Apparent ileal digestibility in broilers of amino acids in meat and bone meal.

Abstract

29A Apparent ileal digestibility in broilers of amino acids in meat and bone meal V. Ravindran1, W.H. Hendriks1, D.V. Thomas1, B.J. Camden1, P.C.H. Morel1 and C. Butts2 1 2 Monogastric Research Centre, Massey University, Palmerston North, New Zealand Crop and Food Research, Palmerston Nor th, New Zealand v.ravindran@massey.ac.nz Meat and bone meal (MBM) is an important feed ingredient in poultry diets in Australia and New Zealand. It has a high protein content, but the digestibility of the amino acids can vary greatly. Nineteen MBM samples were obtained from commercial rendering plants in New Zealand and the apparent ileal digestibility of amino acids were determined using 5_week old male broilers. Assay diets were based on maize starch with meat and bone meal, which was the only source of protein, and their proportions were varied to obtain a dietary crude protein level of 16%. Chromic oxide (0.3%) was included in diets as an indigestible marker. The diets were fed ad libitum for three days, and digesta contents from the terminal ileum were collected and processed. Samples of diets and digesta were analysed for amino acids and chromium, and the digestibility values were calculated. Correlations of chemical composition (crude protein, ash and fat) and in vitro assays (protein solubility in 0.2% potassium hydroxide and protein digestibility by 0.2% pepsin hydrolysis) with ileal amino acid digestibility were also examined. Considerable variation was observed in the contents of crude protein (39 to 67%), ash (13 to 57%), fat (4 to 15%) and gross energy (9.4 to 22.3 MJ/kg) of the MBM samples. The ileal digestibility of essential amino acids and amino acid nitrogen (AA_N) also varied substantially (Table 1). The variation was expected because the meals were obtained from rendering plants that used widely differing raw materials and processing procedures. Cysteine, the first limiting amino acid in MBM, had the lowest digestibility values. The only component that was consistently related to amino acid digestibilities was ash content. All the correlation coefficients were negative and all, with the exception of cystine, threonine and histidine, were significant (P<0.05 and P<0.01). Other measurements were not found to be sensitive indicators of variation in amino acid digestibilities. This study was supported by the Poultry Industry Association of New Zealand and the Public Good Science Fund Project. Table 1 Apparent ileal digestibility of essential amino acids in meat and bone meal for broiler chickens. Amino acid Mean � SD1 Correlation with ash _ 0.66** _ 0.37 _ 0.44* _ 0.54* _ 0.73*** _ 0.50* 0.24 _ 0.58** _ 0.17 _ 0.50* _ 0.61** Arginine Histidine Isoleucine Leucine Lysine Methionine Cysteine Phenylalanine Threonine Valine AA_N 1 0.69 � 0.11 0.60 � 0.11 0.67 � 0.10 0.69 � 0.10 0.68 � 0.11 0.73 � 0.10 0.37 � 0.11 0.71 � 0.10 0.60 � 0.10 0.67 � 0.09 0.65 � 0.09 Mean � SD of 19 samples * P<0.05 ** P<0.01 Recent Advances in Animal Nutrition in Australia, Volume 13 (2001)