

in the present study, to estimate genetic parameters and genetic and phenotypic trends in holstein dairy cows in the north of iran, the records from first lactation of 11398 collected from 1989 to 2006 were used. records were collected from 290 herds. productive traits were 305 day-2x adjusted milk and fat yield and reproductive traits were age at first calving, calving interval and dry days. g...

The effect of reducing the frequency of offi cial milk recording and the number of recorded samples per test-day on the accuracy of predicting daily yield and cumulative 305-day yield was investigated. A control data set consisting of 58 210 primiparous cows with milk test-day records every 4 weeks was used to investigate the infl uence of reduced milk recording frequencies. The accuracy of pre...

Previous studies have demonstrated that the p.Lys232Ala substitution in the acylCoA: diacylglycerol acyltransferase (DGAT1) gene and the p.Phe279Tyr mutation in the growth hormone receptor (GHR) gene are the causative quantitative trait loci underlying milk yield and composition on BTA14 and BTA20 respectively. To examine their applications in the genetic improvement of Chinese dairy cattle pro...

The objective of this study was to estimate the effect of acylCoA-diacylglycerol-acyltransferase 1 (DGAT1), leptin and thyroglobulin (TG) loci on the milk fat, milk protein and milk yield in Holstein Friesian, Jersey and Hungarian Simmental cows. Leptin and DGAT1 genotypes were determined by qPCR assay, while TG genotypes were identified using the polymerase chain reaction-restriction fragment ...

The objective of this study was to estimates the genetic and environmental components for the lactation curve parameters, milk yield, age at first calving (AFC), calving interval (CI) and somatic cell count (SCC) in Iranian Holstein cows. The dataset consisted of 210625 test day records from 25883 cows with milk yield in the first parity recorded from July 2002 to September 2007 in a total of 9...