Digestibility of bacterial protein grown on natural gas in mink, pigs, chicken and Atlantic salmon

The composition and amino acid digestibility of bacterial protein meal (BPM ) produced by Methylococcus capsulatus (Bath), Alcaligenes acidovorans, Bac illus brevis, and Bacillus firmus grown on natural gas were studied. The BP M contained 959 g kg(-1) dry matter, 702 g k(-1) crude protein, 103 g kg(-1 ) fat, and 95 g kg(-1) nucleic acids. The amino acid composition of BPM was similar to that of fish meal, except for less lysine (6.1 vs. 8.6 g/16 g N ) and more tryptophan (2.1 vs. 0.9 g/16 g N). Total tract apparent digestib ility (TTAD) in mink, chickens and pigs, and apparent ileal digestibility ( AID) in pigs, were obtained by feeding BPM as the sole source of protein. I n salmon, TTAD was measured by regression, using diets where BPM substitute d fish meal. The average TTAD of total N from BPM was 79.0%, 85.4%, 80.5%, and 81.9% in mink, pigs, chickens and salmon, respectively. Ileal N digesti bility in pigs was 78.1%. There were substantial differences among digestib ilities of individual amino acids. Arginine and lysine revealed the highest digstibilities and cystine the lowest. The average TTAD coefficients for l ysine were 88.7%, 89.2%, 82.6% and 91.7% in mink, pigs, chickens and salmon , respectively, whereas lysine AID in pigs was 84.5%. Average TTAD for cyst ine was 47.2% in mink, 77.0% in pigs, 44.7% in chickens and 51.9% in salmon . Cystine AID in pigs was 54.9%. Methionine showed TTAD values ranging from 80.9% in chickens to 84.5% in mink, and a pig ALD of 83.8%. There were hig hly significant correlations among the TTAD coefficients of BPM in mink, ch icken and salmon, and among the latter figures and AID in pigs (p<0.001). A lthough highly significant, the TTAD coefficients in pigs were less correla ted to TTAD in mink, chickens and salmon than pig AID (p<0.001). It appears that small intestine digestion and overall uptake of amino acids from BPM were similar among the investigated species. (C) 1998 Elsevier Science B.V.