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 samples free from faecal contamination. This technique was used with growing broilers to study the effects of ambient temperature and dietary sodium bicarbonate (NaHCO3) supplementation on the urinary excretion of mineral ions 1.5-2.0 h after feeding. High ambient temperatures resulted in increases in the absolute retentions of sodium, potassium, calcium, magnesium, phosphorus, and sulfur. The lack of any temperature effect on the urinary excretion of the non-monovalent ions indicated that the changes in retentions of these ions were due to changes in absorption. The increase in potassium retention was related to a decrease in urinary excretion, as would be expected for an ion regulated predominantly 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 excretion of sodium. Other minerals were unaffected by NaHCO3 supplementation other than for a marginally significant (P = 0.05) increase in the absolute retention of sulfur. In order to minimise faecal contamination of the urine samples, birds were fasted for 16 h prior to feeding with experimental diets. Possible problems with tissue catabolism were minimised by supplying birds with a glucose-casein solution during the fasting period.