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

This Article Full Text 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 Freking, B. A. Articles by Leymaster, K. A. Search for Related Content PubMed PubMed Citation Articles by Freking, B. A. Articles by Leymaster, K. A.

Evaluation of the ovine callipyge locus: IV. Genotypic effects on reproductive traits^1,2

USDA, ARS, US Meat Animal Research Center, Clay Center, NE 68933-0166

³ Corresponding author: freking{at}email.marc.usda.gov

A resource population of ewes derived from Dorset and Romanov grandparents was generated over 5 yr to provide genotypic and phenotypic data to estimate effects of each callipyge genotype on component traits of reproduction. Effects on ovulation rate were estimated from data recorded by examination of ovaries from serially slaughtered ewe lambs (n = 174) born in 1994 and 1995. Productivity and longevity through 5 yr of age were recorded on a total of 265 F₂ ewes produced in 1996 through 1998. Number of lambs born, birth weights, and weaning weights of lambs were calculated for each ewe. Weaning weight was recorded for each lamb and adjusted for age to 56 and 32 d for dam- and nursery-reared lambs, respectively. Longevity was determined as a binary trait based on the presence or absence of the ewe in the breeding flock at 5 yr of age. Ewes generated 937 records for breeding weight and 925 records for conception rate, which was determined on ewes exposed and still present at the start of each lambing season. Seven hundred seventeen records were analyzed for traits based on the number of ewes lambing. Genotypes for the causative callipyge mutation were determined using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry assay. Each ewe was classified into 1 of 4 genotypes; N^MatN^Pat, N^MatC^Pat, C^MatN^Pat, or C^MatC^Pat, where N represents wild type and C represents the mutant allele. The mean ovulation rate of the ewe lambs genotyped N^MatN^Pat was greater (P < 0.02) than that exhibited by N^MatC^Pat; however, the estimated difference of 0.25 ovum in the ewe lambs did not affect the number born. The live weight of N^MatC^Pat ewes at breeding was 2.5 kg less than that of other genotypes (P < 0.01). The callipyge genotype class did not significantly affect conception rates, fecundity, maternal ability, or ewe longevity. Maintaining a ewe flock to produce homozygous mutant rams for use in terminal sire mating systems presents no unusual problems from a reproduction standpoint.

Key Words: callipyge • reproduction • sheep