Study On Digestion Of Dietary Nutrients In Hindgut Of Sheep

Four experiments were conducted to investigate the digestion of dietary nutrients in hindgut of sheep. In each trial, four crossbred (Small Tail Han-sheep× Poll Dorset) wethers with permanent ileal cannula were fed a limited intake in 4 × 4 Latin-square design. AIA was used as an endogenous marker. To evaluate the effects of dietary NDF levels on nutrient digestion in hindgut of sheep, wethers were fed four iso-caloric and iso-nitrogen diets containing different NDF levels (30, 35, 40, and 45% of DM) in the first trial. The total apparent digestibility of DM decreased (P < 0.05) with increasing dietary NDF levels. The total apparent digestibility of another nutrient was not affected by dietary NDF levels. Dietary NDF also did not affect the hindgut digestibility of dietary nutrients and the percentage of hindgut digestion of dietary nutrients in total tract digestion. The percentage of hindgut digestion of NDF, ADF, CEL, and HC in total digestion in 30 and 45% NDF diets was higher than that in 35 and 40% NDF diets. To determine the effects of dietary CP levels on nutrient digestion in hindgut of sheep, wethers were fed four iso-caloric and iso-NDF diets with varying CP levels (12, 14, 16, and 18% of DM) in the second trial. The total apparent digestibility of DM increased (P < 0.05) and those of NDF, ADF, CEL, and HC increased (P < 0.01) significantly with increasing dietary CP level. Dietary CP levels did not affect the percentage of hindgut digestion of DM, OM, and HC in total digestion. The percentage of hindgut digestion of CP and NDF in total digestion increased (P < 0.01) and that of ADF and CEL increased (P < 0.05) significantly with increasing dietary CP levels. To evaluate the effects of dietary RDP levels on nutrients digestion in hindgut of sheep, wethers were fed four iso-caloric, iso-nitrogen, and iso-NDF diets containing different RDP levels (50, 55, 60, and 65% of CP) in the third trial. The total apparent digestibility of nutrients was not affected by dietary RDP levels. With increasing dietary RDP levels, the percentage of hindgut digestion of DM, ADF, and CEL in total digestion increased (P < 0.05) and those of OM, NDF, and HC increased numerically, but that of CP decreased (P < 0.01) significantly. To determine the effects of forage particle size on nutrients digestion in hindgut of sheep, wethers were fed a constant concentrate and a hay in baled, long chopped (4—6 cm), short chopped (1~3 cm), and fine ground (0.5 cm) form in the fourth trial. The total apparent digestibility of NDF in the diet containing fine ground hay was lower significantly (P < 0.05). Hay particle size did not affect the total apparent digestibility of another nutrient. The percentage of hindgut digestion of DM, CP, and NDF of the diet containing fine ground hay in total digestion was higher (P < 0.05) and that of ADF of this diet was higher (P < 0.01) than that of corresponding those of other diets. These results suggested that the percentage of hindgut digestion of DM, OM, CP, NDF, ADF, CEL, HC, and starch in total digestion was 26-33%, 19-24%, 11-20%, 22-28%, 19-25%, 18-22%, 23-32% and <1%, respectively. Results indicated that the hindgut of sheep played an important role in the digestion of dietary nutrients.