| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Texas Agricultural Experiment Station, College Station 77843 and Montana Agricultural Experiment Station, Bozeman 59717
Abstract
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.
1 The data were made available through a cooperative agreement between the Montana Agr. Exp. Sta. and the Texas Agr. Exp. Sta. Published with the approval of the Director of the Montana Agr. Exp. Sta., Journal Series No. J 1740.
2 Appreciation is expressed to Mr. J. L. Van Horn for his foresight and dedication in collecting and maintaining the mass of data required for this study and to Dr. P. J. Burfening and Mr. K. L. Colman for maintaining the data set.
3 This study was supported, in part, by the United States Agency for Int. Dev. Title XII Small Ruminant Collaborative Res. Support Program under Grant No. AID/DSAN/XII-G-0049.
4 Present address: Dept. of Anim. Sci., Univ. of Wyoming, Laramie 82071.
5 Dept. of Anim. Sci., Texas A&M Univ., College Station 77843.
6 Dept. of Anim. and Range Sci., Montana State Univ., Bozeman 59717.
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
