The purpose of the heifer herd is to provide replacements for cows leaving the herd and to improve genetic progress. First-lactation cows significantly contribute to herd production and profit. A recommended goal for dairy replacement heifers is to calve at 24 months of age with a targeted postcalving body weight of 1250 pounds. A common misconception is that this goal is either unattainable or...

the aim of this study was to estimate genetic parameters of age at first calving and its relationship with productive traits of holstein dairy cows. a total of 24491 first lactation records (2x 305d) which were collected from 1995 to 2009 were used. the general linear model (glm) procedure was applied to determine effective factors on studied traits. herd-year-season (hys) and age at first calv...

Retrospective data from Sebele Dairy Farm were analysed for reproductive performance of Friesian/Holstein cows. Three hundred records from 1989 to 1995 were used. The herd was zero grazed and the data was analysed for age at first calving (AFC), calf birth weights (BW), calving interval (CI), days open (DO), calving rate (CR), reproductive wastage (RW) and calving difficulty (CD); dystocia, aft...

Estimates of genetic correlations were .17 between first lactation milk yield and concurrent calving interval, .10 between second lactation milk yield and first calving interval, and .82 between first and second milk yields. Corresponding phenotypic correlations were .27, .16, and .58. Heritability estimates were .27 and .25 for first and second lactations and .15 for calving interval. Estimate...

The objectives of this study were to estimate heritability for daily body weight (BW) and genetic correlations of daily BW with daily milk yield (MY), body condition score (BCS), dry matter intake, fat yield, and protein yield. The Afiweigh cow body weighing system records BW of every cow exiting the milking parlor. The Afiweigh system was installed at the Pennsylvania State University dairy he...

The objective of this study was to determine associations between body weight (BW) and body condition score (BCS) variables indicating a more severe negative energy balance in early lactation and events of somatic cell counts (SCC) >250,000 cells/mL and SCC >400,000 cells/mL in dairy cows. We studied lactations from 634 primiparous and 1,086 multiparous Israeli Holstein dairy cows originating f...

Heritabilities of milk yield and fat test were estimated from first lactation records of 196,672 Holstein daughterdam pairs separately for registered and nonregistered cows for four milk yield groups and by years of freshening of the daughter. The model included herdseason and sire of the daughter. Heritability estimates were similar for registered and nonregistered cows averaging about .33 for...

Survival rates and productive herd life were examined for 13.8 million US dairy cows that calved from January 1, 1980, through March 2, 2005. Cows that left the herd for dairy purposes or were from herds that discontinued Dairy Herd Improvement testing were excluded from any calculations to prevent underestimation of population longevity. Mean lactation length for cows without subsequently reco...

Handling large-scale industry data is challenging both in the preliminary screening of data for validation, and also in the subsequent statistical analyses to obtain estimates of fixed effects, genetic parameters and estimated breeding values (EBVs). This paper summarises how a small subset from large industry-derived dairy data records have been explored and edited to be ready for genetic anal...