EFFECTS OF AMBIENT-TEMPERATURE ON BROILER MINERAL BALANCE PARTITIONEDINTO URINARY AND FECAL LOSS

1. Two experiments were conducted on control (intact) and colostomised 4 to 7 week old broilers to evaluate the influence of 24 degrees C, d iurnally cycling 24 to 35 degrees C and chronic 35 degrees C ambient t emperatures on broiler mineral balance, urinary and faecal mineral exc retion and urinary osmolar characteristics. 2. In the first experiment , colostomy had no significant effect on mineral balance. However, bro ilers exposed to high cycling ambient temperature reduced their retent ion of phosphorus, potassium, sodium, magnesium, sulphur, manganese, c opper and zinc compared with birds housed at 24 degrees C. 3. Despite the minimal effect of high ambient temperature on urine production, mi nerals excreted disproportionately excreted in urine included potassiu m, magnesium, phosphorus and sulphur while copper and magnesium were l ost primarily via the faeces. 4. In the second experiment, exposure to 35 degrees C increased urine output from 50.7 ml/12 h per kg of body weight at 24 degrees C to 101.3 ml/12 h per kg of body weight and was associated with an increased urine:water ratio and reduced urine osmol ality. 5. Reduced urinary chloride and higher potassium, phosphorus, s ulphur, sodium, magnesium, calcium and manganese excretion was observe d for broilers housed in under high ambient temperatures compared to 2 4 degrees C. 6. These studies suggest that high ambient temperatures a dversely influence mineral metabolism and, furthermore, that the route of excretion varies with the specific mineral and the environmental t emperature exposure.