Site and extent of nutrient digestion by sheep fed alkaline hydrogen peroxide-treated wheat straw-alfalfa hay combinations at restricted intakes

Atwell, D.G.; Merchen, N.R.; Jaster, E.H.; Fahey, G.C. Jr; Berger, L.L.

Site and extent of nutrient digestion by sheep fed alkaline hydrogen peroxide-treated wheat straw-alfalfa hay combinations at restricted intakes

1991

Atwell, D.G. | Merchen, N.R. | Jaster, E.H. | Fahey, G.C. Jr | Berger, L.L.

Five crossbred wethers (58 kg) fitted with cannulas in the rumen, duodenum, and ileum were used in a 5 X 5 Latin square design to study effects of feeding combinations of alkaline hydrogen peroxide-treated wheat straw (AHP-WS) and alfalfa hay at restricted intakes on site and extent of nutrient digestion. Additionally, flows and disappearance of N and amino acids (AA) in the small intestine were regressed on alfalfa nitrogen intake (ANI) to estimate alfalfa's contribution to postruminal N and AA supplies. Diets consisted of 80: 20 forage:concentrate mixtures; diet designations were 80:0, 80% AHP-WS and no alfalfa; 60:20, 60% AHP-WS and 20% alfalfa; 40:40, 40% AHP-WS and 40% alfalfa; 20:60, 20% AHP-WS and 60% alfalfa; and 0:80, no AHP-WS and 80% alfalfa. A modest positive quadratic (P < .05) response was noted for total tract digestibility (TTD) of OM; values were 76.5% for diets 80:0 and 0:80 vs 78% for diet 40:40. Ruminal digestibility (percentage of intake) of NDF and ADF increased in a quadratic manner from 43 and 30%, respectively, for diet 0:80 to 71 and 70%, respectively, for diet 80:0. Ruminal digestibility of fiber may have been enhanced due to linear (P < .05) decreases in liquid and particulate dilution rates, resulting in increased ruminal residence time of fiber as alfalfa hay replaced AHP-WS. Liquid and particulate dilution rates decreased linearly from 6.4 and 5.2%/h, respectively, for diet 80:0 to 5.4 and 3.49%/h, respectively, for diet 0:80. Regression analysis of N data indicated that alfalfa N had a ruminal escape value of 26%.

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