SIRE X NUTRITION INTERACTIONS AND GENETIC-PARAMETERS FOR ENERGY-INTAKE, PRODUCTION AND EFFICIENCY OF NUTRIENT UTILIZATION IN YOUNG BULLS, HEIFERS AND LACTATING COWS

Sons of 19 Red Danish, 19 Danish Friesian, 2 Danish Red and White and 16 Danish Jersey bulls were reared from 6 weeks to 11 months of age on a high concentrate (C) or high roughage (R) diet. Daughters of the sa me sires were reared on diets formulated to promote low (L), medium (M ) or high (H) daily gain from 6 weeks of age to puberty. Heifers then were managed similarly through 250 days of their first lactation. Sire x diet interactions were significant for traits measured in bulls; ge netic correlations between the same traits expressed in C-versus R-fee ding systems were -0.10 for daily energy intake (DEI), 0.16 for averag e daily gain (ADG), and 0.18 for efficiency of nutrient utilization (E FF), Heritabilities of these traits were higher when expressed in the R-feeding system than in the C-feeding system (1.09 versus 0.29 for DE I, 0.58 versus 0.28 for ADG, and 0.82 versus 0.34 for EFF), whereas ph enotypic variances of the traits were larger under C-feeding. Sire x r earing intensity interactions were not significant for most traits of growing or lactating females. Heritability estimates of DEI, ADG and E FF in females ranged between 0.22 and 0.27; and heritabilities of weig ht at calving, energy corrected milk yield (ECM), and DEI and EFF duri ng lactation were 0.35, 0.50, 0.16 and 0.69, respectively. Weight chan ge patterns related to post-partum energy balance were lowly heritable (0.14 to 0.23). Genetic correlations of ECM were -0.67 with post-part um weight loss, 0.60 with number of days of lactation when minimum bod y weight was reached, 0.50 with DEI during lactation, and 0.91 with la ctation EFF.