SummaryThe effects of coat colours on thermal balance, behaviour and weight gain were studied. Measurements of thermal balance were made over 36 days in strong sunshine on highly contrasting coat colours of three white and three dark steers in each of two breeds, Brahman (B) and Shorthorn (S), and three light- and three medium-red steers in Brahman Hereford-Shorthorn cross breed (BX) where there was less contrast in coat colour. Each steer was measured for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. For B, the difference between colours in mean rate of environmental heat gain at the skin was 64 ± 22·5 W/m2 and for S, 44 ± 20·5 W/m2, while the difference in mean rate of evaporative heat loss, between colours for B and S respectively was 44 ± 15·1 and 42 ± 14·3 W/m2. However, only within S was rectal temperature significantly higher in steers which were dark red and the reasons for this are discussed. Within BX the range of colour shades diminished during the experiment so thermal effects of colour were small. Colour had significant effects on growth; these effects were greatest in S where white steers gained 0·13 kg more per day than dark red ones. There were also differential effects within colour groups on activities at pasture; light steers spent more time in the sun and grazing than dark ones. In addition to colour, deep or woolly type coats negatively affected growth (P < 0·05), time spent in the sun (P < 0·05), and grazing time (P < 0·05); however, between animals within breeds the magnitude of the adverse effect of coat type on growth and behaviour was greater in dark- than light-coloured steers. These results provide evidence that coat colour is a trait which, interacting with coat type, exerts an influence on performance of cattle under heat stress.

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.

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SUMMARYSweating rates were analysed in relation to rectal temperatures of cattle to yield a measure of sweating response within and between animals. The measurements, performed over 36 days, were done in a natural radiant environment on six steers in each of three breeds, Brahman (B), Brahman × Hereford–Shorthorn cross-breds (BX), and Shorthorn (S). Each steer was recorded for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. Sweating response, e.g. the linear slope of the relationship between sweat rate and rectal temperature, was greater for B (294 g/m2. h/°C) than for BX (146 g/m2.h/°C) or S (194 g/m2.h/°C) which did not differ; this helped to explain why the range and mean rectal temperature in B were lower and little affected by environmental heat. Curvilinear models of the sweating response indicated that in the environmental conditions of this study, the limit of sweating for B and BX was not reached, while for S, the sweating response approached a plateau. Between animals, the relationship of sweating response to mean rectal temperature was negative (P < 0·01) and its relationship to the time spent in the sun at pasture positive (P < 0·025). Thus this measure of sweating response was a good indicator of thermoregulatory ability of the cattle. However, the sweating response of the steers did not relate to their grazing time or growth. The reasons for this are discussed. Finally, the sweating response was found to be negatively correlated with metabolic rate between animals within breeds (P < 0·01) and this suggested that it may be difficult to combine the desirable traits of good heat adaptation and high metabolic potential in cattle.

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.