Simulation of digestion in cattle fed sugarcane: prediction of nutrient supply for milk production with locally available supplements

Abstract

SUMMARYA previously described model of digestion in cattle fed sugarcane diets was applied to predict nutrient supply to the host animal from dietary intake, to indicate pre-experimentally the suitability of various supplements to enhance the milk production of dairy cattle in the tropics fed sugarcane–based diets. Potential milk production was calculated according to simulated energy and lipogenic, glucogenic and aminogenic nutrient availability. The addition of small amounts of urea (10 g/kg sugarcane fresh weight) improved microbial efficiency and degradation of substrates in the rumen, but further increases could only be achieved by supplements containing rumen degradable protein. The simulated level of absorbed amino acids was low in comparison with the level of absorbed energy and glucogenic substrates. This low amino acid availability was the factor most limiting milk production on sugarcane diets and supplements which increase the amino acid availability in the gastrointestinal tract are recommended. At increasing supplementation or intake levels, and once amino acid requirements were met, an increased absorption of energy and long chain fatty acids could enhance milk production. These suggestions should be evaluated experimentally in order to improve the model and ultimately, to result in an improved system to evaluate feeds, based on the supply and utilization of individual substrates.