[The effect of physical shape of dried green feed and of various sources of starch on the site of digestion of carbohydrates and proteins and on the protein synthesis in the cow rumen].

The experiments were performed on cows with duodenal bridge fistulae to study the influence of the physical form of roughage (forage rye, chopped or pelleted) and of the starch source (barley or maize) on the place of carbohydrate digestion and on microbial protein synthesis. The organic matter digested in the stomachs contained more than 90% carbohydrates. Their digestibility was not found to be influenced by the physical form of the roughage and by the kind of starch source. Feeding pelleted roughage (30% crude fibre) as against chopped roughage increased the share of intestinal digestion of crude cellulose from 5 to 13%, whilst it remained relatively constant with starch (alpha-polymer bound glucose). Under high-starch feeding (some 2100 g/day) 710 g (maize) and 400 g (barley) of alpha-polmer bound glucose entered the duodenum. This corresponds to 29.6 and 17.6% of the starch consumed with maize and barley, respectively. When feeding the pelleted roughage (as compared to chopped roughage) a large amount of the non-bacterial N derived from feed protein and endogenous N (69.6 and 52.8 g/day) was available in the duodenum. Against this, the synthesis of bacterial N decreased (82.7 and 109.0 g/day). In the intestine, 107.1 and gN were absorbed daily from pelleted and chopped forage rye, respectively. In comparison with maize, barley was found to promote N availibility in the intestine (108.9 and 115.3 g N/day). Out of every 100 g of organic matter digested in the stomachs 28 and 21 g of bacterial protein were synthesized under chop and pellet feeding, respectively. Referred to the same amount, 6.6 g and 6.2 g N were found to enter the duodenum for chopped and pelleted roughage, respectively.