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The objectives were to determine the association of maturing patterns with growth rates and body weights and to estimate heritabilities and genetic and phenotypic correlations among these characters of sheep. Records of 1,109 range ewes from the Montana Agricultural Experiment Station Red Bluff Research Ranch at Norris were analyzed. Body weight and degree of maturity of body weight at birth, weaning, 12 mo of age, 18 mo of age and maturity (body weight only), and absolute growth rate (AGR), absolute maturing rate (AMR) and relative growth rate (RGR) over various age intervals were examined. Mature weight, required to calculate degree of maturity and AMR, was estimated by the average of the fall weights taken at 42, 54, 66 and 78 mo of age. Heritability estimates were .53 +/- .12 for mature weight and from .26 to .46 for immature weights. Genetic correlations among body weights at all ages were positive and generally large between immature weights and mature weights. Heritability estimates for degree of maturity ranged from .63 +/- .12 at 12 mo of age to .19 +/- .11 at 30 mo of age, at which time maturity was being approached. Genetic correlations between degree of maturity and body weight at the same age were positive; however, degree of maturity at all ages was negatively correlated with mature weight. Animals more mature at any age or stage during growth tended to be more mature at later stages, to be lighter at maturity, and to grow faster and weigh more up to 12 mo of age. Heritability estimates for AGR, RGR and AMR were moderate to high and were similar for the same age intervals. Selection for any one of the measures of growth rate would tend to expand the shape of the growth curve toward heavier weights and lower degree of maturity for any interval.

Birth weights (BW) and weaning weights (WW) of 4,423 non-creep-fed Hereford calves were used to estimate direct and maternal sources of variation and maternal phenotypic effects (fm). Seventeen different (co)variances among relatives were estimated through Henderson's Method III and restricted estimated maximum likelihood procedures. Direct and maternal (co)variances and fm were evaluated by multiple regression procedures. Estimates of h2 for BW and WW were .28 and .28 respectively, by the paternal half-sib procedure and .45 and .88, respectively, based on full-sibs. Repeatability estimates were .21 for BW and .30 for WW. Heritabilities based on regression of offspring on dam and offspring on sire were .45 and .21 for BW and .28 and .06 for WW, respectively. Negative correlations were found between solutions for additive genetic direct and additive maternal effects (rG). Estimates of rG ranged from -.86 to -1.05 for BW and from -.57 to -.79 for WW. Estimates of heritability for direct effects (h2o), for maternal effects (h2m) and for total additive genetic effects (h2T) were .16 to .27, .18 to .63 and -.02 to .05 for BW and .26 to .32, .27 to .67 and .10 to .20 for WW. Dominance affected both direct and maternal effects for BW and WW. Values of -.15 (BW) and -.25 (WW) were found for fm (path coefficient between the maternal phenotypes of dam and daughter). These results indicated that selection response would be decreased due to the negative genetic correlation between direct and maternal effects.

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