Department of Animal Science, Faculty of Agriculture, University of Ibadan, Ibadan, Nigeria
Abstract
Standardised Ileal Amino Acid Digestibility (SIAAD) of maize, wheat, soybean meal (SM), groundnut cake (GC) and rice bran (RB) in broiler finisher diets was investigated. Three hundred and sixty 35-day old Arbor Acre broiler chicks were randomly allotted to a Nitrogen-Free Diet (NFD) and five semi-purified diets containing each of the test feedstuffs (maize, wheat, SM, GC and RB) as the sole source of protein. Diets were fed to ten birds of six replicates up to day-42 in a randomised complete block design. Chromic oxide (5 g/kg) was added to the feed as an indigestible dietary marker. Six birds per replicate were asphyxiated with CO2 and digesta samples were collected from terminal ileum on day 42. The endogenous amino acid losses (EAAL), apparent ileal amino acid digestibility (AIAAD) and SIAAD were estimated. Highest EAAL concentration was found in threonine (0.29g/kg), while glutamic acid and alanine (0.03g/kg) had the least. Total AIAAD were 69.47, 59.49, 70.48, 73.04 and 62.21%, in maize, wheat, SM, GC and RB, respectively. Correspondingly, total SIAAD were 70.86, 61.30, 71.76, 75.13 and 64.05%. Least SIAAD values of amino acids were recorded in wheat compared to the other feedstuffs. Isoleucine had the highest increase in wheat and GC with 3.1 and 3.73%, respectively. In SM and maize, threonine had the lowest increase with 8.0 and 0.94%, respectively. Average increase of SIAAD over AIAAD for indispensable amino acid was 1.58, 1.95, 1.37, 2.24 and 2.10% for maize, wheat, SM, GC and RB respectively. Results from the present study showed that correcting AIAAD for endogenous losses using nitrogen-free method resulted in increased digestibility values for all the feedstuffs.
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