HETEROSIS AND BREED ADDITIVE EFFECTS FOR HEREFORD, TARENTAISE, AND THE RECIPROCAL CROSSES FOR CALF TRAITS

Records from 595 straightbred Hereford (HH), straightbred Tarentaise ( TT), and reciprocal-cross (HT) females, randomly mated to HH, TT, or H T bulls, were analyzed for estimates of heterosis and breed additive e ffects for calf traits that included birth weight (BWT), calving diffi culty (DIFF), prebreeding (PRE) and postbreeding (PST) weight, weaning weight (WWT), weaning condition score (WCS), weaning hip height (WHH) , and preweaning average daily gain (ADG). The statistical model inclu ded year, age of dam, sex, regression on age at time of measurement, a nd regressions for the genetic effects of breed individual, breed mate rnal, breed grandmaternal, individual heterosis, and maternal heterosi s. Breed effects were coded to reflect TT HH differences. Age at the t ime of measurement, year, age of dam, and sex were significant for mos t traits. Individual breed effects were important (P < .05) for BWT, P RE, PST, WCS, and WHH but not for WWT, resulting in lower weights, les s condition, and taller animals for TT. Maternal breed effects did not influence BWT, but they were important (P < .05) for PRE,PST, WWT, WC S, WHH, and ADG. Grandmaternal effects were only important for BWT and ADG. Individual and maternal heterosis were important (P < .05) for m ost traits measured, resulting in increased calf size, weight, and bod y condition.