The rapid growth and exceptional weight gain achieved by calves fed high levels of milk solids in the milk-feeding phase may be in jeopardy of being erased after weaning, according to longtime calf researcher Jim Quigley, Calf and Heifer Research and Technical Manager with Provimi North America.
“Feeding large amounts of liquid has been shown to delay starter intake, and, consequently, rumen development,” says Quigley. He defines accelerated liquid feeding as greater than about 700 grams of milk solids from liquid feedings per day, and conventional feeding about 500-700 grams of solids (or about 10% of bodyweight) via liquid per day.
Quigley explains that when calves are weaned, the source of nutrients that fuel growth switches from milk – which is digested primarily in the small intestine – to grain-based feeds fermented in the rumen and/or digested in the small intestine. “After weaning, nutrients are provided by volatile fatty acids absorbed from the rumen, and microbial protein that increases in flow with increasing dry feed intake,” he says.
The problem is, early diets based heavily on milk-based nutrients may delay the age at which dry-feed consumption begins, thus slowing rumen development. If calves are weaned with poorly developed rumens, they are not equipped to digest dry rations put in front of them, however perfectly balanced they may be.
The researcher says the most important factor in promoting rumen development and adaptation in preparation for weaning is consumption of dry feed containing fermentable carbohydrates – particularly sugars and starch – that will be converted to propionate and butyrate by bacteria in the rumen.
Quigley offers the following advice for supporting accelerated-fed calves through the weaning process and promoting rumen development:
- Extending the step-down protocol for milk feedings to 14 days or longer. His review of several studies that reduced liquid feed intake over a period of 7-10 days leading up to weaning showed that, “for calves fed 1 kg of powder per day or greater, this is probably insufficient time for rumen adaptation.”
- Choosing starter rations that support good rumen development prior to and immediately after weaning. Generally, starters containing greater amounts of starch and sugar are more effective in promoting rumen development.
- Providing supplemental nutritional enhancements to preweaned calves such as functional fatty acids and nutrients; and sodium butyrate. Researchers have found that these supplements have helped improve fiber digestion in young calves.
“Taking these specific steps to proactively manage transition is more important than strictly adhering to NRC nutrient guidelines, which do not take into account differences in digestibility caused by age or development of the gastrointestinal tract,” advises Quigley. “The existing NRC model over-predicts the metabolizable energy supply from starters by 12 to 26%.”
To read a more thorough explanation by Quigley and his colleagues on the relationship between preweaning diets and rumen readiness at weaning, and the research studies that support his conclusions, follow this link.