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Effects of milk replacer feeding regimen to the pre-ruminant calf on crude protein utilization, digestibility, and growth
Traditionally, conventional calf feeding programs have restricted the amount of milk replacer (MR) fed during the pre-weaning period in effort to encourage more solid feed intake, minimize the cost of feeding and management, and reduce the potential for diarrhea. More recently, studies have concentrated more on ways to improve average daily gain (ADG) in pre-weaned calves and have demonstrated that calves consuming greater amounts of milk solids, as well as higher protein concentrations in MR, have higher dry matter intakes (DMI), resulting in greater ADG and skeletal measurements. However, these calves consumed less solid feed, which can lead to more stress during weaning and less rumen development, which opposes the goals of conventional programs described above. These accelerated calf feeding programs capitalize on the rapid and efficient early lean growth potential of calves by allowing for increased body protein deposition without excessive fattening. Feeding programs have been developed that are intermediate in nature to accelerated and conventional programs. These programs result in lesser slumps in growth around weaning and fewer digestive setbacks than those on more accelerated feeding programs. A study conducted at the University of New Hampshire used calves assigned to 1 of 3 treatments: 1) 454 g of a conventional MR (CON; 20% crude protein (CP), 20% fat), 2) 680 g of a moderately high protein MR (MOD; 26% CP, 17% fat), or 3) 908 g of a moderately high protein MR (AGG; 26% CP, 17% fat). All calves were fed ad libitum starter and water. Calves fed MOD and AGG had greater ADG and feed efficiencies compared to CON calves and similar but lower nitrogen efficiency than CON calves (45.5% vs. 52.7%; P < 0.05). This could be due to MOD and AGG fed calves having greater urine volume; and thereby, greater urine nitrogen output compared to CON calves (17.6 g/d vs. 12.1 g/d; P < 0.05). A similar study conducted at the Nurture Research Center (Provimi) showed that calves fed AGG had lower digestibility of nutrients post-weaning, which indicates that post-weaning digestion is lower than optimal, and contributes to lower post-weaning growth in calves fed AGG compared to conventional or MOD programs. In conclusion, calves fed AGG had improved feed efficiency and increased ADG but had reduced starter intake and lower nitrogen efficiency during the pre-weaning period, as well as reduced digestibility of nutrients during the post-weaning period.
Keywords: calf, milk replacer, protein