The objectives of this study were to relate concentrations of plasma (PUN) and milk (MUN) urea nitrogen to pregnancy rate in dairy cows and compare various methods of analysis and preparation of milk for measuring MUN. In two experiments, blood or milk samples were collected on the day of AI from Holstein cows (n = 160 and n = 155, respectively). Three methods of MUN analysis were compared. Two...

The aim of this study was to investigate effects of DGAT1, OPN and PPARGC1A candidate genes on milk production traits in Iranian Holstein cattle. Several papers have studied single nucleotide polymorphisms (SNPs) and their association with economic traits in dairy cows, but the combined effect of these genes has not been examined in Iranian Holstein cattle population. Blood samples were collect...

the objective of the study was to evaluate the uterine histopathological changes in holstein dairy cows, within the range of 90-145 day in milk, with or without clinical history of reproduction system disorders. lactating holstein cows (n =133) with (n=92, 69.17%) or without (n= 41, 30.82%) recorded clinical signs of reproduction diseases were examined for uterine histopathological lesions. the...

Crossbreeding is a popular tool for genetic improvement of pigs, beef cattle, and other livestock species, but its use in US dairy cattle has been limited for several reasons. The primary reason is the advantage of Holstein cows in milk volume, coupled with a milk pricing system that still tends to reward quantity, rather than quality, in many regions of the country (i.e., through volume premiu...

The accuracy and precision of 3 lactation models was estimated by summarizing means and variability in projection error for next-test milk and actual 305-d milk yield (M305) for 50-d intervals in a large Dairy Herd Improvement Association data set. Lactations were grouped by breed (Holstein, Jersey, and crossbred) and parity (first vs. later). A smaller, single-herd data set with both Dairy Her...

The diversity of the uterine bacterial composition in dairy cows is still poorly understood, although the emerging picture has shown to be increasingly complex. Understanding the complexity and ecology of microorganisms in the uterus of postpartum dairy cows is critical for developing strategies to block their action in reproductive disorders, such as metritis/endometritis. Here, we used PCR-De...

There is a general need for higher objectivity and accuracy in describing the physiological fertility performance of dairy cows. To develop the alternative meaningful starting points for the selection of genetically superior dairy cows, this study focused on the detection of low progesterone concentrations, which are indicative of estrus events. Three mathematical approaches were used: one base...

The objective of the present study was to assess the effects of genomic inbreeding on production, reproduction, and udder health in Holstein dairy cows. First and second lactation data were collected from 1,061 Holstein dairy cows, which were born between 2006 and 2008, from 5 commercial herds across the United States. All cows were genotyped for 54,609 single nucleotide polymorphism (SNP) mark...

This study was carried out to evaluate the effects of replacing alfalfa hay with ensiled mixed tomato and apple pomace (EMTAP) on ruminal fermentation and apparent digestibility of diets. Six multiparous Holstein dairy cows in mid lactation were used in 3×3 Latin square design and fed alfalfa hay plus concentrate mixture with three levels replacement with EMTAP (0, 15, 30%) during 63 days. Resu...

The objective of this study was to evaluate the effect of ruminally protected amino acids (RPAAs) and ruminally protected fat (RPF) supplementation on ruminal fermentation characteristics (in vitro) and milk yield and milk composition (in vivo). Fourteen mid-lactating Holstein dairy cows (mean weight 653±62.59 kg) were divided into two groups according to mean milk yield and number of days of p...