Supplementary feeding of Merino wethers grazing weed-free stubble pastures

Abstract

A field trial was conducted in the Wimmera region of Victoria to investigate the effect of several supplements on 4-year-old Merino wethers grazing a weed-free wheat stubble for 3 months, The four treatments were: a control (no supplement), urea/molasses block, 100 g/head day-1 of lupin grain, and 2 g urea plus 0.5 g Na2SO4 l-1 in the drinking water. Twenty sheep per treatment were used, and liveweight change and wool growth were measured. Although all groups lost weight, the lupin group lost only 0.5 kg per head over the 3 months of the trial, and was 3.8 kg heavier (P <0.01) than the control group, while the urea/molasses group was 2.2 kg heavier (P <0.01) than the control group. There was no effect of the urea plus sulfur supplement in the drinking water on liveweight or wool production. The urea/molasses block did not affect wool production but lupin grain stimulated wool production by 0.08 kg (P <0.05). The sheep were weighed and shorn four and a half months after the trial (August), during which time all groups grazed together on green feed. The experimental liveweight differences had disappeared, apparently due to compensatory growth. In addition, a digestibility trial was conducted in an attempt to explain some of the field results. The treatments were designed to simulate those used in the field. Lupin grain stimulated intake by 129 g day-1 (P <0.05) but had no effect on apparent digestibility of straw. The treatment simulating the urea/ molasses block (urea plus sulfur plus sucrose in the drinking water) stimulated intake by 159 g day-l (P <0.05) and tended to increase digestibility (P > 0.05). It was concluded that supplementary feeding of Merino wethers grazing weed-free stubble is unlikely to be an economic farm practice.