a pedigree file of 382831 holstein cows and bulls, collected from herds registered by animal breeding center of iran during 1967 to 1999, was used to calculate the inbreeding coefficient. the mean inbreeding coefficient for the whole population (male and female), on a base year of 1946, was 0.184%. the means for cows (94 percent of the whole population) and bulls (6 percent of the whole populat...

The study was carried out in a Polish Black-and-White cattle population, represented by 167 AI sires, 200 young tested bulls, 190 bull-dams, and 606 randomly chosen cows from commercial herds. The fragment of the bovine prion protein gene (PRNP) coding the octapeptide-repeat sequence, was identified by PCR analysis. Two different gene variants of 349 bp and 373 bp in size, produced three genoty...

The objective of this study was to determine if factors associated with the biostimulatory effect of bulls alter breeding performance of primiparous, suckled beef cows using a progestin-based estrous synchronization protocol. We tested the hypotheses that the estrous synchronization response and AI pregnancy rates differ among cows exposed to bulls, continuously exposed to bull urine, and expos...

Small reference populations limit the accuracy of genomic prediction in numerically small breeds, such like Danish Jersey. The objective of this study was to investigate two approaches to improve genomic prediction by increasing size of reference population in Danish Jersey. The first approach was to include North American Jersey bulls in Danish Jersey reference population. The second was to ge...

The objective of this experiment was to determine if continuous exposure to bull urine alters resumption of ovarian cycling activity of primiparous, suckled beef cows. We tested the hypotheses that interval from urine exposure to resumption of luteal activity and proportions of cows that resume luteal activity by the end of the urine-exposure period do not differ between cows exposed to mature ...

In a previous study from 2014 it was found that US Holstein cows that gave birth to heifer calves produced more milk than cows having bull calves. We wanted to assess whether this is also true for Danish cattle. Data from 578 Danish Holstein herds were analysed with a mixed effect model and contrary to the findings in the US, we found that cows produced higher volumes of milk if they had a bull...

A total of 135 postpartum suckled zebu cows were assigned randomly at calving to two treatments: cows exposed to vasectomised bulls (Mature Bull Exposure, MBE) and cows not exposed to bulls (No Bull Exposure, NBE) for a period of 150 days postpartum. This study was conducted to determine the influence of bull biostimulation, season and parity on postpartum reproductive performance of Bos indicu...

Twoand 3-year-old beef bulls were exposed to 25 or 40 beef cows on pasture during a 90-day breeding period. Reproductive performance of bulls by age of bull and size of cow group was evaluated in terms of percentage calf crop. Results indicated that reproductive performance of 2-year-old bulls was higher, but not significantly different (P>.05), than that of 3-year-old bulls. The percentage cal...

ity of a beef operation is the percentage of the calf crop weaned, which, in turn, is determined mainly by the number of cows bred during the breeding season. The herd bull influences overall herd fertility more than any other single animal. Because the bull also supplies half of the genetics to all of the calves he sires, bull selection can be the most powerful method of genetic improvement in...