MICROBIAL PROTEIN PRODUCTION IN THE RUMEN OF STEERS FED LOW QUALITY FORAGE SUPPLEMENTED WITH VARIOUS LEVELS OF BARLEY GRAIN OR BARLEY GRAIN PLUS PROTEIN

ABSTRACT An experiment was conducted to examine the effects of increasing intake of barley grain or barley grain plus protein as supplement on microbial crude protein (MCP) production, efficiency of microbial crude protein production (eMCP) in the rumen of Brahman steers consuming low quality forage. Ten steers were used and allocated to two supplement groups namely barley grain (B) and barley plus protein (BP). The experimental design was two incomplete 5x5 Latin Squares, each with three runs. Each run consisted of a 21 d adaptation and 7 d collection period. Steers received Green panic hay ad libitum with one of five levels of B or BP (0; 0.5; 1.0; 1.5 and 2.0% of body weight per day (W/d)). MCP production in the rumen increased linearly (P<0.05) with increasing intake of B or BP supplements. The MCP in the rumen increased linearly (P<0.05) and quadratically (P<0.05) by increased B and BP intakes, respectively. Generally, steers supplemened with BP had greater (P<0.01) MCP production and eMCP in the rumen than B supplemented steers. The concentration of rumen NH3-N (samples taken at 3 h after feeding) increased linearly with increased B or BP intakes. For samples taken at 24 h post feeding, the concentration of rumen NH3-N was not changed (P>0.05) with increased B intake but increased linearly (P<0.01) with increased BP intake. Ruminal pH at 3 h after feeding decreased linearly (P<0.05) due to increased B intake, but was not altered (P>0.05) by increased BP intake. For samples taken at 24 h post feeding in contrast, was not influenced (P>0.05) by intake of B or BP. It was concluded that although both supplements increased MCP production and eMCP in the rumen of steers receiving low quality forage, BP supplementation had much more beneficial effect than B supplementation. Keywords: barley, protein, rumen, steer, forag