This paper describes the employment of two experienced graziers as consultants to apply and evaluate a model for calculating 'safe' long-term grazing capacities of individual properties. The model was based on ecological principles and entailed estimates of average annual forage grown (kglha) on the different land systems on each property and the calculation of the number of livestock (dry sheep equivalents, DSE) required to 'safely' utilise this forage. The grazier consultants applied and evaluated the 'safe' grazing capacity model on 20 properties of their choosing. For evaluation, model results were compared with; (a) the Department of Lands rated carrying capacities for those properties and (b) the grazing capacity assessed independently by the owners of those properties. For the 20 properties, the average 'safe' grazing capacity calculated by the model (21.0 DSE/kmZ) was 8% lighter than the average of the owner assessed capacities (22.7 DSE/kmZ), which in tum was 37% lighter than the average of the pre-1989 Department of Lands rated carrying capacity (31.0 DSE/kmZ). The grazing land management and administrative implications of these results and the role graziers played as consultants are discussed.

The botanical composition and nutrient content of diets selected by sheep grazing Mitchell grass (Astrebla spp.) and mulga (Acacia aneura)/grassland pastures in south-west Queensland were studied during a four-year period. Forbs, when present in the sward, contributed significantly to the diets on both grassland types. Under drought conditions grasses were the major components of the diets of sheep grazing Mitchell grassland pastures, while under similar conditions on the mulga/grassland pastures at least 35% of the diet was mulga (Acacia aneura); some mulga was present in the diet at all times. In general, the nutrient content of the green leaves of grasses and forbs growing on the mulga/ grassland association was similar, whereas on the Mitchell grass association green forbs had a higher nutrient concentration than did the leaves of green grasses. Both the grasses and forbs on the mulga/ grassland site had lower P and sodium concentrations than those on the Mitchell grassland site. When seasonal conditions were average to good the concentrations of all nutrients in the diets of sheep grazing the Mitchell grass association were judged to be adequate. However, when the pastures dried out the diets contained low concentrations of N (7.0 g/kg DM), P (0.9 g/kg DM), sodium (O.lg/kg DM) and copper (3.8 mg/kg DM). On the mulga/grassland site dietary concentrations of P and sodium were low at all times and under drought conditions the N:S ratio fell to 16.8:1. The concentrations of other nutrients in the diets were high enough to provide the sheep's theoretical requirements at all times.

Results of a detailed botanical survey in two mulga (Acacia aneura) areas of semiarid south-western Queensland are presented. Two 20 mile belt transects permanently identified for future relocation were used to record woody vegetation. The results for each of the study areas are interpreted by means of association analysis. Several site groups were recognized, in which increasing elevation from the flats to the ridges seems to be the main factor consistent with community changes. The density of seedling and young mulga is considered inadequate for future drought reserves at one site. No large species groups exist on either site, and both areas represent small mosaics. It is suggested that microtopography is an important determinant of species distribution in the sites studied.

The intake and digestion of organic matter and nitrogen by sheep grazing two Mitchell and one mulga/ grassland association was studied under a variety of seasonal conditions. The in vitro digestibility of the diets selected by sheep grazing both pasture types was in the range 60-70% when seasonal conditions were good, but fell to 52.3% and 48.2% for the Mitchell and mulga/ grasslands respectively when the pasture were dry. Digestible organic matter intakes of intact sheep grazing the Mitchell grass pastures were 14.0-16.3 g (kg W)-1 day-1 when seasonal conditions were average to good and 13.5 g (kg W)-1 day-1 after the pastures had dried out. Comparable figures on the mulga/grassland pastures were 17.8-18- 1 g (kg W)- day- with good seasonal conditions and 11.8 g (kg W)-1 day-1 with dry pasture. The nitrogen concentrations in the diets varied from 7 to 26 g/kg OM on the Mitchell grass associations and from 17 to 34 g/kg OM on the mulga/grassland. Apparent digestion of dietary N within the rumen ranged from 70% to 90% on both sites when there was green forage in the diets, but fell to 58.5% and 37.6% on the Mitchell and mulga/grassland respectively when the pastures were drought affected. Under the latter conditions the quantity of amino acid N absorbed from the small intestines was depressed at both sites, as was the efficiency of microbial N production in sheep grazing the Mitchell grass pastures. These findings are discussed in relation to the protein and energy requirements of sheep grazing the two pasture associations.

The lambing performance of a group of ewes grazing a dry Mitchell grass pasture association in central-westem Queensland was recorded and found to be very poor. A portion of the ewe flock received a urea-molasses supplement those ewes did not exhibit an increase in lamb or ewe survival and it is likely that most did not consume the supplement. One week prior to the ewes' expected date of lambing, intact wethers and other wethers with oesophageal fistulas or rumen and abomasal cannulas were grazed on the pasture and the intake and digestion of nutrients by these animals were determined. Extrapolating the results from the wethers to the ewes indicated that the major limiting nutrients for the ewes were energy and, at least during the latter stages of lactation, rumen digestible nitrogen. Other nutrients that may have been deficient in the diet were copper and zinc.