High-quality heifers to maximize milk production

The goal of most heifer replacement programs is to raise high-quality, healthy heifers efficiently and economically. High-quality heifers have the genetics, frame, body condition and management background to conceive in a timely manner, reach their potential for high first-lactation milk yield and become profitable replacements to the herd. Today’s low heifer replacement inventory and high heifer replacement values make these targets more valuable than ever.

Heifer rearing costs are the second- or third-largest cost on most U.S. dairy farms today. First-lactation heifers make up between 30% and 45% of the milk cows in most dairy herds. First-lactation performance also sets the stage for future production. Here are a few factors impacting first-lactation milk production.

In utero period

Recent research has explored the conditions calves face in utero and the long-term performance impacts they may have. Perhaps the best example of this is heat stress in dry cows. University of Florida research has repeatedly shown significantly lower birth bodyweight and decreased future production for calves born from dams under heat stress.

This reduced production continues when these cows are followed through the second and third lactation. Continued research at the University of Wisconsin-Madison took this a step further and showed granddaughters born of these heat-stressed dry cows also had a significant reduction in milk production through 35 weeks of lactation. Heat stress in dry cows is a multi-generational problem.

Preweaning period

Feeding 3-4 quarts of high-quality colostrum to calves within a few hours of birth continues to be a key component in calf health and performance as well as first-lactation milk production. Calves are born with no passive immunity, so they must acquire it from colostrum immunoglobulin consumption. Today, many farms have implemented a second colostrum feeding as well.

Serum total protein analysis is a simple and repeatable way to evaluate passive transfer of IgGs in dairy calves 2-5 days of age. In addition to having lower mortality and morbidity, research has reported that calves with serum total protein concentration greater than 6.0 g/dL produced 3,400 pounds more milk through their first lactation compared to their counterparts below that threshold.

Preweaning growth rates are associated with increased milk production in first lactation, as shown in studies both from Cornell University in 2012 and 2013 and the University of Minnesota in 2017. Pennsylvania State University research also shows a positive correlation between starter intake preweaning and first-lactation milk production. Increased starter intake in the first two months of life also results in greater rumen development and a more consistent growth pattern through weaning. Dry matter intake from liquid and dry feed has a synergistic effect and both are needed to increase first-lactation milk production.

Prepubertal growth

Some refer to the prepubertal time between weaning and breeding as a “forgotten period,” yet this 4- to 10-month age is a critical period to maintain heifer growth to carry them into the milking string. Target growth rates from 1.8 to 2.0 pounds per day to bring heifers through this prepuberty period on time and set up their future success as cows.

Bodyweight at first calving

Bodyweight of a heifer at the time of first calving is a proxy for growth and size. If heifers have not reached the desired size at calving, they will continue to grow during lactation. This is much less efficient and happens at the expense of milk production. Dr. Tom Overton, Cornell University, estimates that 1 pound of growth during lactation costs 7 pounds of milk.

How big should heifers be at the time of calving? To answer this question, a farm must know the average weight of mature cows in the herd. Cows typically do not reach their mature size until their third to fourth lactation. A subset of these cows between 80 and 120 days in milk should be used as the predictor for mature size. It is not advised to use the last load of cull cows, as they may be long DIM with excess body condition.

Fresh heifers should weigh 85% of their mature bodyweight post-calving. If springing heifers are easier to weigh, they should be closer to 95% of this mature bodyweight shortly before calving. To reach these goals, farms must maintain an ambitious daily rate of gain during the rearing process.

If your first-lactation heifers do not meet production expectations, assess these different stages of your calf and heifer program and work with your consultants to adjust and capitalize on this high-value investment.

Barry Visser is a nutritionist for Vita Plus.