Early care can affect heifers for life
The first few weeks of a heifer’s life matter – a lot. Adam Beard, Ph.D. with Cornell University’s College of Veterinary Medicine, presented “Early Calf Management: Key Influence on Heifer Development” as part of Cornell’s ongoing “Boots in the Barn” webinar series.
Beard discussed the developmental plasticity during the period from two months before birth through two months after birth.
Before birth, the calf receives nutrients and biological “communication” from the mother, which during the post-natal period “makes you wonder if maternal influences are still there,” Beard said. “Nature by design would say ‘yes,’ as that offspring is still consuming milk. In the U.S. dairy industry, this is typically not sustainable to have a relationship between the calf and dam.”
During the two months post-birth, calves typically receive whole milk, processed milk or waste milk that may or may not be pasteurized. Beard views developmental plasticity as either an opportunity or a risk, as the increase in the calf’s weight and development of its systems from birth through weaning tends to taper off at two months after birth.
Beard said the key maternal influences on heifer development include colostrum and diet; health and growth; reproduction; and mammary gland health and development.
He referred to research from the American Dairy Science Association, which indicates that in utero heat stress of dams compromises their offspring’s overall growth and mammary development from post-weaning through puberty. On a commercial dairy in Florida, the use of shade, fans and soakers in one group of dams compared with only shade and natural vent in another group proved that their calves, despite receiving the same management, developed differently.
“Late-gestation heat stress causes lighter bodyweight and body length; smaller mammary glands; shorter teats; fewer proliferating cell; smaller ovulatory follicles; and smaller corpus luteum,” Beard said.
In a 2025 report from Cornell, researchers looked at the effects of feeding colostrum volume at 6%, 8%, 10% or 12% of birth bodyweight on efficiency of immunoglobulin G absorption, gastric emptying and post-feeding behavior. The Holstein calves in the study were offered four liters of colostrum, which Beard said is “pretty standard and is not often finished voluntarily by a calf.”
All of the calves were fed colostrum that was pooled, pasteurized and frozen, administered by esophageal tube feeding. Researchers found that large volume feeding can slow down passage of colostrum to the small intestine, the site of immunoglobulin G absorption.
Feeding 8% to 10% of birthweight was seen as the “intermediate optimum” as the calves experienced increased serum and excellent TPI compared with those fed colostrum at a rate of 6% of their birthweight.
“They had faster and more efficient absorption than those fed 12% of their bodyweight,” Beard said. He noted that this was good quality colostrum and the study did not observe long-term effects.
Beard shared further Cornell surveys about Holstein colostrum production. Researchers looked at 19 New York-based Holstein herds ranging between 620 and 4,600 head between 2019 and 2021.
Ninety-five percent of the farms feed heifers one gallon (four quarts) of colostrum at their first meal and 74% of the farms feed colostrum at more than two feedings.
“If we take that four quarts, 10% would be for an 83-lb. calf and 8% for a 104-lb. calf,” Beard said. “We’re not seeing a lot of 104-lb. Holstein heifer calves.”
As for what pre-weaned calves are eating in New York, 21.1% have milk replacer, followed by acidified waste milk (10.5%); pasteurized waste milk (36.8%); raw waste milk (10.5%); pasteurized whole milk (10.5%); and raw whole milk (10.5%).
“Milk directly from the dam is happening much less,” Beard noted.
Transition milk is different than mature milk in that it has “greater solids, protein and fat, along with greater insulin and growth factors,” Beard said. “That’s decreasing as the milk becomes more mature.”
Although there’s mixed results about bodyweight, transition milk has higher health scores among preweaned calves compared with milk replacer, including decreased markers of inflammation, mucosal and submucosal development of the GI tract and increased solid feed intake at weaning.
Delaying cow/calf separation represents one way to increase the benefits of transition milk feeding. Beard’s study from April – November 2024 and March – June 2025 among 160 cows in a free-stall barn indicated that calves receiving transition milk with full social contact and unrestricted time with the dam had outcomes that “weren’t any worse for having the calf in the environment with the cow, which some night suspect would make them more vulnerable for health issues,” Beard said.
The researchers had no issues with cows stepping on calves or other injuries and no behavior-related injuries with humans interacting with dam and calf.
“After a calf is separated, the milk quantity rebounds within 24 hours,” Beard said.
The group of calves free to suckle recovered more quickly from infections present at calving than calves not free to suckle.
The calves fed by nipple bucket received 10% of their daily morning bodyweight in two feedings of transition milk.
“The progesterone in a whole milk diet is not native in the newly postpartum dam which can have effects on their developmental plasticity and ovarian and neuroendocrine programming,” Beard said. “We have a myriad of diets, like waste milk, milk replacer and bulk tank milk. What is known about this? Not much.”
An Israeli study looked at Holstein heifers receiving waste milk or milk replacer. Calves that received waste milk had an earlier age at first insemination and calving, no difference in age at first conception and earlier puberty but no effect on bodyweight at puberty. Comparing milk replacer with maternal milk via suckling for six weeks resulted in earlier first conception and calving and higher conception rate and bodyweight. Beard wants to see more studies comparing calf management.
“The quality of the milk replacer is not well described,” he added. “What we need is more data about milk replacer versus maternal milk on the same farm with the same reproductive management on the same farm. It’s hard to find.
“There’s not enough data to classify any of these as a risk, but I do see some opportunities to optimize heifer reproductive development by implementing changes to early life management or an opportunity to redefine heifer milestones and repro protocols according to their current pre-weaning system.”
Beard has undertaken unpublished studies that look at anti-Müllerian hormone as a possible opportunity. Produced by the ovarian follicles, this hormone affects sexual differentiation and indicates egg count. Could this be associated with some positive fertility outcomes? For adult cows, this is not a dynamic hormone.
Research indicates that “transition milk is higher in insulin and IGF-1 which could contribute to surges in hormones,” Beard said. “We don’t have that data produced as these heifers are nearing one year in age.”
