The author is a professor of animal sciences at the University of Illinois Urbana-Champaign.
I was recently asked what significant changes I have seen in calf nutrition and growth over my nearly 35-year career at the University of Illinois. Research on calf nutrition and management has exploded in the last 25 years, and interest in calves has never been higher.
Calf nutrition has progressed from a simple, one-size-fits-all approach to a more sophisticated understanding of the role that early nutrition plays in growth, health, and future productivity. The industry has moved away, slowly, from the idea that calf nutrition is “one bag of milk replacer per calf and all the starter they’ll eat” to evaluating the desired performance objectives and designing a feeding program to achieve the goals.
More milk is the norm
The milk-feeding period is certainly a front and center welfare concern, as well as a huge economic opportunity for producers and calf specialists alike. The old practice of feeding a pound or a pound and a quarter of milk replacer to calves is slowly being replaced by intakes of more nutritious milk replacer that perhaps are twice as great, which approach “natural” intake levels.
The last National Animal Health Monitoring System (NAHMS) study conducted in 2014 found that the average amount of milk fed on U.S. dairy farms was about 5.7 quarts per day per calf, which equates to about 1.6 pounds per day of milk solids. That average likely has continued to rise in the decade since the survey was performed, with many farms feeding 6 to more than 8 quarts of milk or milk replacer daily.
The new National Academies of Sciences, Engineering, and Medicine (NASEM) guidelines published in 2021 stated that the minimum amount of milk solids to be fed should be 1.5% of birth body weight, which for a 95-pound Holstein heifer would be about 1.4 pounds of solids or more than 11 pounds of whole milk. Clearly, many farms feed more than this minimum amount.
Colostrum research has flourished in the last 25 years, emphasizing its important role in immunity, nutrition, and provision of growth and health promoting substances. A new set of guidelines for assessing colostrum adequacy and success of transfer of passive immunity has been developed. Transfer of passive immunity is classified into four groups, ranging from excellent to poor. Using data from the last NAHMS survey, the authors of the study showed that mortality and sickness declined as colostrum status went from poor to excellent.
Room to grow
Calf nutrition changed fundamentally with the publication of a seminal article by Carolina Diaz and Mike Van Amburgh at Cornell University in 2001. This research demonstrated that tremendous rates of growth are possible when newborn calves are fed greater amounts of milk replacer formulated to not be limiting in crude protein. Growth rates and feed efficiency rose linearly with more milk replacer fed, and the calves did not fatten with greater growth rates.
This research shocked the industry, which had become complacent about feeding limited amounts of milk or milk replacer, despite an abundance of early studies showing greater growth rates when larger quantities of milk were fed. The Cornell University publication spurred many subsequent research trials on greater milk feeding, which continue today.
Researchers in British Columbia found that calves allowed ad libitum access to milk from birth consumed enough nutrients to grow at a rate of 2.2 pounds per day during the first two weeks of life, compared with 0.8 pounds per day for calves fed milk at 10% of body weight. Feed efficiencies (pound of gain per pound of feed) of greater than 0.80 can be achieved by young calves when they are fed large amounts of milk, equivalent to the efficiencies achieved by young pigs and lambs.
Many skeptics will argue that there is no economic benefit to greater feed efficiency in young dairy calf growth as there is in meat animal production. However, as animal scientists, we should be concerned with getting maximum value out of feed resources at any stage of life. This lowers the cost of body weight gain, which should be our economic metric rather than feed cost per day. Boosting early growth and feed efficiency results in calves reaching breeding size sooner and with less feed input.
Calves fed more milk are better able to withstand the effects of infection than underfed calves. And, perhaps most importantly, evidence continues to accumulate that healthier calves grow more rapidly end up producing more milk in the first lactation — and subsequent lactations — than slower growing calves. Practitioners should help producers view calves and heifers as an investment in their dairy rather than as a cost center.
Another key development was the publication of the National Research Council (NRC) guidelines in 2001, which adopted a different approach to calculation of calf requirements than previous editions. The computer program produced with the document became widely used in the industry. The model predicted growth for calves fed different amounts of milk and starter and different metabolizable energy contents of the diet. It also demonstrated the detrimental effects of cold stress on growth. The publication and its computer model helped establish that calves had variable requirements depending on desired growth rates, and has been a great educational tool for the industry.
An eye on behavior
One of the most important advancements in calf management over the last 25 years is the proliferation of research related to behavior and welfare. Work in this area has demonstrated clear indications of hunger in calves fed conventional, limited-milk programs, including more vocalization and restlessness. Such signs are not evident in calves fed greater amounts of milk. With growing scrutiny of calf raising practices by consumers, we should not allow underfeeding. The behavior research also resulted in practices such as pair housing, which has become more popular in recent years.
Finally, an important tool available to assist in feeding and management is the NASEM system and model published in 2021. The text provides a state-of-the-art review of dairy calf nutrition and feeding. The equations developed in this publication accurately predict average calf growth with different feeding programs and can illustrate the effects of heat and cold stress on performance. Use the computer model that comes with the publication or a spreadsheet adaptation of the model to apply the equations in practice.
These areas I have highlighted are certainly not the only important advancements in dairy calf nutrition and growth over the last 35 years. Given the current focus on young calves, keep watching for more research-based innovations in calf raising.
