Abomasum emptying in dairy calves fed milk replacers with varying fat and sources of protein.

Young Holstein male calves fitted with reentrant duodenal fistulae were in two 3 x 3 Latin square experiments. In the first experiment the calves were fed milk replacers containing either 5%, 15%, or 25% lard. Total nitrogen, protein nitrogen, and fat left the abomasum more slowly for the 5% fat milk replacer than for the other two milk replacers. In the second experiment, the calves were fed milk replacers containing either whey proteins, whey, and fish proteins (50:50), or whey and soybean proteins (50:50). Dry matter, total nitrogen, protein nitrogen, and nonprotein nitrogen left the abomasum more slowly for the milk replacer containing whey and soybean proteins than for the other two milk replacers. In both experiments, milk replacers did not differ in rates of passage of fresh matter, reducing substances, ash, gastric secretion of hydrochloric acid, gastric proteolysis, and diarrhea. In Experiment 1, milk replacers did not differ in rates of passage of dry matter and nonprotein nitrogen. In Experiment 2, milk replacers did not differ in rate of passage of fat. Circadian rhythm had no influence.