In the first 2019 installment of the Dairy Cattle Welfare Council (DCWC) webinar series, dairy scientist Michael Steele, PhD, University of Guelph, outlined current research on calf nutrition, health and development.
Steele and his group focus on dairy calf nutrition during the pre- and post-weaning phase, particularly looking at how early nutritional factors contribute to long-term health and productivity. Research increasingly shows, he says, that dietary regimens for heifer calves influence their productivity well past their first lactation.
Steele cited multiple studies on feeding heifer calves for accelerated growth during the pre-weaning phase. Most indicated significant positive benefits on lifetime performance. Some showed numeric, but not statistically significant advantages and a few showed no advantage, but none of the studies indicated any negative impacts.
Steele uses the term “nutritional programming” to describe calf-feeding strategies intended to influence lifetime productivity. He points out that dairies in North America average around 50% calf morbidity and 10% mortality, with a 19% failure of passive immunity contributing to the challenges. Research shows a clear association between antibiotic treatments in pre-weaned calves and lower lifetime milk production.
The weaning period, during which a calf’s digestive system morphs from a pre-ruminant stage to a true ruminant, is one of the most profound transition among all mammals. Steele also stresses the importance of early development of the large and small intestines, including establishment of a diversity of the gut microbiome, for long-term productivity.
As for tube versus bottle for initial colostrum feeding, Steele says his research has shown that tube feeding delivers more colostrum to the rumen, while bottle feeding delivers more to the abomasum. But in tests feeding three liters of colostrum during the first hour, researchers found no difference in absorption rates. Either method is fine, he says, as long as the calf receives adequate colostrum soon after birth.
Steele and his team have conducted experiments comparing feeding colostrum at hour zero, hour six and hour 12 post-partem. They have found that delaying colostrum feeding results in slower, less efficient passive transfer and delayed establishment of beneficial bacteria in the intestine, leading to a higher rate of calfhood diarrhea.
Studies also have shown that pasteurized colostrum can offer benefits in addition to sanitation. In tests comparing heat-treated colostrum with fresh, the pasteurized product provided more absorption of immunoglobulins at six hours post-feeding compared with fresh. Also, pasteurizing heat converts colostrum proteins and lipids into higher concentrations of oligosaccharide in colostrum, which acts as a prebiotic to encourage beneficial bacteria colonization in the calf’s gut.
Dairies also might benefit by fine-tuning the way they manage the calf’s transition from colostrum to milk. While the first milking after parturition contains the highest concentration of bioactive colostrum components, the second, third and even fourth milking supply significant amounts of immunoglobulin along with higher energy compared with milk from later milkings. Left to nurse naturally, the calf receives these colostrum components over several feedings.
Steele and his team have run experiments in which they have fed one meal of colostrum to newborn calves, followed by either 100% milk, 100% colostrum or a 50/50 blend. They found good passive transfer in each group after one colostrum feeding, but formation of papillae in the gut was highest in the group receiving a second meal of colostrum and intermediate in the 50/50 group.
Through the pre-weaning period, most dairy calves probably can benefit from consuming higher volumes of milk. Steele says most calves with ad-libitum access to milk will consume more than conventional recommendations. Frequency of feeding presents a challenge though, as larger, more frequent meals can lead to abomasum inflammation and lesions, milk overflow into the rumen and ruminal acidosis. Calves naturally nurse six to 12 times daily, Steele points out. Research has shown though, that feeding up to eight liters of milk per day, in two or three feedings, will provide faster growth without evidence of increased post-prandial hyperglycemia or hyperinosemia and no difference in glucose tolerance. Calves, he says, have a good ability to regulate their own gastric emptying to optimize nutrient absorption while avoiding clinical acidosis.
As for whole milk versus milk replacer, Steele says protein levels generally are similar, but milk replacers tend to be higher in lactose and lower in fat. Better understanding of nutritional physiology in calves will lead to continuing refinements in milk replacer formulations.
Weaning and post weaning
The weaning period brings dramatic growth in the calf’s rumen volume and rumen papillae. Rumen pH tends to run high at weaning and decline over the next six weeks, Steele says. Rumen gene expression also changes, with new genes activated at weaning, mostly associated with metabolic processes. Later weaning and a slower dietary transition tend to benefit intake, growth and lifetime performance, Steele says. He adds that rumen samples taken before, during and after weaning indicate the rumen microbiome has the greatest diversity before weaning, with a decline in diversity after weaning. Later weaning allows the microbial population to begin that transition, becoming more like post-weaning populations and helping facilitate the transition.
Ideally, Steele says, dairies would wean calves later, at eight weeks of age or older, and use a 10-day to two-week step-down protocol.
Most calf research has focused on the first few months of age through weaning, Steele points out, adding that more studies into the effects of early nutrition on performance out to 24 months or longer could open opportunities to ensure better lifetime health and productivity in dairy females.
Take-home messages from Steele’s DCWC presentation include:
- There are still some basic concepts in calf biology and nutrition that we do not understand.
- Not much difference between tube versus bottle feeding colostrum for passive transfer
- Delaying colostrum by six hours can impact passive transfer and gut microbiology.
- Pasteurizing colostrum may help improve calf gut health if manage properly.
- An abrupt transition from colostrum to milk can compromise gut development.
- Elevated plane of milk can be fed early in life.
- Elevated plane of milk can be fed in twice-daily feeding schemes.
- Milk replacer formulations high in lactose may impact gut health and insulin sensitivity.
- Later weaning and a slower transition from milk to solid feeds improve gains and long-term performance.
A recorded version of the webinar will be available to members on the DCWC website.
For more on dairy-calf nutrition, see these articles on BovineVetOnline: