Influence of dairy cow genotype on milksolids, body condition and reproduction response to concentrate supplementation

摘要

Responses to supplementary feeding overseas (OS) and New Zealand (NZ) Holstein-Friesian (HF) cows were investigated over two years using 57 cows receiving a high pasture allowance and 0, 3 or 6 kg concentrate DM/cow/day. Cows of similar Breeding Worth( dollar BW) grazed as a single herd and were individually fed a grain-based supplement. Important production genotype X diet interactions of a scaling nature were detected. Across all supplementation levels, OS cows gave a greater (P < 0.05) linear production response than NZ cows (74 vs 37 g MS/kg concentrate DM; 1.22 vs 0.67 kg milk/kg concentrate DM consumed, respectively), but gave a similar response in live weight and condition score gain during lactation per kg of concentrate DM consumed. However, because OS HF appeared to have a larger relative feed deficit than NZ HF when fed ad libitum on pasture, OS HF maintained a lower body condition score throughout lactation and produced less milksolids (as a % of live weight). Current supplementary feeding decision rules which recommend reducing supplementary feed use when abundant pasture is available remain appropriate for high dollar BW NZ HF cows. However, reasonable responses to high-energy supplements will continue to be obtained from high dollar BW OS HF cows, even when pasture supply appears adequate to meet cow requirements. Use of indicators of relative feed deficit such as milksolids as a % of live weight and body condition score, may be a better guide to predicting the production responseto supplementation, rather than decision rules based on genotype.