Energy and protein utilization in calves fed via rumen by-pass.

Abstract

Energy and protein balance experiments and feeding trials were conducted with calves to compare the effects of feeding milk replacer via the rumen vs. the abomasum on feed, energy, and protein utilization efficiencies. Identical diets and similar intake (based on body weight0.75) were fed to paired Holstein bull calves with one receiving the milk replacer portion of the diet as liquid and the other calf receiving dry milk replacer. Bottle fed milk replacer was found to completely by-pass the rumen. In experiment 1, three pairs of calves from 10 to 15 weeks of age received milk replacer at 50% of total intake. Experiment 2 utilized five pairs of calves from 10 to 14 weeks of age that were fed 32% of intake as milk replacer. Energy and nitrogen balances were determined at the conclusion of these feeding periods. Feed efficiency (feed/gain) in experiment 1 was 2.35 and 3.17 and in experiment 2 was 2.83 and 3.72 for the bottle and dry fed calves, respectively (P<.05). Protein digestibility in experiment 1 was 83.5% and 78.8% and for experiment 2 was 78.7% and 71.8% for the bottle and dry feel calves, respectively (P<.05). The slightly higher nitrogen retention (expressed as a percent of nitrogen intake) for the bottle fed calves, 17% in experiment 1 and 7% in experiment 2, was not statistically significant. Energy digestibility in experiment 1 was 86.8% and 82.0%, and in experiment 2 was 80.7% and 76.4% for the bottle and dry fed calves, respectively (P<.05). Methane production ranged from 1 to 2% of gross energy in both experiments with no effect of treatment. The efficiency of utilization of metabolizable energy for maintenance and gain was approximately 8% better for the bottle fed calves. Fasting heat production was significantly higher (120 vs. 109 kcal/kg0.75) for the bottle fed calves. Thus, by-passing the rumen with milk replacer improved feed efficiency, protein and energy digestibility, and metabolizable energy utilization, but had no effect on nitrogen retention or methane production.