Animal nutrition studies require large resource outlays for paddock and treatment replication to ensure treatment outcomes are valid. In addition to paddock variations there can be large variations in supplement intake if voluntary feeding is paxt of a treatment. To overcome these problems, a technique for trapping grazing sheep at the watering point each day was investigated. Two studies were conducted under dry seasonal conditions, one using pregnant ewes, the other using wethers. Two other studies were conducted under more favourable green pasture conditions, again with pregnant ewes and wethers. In each study, the sheep were educated to enter the yard surrounding the water trough through a trap consisting of two weldmesh panels, each 2m in length. Lucerne hay was used in the first week to coax the sheep between the panels and into the yard. After the education period, treatments were administered to sheep within a race inside the trap yard. In one dry season study some sheep were returning to the trap yard six to eight hours after release. A standard alarm clock was then installed to open this trap at 6.00 a.m., two to three hours before treatments were administered. This procedure was successful in that all sheep continued to be trapped. More than 98% of the sheep were trapped over the treatment period in both dry season studies. However, under green pasture conditions an average of 86% of pregnant ewes and <50% of wethers were trapped. Aversion to the treatments applied in the latter study may have been partly responsible for the poor trapping result which had followed a successful education period. Trapping during dry seasonal conditions offers several advantages for grazing experimentation.

The effect of three different pasture management strategies on liveweight gain and wool growth rate of young(weaner) sheep was examined immediately after weaning on Mitchell grass-Flinders grass pastures during the dry season of north-west Queensland. The pasture management strategies were designed to mimic various industry situations, while the performance of four different progeny groups was compared and used to provide an overall assessment of pasture quality. Pasture treatments (experiment 1) consisted of three paddocks, a harvested (c. 8% of pasture harvested and baled) and spelled, a spelled, and a continuously grazed paddock. Spelled paddocks were not grazed during and after the wet season for a period of six months while the continuously grazed paddock was continuously stocked before the experiment. Experiment 2 consisted of spelled and continuously grazed paddocks. Pastures were evaluated by measuring the changes in composition and quality (experiment 1) and the responses in liveweight gain (experiments 1 and 2) and wool growth of the weaners (experiment 1). Marked improvements (c. 100%) in weaner growth rates occurred in the spelled paddocks. Greasy wool production by three groups of ewes in experiment I was about 14% greater in the harvested paddock than in the others. At the start of the trial there were no significant differences in dry matter yield but a significant difference in botanical composition occurred between paddocks. The changes in dry matter that occurred between the beginning and end of grazing were not significantly different between paddocks. Before gazing, forbs made up approximately 16%, 4% and 1% of pastures in harvested, spelled and continuously grazed paddocks respectively. The change in the percentage forbs that occurred between the beginning and end of the grazing period was significantly greater in the harvested paddock than in the other paddocks indicating preferential selection and intake by sheep. The differences in weaner live weight and wool growth between paddocks suggest that paddock management can improve weaner productivity. The study also indicates that paddock management could be successfully used to increase the percentage of forbs and quality of the pasture during the dry season. The superior wool growth of two progeny groups also suggests that improved productivity of breeding flocks in the tropics is possible if superior sheep can be identified. The results highlight the importance of preferential management of pasture for weaners so that productivity advantages can be exploited.

A yearly management program for sheep in north-west Queensland has increased lambing percentage by > 20% compared with the district average. Greasy wool production of ewes over 4 years (1988-91) averaged 4.3 kg and wethers over 2 years (1990-91) averaged 5.7 kg. Managing sheep using this program increased wool production of the flock compared with the district average. The economic advantages of running breeding ewes or wethers was influenced by wool and sheep markets. During low wool prices ($2.82/kg net selling costs, 1990; $2.44/kg net selling costs, 1991) it was estimated that a 65% lamb weaning rate was needed for returns from the ewe and wether flock to be equal. Gross margins ($/DSE) for the ewe flock were 21.80, 17.07, 8.53 and 5.42 in years 1988, 1989, 1990, 1991 respectively and 5.82 and 5.01 for wethers in 1990 and 1991 respectively. Gross margin ($/DSE) of combined ewe and wether enterprises on properties representing the district, averaged 16.50, 14.20, 8.00 and 5.00 in years 1988, 1989, 1990 and 1991 respectively. The management program implemented at Toorak generated higher gross margins than the district average particularly during the years of higher wool prices.

Three experiments were conducted to provide information on the wool production and reproductive rates of different strains of Merino sheep, and on the role of heat tolerance in determining the productivity of sheep in north-western Queensland. The locally bred Peppin Merinos had a significantly (P<0.05) lower rectal temperature (RT) and respiratory rate (RR) under heat load than the South Australian (SA) strain Merinos. Place of birth of SA Merinos had no effect on their RT and RR. At 16 months of age the Peppin sheep produced significantly (P<0.05) less clean wool (1.55 v. 1.82 kg) and had significantly (P<0.05) lower liveweights (28.5 v. 31.6 kg) than the SA group reared in the same environment. Although differences between the groups were not always statistically significant, there was a trend for a consistent increase in wool production, fibre diameter and liveweight as the proportion of SA in the cross increased. The impact of these differences on proceeds from wool sales is discussed. At maturity the SA strain ewes were heavier (P<0.05) than their Peppin counterparts (48.4 v. 44.1 kg) and produced heavier (P<0.05) lambs at 6 weeks of age (7.0 v. 6.2 kg) and at weaning (13.9 v. 12.5 kg). Milk yield at 6 weeks post-lambing was significantly (P<0.05) greater for the SA sheep than the Peppin Merinos (303 v. 216 mL/day). Lamb survival from 6 weeks to 3 months was 64% for the SA Merinos and 45% for the Peppin Merinos, but this difference was not statistically significant. The SA strain Merinos produced more clean wool and heavier offspring than locally bred Peppin sheep and demonstrated a similar reproduction rate in the face of severe drought conditions.