title: 50 years of the Wyoming ram test: How sheep have changed.
abstract: Production characteristics of white-faced rams have been systematically evaluated over a 140-d test in Wyoming since 1961. Individual test records ( = 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 ( < 0.001) since 1961. Weight off test increased 22.7 kg and contributed to an increase ( < 0.001) in clean fleece weight. Rate of gain ( < 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 ( > 0.15). Average daily gain correlated ( > 0.67; < 0.001) with lamb and feeder lamb price, with the strongest correlation at a 2-yr ( > 0.76) time lag. U.S. sheep inventory was negatively correlated ( > -0.72; < 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 ( < 0.1; ≥ 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.
authors.forename: D J
authors.initials: DJ
authors.lastname: Burton
authors.forename: P A
authors.initials: PA
authors.lastname: Ludden
authors.forename: R H
authors.initials: RH
authors.lastname: Stobart
authors.forename: B M
authors.initials: BM
authors.lastname: Alexander
mesh_terms: D000818:Animals; D001835:Body Weight / Q000235:genetics* / Q000502:physiology*; D001947:Breeding; D008297:Male; D012756:Sheep / Q000235:genetics* / Q000502:physiology*; D013997:Time Factors; D014935:Wool / Q000254:growth & development*; D014959:Wyoming