GENETIC-VARIATION IN THE FEEDING VALUE OF ALFALFA GENOTYPES EVALUATEDFROM EXPERIMENTS WITH DAIRY-COWS

An alfalfa (Medicago sativa L) with improved digestibility, 6328P, was fed to dairy cows in order to determine the effects of its nutritive value on milk production. Three different trials lasting 20, 9 and 16 days were conducted on two groups of ten dairy cows each. Animals were fed either the 6328P alfalfa or the widely used alfalfa variety, Euro pe. Alfalfa quality and its intake as well as milk production and milk fat and protein contents were recorded. The 6328P alfalfa had a highe r leaf/stem ratio and a higher crude protein content than Europe. In v itro as well as in vivo digestibilities increased by 1-9% for the 6328 P alfalfa compared with Europe. With 6328P, alfalfa intake increased b y 12% (1.9 kg d(-1)), while milk production was raised by an average o f 7% (1.4 kg milk d(-1)). This overall increase in milk production was responsible for increased milk fat and milk protein yields despite a lower fat content and only a slightly higher protein content in the mi lk produced by cows fed the 6328P alfalfa. Clearly genetic variability in the nutritive value of alfalfa exists, and using this variability will improve dairy cow performance.