Total mixed rations versus pasture diets: evidence for a genotype x diet interaction in dairy cow performance.

摘要

The performance of overseas (OS) and New Zealand (NZ) Holstein Friesian (HF) dairy cows were compared on an all-pasture diet (Grass) or a total mixed ration (TMR). Dietary treatments had been imposed for two years prior to the 2000-2001 season for which these results are reported. The four treatments were NZ Grass (n=14), OS Grass (n=13), NZ TMR (n=14) and OS TMR (n=14). Genotype x diet interactions were observed for annual milk yield, milk solids yield, efficiency of milk solids production, liveweight gain during lactation, and the proportion of cows not in calf. Measurement of individual cow intake using alkane markers during early, mid and late lactation identified when these genotype x diet interactions occurred. When fed TMR, OS HF performedbetter than NZ HF, but on grass NZ HF performed better than OS HF. This has implications for the selection of sires for the national herd, and for the use of different dairy cow genotypes in different dairying systems.