MINERAL BALANCE AND URINARY AND FECAL MINERAL EXCRETION PROFILE OF BROILERS HOUSED IN THERMONEUTRAL AND HEAT-DISTRESSED ENVIRONMENTS

Two experiments were conducted utilizing 4- to 7-wk posthatching Vantress x Arbor Acres male broilers to-evaluate heat di effects on mineral balance partitioned into urinary and fecal loss. In the first study, 8 colostomized and 14 intact birds were allotted to two environmental chambers maintained at either a thermoneutral temperature (24 C) or a cycling temperature heat distress (24 to 35 C) in a switch-back design. Birds were precision-fed 2% of body weight thrice daily to equalize consumption prior to and over each 48-h experimental period. Feces and urine for colostomized birds and total excrement for intact birds were collected and analyzed for mineral content. Averaging across surgical classification, heat distress increased (P < .05) excretion of K, P, S, Mg, Cu, Mo, and Zn. Despite little heat distress effect on urine production, minerals disproportionately excreted in urine included K, Mg, P, and S; Cu and Mg were lost primarily in feces. In the second study 42 colostomized birds were used to expand the urinary excretion data with the period of heat distress held at 35 C for 36 h. Heat distress increased (P < .05) urine output from 52.3 +/- 5.3 to 109.9 +/- 4.5 mL/12 h and also increased total urinary K, P, S, Na, Mg, Ca, and Mn excretion. The present data provide evidence that heat distress adversely impacts bird mineral balance and that the excretion route for this effect varies with the specific mineral and possibly, heat distress severity.