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 distress 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 less than .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 less than .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.

Effect of dietary acidification and alkalinization on urolith formation and renal function in Single Comb White Leghorn laying hens.

One of the major causes of mortality in poultry is urolithiasis. Although two of the major causes of urolithiasis have been defined, active and preventative treatments for this disease have not been extensively field tested. Previous research demonstrated that a diet acidified with NH4Cl was effective in preventing the formation of uroliths in 16-wk-old pullets. In the present study, experiments were designed to evaluate the effects of dietary acidification and alkalinization on preformed uroliths in mature laying hens. Urolithiasis was induced by feeding excess dietary Ca (in commercial layer ration) during pullet growout (6 to 18 wk of age) and during the early laying period (18 to 32 wk of age). At 32 wk of age birds were randomly divided into three diet treatment groups: a normal layer ration group, an acidified layer ration group (1% NH4Cl added); and an alkalinized layer ration group (1% NaHCO3 added). Each group received the respective diets until 52 wk of age, when the experiment was terminated. Blood gas analysis at 44 wk of age demonstrated that hens fed the acidified diet had significantly higher blood H+ concentrations, lower blood bicarbonate concentrations, and lower total blood carbon dioxide levels than hens fed the alkalinized layer ration. At 52 wk of age, hens fed the acidified layer ration had higher urinary H+ concentrations, higher blood H+ concentrations, and lower blood HCO3 and total CO2 concentrations than hens fed the normal and alkalinized layer rations. The acidified layer ration group had no uroliths present in their ureters (0% urolithiasis), whereas the normal and alkalinized layer ration groups had 8.3 and 13.1% incidences of urolithiasis.(ABSTRACT TRUNCATED AT 250 WORDS)