Test day data on milk yield for individual cows were generated using Monte Carlo simulation consisting of 1000 herds. Each herd contained 30 second lactation cows for each of 2 yr. Three scenarios were simulated with increasing effects of test day and seasonality. For each test day, several statistics were calculated for each cow: test day data on yield deviated from expectations, deviated test...

Background: Metabolic profiles have been used in efforts to predict pre parturient problems and fertility, to diagnose metabolic diseases, and to assess nutritional status in dairy cows. These profiles may help to confirm the diagnosis of sub clinical diseases, to be aware of possible causes of infertility in the herds, or to monitor improvement in herd animals. OBJECTIVES: This study investiga...

The transition from gestation to lactation is marked by significant physiological changes for the individual cow such that disease incidence is highest in early lactation. Around the time of calving, cows rely on mobilisation of body energy reserves to fill the energy deficit created by an increase in nutrient demands at a time of restricted feed intake. It is well established that monitoring o...

The objectives of this research were to characterize dry period lengths for US Jerseys, determine the effects of days dry (DD) on subsequent lactation actual milk, fat, and protein yields, fat and protein percentages, somatic cell score (SCS), and days open (DO), and to determine the dry period length that maximizes yield across lactations. Field data, collected through the Dairy Herd Improveme...

The primary objectives of this research were to determine the dry period lengths that maximize production across adjacent lactations and also dry period length that maximizes lifetime yield. Effect of days dry (DD) after lactations 1 through 3 were determined separately for both adjacent lactation sums and lifetime yield. Field data, collected through the Dairy Herd Improvement Association, on ...

This study predicts the magnitude and between herd variation in changes of methane emissions and production efficiency associated with interventions to improve reproductive efficiency in dairy cows. Data for 10,000 herds of 200 cows were simulated. Probability of conception was predicted daily from the start of the study (parturition) for each cow up to day 300 of lactation. Four scenarios of d...

the objective of this study was to estimates the genetic and environmental components for the lactation curve parameters, milk yield, age at first calving (afc), calving interval (ci) and somatic cell count (scc) in iranian holstein cows. the dataset consisted of 210625 test day records from 25883 cows with milk yield in the first parity recorded from july 2002 to september 2007 in a total of 9...

Lactation means of somatic cell scores from sample days were used to estimate the components of variation for additive genetic, permanent environmental, and herd-sire interaction effects. Data included records of 4314 Ayrshire, 7845 Brown Swiss, 18,115 Guernsey, 1,135,752 Holstein, 67,862 Jersey, and 787 Milking Shorthorn cows from across the US. Records were preadjusted for length of lactation...