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D. J. Burton, P. A. Ludden, R. H. Stobart, B. M. Alexander, 50 years of the Wyoming ram test: How sheep have changed, Journal of Animal Science, Volume 93, Issue 3, March 2015, Pages 1327–1331, https://doi.org/10.2527/jas.2014-8150
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ABSTRACT
Production characteristics of white-faced rams have been systematically evaluated over a 140-d test in Wyoming since 1961. Individual test records (n = 4,240) from rams on test were analyzed to determine change over the past 52 yr. Although rams on test are not older, weight on and off test has increased (P < 0.001) since 1961. Weight off test increased 22.7 kg and contributed to an increase (P < 0.001) in clean fleece weight. Rate of gain (P < 0.001) almost doubled over this 50-yr period. Growth efficiency improved from 0.23 ± 0.01 kg/d from 1961 to 1966 to 0.39 ± 0.01 kg/d from 2008 to 2013. Cubic, rather than linear, effects better explain the change in growth characteristics, suggesting a plateau or tapering of these traits. Wool characteristics remain an important component of the test index, and despite increases in body size and gain, wool diameter was unchanged (P > 0.15). Average daily gain correlated (r2 > 0.67; P < 0.001) with lamb and feeder lamb price, with the strongest correlation at a 2-yr (r2 > 0.76) time lag. U.S. sheep inventory was negatively correlated (r2 > −0.72; P < 0.001) with sheep price and ADG, with the greatest correlation at no time lag. Wool price 0, 2, or 5 yr prior did not correlate (r2 < 0.1; P ≥ 0.5) with spinning count. Influences on white-faced ram selection appear to have largely impacted growth traits while avoiding negative impacts on wool quality.
