EFFECT OF TEMPERATURE AND DIETARY-SODIUM BICARBONATE SUPPLEMENTATION ON THE MINERAL EXCRETION OF BROILERS

A non-surgical technique was developed for the collection of urine sam ples free from faecal contamination. This technique was used with grow ing broilers to study the effects of ambient temperature and dietary s odium bicarbonate (NaHCO3) supplementation on the urinary excretion of mineral ions 1.5-2.0 h after feeding. High ambient temperatures resul ted in increases in the absolute retentions of sodium, potassium, calc ium, magnesium, phosphorus, and sulfur. The lack of any temperature ef fect on the urinary excretion of the non-monovalent ions indicated tha t the changes in retentions of these ions were due to changes in absor ption. The increase in potassium retention was related to a decrease i n urinary excretion, as would be expected for an ion regulated predomi nantly by the kidneys. However, no effect of temperature was observed on the urinary excretion of sodium. Sodium bicarbonate supplementation resulted in an increase in both the absolute retention and urinary ex cretion of sodium. Other minerals were unaffected by NaHCO3 supplement ation other than for a marginally significant (P = 0.05) increase in t he absolute retention of sulfur. In order to minimise faecal contamina tion of the urine samples, birds were fasted for 16 h prior to feeding with experimental diets. Possible problems with tissue catabolism wer e minimised by supplying birds with a glucose-casein solution during t he fasting period.