The effect of oral administration of methionine, bentonite, methionine/bentonite and methionine/oil homogenates on wool production of grazing and penned sheep in a semi-arid tropical environment

Abstract

Penned and grazing sheep were supplemented in 3 experiments with either methionine (Me 2.5 g/sheep.day), bentonite (Bent 5 or 10 g), Me + Bent (1 : 2 and 1 : 4) or Me/oil homogenates. These supplements were added to the drinking water or in molasses-based licks for treatment periods of 4-6 weeks duration. The effects of supplements on wool growth, liveweight, and ammonia concentration in rumen liquor were determined. In experiment 1, penned sheep fed a maintenance diet (750 g/sheep.day) of pelleted lucerne and supplemented via the drinking water, showed increased (P<0.05) mean wool growth for the 4 treatment periods of 31% (Me + bent), 16% (Bent), 18% (Me/tallow) and 21% (Me). Factorial analysis revealed main effects of 12% for bentonite (P<0.05) and 17% for Me (P<0.01) supplements. In experiment 2, grazing sheep supplemented via the drinking water, increased (P<0.01) wool growth over 5 treatment periods by up to 32% (Me + bent), 15% (Bent), 20% (Me) and 26% (Me/oil). In experiment 3, penned sheep fed a maintenance diet of pelleted lucerne were supplemented with molasses licks containing Me, Bent, or Me + bent, mixed using either artesian bore water or rain water. No individual treatment effect on wool growth was recorded. However, factorial analysis revealed an 18% wool growth advantage (P<0.05) for bentonite supplements mixed in artesian bore water. Treatment had no consistent effect on liveweight of sheep or level of ammonia in rumen liquor. Responses in wool production to supplements were greatest when rumen ammonia values were >5 mg%. Considerable variation in apparent wool response occurred between treatments and treatment periods for both bentonite and methionine supplements. The greatest responses to methionine supplements occurred in experiments 1 and 2 when basal wool production in the control treatments was lowest. The homogenisation procedures used to prepare Me/oil supplements, did not demonstrate any consistent advantages in terms of extra wool response.