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

Abstract

S U M M A R YA 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.

Performance of dairy goats fed whole sugarcane

“…However, several studies reported lower milk yield for cows fed WSC relative to those fed other tropical forages (Alvarez and Preston 1976;Alvarez et al 1978;Paiva et al 1991). Using digestion models, Dijkstra et al (1996) and Kebreab et al (2001) suggested that low availability of amino acids is probably the factor that a Urea was applied at the rate of 50 g kg -1 , dry matter basis most severely limits milk production by dairy cows fed unsupplemented WSC diets. Other less limiting factors are energy and long chain fatty acids.…”

“…However, milk yield of cows fed sugarcane was generally lower than that of cows fed other forages (Preston 1988). Limited supplies of absorbed amino acids and energy are likely the reasons for the low productivity of cows fed sugarcane (Dijkstra et al 1996;Kebreab et al 2001). Supplementation with other tropical legumes such as Leucaena leucocephala increased milk yield of cows fed sugarcane-based diets (Alvarez and Preston 1976;Alvarez et al 1978).…”

Mammary gland utilization of amino acids and energy metabolites differs when dairy cow rations are isoenergetically supplemented with protein and fat

“…Positive AV differences and uptakes indicate metabolite removal from plasma, whereas negative values indicate net metabolite release from the mammary glands. Mammary gland nutrient balances were calculated using mean milk protein AA composition reported by Mepham (1987) and Lapierre et al (2012) for AA uptake: output ratios (U:O) and according to estimations of Dijkstra et al (1996) for glucose, 2C compounds (acetate and BHB), and LCFA. Of C16 FA in milk, 50% were assumed to be synthesized de novo from 2C compounds and 50% were assumed to be sequestered as preformed FA.…”

“…Overall, the mammary gland sequestered glucose in excess of estimated requirements for lactose and fat synthesis, assuming that 1.05 and 0.31 g of glucose is required to synthesize 1 g of lactose and fat, respectively (Dijkstra et al, 1996). On average across all diets, 61% of glucose uptake contributed to lactose synthesis.…”

Simulation model for particle dynamics in rumen of cattle fed sugarcane diet

“…Fatty acid fractions include long chain fatty acids (Ld) and volatile fatty acids (Va) and, the rumen microbial DM (Mi) is represented by one state variable. Detailed description of the model and applications are described in Dijkstra et al (1996a;1996b).…”