The effect in sheep of physical form on the sites of digestion of a dried lucerne diet

I .The effect of altering the physical form of a regrowth crop of dried lucerne (Medicago sutivu L. var.Chartuinvilliers) on the sites of organic matter, energy and carbohydrate digestion was studied with sheep fitted with re-entrant cannulas at the proximal duodenum and at the terminal ileum.2. Chopped, cobbed, and ground and pelleted diets with moduli of fineness of 3.~~2.7 and 1-5 respectively were prcpared from the same high-temperature dried crop and given twice daily to sheep at a level of intake of 910 g dry matter/d.3. Physical form did not affect the apparent digestibility of the organic matter.On the cobbed and pelleted diets losses of digestible organic matter before the small intestine were significantly lower ( P < 0.05; P < 0.001 respectively) and losses in the small intestine were significantly higher ( P < 0 .0 5 ) than for the chopped diet. 4.Apparent digestibility of the gross energy of the three physical forms was similar, but the flow of energy into, and digestion within, the small intestine were markedly greater ( P < 0.05) for the ground and pelleted diet than for either the chopped or cobbed diet, for which the values did not differ.Energy digestion in the caecum and colon was similar for the three physical forms.5. Total cellulose and hemicellulose digestibilities were not affected by processing, but the proportion of the digestible cellulose and digestible hemicellulose digested in the fore-stomachs of sheep given the ground and pelleted diet (63 and 55 % respectively) was less than for the chopped diet (85 and 68 yo).The digestibility of the cobbed diet was intermediate.Digestion in the caecum and colon compensated for these differences in digestion of cellulose and hemicellulose in the fore-stomachs. 6.Volatile fatty acid (VFA) concentration in the rumen liquor was lower in sheep given ground, pelleted lucerne than in those on the chopped diet, but the VFA proportions were very similar.The implications of the change in site of energy and carbohydrate digestion with grinding and pelleting are discussed.The nutritional evaluation of processed forage crops has been the subject of investigation for some considerable time.Experiments examining the effects of altering the physical form of the diet on voluntary food intake, apparent digestibility, energy utilization and animal production with processed forage diets given alone, or in combination with other feeds, have been reviewed by Minson (1963), Moore (1964), Beardsley (1964) and Meyer, Kromann & Garrett (1965).Previous work has shown that voluntary food intake of forage diets is normally increased when the forage is ground and pelleted (Meyer, Gaskill, Stoewsand &Weir, I959), and apparent digestibility is generally depressed (Blaxter & Graham, 1956).The extent of these increases in voluntary food intake and depressions in apparent digesti-