RELATIONSHIP BETWEEN FREQUENT MILKING OR SUCKLING IN EARLY LACTATION AND MILK-PRODUCTION OF HIGH PRODUCING DAIRY-COWS

Groups of 9 or 10 cows were assigned to one of three treatments 1) mac hine-milking three times daily, 2) machine-milking six times daily, an d 3) suckling three times daily in addition to machine-milking three t imes daily. Treatments were conducted during the first 6 wk postpartum ; thereafter, all cows were milked three times daily. During treatment , milk production was highest for suckled cows and lowest for cows mil ked three times daily. The DMI were similar for suckled cows and cows milked three times daily but higher for those milked six times daily. Body weight loss was greatest for suckled cows and least for cows milk ed three times daily. During wk 7 to 18 postpartum, cows milked six ti mes daily exhibited a carry-over effect on milk production that was gr eater than that of other groups. During treatment, plasma growth hormo ne and IGF-I concentrations were elevated for suckled cows and, to a l esser extent, for cows milked six times daily. Prolactin and oxytocin similarly increased, but insulin decreased in suckled cows and, to a l esser extent, in cows milked six times daily. Posttreatment difference s persisted for insulin and IGF-I, but not for the other hormones. Inc reased frequency of udder emptying increased milk production, and suck ling was superior to machine-milking. High milk production was associa ted with elevated growth hormone, IGF-I, prolactin, and oxytocin, alth ough cause and effect could not be established. The failure of suckled cows to increase feed intake to match output requires further investi gation.