Nutritional regulation of gastrointestinal function in calves post-weaning – Dr. Michael Steele, University of Alberta
By Brittany Olson, contributing writer
Going from life as a monogastric animal to life as a ruminant animal will be one of the most significant changes a calf will make in her lifetime. How she makes that transition will set the stage for her future growth and development.
“A smooth transition from a monogastric to a ruminant decreases morbidity and mortality, and increases gain,” said Dr. Michael Steele, assistant professor at the University of Alberta, during his breakout session at Vita Plus Calf Summit.
Typically, around week 8 of life, the rumen greatly increases in size even though the abomasum is doing all of the work in terms of milk digestion. While the rumen looks larger on the outside, the development of papillae on the inside will make or break a calf’s transition to life as a ruminating animal.
Papillae are fingerlike projections that aid in digestion and absorption and are developed through the consumption of solid feeds, like calf starter, and volatile fatty acids (VFA), which promote cellular growth and blood flow to the developing papillae. Steele said that, of all the VFAs, butyrate is the most critical compound to developing proper circulation and cellular reproduction.
Abrasive feeds, like calf starter, also act as an exfoliating treatment for the rumen and prevent parakeratosis, or hardening of the papillae, which has been identified as a common roadblock during weaning. Having water available at all times positively impacts starter intake, and vice versa.
Steele also pointed out that how we wean dairy calves is completely different from how they wean in nature, such as beef calves.
“Calves getting more milk in fewer, larger meals have more weaning challenges than those who feed in smaller, more frequent meals throughout the day,” according to Steele.
To make the weaning process less stressful, Steele recommended weaning later than six weeks of age and with a step-down process. This involves cutting one daily feeding in the final week or two before weaning when the calf is no longer receiving milk or milk replacer.
Steele cited his research that showed a two-pound per week weight gain in calves weaned at eight weeks compared to those weaned at six weeks. He said if you’re feeding twice a day, only feed milk at night during the last week before weaning.
“If you can wean calves more gradually, you’ll have more growth,” Steele said.
As much as research has focused on rumen development, developing the hindgut in calves is crucial, too. For example, calves weaned using the step-down approach displayed more diversity in their fecal microbiota, or beneficial bacteria, compared to those cut off abruptly from milk consumption.
Steele said, with post-weaning nutritional regulation, the hindgut is important to look at too. Keeping starter and grower rations free of dust and fines decreases the risk of hindgut fermentation, which can cause diarrhea and unwanted growth checks in older calves. Forages can slowly be introduced, but keep in mind most newly weaned calves will not or cannot eat more than half a pound of forage per day for the first couple of weeks after weaning.
Steele concluded with a call to action. He said 95 percent of calf research takes place before the calf is two months old. While weaning is one of the biggest gut transformations in nature and can cause gut health problems if calves are not weaned carefully, he said nutrition in life after milk is largely a frontier waiting to be discovered.
“We have been too focused on preweaning nutrition for a very long time, and now we need to focus on periods after weaning.”
Calf and heifer nutrition
Starting Strong - Calf Care