Breeding herd performance and husbandry were surveyed on 375 northern Australian beef properties in 8 regions during 1996 and 1997. Mean branding rates ranged from 62.6% in the Northern Territory to 77.1% in the Maranoa South West regions of Queensland with considerable variation within regional herds. The proportion of herds using controlled mating was highest in the Central Coastal, Central Highlands and Maranoa South West. Mean mating period across all regions varied from 5.6 to 11.8 months. Calving was seasonal with peak activity in the August–December period. Calving commenced earlier in the south (August) than it did in northern regions (September–November). Rainfall influenced the timing of commencement of calving and peak calving activity. The use of pregnancy testing was widespread but selective and often not all females were pregnancy tested. About 97% of properties used weaning strategies with a peak in calf weaning in April–July, and a minor peak in September–October. Although mean weaner ages were similar across regions (5.9–6.9 months), mean weaner liveweight varied markedly with weaners in the more northern regions being lightest (<190 kg) while those in southern regions tended to be >200 kg. Culling criteria for cows and heifers focused on temperament, conformation and reproductive failure; age was also important for cows with a common culling age of 10 years. Bulls were more commonly culled at 7–8 years of age. In addition to age, bulls were culled for physical defects, reproductive problems, temperament and poor quality/performing calves. Four to 5 criteria were commonly used to select bulls. Structural soundness and temperament ranked highest followed by conformation, weight for age, Breedplan and colour. Producers using Breedplan tended to use structural soundness and temperament also as selection criteria. The results suggest that producers associated increasing turn-off weight or decreasing turn-off age more with pasture improvement than with bulls of higher genetic merit for growth. Supplementation of the breeding herd increased in the last half of the calendar year. Supplements containing molasses, urea, phosphate source, salt, and sulphate of ammonia were the most commonly supplied supplementary nutrients. Vaccination for botulism was quite common (>30% of regional survey groups) in all regions except Central Coastal and Maranoa South West regions of Queensland. Comparisons with previous surveys show that there have been marked improvements in breeding herd performance and management over an extended period. The results are discussed in relation to scientific developments over the last 2 decades and future development of the northern Australian beef industry.

In a 15-week animal-house experiment, 24 steers were offered one of six diets based on molasses and ad libitum barley straw. Three levels of dietary nitrogen (N) and three levels of dietary phosphorus (P), in factorial combination, were formulated by the addition of urea, formaldehyde-treated wheat gluten and monosodium orthophosphate. Food intake, liveweight gain, plasma metabolites and P kinetics were measured under dietary regimens similar to those experienced by cattle grazing Australia's northern semi-arid rangelands.The adverse effect of the low dietary N on both liveweight change and feed intake was greater and more immediate than that of the dietary P deficiency. The reduction in feed intake due to the P deficiency approached that caused by the N deficiency after 10 weeks. Under conditions of adequate dietary N, there was a trend for the effects of P deficiency on liveweight gain to be exacerbated. Dietary N and P deficiency reduced the concentrations of plasma urea-N and inorganic P respectively. Dietary N deficiency had no effect on cortical rib bone thickness but P deficiency markedly decreased bone thickness. Faecal endogenous loss of P and P absorption efficiency ranged from 9 to 21 mg/kg LW and 063 to 0-82 respectively for P intakes from 6 to 41 mg/kg LW. Faecal endogenous losses were closely related to dry matter intake and plasma inorganic P together. Dietary N deficiency affected the efficiency of absorption of P.The results of this experiment indicate that cattle consuming diets containing low levels of N and P require supplementary N and P in combination to avoid severe depletion since an increase in N intake alone exacerbated the P deficiency. The results are also discussed in relation to the published findings regarding P metabolism and the implications for the calculation of P requirements.

During 1996 and 1997, a survey examined the business activities of 375 selected northern Australian beef producers during the 1991 and 1992 to 1995 and 1996 financial years. The producers represented a broad cross-section of the northern beef industry in terms of geographical location, size of enterprise and herd, and ownership structures. The survey examined the enterprise structures and herd productivity of the participating properties. A diverse range of production activities were carried out with breeding and finishing, of which breeding stores and live cattle export being the most common activities. About 50% of the survey properties were run in conjunction with another property, both of which tended to be located in the same survey region. The additional properties served various purposes, depending on their location. There was evidence of specialist roles for the additional properties. The purchase of store cattle tended to be an opportunistic activity with younger cattle (<2 years old) being most preferred. Survey properties tended to target a range of markets; Northern Territory and northern Western Australian properties being the most likely to target a single market (live export). Aspiring to supply the slaughter markets was of greatest interest to Queensland beef producers. Aspiring to supply the USA manufacturing beef market was lowest where interest in live export was greatest. During the survey period, the USA manufacturing beef market, store and live cattle export markets were important outlets for cattle. Many herd and pasture-related improvements were planned to boost profitability in the 5 years post-survey (1997–2002). Increasing turn-off weight and branding rate, and decreasing turn-off age were of greatest interest to surveyed beef producers. Pasture improvement and improving pasture management also rated highly. The survey data indicated that the female genotype of the northern Australian herd had changed significantly over a 10- and 30-year period, with Bos indicus, Bos indicus cross and Taurindicus breeds being the most commonly reported breeds. The bull breeds present in regional herds suggest crossbreeding is occurring in conjunction with pure breeding. Most herds had more than 1 bull and female breed. Regional patterns were also found to exist for female and bull breeds with Bos indicus being common in herds in the northern parts of the survey area and Taurindicus breeds popular in southern herds. The results of this survey are discussed in relation to future developments in the northern Australian beef industry.

The herd performance of 375 northern Australian beef producers during the 1991 and 1992 to 1995 and 1996 financial years was surveyed in 1996 and 1997. Estimates were made of annual liveweight gain from production systems based on native and improved pastures together with hormonal growth promotant use and supplementation practices. The most commonly used pasture communities for growing and finishing cattle were black speargrass and brigalow communities in Central Coastal Queensland and the Central Highlands; black speargrass in Northern Queensland; Mitchell grass and gidgee in Central Western and North-west Queensland; Mitchell grass in the Northern Territory and northern Western Australia regions and brigalow–softwood scrub in the Maranoa South West. There was considerable variation and overlap in the production ranges of the various pasture communities. The estimates and ranges of annual liveweight gains were comparable with measurements from scientific and commercial studies for 3 major pasture communities (black speargrass, brigalow and Mitchell grass). On this basis, the annual liveweight gain data are considered to represent sound estimates of performance from the pasture communities and husbandry systems in use in northern Australia. Mean annual gains for pasture communities in the more northern regions tended to be <150 kg/year. Half the survey group used hormonal growth promotants but use varied between regions with lowest levels in Central Coastal Queensland (30%) and highest usage in the Central Highlands (59%). Steers and bullocks were the most commonly implanted class of cattle. Supplementation periods tended to be longest in more northern regions. Nitrogen was a component of >90% of the supplements offered. The percentage of producers supplementing various classes of cattle varied widely (0–77%). Steers were often the least supplemented class and weaners were the most common. The highest percentage of producers (>68%) supplementing weaners was found in North-west and Northern Queensland, the Northern Territory and northern Western Australia. Significant correlations explaining 3–23% of the variance were found between annual liveweight gain and latitude and/or longitude for native black speargrass and Mitchell grass pasture communities and improved brigalow pastures. Generally, annual liveweight gain increased with increasing latitude and longitude. The results are discussed in relation to herd management practices and sources of variation in the northern Australian production environment.

The results of six experiments on growing cattle weighing 140-480 kg, and with liveweight gains of -0-46 to 1-11 kg/day, were reanalysed to provide estimates of their phosphorus (P) requirements. The 158 data sets were from individually penned cattle offered barley straw-based diets ad libitum with dry matter digestibilities of 0-53-O-65, or from cattle grazing tropical pastures with in vitro dry matter digestibilities ranging from 0-50 to 0-62. Various concentrations of dietary energy, nitrogen (N), calcium (Ca) and P were imposed during the course of the experiments with the penned cattle and various rates of application of P fertilizer changed the botanic and nutrient composition of the forages available to the grazing cattle. The P balances and P kinetics of the cattle were studied using 32 P as a tracer. Over the range of P intakes normally observed in cattle consuming forage diets (10-60 mg/kg LW), the coefficient of P absorption was high and not affected by age or liveweight. The regression coefficient relating P intake to P absorption was 0-77 for unsupplemented grazing cattle and 082 for penned supplemented cattle. When the plasma inorganic P concentrations were < 50 mg/1, urinary P excretion of the penned cattle was low, as were the endogenous faecal P losses of both the penned and grazing cattle. These losses were concluded to represent obligatory losses and were related to dry matter intake (r = 0-73) in the range 9-17 mg P/kg LW.The total P requirements of growing cattle were estimated as g/day and g/kg DM intake from this data. The requirements of cattle consuming forage diets were 40-50% lower than those published by the Agricultural and Food Research Council (AFRC 1991), even though the same equation for the net requirements for growth was utilized.