EFFECTS OF BUFFER ADDITIONS ON FERMENTATION OF DORMANT RANGE GRASSES

Replicated two-stage in vitro studies were conducted to determine the effects of single amino acid or branched-chain volatile fatty acid buf fer additions on in vitro dry matter disappearance, neutral detergent fiber disappearance, and fermentation kinetics of dormant range grasse s. Substrates consisted of separate samples of 2 cool season mid-grass es, western wheatgrass (Agropyron smithii Rydb.) and Japanese brome (B romus japonicus Thunb.), and a mixture of warm season shortgrasses, bu ffalograss (Bunchloe dactyloids [Nutt.] Engelm.), and blue grama (Bout eloua gracilis [H.B.K.] Lag. ex Steud.), hand clipped from standing fo rage in mid-March. Isonitrogenous treatments included buffer containin g urea with or without amino acids, branched-chain volatile fatty acid s, sodium sulfate, or starch. Urea increased (P<0.05) in vitro dry mat ter disappearance and in vitro neutral detergent fiber disappearance o f the cool season grasses over N free buffer. Methionine addition incr eased (P<0.05) in vitro neutral detergent fiber disappearance and rate of fermentation of both cool season grasses and in vitro dry matter d isappearance of Japanese brome over urea alone. Sodium sulfate increas ed (P<0.05) in vitro neutral detergent fiber disappearance of Japanese brome compared to urea alone. None of the branched-chain volatile fat ty acids tested increased dry matter disappearance, neutral detergent fiber disappearance, or rate of fermentation of the dormant range gras ses. Addition of urea or amino acids did not increase in vitro dry mat ter disappearance or in vitro neutral detergent fiber disappearance of the short-grass mixture. In vitro screening of amino acid and branche d-chain volatile fatty acid buffer additions to dormant range grasses showed that methionine supplementation with urea offers the greatest p otential, among the supplements evaluated, for improving digestibility and rate of fermentation of cool season grasses. None of the buffer s upplements improved fermentation of the warm season grasses.