The effect in sheep of physical form and stage of growth on the sites of digestion of a dried grass

I . The efyect of grinding and pelleting artificially dried S 24 perennial rye-grass (LoZium perenne L.) cut at two stages of maturity on sites of digestion of organic matter, energy and carbohydratc were studied in sheep with re-entrant intestinal cannulas fitted at the proximal duodenum and terminal ileum. Chopped and pelleted grasses at both stages of maturity were each given at 900 g dry matter/zq h to each of five sheep; the two forms of the early-cut grass were also given at 1400 g dry msltter/zq h each to four of the fivc shccp. 2. With the carly-cut grass, grinding and pelleting caused a depression in digestibility of organic matter (low level, P < 0 . 0 5 ; high level, P < woor), lo\vered the proportion of the digested organic matter disappearing before the small intestine (low level only, P < 0.05) and significantly increased that disappearing in the caccum and colon (low level, P 4 0.05 ; high level, P < OYJOI). Increase in stagc of maturity significantly depressed digestibility of organic matter ( P < 0001) with both forms of grass and, with the chopped form, significantly increased the proportion of digestible organic matter disappearing in the caecum and colon (P < 0.01). Increase in level of feeding of the pelleted, early-cut grass significantly lowered organic matter digestibility ( P < O . O ~ ) , reduced the proportion of digestible organic matter disappearing in the small intestine ( P 4 005) and increased that occurring in the caecum and colon ( P < 0.05). 3. With the early-cut grass, grinding and pelleting caused 3 depression in digestibility of gross energy only at the higher level of intake ( P < O O I ) , and reduced the proportion of apparently digestible energy disappearing before the small intestine (IOW level, P < 0.001 ; high level, P < 0.05). Only with the chopped form did stagc of maturity affect sites of energy digestion; with the more mature grass disappearance of energy in the reticulo-rumen declined (P < 0.01) and that in the caecum and colon increascd (P < 0301). The effects of level of feeding were similar to those observed for organic matter. 4. With the early-cut grass, and at both levels of intake, digcstibilities of cellulose and hemicellulose were depressed by grinding and pelleting (P < O.OOI), as were the proportions of digestible cellulose and hemicellulose disappearing before the small intestinc (P < 0.001). Thc proportions of these digestible fractions disappearing in the caecum and colon werc significantly increased (P < 0.001). Increase in stage of maturity depresscd cellulose digcstibility (P i 0.001) of the chopped but not pelletcd grass and depressed hemicellulose digestibility of both forms (P < 0001). The effects of increase in maturity at harvest on sites of digestion depended upon the form of the grass, With the chopped form, as stage of maturity increased, the proportion of digestible hemiccllulose disappearing in the reticulo-rumen fell ( P < 0.01) and that, and the proportion of digestible cellulose, disappearing in the caecum and colon increased ( P < 0'01 and P < 0.05 respectively); with the pelleted form, the proportions of digcstible cellulose and digestible hemicellulose disappearing in the reticula-rumen increased ( P < 0.001 and P < OOI respectivcly) whereasthosedisappearingin the caecum and colon declined ( P < 0.01). With the pelleted, early-cut grass increase in intake resulted in a depression in cellulose and hemicellulose digestion ( P < 0 0 5 and P < 0.001 respectidy) and increased proportional losses of digestible cellulose and digestible hcmiccllulose in the caecum and colon ( P 4 0'01 and P < 0.05 respectively).