Evaluation of Cornell Net Carbohydrate and Protein System predictions of milk production, intake and liveweight change of grazing dairy cows fed contrast silages

摘要: The importance of mechanistic models for ration balancing with forages is indicated and physical limitations to intake emphasized, because these limit energy nutrient supply cows grazing forages, especially grass. Ration-balancing using fresh or ensiled complement pasture will need accommodate due rumen fill, clearance, chewing other criteria. potential the Cornell Net Carbohydrate Protein System (CNCPS) model predict milk production from diets based on forage supplements was tested data two experiments. Data were obtained studies in which complemented contrasting silages including maize, pasture, sulla, lotus mixtures, comprising 0·30-0·40 dry matter (DMI). Twelve used evaluation. DMI, liveweight (LW), days milk, diet composition determined during trials as inputs model. Across all diets, a significant relationship existed between predicted actual values DMI (R2 = 0·58), yield 0·59) LW change 0·51), but there still large unexplained sources variation. No mean bias observed any variables, slope residual differences against significantly different zero yield, (P < 0·06). results indicate satisfactory prediction when are neither gaining nor losing weight, that systematic exists probably failure CNCPS account partitioning.