Researchers examine milk replacer composition
A study performed by researchers at Virginia Tech in conjunction with the USDA Agricultural Research Center in Beltsville, Md., evaluates the effect of varying milk replacer protein and energy content on calf performance.
During the study, researchers fed 24 newborn Holstein heifer calves one of four milk replacers. The composition of the four milk replacers is as follows:
- Control (20 percent crude protein, 21 percent fat; fed at 441 grams per day.)
- High-protein/low-fat (28 percent crude protein, 20 percent fat; fed at 951 grams per day.)
- High-protein/high-fat (27 percent crude protein, 28 percent fat; fed at 951 grams per day.)
- High-protein/high-fat fed at a higher rate (27 percent crude protein, 28 percent fat; fed at 1,431 grams per day.)
The researchers offered a dry calf starter containing 20 percent crude protein and 1.43 percent fat free-choice. The starter included ground corn (44.4 percent of starter dry matter), 48-percent crude protein soybean meal (44.4 percent of starter dry matter), cottonseed hulls (11.2 percent of starter dry matter) and molasses (1.0 percent of starter dry matter.)
Calves fed the control diet consumed more starter than those fed the other treatment diets, but their total dry matter intake was lowest. The high-protein/high-fat milk replacer did not improve average daily gain or frame measures compared to calves fed the high-protein/low-fat milk replacer. The high-protein/high-fat milk replacer fed at a higher level increased calf growth rate. However, calves fed at the higher rate were neither taller nor longer than calves fed the high-protein/high-fat milk replacer.
The researchers saw improvements in growth and nutrient retention in calves fed the more nutrient-dense diets. However, most of the improvement resulted from the increased protein intake (relative to the control milk replacer.)
The researchers concluded that feeding a more nutrient-dense milk replacer alters body composition. However, additional fat in a high-protein milk replacer did not improve lean-tissue gain or calf height and weight. Similarly, increasing the feeding rate of a high-protein/high-fat milk replacer increased protein and fat deposition, but did not produce taller or longer heifers.
