BREED AND NUTRITIONAL EFFECTS AND INTERACTIONS ON ENERGY-INTAKE, PRODUCTION AND EFFICIENCY OF NUTRIENT UTILIZATION IN YOUNG BULLS, HEIFERS AND LACTATING COWS

Red Danish (RD), Danish Friesian (DF), Danish Red and White (RW) and D anish Jersey (DJ) heifers had ad libitum access to total mixed rations designed to promote low (L), medium (M) or high (H) growth rate from 6 weeks of age to approximately the time of puberty. Heifers then were managed uniformly through 250 days of their first lactation. Paternal half-brothers of the heifers were tested from 6 weeks to 11 months of age on a high concentrate or on a roughage diet. For prepubertal feed intake, growth and efficiency of feed utilization of heifers, breed a nd rearing intensity effects were important, but breed x rearing inten sity interactions were non-significant or inconsistent. Breed and rear ing intensity effects were important but their interaction was not for precalving weight gain, calving weight, milk yield, and feed intake a nd efficiency during lactation. Females of the larger breeds ate more, grew more rapidly, were heavier and produced more energy corrected mi lk than Danish Jerseys; but breeds did not differ for efficiency of nu trient utilization during lactation or for post-partum weight change p atterns. Increased prepubertal daily gains induced by higher-energy di ets were associated with lower subsequent milk yield and reduced energ y intake during lactation. The RD, DF and RW bulls ate more and grew m ore rapidly than DJ bulls. Daily energy intake and gain were higher fo r concentrate-fed than for roughage-fed bulls. Breed and dietary energ y level did not interact significantly for these traits. In conclusion , there was little evidence that Danish dairy and dual-purpose cattle breeds differed in the sensitivity of their subsequent milk yield to e xcessive rates of gain during the rearing period or in response of you ng bulls to high concentrate versus roughage diets.