For decades, nearly all of the research on dairy calf nutrition around the world has focused on the preweaning diet.
While a great deal has been learned from that intense scientific focus on the intricacies of feeding calves milk and milk replacer, University of Guelph researcher Michael Steele said the transition to weaning and the postweaning phase beg for more knowledge and precision. He believes there is much to be learned about the nutrition of older heifers that could further maximize their performance.
“Most studies do not extend beyond six months of age, and a good share of them end with weaning weights,” he said. “Given what we have learned about the significant impact early life nutrition has on lifetime productivity, there is tremendous value in exploring and maximizing nutrition in the transition and grower phases as well.”
Steele has focused much of his own research efforts in this post-weaning arena. He said the transition from a monogastric to a ruminant takes place at about 8 weeks of life, which is, coincidentally, about the time most dairy calves are weaned. At this time, the calf’s rumen expands from about 25% of the stomach system to 80%.
“While the physical expansion of the rumen is dramatic, it’s what’s happening inside, with the development of rumen papillae, that matters most,” shared Steele. “These finger-like projections are crucial to digestion and nutrient absorption, and are developed through the consumption of starter feeds and volatile fatty acids.”
He said solid, abrasive feeds act as an exfoliating treatment to the interior rumen surface (hence the expression, “rumen scratch”). This helps prevent rumen parakeratosis, or hardening of the papillae, which can cause post-weaning stall-out.
In addition to rumen development, Steele said the hindgut is another important area of focus. He has found that calves weaned more gradually had more diversity in beneficial fecal bacteria, an important indicator of gut health.
“Compared to the way a beef calf is weaned, dairy calves usually are transitioned off of milk much earlier and more abruptly,” noted Steele. His advice for easing that process included:
- Wean at later than 6 weeks of age.
- Step down milk feedings by gradually reducing them to one feeding a day, versus abruptly stopping milk or milk replacer.
- Provide clean, free-choice water before, during and after weaning to promote starter-grain intake.
- Keep starter grain free of dust and fines, which can contribute to hindgut fermentation and diarrhea in older calves.
- Offer forages beginning at weaning, keeping in mind that most newly weaned calves are not able to consume more than a half pound of forage per day for the first few weeks after weaning.
Steele’s research has shown a 2-pound-per-week weight-gain advantage for dairy calves weaned at 8 weeks versus 6 weeks.