using monthly test day records the genetic parameters of iranian holstein cattle in first lactation were studied. data of 277400 test-day milk records from 65320 cows and 2210 sires were analyzed by an animal random regression model using restricted maximum likelihood methodology. the model included herd-test-date, interaction between year-season of calving, days in milk (linear and quadratic) ...

Milk records of up to the first three lactations of artificially sired Holstein daughters and their dams were used to estimate heritability from both daughter-dam regression and paternal half-sib correlation. The within-herd estimates h'om records expressed as deviations from herd-mate averages were :37, .30, and .24 from daughterdam regression for the first three lactations ; and the correspon...

Survival analysis in a Weibull proportional hazards model was used to evaluate the impact of somatic cell count (SCC) on the involuntary culling rate of US Holstein and Jersey cows with first calvings from 1990 to 2000. The full data set, consisting of records from 978,043 Holstein and 250,835 Jersey cows, was divided into subsets (5 for Holsteins and 3 for Jerseys) based on herd average lactat...

The association of birth type (single vs. double) and pregnancy type (single vs. double) with lactation performance and lactation curve was investigated in Holstein cows in Iran. Data of 243298 lactations on 138021 cows in 261 herds collected during January 2000 to December 2012 were used. The average twinning rate was 3.64% and ranged from 1.44% (primiparous) to 5.41% (multiparous). Factors as...

BACKGROUND This study was carried out to determine if an association exists between the shape of the lactation curve before it is influenced by the event of conception and the time from calving to conception in Norwegian dairy cattle. Lactation curves of Norwegian Red cows during 5 to 42 days in milk (DIM) were compared between cows conceiving between 43 and 93 DIM and cows conceiving after 93 ...

Within-herd contemporary comparisons of the first-lactation production of registered and nonregistered cows in herds enrolled in the New York Dail T Herd Improvement Associations suggest only small genetic differences between registered and nonregistered cows. In general, the registered Holsteins exceeded in production their nonregistered herd-mates, whereas the nonregistered cows had a slight ...

The objective of this study was to investigate the effect of birth weight (BW) on future milk production and reproductive performance in Iranian Holstein cattle. Records of Holstein cows between 1967 and 2010 were obtained from the Animal Breeding Center of Iran. Birth weights within each herd were grouped into five categories based on the standard normal distribution curves (z ≤-0.8416, -0.841...

Minerals and some biochemical parameters determined from blood serum analyses in left displacement abomasum (LDA) affected and healthy dairy cows to evaluate the effect of displacement abomasum on mineral status, energy metabolism and liver function. Samples were collected from 60 affected cows and 60 healthy control cows matched with cases, based on herd, parity, and stage of lactation. Concen...