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ARS Home » Pacific West Area » Dubois, Idaho » Range Sheep Production Efficiency Research » Research » Publications at this Location » Publication #148395
Title: GENETIC RELATIONSHIPS BETWEEN EWE MATURE SIZE AND MEASURES OF LAMB FEED EFFICIENCY AND POSTWEANING GROWTH IN TARGHEE SHEEP

Author
item Woodward, Brent
item Snowder, Gary

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/4/2003
Publication Date: 4/4/2003
Citation: Woodward, B.W., Snowder, G.D. Genetic relationship between ewe mature size and measures of lamb feed efficiency and postweaning growth in Targhee sheep. Journal of Animal Science. 2003. v. 81 (Suppl.1) p. 253.

Interpretive Summary:

Technical Abstract: The purpose of this study was to estimate the genetic relationships between ewe mature size and measures of lamb feed efficiency and postweaning growth in Targhee sheep. Mature size (weight) was the average fall weight after weaning for ewes with records from age 3 to 6 yr born between 1977 and 1983 (n = 373). Overall average mature weight was 69.3 ± 0.39 kg. Ram and ewe lamb data collected from 1978 to 1984 were used to estimate residual and total feed intake, gain to feed ratio (952 records), and postweaning ADG (1,047 records). Approximately 21 d after weaning, lambs were group fed for 4 wk, and then individually fed for 6 wk before returning to group feeding for another 4 wk. Overall average total feed intake, gain to feed ratio, and ADG were 89.5 ± 0.5 kg, 0.116 ± 0.001, and 0.250 ± 0.002 kg/d, respectively. Estimates of heritabilities and correlations were obtained by running two-trait animal models using REML. The single-trait model heritability estimate for mature weight was 0.66, which was similar to two-trait model estimates (0.60 to 0.66). Genetic correlations of mature weight with residual feed intake, total feed intake, gain to feed ratio, and ADG were 0.22, 0.53, 0.50, and 0.63, respectively. Heritability estimates for these same traits from the two-trait models were 0.28, 0.32, 0.11, and 0.38, respectively. Environmental correlations were low (-0.23 to 0.14). Estimated genetic parameters suggest selection could improve feed efficiency and postweaning growth, with associated changes in mature size. Selection against residual or total feed intake would be accompanied by a corresponding decrease in mature size. Conversely, selection for increased gain to feed ratio and ADG would indirectly increase mature size. Appropriate use of selection pressure through a selection index, for example, could result in increased feed efficiency and postweaning growth, while maintaining mature size and(or) moderating the amount of change in mature size.