348 Including Alfalfa in the Diet of Steers fed TMR: Effect on Rumen Fermentation and Performance

Abstract

The aim of this study was to evaluate the effects on dry matter intake (DMI), daily gain (DG), feed efficiency (FE) and rumen fermentation of including fresh alfalfa (FA) on a restricted TMR diet of finishing steers. Twenty steers (8 with 8-mm ruminal catheters), fed a TMR diet (ground corn grain, soybean meal, pasture hay, mineral-vitamin concentrate and Anavrin; 65% DM, 12.8% CP, 23% NDF) were blocked by BW and distributed in 2 feeding treatments (n=10/treatment): 1) TMR offered at a level of 2.8% of BW (DM basis): ‘TMR’ or 2) TMR offered at a level of 1.7% of BW (DM basis) plus FA (22.1% DM, 14.5% CP, 50.3% NDF) offered in an unlimited quantity: ‘PMR+FF’. The experiment lasted 60 d, and steers were weighed every 12 d, for 2 consecutive days each time. DMI was individually measured 3 times for 5 consecutive days, beginning days 20, 34 and 48 days, by difference offered-refused for each feedstuff. Ruminal pH, N-NH3 and volatile fatty acids (VFA) were measured on days 19, 33 and 47, at 0930, 1300, 1500, 1700, 1900, 2100, 0300 and 0930 h. The inclusion of fresh forage resulted in 40% of the total DMI, with no differences on intake (Table 1). However, in the PMR+FF treatment DG and FE tended to be reduced, possibly due to a reduced energy ingestion, considering the fiber content of FA and TMR. As expected, the inclusion of FA in the diet increased pH and acetate, and reduced propionate ruminal percentage, resulting in triplicated acetic/propionate rate. Overall, the inclusion of fresh alfalfa in the diet increased ruminal pH and acetic/propionate rate without affecting DMI. Including fresh alfalfa in finishing steers’ diet could have positive implications on feed costs and meat composition without negatively affecting productivity, but more studies are needed.