PSVIII-27 Interactions between the stage of maturity of Eragrostis tef hay and supplemental energy source on forage utilization in beef heifers

This study evaluated the interaction between the stage of maturity of Eragrostis tef (teff) grass and supplemental energy source on ruminal fermentation characteristics and nitrogen (N) utilization. Six ruminally-fistulated beef heifers were used in a 3 × 3 split-plot design (21 d periods). The whole plot factor was stage of maturity of teff hay [early- (EH) or late-heading (LH)], and the subplot factor was supplemental energy source [no supplement (CON), rolled corn grain or beet pulp pellet (BP)] fed at 0.5% of body weight. Feed intake was measured daily. Indwelling pH loggers were used to measure ruminal pH (d 14 to 21) and ruminal fluid was collected from d 19 to 21 to determine fermentation characteristics, as were feces and urine to measure N excretion. Data was analyzed using PROC MIXED in SAS. There was no stage of maturity × supplement interaction for all measurements (P ≥ 0.17). Although dry matter intake (DMI) tended to be greater (P = 0.07) for heifers fed EH than LH hay, it did not differ (P = 0.88) across supplements. Ruminal acetate concentration tended (P = 0.098) to be greater for EH than LH heifers, whereas butyrate, isobutyrate, and isovalerate concentrations were greater (P ≤ 0.045) for BPP than CON heifers. However, the duration and area pH < 6.2 and 5.8 did not differ (P > 0.12) across treatments. Except for microbial N flow, which was greater (P < 0.01) for EH than LH heifers, there was no stage of maturity or supplement effect (P ≥ 0.14) on measures of N utilization. In summary, feeding teff hay harvested at the EH than LH stage of maturity increased DMI and microbial N supply, whereas feeding corn and BP as energy supplements to beef heifers had no effect on ruminal pH.