Create a Smooth Weaning Process
Weaning requires a shift in nutrient supply from milk nutrients to the end-products of fermentation (microbial protein and volatile fatty acids). Ideally, the weaning process results in minimal disruptions in nutrient supply to the calf and, in turn, accelerates grain intake, leading to greater microbial fermentation in the rumen. Weaning age, starter intake at the onset of weaning, and weaning strategy are all components of a smooth transition into the grower phase.
A traditional weaning strategy starts the process at six weeks of age with one milk feeding per day for one week, no milk in week seven, and moving out of individual pens at eight or nine weeks.
Precisely weaning according to age reduces variation in postweaning growth compared to weaning by hutch row or by pen. Additionally, youngstock managers who recognize factors causing variation – such as birth bodyweight, twins, and individual calf health constraints – can extend the weaning age to provide calves the opportunity to catch up to their peers or provide a best-fit group for the calf’s maturity.
Achieving at least modest amounts of starter grain intake in the nursery phase is an important factor contributing to success at weaning. The energy concentration and amount of milk fed relative to requirements for maintenance and growth impacts the slope of the starter grain curve during the nursery phase. Starter intake drives microbial populations in the gastrointestinal tract (GIT) important to fiber digestion postweaning.
Key factors influencing starter grain intake in the nursery phase include:
- Feeding palatable starter grain
- Making starter grain available in the first days
- Keeping starter fresh by offering appropriate amounts to slightly exceed daily intake
- Offering fresh, warm drinking water
In addition to amount, the formulation of starter grain also has carryover effects on nutrient digestibility (specifically fiber digestibility) postweaning. Consuming effective amounts of a coccidiostat is also key to achieving appropriate starter intake per pound of bodyweight at weaning.
Research using biological markers indicates abrupt weaning – and the rapid increase in starter grain intake to meet protein and energy demands – raises intestinal permeability or “leakiness” between intestinal cells. Greater intestinal permeability elevates maintenance requirements of the immune system as well as the risk of infection by pathogens. Recent data suggest milk feeding amount and weaning strategy impact ruminal and fecal bacterial communities.
Nursery programs with diets formulated to feed a larger proportion of nutrients from milk might realize benefits to an extended weaning strategy. An extended weaning strategy is achieved by stretching out the days on reduced milk feeding, giving calves time to ramp up starter grain intake so the protein and energy from starter fills the gap created by weaning from milk. For example, this might mean weaning over 10 to 14 days versus a traditional seven-day weaning period.
We can use an example calculation to better understand the impact of weaning strategy on protein and energy supply for maintenance and growth. Table 1 shows predicted average daily gain (ADG) based on three example weaning strategies.
This article was originally written for the September 25, 2020, issue of Hoard’s Dairyman.
Calf and heifer nutrition
Starting Strong - Calf Care
Transition and reproduction