Ruminal Degradation and Intestinal Absorption of Alfalfa Protein Concentrate by Sheep

Mature wethers were fitted with duodenal reentrant cannulas and used to evaluate alfalfa protein concentrate as a protein supplement for ruminants. Isofermentable diets containing 0, 9, 18 and 27% alfalfa protein concentrate were fed. Levels of dietary crude protein were 13, 14, 18 and 22%. Dry matter intake averaged 930, 912, 934 and 879 g/d with the four diets. Duodenal digesta flow decreased (P<.05) from 10.4 to 7.0 liters/d as dietary crude protein increased. Duodenal digesta flow was positively correlated to intake of acid detergent fiber (r = .88, P<.001). Protein and fiber effects on flow were confounded. Organic matter digested in the stomach averaged 393 to 462 g/d, while 47 to 59% of the organic matter reaching the duodenum disappeared in the intestines. Total N and honammonia N flow to the duodenum did not increase with increasing intake of N. Bacterial N flow to the duodenum and bacterial N synthesis (grams bacterial N/100 g organic matter digested) decreased as intake of N and(or) alfalfa protein concentrate increased. Approximately 44% of alfalfa protein concentrate escaped microbial degradation in the rumen. Total or individual amino acid flow to the duodenum (grams/day) did not increase with increasing N intake. Between 77 and 81% of the amino acids reaching the duodenum disappeared in the intestines. Essential and nonessential amino acids appeared to be equally absorbed.