Heritabilities and Genetic Correlations in Growth and Wool Traits of Rambouillet and Romnelet Sheep

Estimates of genetic parameters and selection strategies to improve the economic efficiency of postweaning growth in lambs1

“…The mean of the feed conversion ratio (gain/feed) for the 6-wk individual feed trial period was 0.116, which is in agreement with the report by Vesely et al (1970) for Rambouillet (0.093) and Romnelet (0.091) ram lambs fed a diet similar to that in the present study. Notter et al (1984) reported feed conversion ratio values for Rambouillet (0.172), Dorset (0.161), and Finnish Landrace (0.133) rams growing in the range of 22 to 38 kg live weight.…”

“…The heritability estimate for mid-test weight was moderate (0.22) and agrees with the review of Fogarty (1995) of genetic parameters for postweaning weights. The heritability estimate for the feed conversion ratio was low (0.10) and in agreement with estimates of 0.06 for Rambouillet and 0.18 for Romnelet ram lambs reported by Vesely et al (1970). Estimates for other species have been low to moderate (0.12 for goats, Khan and Singh, 1995;0.16 and 0.26 for beef cattle, Fan et al, 1995 andBishop et al, 1991, respectively;0.12 for swine, Jungst et al, 1981;and, 0.27 for mice, Sutherland et al, 1970).…”

“…Previously reported heritability estimates for postweaning ADG ranged from 0.21 (Vesely et al, 1970;Mousa et al, 1999) to 0.38 (Harrington et al, 1962). The heritability estimate for ADG during the 6-wk individual feeding period (0.25) was in agreement with 0.27 reported by Leymaster et al (2002) for ADG of composite lambs during a 7-wk postweaning period; however, Francois et al (2002) reported a higher estimate of 0.43 for the French INRA401 breed.…”

Parameter estimates for greasy fleece weight of Rambouillet sheep at different ages.

“…Saboulard et al (1995) estimated direct heritabilities for clean fleece weight to be .60 also for Rambouillet sheep. Vesely et al (1970) estimated heritability to be .31 for greasy fleece weight and to be .23 for clean fleece weight for Rambouillet sheep. Shelton and Menzies (1968) obtained estimates of heritabilities to be .58 by the paternal half-sib method and .52 by the dam-offspring regression method for mean greasy fleece weight for Rambouillet sheep.…”

“…Previous studies have reported estimates of heritabilities and genetic correlations for several traits in sheep (Shelton and Menzies, 1968;Vesely et al, 1970;Coelli et al, 1998). Fogarty (1995) summarized estimates of genetic parameters for live weight, wool, and reproduction traits.…”