Producing milk with 2.5% fat - The biology and health implications for dairy cows

Consumer demand for the major components of milk has changed considerably over the past 10 years. The trend in recent years is for reduced consumption of milk fat as a component of fluid milk and in dairy products such as butter, cheese and yoghurt. Matching production of milk components to demand improves biological efficiency and ultimately enhances the overall profitability of the dairy industry. Genetic selection of dairy cattle allows the dairy industry to respond to consumer demand in the long-term. However, it is not a satisfactory means of manipulating milk composition in the short- or medium-term. The potential of nutrition as a tool to alter the composition of milk - especially milk fat percentage - has not been fully exploited. Changes in the composition of the diet, in particular the forage to concentrate ratio, can result in changes in milk fat percentage in the range of 2.0 to 4.0%. The largest reduction in milk fat is achieved in mid- to late-lactation and this is also a time when cows are less susceptible to metabolic disorders. Although experiments designed to evaluate the long-term effects of feeding extreme fat-depressing diets have not been conducted there are sufficient examples of apparently healthy herds which produce milk with a fat content in the range of 2.5 to 3.0% to allow cautious optimism that low milk fat is not necessarily incompatible with 'healthy' cows.