A comparison of the amounts of energy and nitrogen voided as excreta by cockerels housed over trays or fitted with harnesses and plastic collection bags.

Three experiments using adult Single Comb White Leghorn cockerels were made to compare the amounts of energy and nitrogen voided as excreta when collected either in plastic bags held in place by harnesses (H) or on trays placed below the wire-floored cages (T). In the first experiment, previously fasted birds were given, by intubation into the crop, 30 g of ground yellow corn or meat meal; other birds continued to be fasted. Excreta were collected for 48 h. The second experiment was similar but included five feedingstuffs and a second excreta collection was made on trays during the 48 to 72-h period postfeeding. The third experiment also involved 0 to 48 and 48 to 72-h collections but the input was a laying hen diet in amounts ranging from 0 to 50 g by 10 g increments. Birds fitted with harnesses voided less excreta energy than T-birds but the output of excreta nitrogen was independent of the collection method. The differences between H and T-birds were independent of the nature and amount of feed input. Removal of harnesses resulted in compensatory excreta energy output in the subsequent 24 h. The H minus T differences were not attributable to outliers within a group because variances were generally similar among collection methods. The reduced excreta energy outputs of H-birds tended to cause higher estimates of true metabolizable energy for the feedingstuffs but the effect was modified because both fasted and fed birds were affected by the harnesses.