Production responses of lactating dairy cows fed silage-based diets to changes in nutrient supply

摘要: Abstract The objective of this meta-analysis was to develop empirical prediction equations for milk and component yields using energy protein intake dietary composition as independent variables. A dataset 1125 treatment means from 245 production studies in dairy cows collected. diets were mainly based on grass silage or partly completely replaced by leguminous whole crop silages. Concentrates fed a flat rate basis. They composed cereal grains, fibrous by-products different supplements. Dietary characteristics [crude (CP), ether extract (EE), neutral detergent fibre (NDF), starch, non-fibre carbohydrates (NFC) fermentation] feed values [metabolizable (ME) (MP), ruminal CP balance Feed MP] recorded the dataset. Production variables showed wide ranges: days (38–232), dry matter (DM) (9.9–25.2 kg/d), (MY; 13.0–45.8) kg/d, corrected (ECM; 12.8–43.5 kg), fat (479–1830 g/d) (PY, 359–1449 g/d). Mixed model regression analysis with random study effect used MY, ECM PY. best-fit models MY included linear quadratic effects ME available (MEI) concentrations NFC concentrate MP concentration significant variables, MEI being most pronounced. Correcting feeding level associative further improved fit models. equation PY fat. adjusted root mean squared errors 0.424 kg/d, 0.497 kg/d 15.2 g/d equations, respectively. Cross-validation only marginally greater than calibration almost all error variance due variation. basic structure confirmed well established concept diminishing returns incremental increases nutrient intake. results demonstrated that predicted responses changes supply reasonable accuracy. It is concluded can be optimization cow rations practical farms maximize income over costs.