R.W. Everett

Preweaning milk replacer intake and effects on long-term productivity of dairy calves

The preweaning management of dairy calves over the last 30 yr has focused on mortality, early weaning, and rumen development. Recent studies suggest that nutrient intake from milk or milk replacer during the preweaning period alters the phenotypic expression for milk yield. The objective of this study was to investigate the relationship between nutrient intake from milk replacer and pre- and postweaning growth rate with lactation performance in the Cornell dairy herd and a commercial dairy farm. The analysis was conducted using traditional 305-d first-lactation milk yield and residual lactation yield estimates from a test-day model (TDM) to analyze the lactation records over multiple lactations. The overall objective of the calf nutrition program in both herds was to double the birth weight of calves by weaning through increased milk replacer and starter intake. First-lactation 305-d milk yield and residuals from the TDM were generated from 1,244 and 624 heifers from the Cornell herd and from the commercial farm, respectively. The TDM was used to generate lactation residuals after accounting for the effects of test day, calving season, days in milk, days pregnant, lactation number, and year. In addition, lactation residuals were generated for cattle with multiple lactations to determine if the effect of preweaning nutrition could be associated with lifetime milk yield. Factors such as preweaning average daily gain (ADG), energy intake from milk replacer as a multiple of maintenance, and other growth outcomes and management variables were regressed on TDM milk yield data. In the Cornell herd, preweaning ADG, ranged from 0.10 to 1.58 kg, and was significantly correlated with first-lactation yield; for every 1 kg of preweaning ADG, heifers, on average, produced 850 kg more milk during their first lactation and 235 kg more milk for every Mcal of metabolizable energy intake above maintenance. In the commercial herd, for every 1 kg of preweaning ADG, milk yield increased by 1,113 kg in the first lactation and further, every 1 kg of prepubertal ADG was associated with a 3,281 kg increase in first-lactation milk yield. Among the 2 herds, preweaning ADG accounted for 22% of the variation in first-lactation milk yield as analyzed with the TDM. These results indicate that increased growth rate before weaning results in some form of epigenetic programming that is yet to be understood, but has positive effects on lactation milk yield. This analysis identifies nutrition and management of the preweaned calf as major environmental factors influencing the expression of the genetic capacity of the animal for milk yield.

Management and economics of extended calving intervals with use of bovine somatotropin

The objective of this study was to investigate a reproductive management strategy that optimized profitability per cow per day of productive life when bovine somatotropin (bST) was used. Nine herds were involved with a portion of animals randomly assigned to one of four treatments: breeding at first oestrus after 60 days in milk (DIM, 13.2-month calving interval (CI)); breeding at first oestrus after 150 days in milk (16.5-month calving interval); first lactation animals never re-bred; and second lactation animals never re-bred. All herdmates not assigned to the study served as controls. All treatment animals received bST commencing at 63 days after parturition. Effects of bST supplementation with delayed pregnancy and without pregnancy were determined using the Test Day Model© (TDM). Results indicated that with bST use a 16.5-month calving interval increased (P < 0.05) milk yield over animals managed for a 13.2-month calving interval. Milk yield response to bST increased as lactation progressed, leading to a significant increase in persistency. When days of productive life were standardized to 4.35 yrs as the typical life cycle and a calving interval of 16.5 months was used, milk was increased 4468 kg for the animals with the extended calving interval compared with a 13.2-month calving interval. Profitability was increased by approximately US

Reduced age at first calving: effects on lifetime production, longevity, and profitability

0.75 per day per animal for animals on a 16.5-month calving interval as compared to a 13.2-month calving interval. On a herd basis, through two years of study, extended calving interval resulted to fewer calvings, lower incidence of postpartum metabolic diseases, lower veterinary costs, less culling with fewer replacements needed, and an overall improvement in herd life, animal well-being and dairy farm profitability.

Fertility in New York Artificially Inseminated Holstein Herds in Dairy Herd Improvement

The primary advantages of reducing age at first calving (AFC) include reducing rearing costs as well as reducing time in which the heifer is only a capital drain on farm resources. The primary disadvantage of reducing AFC is that it is frequently associated with a reduction in first-lactation milk yield. Despite this reduction in first-lactation milk yield, production per year of herd life is typically increased by reduced AFC. Furthermore, although the first lactation yield may be influenced by AFC, future lactations are decidedly not. In addition, stayability and health of cows are not influenced by reduced AFC as long as heifers freshen at an adequate weight. Most analyses indicate that the financial advantage afforded from heifers that freshen at a low AFC seems to at the least offset any milk lost during the first lactation. Furthermore, when the time value of money is considered in this analysis, a reduced AFC (~22 months) seems likely to represent a more fiscally sound management decision. When applying these ideas on the farm, a properly managed feeding and breeding program should permit a firstlactation cow to weigh ~1,210 lb after freshening at 22 months of age. The National Research Council recommends a postpartum weight equal to 82% of her mature body weight. This can be achieved with a maximal prepubertal average daily gain (ADG) of 2 lb/day when a traditional preweaning program is employed or 1.8 lb/day when an intensified preweaning program is employed. Because of the well defined link between inadequate body weight at calving and increased mortality and morbidity in first-lactation cows, achieving this target post-calving body weight is of critical importance.