Corn supplementation of lambs grazing alfalfa

We investigated the effects of supplementing Rambouillet X Suffolk wether lambs grazing irrigated 'Cimarron' alfalfa (Medicago sativa L.) with three levels (0 [C(0)], 123 [C(123)], and 247 [C(247)] g of DM.lamb-1.d-1) of cracked corn. Each treatment group also received 190 g of a supplement designed to prevent bloat. Replicated pastures (three per treatment) grown on a fine, mixed, thermic Torretic Paleustoll soil were grazed rotationally (forage plus supplement allowance of 6.5% of BW/d) by lambs for 85 d during spring 1992. Supplemental corn levels were analyzed as single degree of freedom contrasts for linear and quadratic effects. At the start of the experiment, lambs weighed 30.7 +/- 0.32 kg. Average daily gains for C(0), C(123), and C(247) were 141, 154, and 169 g/d, respectively. Lamb production per hectare increased quadratically (P 0.01) with increasing corn level (C(0) [716 kg of lamb/ha], C(123) [816 kg of lamb/ ha], and C(247) [964 kg of lamb/ha]). Supplementation with C(247) vs C(0) increased carcass weights (11%), dressing percentage (6%), and backfat thickness (30%). Plasma urea N (PUN) concentrations did not differ (P 0.10) between C(0) and C(123) after 27 d of corn supplementation, but after 75 d PUN concentrations between C(0) and C(123) had decreased (P 0.10) by 11%. For C(247), PUN concentrations after 27 and 75 d of corn supplementation had decreased (P 0.10) by 17 and 18%, respectively, compared with C(0). Plasma urea N concentrations increased (P 0.01) linearly (r2