Gj. Lee et al., VARIATION BETWEEN MERINO EWES IN PASTURE INTAKE .2. WITHIN-FLOCK GENETIC-PARAMETERS FOR INTAKE AND SOME PRODUCTION TRAITS, Livestock production science, 41(2), 1995, pp. 143-150
Genetic parameters were estimated for pasture feed intake, liveweight,
ultrasonic fat depth, clean wool growth and clean wool growth efficie
ncy of approx. 300 grazing adult Merino ewes in each of 2 years, over
four seasons representing different stages of the annual reproductive
cycle. Measurements were made on a total of 515 individual ewes (with
87 measured in both years), the progeny of 126 sires. The genetic para
meters were estimated using a sire model REML analysis. Digestible org
anic matter intake (DOMI) had a heritability of 0.12 +/- 0.07, pooled
across seasons. Adjusting for liveweight did not affect the pooled her
itability estimate. The pooled heritability estimates for liveweight,
fat depth, clean wool growth and wool growth efficiency were 0.67, 0.4
7, 0.41 and 0.21, respectively. Clean wool growth, liveweight and fat
depth had moderate to strong positive genetic correlations with DOMI i
n all seasons except spring (mid-lactation). Wool growth rate and wool
growth efficiency had a strong positive genetic association (0.77 +/-
0.34, pooled across seasons), as did liveweight and fat depth (0.54 /- 0.14). It was concluded that selection for wool growth will result
in genetic improvement in efficiency and some increase in intake. Opti
mising responses in efficiency will require more precise estimates of
genetic parameters.