Subjective assessment is emphasized in the breed improvement of South African Dorper sheep. Data from the National Small Stock Improvement Scheme yielded estimates of 0.190.02 for h2, 0.100.02 for m2 and 0.070.01 for c2 in the case of weaning weight (WW). Estimates for post weaning weight (PWW) were 0.230.03 for h2 and 0.140.02 for m2. Estimates of h2 for reproduction traits were low, ranging from 0.04 to 0.07. For the type traits, estimates of h2 were low for conformation (0.11) and type (0.10), while size was moderately heritable at 0.250.02. Conformation and type were favourably correlated to WW and PWW, the correlation ranging from low to moderate. These traits were unfavourably correlated to TWW. Realised genetic trends (per annum) were 0.009 kg for direct WW, 0.009 kg for maternal WW, 0.11 kg for PWW and -0.03 kg lamb per ewe lambed for TWW. It seems reasonable that slow genetic gains in production traits (and a lack of progress in reproduction) could be attributed to type traits being overly accentuated.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 04.10, 2006
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