Standard Lactation Curves were derived for South African Holstein and Jersey cows, using 20 herd-, 18 ageand six season classes. Six herd classes were below and 13 above the average production level for both breeds. A standard lactation curve was estimated for each combination of herd-, ageand season class, which resulted in 2 160 curves per trait per breed. Variation in Holstein yields was muc...

A multivariate linear model was used to estimate sire variance and covariance components and residual variance components for first lactation milk yield and logarithms of yield at three herd production levels using Restricted Maximum Likelihood with the Expectation-Maximization algorithm. Data for four separate analyses were 305-d, mature equivalent first lactation milk records from cows sired ...

Clinical mastitis (CM) and monthly test-day somatic cell count (SCC) records on Holstein cows were used to investigate the genetic and economic relationship of lactation average (of natural logarithms of) monthly test-day SCC (LSCC) with CM. After editing, there were 23663 lactation records on 17937 cows from 257 herds. Three groups of herds were first identified as having low (L), medium (M) a...

the fixed regression test-day model (frm) and random regression test-day model (rrm) for genetic evaluation of milk yield trait of dairy cattle in khorasan razavi province were studied. breeding values and genetic parameters of milk yield trait from two models were compared. a total of 164391 monthly test day milk records (three times milking per day) obtained from 19217 holstein cows distribut...

Milk records from Ayrshire, Brown Swiss, Guernsey, Jersey, and Milking Shorthorn cows that first calved between 18 and 35 mo were combined with scores for linear type traits collected before 43 mo during first lactation to study herd life and lifetime profitability. Profitability (discounted relative net income) was the value of milk, calves, and cow salvage minus fixed costs, operating costs, ...

the objective of the present study was to estimate genetic trends for lactation milk yield, persistency of milk yield, somatic cell count and interval between first and second calving in holstein dairy cows of iran. the dataset consisted of 210,625 test day and 25,883 first parity cows with milk yield recorded from july 2002 to september 2007 comprising 97 herds in iran. breeding values of anim...

The purpose of this study was to evaluate the effect rumination times and days spent in a close-up group before calving (DCU) on early-lactation health reproductive outcomes dairy cows. Data were gathered for 719 cows located single herd. Herd management records analyzed receiving treatment first 30 d lactation (days milk; DIM) clinical mastitis, tract disease, ketosis, milk fever, displaced ab...

To estimate the prevalence of subacute ruminal acidosis (SARA) in dairy cows, a total of 196 ruminalfluid samples were drawn by rumenocentesis from 10 dairy herds of Khorasan Razavi province, northeast ofIran. Two groups of 12 cows, early lactation and mid-lactation cows were sampled in each dairy herd andruminal pH was determined immediately using a portable pH-meter. A total of 54 cows (27.6%...

In the United States, lactation yields are calculated using best prediction (BP), a method in which test-day (TD) data are compared with breed- and parity-specific herd lactation curves that do not account for differences among regions of the country or seasons of calving. Complete data from 538,090 lactations of 348,123 Holstein cows with lactation lengths between 250 and 500 d, records made i...