The effect of changing the carbohydrate composition of the concentrate component of the diet of grass silage fed cows on milk yield and composition

Abstract

With the current production targets and pricing structures prevailing within the UK dairy industry, the incentives for the dairy farmer are to maximise milk protein content whilst controlling the yield of milk and milk fat widiin individual farm quotas. Manipulation of milk fat content by nutritional means is relatively easy, but increasing die protein content of milk by similar means is more difficult and certainly less predictable. Increasing the crude protein content of the diet will invariably stimulate the synthesis of milk protein, but tiiese changes are often associated with a parallel increase in milk volume, such mat milk protein content shows little change. In contrast, several studies have shown mat changing the nature and amount of carbohydrate in the diet can substantially improve milk protein content; Krohn et al., (1985), Roberts & Martindale, (1990), Yan & Roberts (1992, 1993) and Phipps et al (1993). At the same time, the increased use of caustic treated wheat (soda grain) on U.K dairy farms has in part been associated with consistent improvements which have been observed in milk protein content. The primary aim of this study was to consider the effect of replacing part or all of the concentrate portion of grass silage fed cows with alternative carbohydrate rich feeds on me yield of milk and milk constituents. The second objective was to compare the use of soda grain with a 50:50 mixture of rolled wheat and sugarbeet feed on dairy cow performance.