A NOTE ON THE EFFECT OF LAMB GROWTH-POTENTIAL, LITTER SIZE, AND CONCENTRATE SUPPLEMENTS ON PERFORMANCE OF LAMBS AND LACTATING EWES CONSUMING LOW TO MODERATE QUALITY GRASS HAY

Thirty-eight multiparous St. Croix ewes bred to Romanov or Suffolk ram s were used in an 8-week experiment beginning 2.9 +/- 0.15 days after parturition to determine effects of sire breed (i.e., lamb growth pote ntial), litter size (i.e., single vs twins), and different supplementa l concentrate treatments on ewe and lamb performance. Wheat hay (10% c rude protein and 71% NDF; DM basis) consumed ad libitum by ewes and la mbs was supplemented for ewes (DM basis) with: 0.25% body weight (BW) of ground maize (control); 1.25% BW of maize, 0.3% BW of a mixture of fish (38.8%), blood (30.6%), and feather meals (30.6%; MR); or 1.25% B W of maize alone in weeks 1 to 3 and with high-protein feedstuffs in w eeks 4 to 8 (M-MR). Control ewe BW decreased during the experiment at a rate of 67 g/day, whereas BW change for MR and M-MR treatments was 1 6 and -8 g/day, respectively (control vs MR and M-MR, P < 0.05; SE 7.8 ). Lamb BW gain also was lower for control than for MR (P < 0.05) and M-MR (P = 0.08), 144, 205, and 190 g/day for control, MR, and M-MR, re spectively (SE 12.9). Lamb BW gain was greater (P < 0.05) for Romanov- vs Suffolk-sired lambs (196 vs 163 g/day; SE 8.7) and for single than for twin lambs (198 vs 162 g/day; SE 9.0).