Scrotal circumferences from rams lambs were measured at weaning (SCW) and at the end of a 70 d feed test (SCUNA). The scrotal circumferences were also adjusted for body weight (BW) at the end of test (SCADJ). These three dependent variables that were analyzed using MTDFREML procedures to estimate the heritability of scrotal circumference. Body weight at the time of SC measurement was also included as a covariate Also ewe progeny records were collected for number bom per ewe exposed for breeding, ewe body weight, ewe fleece weight and fleece grade. MTDFREML procedures were also used to estimate the heritabilities of the ewe traits and to estimate the covariances between SCW, SCUNA and SCADJ with the ewe traits. Heritability was .19, .30, and .21 for SCW, SCUNA and SCADJ, respectively, when BW was not included and were .33, .31 and .24 for SCW, SCUNA and SCADJ when BW was included as a covariate. Genetic correlations with ewe traits were larger when BW was included in the model and were .20, -.59, -.31 and -.15 for no. bom, ewe body weight, fleece weight, and fleece grade respectively with SCUNA. These results show that scrotal circumference is moderately heritable, and when adjusted for body weight has a positive genetic correlation with number of lambs bom and a negative genetic correlation with ewe body weight, fleece weight and fleece grade.

P. J Burfening, K. C Davis

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 19. Selection and quantitative genetics; growth; reproduction; lactation; fish; fiber; meat., , 284–287, 1994
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