Effects of forage ensiling and ration fermentation on total mixed ration pH, ruminal fermentation and performance of growing Holstein-Zebu cross steers.

Abstract

Our objective was to determine the effect of forage ensiling and ration fermentation on total mixed ration pH, ruminal fermentation and animal performance. Thirty Holstein-Zebu cross steers were allotted to feeding treatments for 188days in a randomized complete block design including: fresh grass-total mixed ration (GTMR; pH 4.7), grass silage-TMR (STMR; pH 4.0) and fermented-TMR (FTMR; pH 3.5). Average daily gain for STMR was greatest during the first 3months period; however, that for FTMR tended to be greater than GTMR during the second 3 months period (P<0.10). During the second period dry matter intake for STMR was the greatest (P<0.01), but feed conversion ratio (P<0.01) and cost per gain (P<0.01) were the least for FTMR. Protein digestibility tended (P<0.10) to be greater for FTMR than STMR and fat digestibility was greater (P<0.05) for GTMR and FTMR than STMR. FTMR had less (P<0.01) ruminal NH3 -N content than STMR. Total volatile fatty acids post-feeding was greatest for GTMR (P<0.01). Ruminal proportions of acetic and butyric acids were greater for FTMR than GTMR (P<0.05); in contrast, propionic acid was greater for GTMR (P<0.05). Utilizing silage or total ration fermentation did not negatively impact on ruminal pH. STMR and FTMRs can be used to maintain performance of growing crossbred Holstein steers.