EFFECTIVE RUMEN DEGRADABILITY AND INTESTINAL DIGESTIBILITY OF INDIVIDUAL AMINO-ACIDS IN DIFFERENT CONCENTRATES DETERMINED IN-SITU

Fifteen different concentrates (xylose treated soyabean meal (Soypass) , coconut cake, maize gluten meal, barley, heat treated barley, potato protein (Protamyl), heat treated rapeseed meal, rapeseed meal, heat t reated rapeseed cake, wheat, heat treated wheat, cottonseed cake, palm kernel cake, maize gluten feed and sunflower meal) were examined for effective degradability in the rumen and intestinal digestibility of i ndividual amino acids using in situ methods. The proportions of amino acid (AA) nitrogen (N) in total N in the intact feeds varied from 0.63 in maize gluten feed to 0.88 in Protamyl. Effective AA degradabilitie s calculated at a rumen fractional outflow rate of 5%/h varied from 0. 51 for Soypass to 0.94 for wheat, and were generally similar to effect ive protein degradability, After correction for particulate loss from the nylon bags, effective degradabilities of protein were higher compa red with effective degradabilities of AA due to higher true water solu bilities of crude protein compared with AA. Arginine, cystine and glut amic acid had higher, and valine, isoleucine and threonine had lower, effective degradabilities compared to total AA, Intestinal digestibili ty of total AA in intact feed varied from 0.84 in cottonseed cake to 0 .98 in Protamyl, and generally total AA digestibilities were similar t o protein digestibilities. Glutamic acid and arginine had higher and l ysine, threonine and glycine lower digestibilities compared with total AA.