Study Shows no Long-term Impact of Higher Milk Replacer Feeding Rates
Posted: December 15, 2009
Researchers from the United Kingdom recently studied the impact of milk replacer feeding rate and protein concentration on animal performance through the second lactation. Holstein-Friesian calves (88 heifers and 65 bulls) with an average birth weight of 95 pounds began the study at 5 days of age.
Calves were fed 1.32 or 2.64 pounds per day of milk replacer containing 21 or 27% crude protein and 17% fat until weaning at 56 days of age. All calves were housed in groups by treatment and fed via automated feeders. Water and calf starter were available free-choice during the milk-feeding period. After weaning, heifer calves remained in treatment groups through 12 weeks of age; bull calves were removed from the study at weaning. All animals were offered the same diet from weaning through the remainder of the experiment. Heifers were bred after reaching 13.5 months of age and 695 pounds of body weight. Milk production data were collected for 81 first- and 66 second-lactation cows.
Calves fed the 2.64 lb/d of milk replacer gained 0.35 lb/d more during the pre-weaning period and were 20 pounds heavier and 1.2 inches taller at weaning than calves fed 1.32 lb/d, but there were no differences in daily weight gain after weaning. Calves fed 1.32 lb/d of milk replacer on average consumed 54% more calf starter than calves fed 2.64 lb/d; grain is the feed component of calf’s diet that enhances rumen development, making the transition at weaning smoother.
At 90 days of age, calves fed more milk replacer weighed 14 pounds more, but body weight and height differences disappeared by 6 months of age. Protein content of the milk replacer did not affect body weight in the pre-weaning period. Age at first breeding was not affected by treatment, nor was age (24 months) or body weight (1117 lb) at first calving. Milk production during first and second lactation was also similar regardless of treatment.
The study (Morrison et al., 2009; published in the peer reviewed journal Animal) is one of several that have found no benefit to increased milk replacer feeding rates and it is the first to report milk production results through the second lactation. Although there are at least four reports of improved milk production due to increased feeding rate before weaning (Bar-Peled et al., 1997; Shamay et al., 2005; Moallem et al., 2006; Drackley et al., 2007), all but one of these studies had serious confounding factors that make it impossible to interpret the results related to increased milk intake alone.
The Drackley study has so far only been presented as an abstract, which means the full description of the experiment has not yet been reviewed by other scientists. This study by Morrison et al. also showed that the addition of increased protein for the young calf had no beneficial effect for the calf in terms of growth or lactation performance. This finding is also in agreement with other peer reviewed published studies specifically focused on this issue.
In controlled experiments where we can make valid comparisons, results have repeatedly shown that the early growth advantage is lost after weaning. Feeding extremely high levels of milk replacer hasn’t impacted age at first service or lowered age at first calving.
There is still debate about effects on milk production, and sorting this out is complicated due to the long lag between treatment and effect. We conclude that it is hard to justify the high cost of feeding so much milk replacer (especially when it is a higher cost product due to high protein content) when research is not available to prove that it makes a difference in the long run. Stepping up from feeding calves just enough to keep them alive through weaning is important, but going too far in the direction of “enhanced” nutrition is likely to cost more money without real benefit.
Coleen Jones, Research Associate, Javier Suárez, Graduate Student, Jud Heinrichs, Professor of Dairy and Animal Science