PSXIV-38 Short-term adaptation of milk yield and feed efficiency to individualized dietary changes

Abstract

Abstract Automated in-parlor feeding and other precision individual animal feeding strategies are a primary interest of efforts to enhance precision animal nutrition. Our objective was to determine short-term effects of changes in diet composition on milk yield and feed efficiency in dairy cattle. A replicated latin square with 4 groups of 6 cows was used to evaluate responses to feeding increasing amounts of ground corn (GC), soybean meal (SBM), chopped grass hay (GH), or total mixed ration (TMR) for 9 d periods. Throughout each period, treatments were top dressed at incrementally increasing rates to provide 0 to 20 percent of calculated net energy intake. Cows were group housed and fed once daily in Calan gates for 36 days. Mean milk yield, efficiency, and the linear slopes of these responses to top dress intake were analyzed during each 9 day period. Mean responses and response slopes were analyzed using a mixed-effect model with fixed effects for top dress and random effects for animal, period, and square. Milk yield was significantly affected by top dress type (P = 0.010) and GH differed significantly from SBM (P = 0.015). However, feed efficiency did not differ with top dress type. The milk yield slope was not affected by top dress type (P = 0.268), but the efficiency slope was affected (P = 0.011). The efficiency response to dietary changes was greater for added SBM than for added GH (P = 0.012), but SBM responses did not differ from GC (P = 0.484) or TMR (P = 0.772). These results suggest opportunity to use individualized, automated feeding strategies to adjust dietary composition in the short-term to target economically optimal formulations without sacrificing production.