Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: October 15, 2000
Publication Date: January 27, 2001
Citation: BROWN, M.A., PHILLIPS, W.A., APPEDDU, L.A. ADAPTATION OF DORSET, ST. CROIX, AND CROSSBRED LAMBS TO WHEAT PASTURE. JOURNAL OF ANIMAL SCIENCE. 2001. Vol. 79(Suppl. 2): Abstract p. 10. Interpretive Summary: Abstract Only.
Technical Abstract: Purebred and crossbred stocker lambs (n=59) were used to evaluate adaptation to wheat pasture. Breed groups included Dorset (D), St. Croix (S), Dorset x St. Croix (DS) and St. Croix x Dorset (SD). Fall-born lambs were weaned in December and one-half of each breed group was placed in drylot (DL) or on wheat pasture (WP) in January. Lambs in DL were fed a high roughage diet formulated to approximate lamb gains on wheat pasture. Weight change in DL and WP lambs was measured weekly from January 18 to February 28 after which both DL and WP lambs grazed wheat pasture. From February 28 to March 28, adaptation of DL treatment to wheat pasture was measured. Averaged over breed group, lamb gains on WP were less than in DL for the first three weeks of the trial (P<.05). For the next three weeks, gains were similar between DL and WP treatments, suggesting adaption to wheat pasture had occurred. When both treatments were grazing wheat pasture, DL lambs were lower than WP for the first week (P<.01) and simila thereafter. Based on adaptation results, data were categorized and summarized into three time periods for breed group comparisons: period 1 was the first three weeks; period 2 the second three weeks; and period 3 the last 4 weeks. There was a trend for larger differences in ADG between DL and WP in periods 1 and 3 in D and SD compared to DS and S, but not in period 2. These data suggest up to three weeks are required for stocker lambs to adapt to wheat forage, but adaptation time may be shorter when lambs naive to wheat pasture are mixed with those previously exposed to wheat pasture. Magnitude of adaptation relating to rate of gain within a period may be influenced by animal genetics, but not length of adaptation.