Bovine Respiratory Disease (BRD) results from a complex, multifactorial interaction of stressors, animal susceptibility, and respiratory pathogens. The infectious agents associated with BRD are ubiquitous among cattle populations. Typically, one or a combination of stressors are necessary to initiate BRD. Prevention of BRD should, therefore, address management procedures to minimise stressors. Administration of vaccines against BRD agents may help reduce the incidence of BRD but is unlikely to eliminate the condition. The effectiveness of antimicrobials in the treatment of BRD depends primarily on early recognition and treatment. The use of antioxidant vitamins, minerals or other agents in the prevention and treatment of BRD warrants further research.

This study indicates that breed can affect growth rate and health, specifically the occurrence of BRD, in Australian domestic feedlot cattle. The moderate correlation between minimum daily temperature and the occurrence of BRD indicates potential associations between climate and BRD incidence in Australian feedlots.

Summary Intakes of milk and milk nutrients were determined for 8 foals at 11–18 days of age and for 10 foals at 30–44 days and 60–74 days of age while sucking grazing mares. Water intakes (sources other than milk) of the foals were determined at 30–44 days and 60–74 days of age. Five of the 10 mares were fed a protein supplement (24% crude protein) in addition to grazing during the stud season. The protein supplement did not influence foal intakes of milk and milk nutrients, milk composition, weight gains of the mares or the growth rate of the foals. Foal milk intakes increased (P<0.05) from 16.9 kg/day at 11–18 days to 18.1 kg/day at 60–74 days of age. The water intakes of the foals increased (P<0.01) from 3.9 kg/day at 30–44 days to 5.5 kg/day at 60–74 days of age. Total fluid intakes per kg foal liveweight were 246, 202 and 172 g at 11–18, 30–44 and 60–74 days of age, respectively. For each kg of weight gain, foals consumed 12.8, 15.7 and 16.4 kg milk at 11–18, 30–44 and 60–74 days of age. Stage of lactation had a significant effect on the total solids, lactose and protein content of milk. The fat and gross energy content of milk remained constant.

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.

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