This study compared genetic evaluations from 3 test-day (TD) models with different assumptions about the environmental covariance structure for TD records and genetic evaluations from 305-d lactation records for dairy cows. Estimates of genetic values of 12,071 first-lactation Holstein cows were obtained with the 3 TD models using 106,472 TD records. The compound symmetry (CS) model was a simpl...

The results of the studies showed that by prolactin gene (PRL), highest yield was found in first-calf heifers with PRLBB genotype 4.7% -10.5% as compared to herd-mates other genotypes; and cows second third lactations – PRLAB 2.6-10.6%. In terms milk fat, animals had a higher rate than PRLAA genotypes 0.04-0.17 pp, especially lactation having most noticeable changes. By beta-lactoglobulin (BLG)...

Hemorrhagic bowel syndrome is a highly fatal intestinal disease of adult dairy cattle with uncertain cause. In a dairy herd in KhorasanRazavi province, Northeast of Iran, two cows showed depression, anorexia, decrease in milk production, ruminal hypomotility, bruxism and dehydration. At necropsy, massive hemorrhage and clot formation was observed within the jejunum and bacterial culture of the ...

The aim of this study was to investigate the effect of milking frequency (three times daily vs. two times daily) on the lactation curve shape, partial and 305-d lactation performance in Holstein dairy cows in Iran. Data from February 2000 to December 2012 comprising 217345 lactations on 141364 cows distributed in 324 herds collected by the Animal Breeding Center of Iran were used. The mean milk...

An animal model with a REML algorithm was used to estimate variances of additive genetic effects and interaction effects of sire and herd. Milk and fat yields were analyzed for first, second, and third lactations of Holsteins from California, New York, and Pennsylvania. Twenty samples of data were used in the study: 10 from California, 4 from New York, and 6 from Pennsylvania. Mean number of la...

The aim of the present study was to show the distribution of cows by days in milk (DIM) at first AI, effect of DIM at first AI on reproductive performance and some factors influencing DIM at first AI. A total of 767 Holstein Frisian cows that calved from January 2004 to December 2007 in 14 dairy herds were used. The first AI conception rate (FAICR) was 34.0%. Seventy-five percent of the cows we...