Stocking Rate and Supplementation Effects on Performance of Lambs Grazing Triticale and Ryegrass Sward in Uruguay

An experiment was carried out from 9 June to 2 October 1997, using a Lolium multiflorum Lom. (Ryegrass) and X Triticosecale Wittmack (triticale) sward to evaluate the effect of stocking rate (SR; 20, 30 and 40 lambs/ha), and supplementation (S; with or without) on Corriedale lamb performance. SR had a significant effect on: liveweight gain (160, 130 and 90 g/an/d, P\u3c 0.01); greasy fleece weight (2.8, 2.7 and 2.3 kg, P\u3c 0.01); fiber diameter (28, 27, and 26 microns, P\u3c 0.05); rib eye depth (2.4, 2.1 and 2.0 cm, P\u3c 0.05); fat cover (3.2, 2.1 and 1.5 cm, P\u3c 0.01); hot carcass weight (17.7, 15.6 and 13.5 kg/an, P\u3c 0.01); GR (10.5, 6.6 and 4.2 mm, P\u3c 0.01) and boneless leg weight (1.56, 1.42 and 1.24 kg, P\u3c 0.05), for 20, 30 and 40 lambs per ha, respectively. At the highest SR, lambs increased grazing time (59 vs 52%) and biting rate (29 vs 26 bites/lamb/min). The mayor influence of S on lamb performance was found in grazing behavior variables: (grazing time (63 vs 50%, P\u3c 0.01); biting rate (26.8 vs 28.4 bites/lamb/min, P\u3c 0.01)), carcass characteristics: (hot carcass weight (15.3 vs 16.0 kg, P\u3c 0.05); GR (7.9 and 6.3 mm, P\u3c 0.05)) for with and without supplement, respectively. Over the experimental period (115 days), liveweight production and wool production ranged from 358 to 437 kg/ha for 20 and 30 lambs/ha respectively, and wool production from 55 to 93 kg/ha for 20 and 40 lambs/ha respectively. These results show the potential use of mixed ryegrass and triticale swards to produce high quality lamb meat even at high SRs, and the convenience of using supplements only when sward conditions are not sufficient to maintain an adequate lamb performance, particularly when high lamb SRs are used