genetic parameters and trends for milk and fat yields as well as for fat percentage were estimated from 35,438 milk production records (305d, 2x) of 17,971 holstein dairy cattle in 133 herds during the period of 1990-2003 in khorasan province. variance components were estimated using restricted maximum likelihood statistical method applying univariate and repeatability animal models. for the un...

a total of 153 samples of milk were collected from one to none months lactating mothers age 17 to 44 years. the protein, total nitrogen, fat, lactose and calcium content 0f these milks were determined. marked individual variation existed in the protein lactose and fat content of the milks, which was in agreement with finding of other investigators. a gradual decrease was noticed in the protein ...

Combined linkage and linkage disequilibrium analysis were used to refine the position of a previously detected QTL affecting milk production traits on bovine chromosome 6. Through a series of single- and multitrait and single- and multipoint QTL analyses, the QTL could be positioned to a 7.5-cM interval surrounded by the markers BMS2508 and FBN12. The most significant results were found for fat...

Calving records from April 1996 to December 2005 comprising 31863 calving events of 1173 dairy cows in a large commercial dairy herd were used to evaluate the effects of heat stress, using temperature-humidity index (THI) on milk yield and composition and reproductive performance of Holstein dairy cows under humid climatic conditions of Rasht in Iran. THI values were grouped into six groups: 30...

the objective of this study was to analyze the association of somatic cell score (scs) with milk, fat and protein yields across parities. records of production traits and somatic cell counts (scc) from first, second and third parity that were collected by the animal breeding center of iran from 1993 to 2010 were used.all animals were grouped into six classes according to scc and production trai...

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...