a1 Department of Animal and Dairy Sciences, Auburn University, AL 36849, USA
a2 Sand Mountain Substation, Auburn University, AL 36849, USA
Broiler poultry litter was deep-stacked (2·5 m high) in three ways: (1) uncovered, (2) covered with 0·1524 mm clear polyethylene and (3) surface-watered to form a 2·5 cm crust upon drying. After 30 days, each litter was used to formulate two diets containing proportionately 0·25 or 0·50 poultry litter (dry-matter basis). Urea was used as the nitrogen source in the control diet. All diets contained 100 g/kg cottonseed hulls, 20 g/kg limestone and cracked maize. Each of the seven diets was offered to 12 crossbred steers (two pens per diet; initial body weight 204 kg) for 84 days. Blood was collected and body weights measured every 28 days. After 84 days, liver biopsies were obtained from four steers per diet and an additional three steers per diet were penned individually and nutrient apparent digestibilities were determined. Steers gained 1·6 kg/day on the urea diet and 1·2, 1·3 and 1·2 kg/day on the diets containing 0·25 litter, uncovered, covered or watered, respectively. Steers consuming the 0·50 litter diets gained 1·0, 0·9 and 1·0 kg/day, respectively (significant linear decrease; P < 0·01). Litter depressed (P < 0·04) apparent dry matter, organic matter and gross energy digestibilities regardless of stacking method. However, nitrogen apparent digestibility was decreased by uncovered and watered litter only. Increased proportion of litter in the diet resulted in increased serum sorbitol dehydrogenase and aspartate aminotransferase and liver copper concentrations (P < 0·07); however, clinical copper toxicosis (haemolytic crisis) was not observed. Dietary inclusion of broiler poultry litter also increased serum phosphorus and decreased serum calcium concentrations (P < 0·07). Covering deep-stacked litter preserved nitrogen quality, but improvements over uncovered litter were not of sufficient magnitude to elicit improved animal performance in this study.
(Received October 20 1992)
(Accepted January 08 1993)
p1 Present address: Upper Coastal Plain Research Station, Rocky Mount, North Carolina, 27801, USA