| P.A. Momont, R.J. Pruitt, R.H. Pritchard and P.S. Johnson |
| Authors are former graduate assistant, associate professor, professor, and associate professor, Department of Animal and Range Sciences, South Dakota State University, Brookings, 57007-0392. P.A. Momont is currently assistant professor, Department of Animal Science, Southwest Research and Extension Center, Caldwell, ID., 83605. |
Abstract |
| Replicated two-stage in vitro studies were conducted to determine the effects of single amino acid or branched-chain volatile fatty acid buffer additions on in vitro dry matter disappearance, neutral detergent fiber disappearance, and fermentation kinetics of dormant range grasses. Substrates consisted of separate samples of 2 cool season mid-grasses, western wheatgrass (Agropyron smithii Rydb.) and Japanese brome (Bromus japonicus Thunb.), and a mixture of warm season shortgrasses, buffalograss (Buchloe dactyloids [Nutt.] Engelm.), and blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Steud.), hand clipped from standing forage in mid-March. Isonitrogenous treatments included buffer containing urea with or without amino acids, branched-chain volatile fatty acids, sodium sulfate, or starch. Urea increased (P<0.05) in vitro dry matter disappearance and in vitro neutral detergent fiber disappearance of the cool season grasses over N free buffer. Methionine addition increased (P<0.05) in vitro neutral detergent fiber disappearance and rate of fermentation of both cool season grasses and in vitro dry matter disappearance of Japanese brome over urea alone. Sodium sulfate increased (P<0.05) in vitro neutral detergent fiber disappearance of Japanese brome compared to urea alone. None of the branched-chain volatile fatty acids tested increased dry matter disappearance, neutral detergent fiber disappearance, or rate of fermentation of the dormant range grasses. Addition of urea or amino acids did not increase in vitro dry matter disappearance or in vitro neutral detergent fiber disappearance of the shortgrass mixture. In vitro screening of amino acid and branched-chain volatile fatty acid buffer additions to dormant range grasses showed that methionine supplementation with urea offers the greatest potential, among the supplements evaluated, for improving digestibility and rate of fermentation of cool season grasses. None of the buffer supplements improved fermentation of the warm season grasses. |
| Key Words: gas production, fiber disappearance, urea, sulfur, starch |