HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Stobart, R. H. Articles by Bassett, J. W. Search for Related Content PubMed PubMed Citation Articles by Stobart, R. H. Articles by Bassett, J. W.

Relationships between Growth and Productivity of Range Ewes^1,2,

Montana Agricultural Experiment Station, Bozeman 59717 and Texas Agricultural Experiment Station, College Station 77843

Abstract

The relationships between various measures of growth and productivity of range sheep were investigated, utilizing records of 1,109 range ewes sired by 269 rams. Body weights and degree of maturity of body weight at birth, weaning, 12 mo, 18 mo, 30 mo and absolute growth rate, absolute maturing rate and relative growth rate over various age intervals were studied relative to their relationship with productivity characters. Measures of ewe productivity were average annual production for the 4-yr period, 2 through 5 yr of age, for grease fleece weight, number of lambs born, number of lambs weaned and weight of lambs weaned. Heritability estimates were .31 ± .11 for grease fleece weight, .42 ± .12 for number of lambs born, .08 ± .10 for number of lambs weaned and .03 ± .10 for weight of lambs weaned. All production characters had positive phenotypic correlations (.04 to .22) with body weight at all ages. Both number of lambs born and weight of lambs weaned had small, positive phenotypic correlations with growth rates over the 12- to 18-mo age interval. The genetic correlations between ewe productivity and weights at different ages were variable, ranging from –.71 between weaning weight and grease fleece weight to values greater than 1.00 for correlations between weight of lambs weaned and weights at birth, weaning and 18-mo. Degree of maturity at 12 mo had positive genetic correlations with all production characters. Estimated genetic correlations between number of lambs born and absolute growth rate, relative growth rate and absolute maturing rate over the 12- to 18-mo age interval were positive.

¹ The data were made available through a cooperative agreement between the Montana Agric. Exp. Sta. and the Texas Agric. Exp. Sta. Published with the approval of the Director of the Montana Agric. Exp. Sta., Journal Series No. J-1941.

² 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.

³ Present address: Dept. of Anim. Sci., Univ. of Wyoming, Laramie 82071.

⁴ Dept. of Anim. and Range Sci., Montana State Univ., Bozeman 59717.

⁵ Dept. of Anim. Sci., Texas A&M Univ., College Station 77843.