PRODUCING MILK WITH 2.5-PERCENT FAT - THE BIOLOGY AND HEALTH IMPLICATIONS FOR DAIRY-COWS

Consumer demand for the major components of milk has changed considera bly over the past 10 years. The trend in recent years is for reduced c onsumption of milk fat as a component of fluid milk and in dairy produ cts such as butter, cheese and yoghurt. Matching production of milk co mponents to demand improves biological efficiency and ultimately enhan ces the overall profitability of the dairy industry. Genetic selection of dairy cattle allows the dairy industry to respond to consumer dema nd in the long-term. However, it is not a satisfactory means of manipu lating milk composition in the short- or medium-term. The potential of nutrition as a tool to alter the composition of milk - especially mil k fat percentage - has not been fully exploited. Changes in the compos ition 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-lactatio n and this is also a time when cows are less susceptible to metabolic disorders. Although experiments designed to evaluate the long-term eff ects of feeding extreme fat-depressing diets have not been conducted t here 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 'heal thy' cows.