The Effect of the Age of the Assay Bird on the True Metabolizable Energy Values of Feedingstuffs

Abstract

Two experiments were made to measure the effect of bird age on the true metabolizable energy (TME) values of four diets. The diets consisted of a basal supplemented with 10% of beef tallow, rapeseed oil, and wheat shorts. In the first experiment broiler chicks aged 24, 38, and 58 days were used as were adult Single Comb White Leghorn (SCWL) roosters. The second experiment was similar, but the birds used were SCWL males aged 29, 43, and 57 days together with adults. The diets used in the two experiments had the same formulations but were prepared from different lots of ingredients.Most of the variance within the TME data was associated with the differences between the diets. Significant age effects were observed within certain diets but they were not consistent. A simple trend with age was apparent in only two instances; these occurred only in the second experiment. Many of the age effects could be explained by the atypical value of a single treatment group within the diet group. It was observed that TME values for adult birds on the same diet were less variable than those for chicks.It seems probable that TME values obtained with adult roosters can be used in the formulation of diets for younger birds; however, additional confirmatory work is required.