The effects on performance of out-wintering replacement heifers in a high- output dairy system

摘要

Out-wintering replacement dairy heifers is commonly practised among low input pasture-based dairy systems, and is potentially an option to facilitate expansion for high output dairy farms. The effects on performance of Holstein dairy heifers out-winteredon perennial ryegrass, fodder beet, or housed during the winter of 2013/2014 in the UK were examined. Forty eight, 23-(±2.8) month-old, in-calf heifers were randomly assigned to one of three treatments: out-wintered on perennial ryegrass and grass silage(G) ; out-wintered on fodder beet and grass silage (F); or housed and fed grass silage and concentrate(H) . Ike study commenced in November 2013, with heifers continuing on their respective treatments for 13 weeks, before being housed for six weeks before parturition. Post-partum all animals received the v same diet with performance measured for 12 weeks. Mean live weight (Lwt) and body condition score (BCS) during the winter was unaffected by treatment, but BCS of heifers that received G tended to be lower (P=O.090) at housing. Post-partum, mean Lwt was unaffected by treatment; however, mean BCS was lower (P=0.022) in animals that received G. Milk yield was not affected by treatment, but milk fat (gkg"1) was lowest (P=0.027) and milk protein (gkg"1) highest (P=0.026), in F. The results indicate that Holstein heifers can be successfully out-wintered without impacting on first lactation performance in a high output dairy system.