Influence of processing supplemental alfalfa on intake and digestion of dormant bluestem-range forage by steers

Four ruminally and duodenally fistulated, 2-yr-old Angus x Hereford steers (average initial BW = 370 kg) were used to evaluate the effect of method of processing supplemental alfalfa on intake and digestion of dormant bluestem-range forage (2.8% CP, 78% NDF). Treatments (4 x 4 Latin square) were 1) control, no supplement; 2) ground and pelleted alfalfa hay (PELLET; 21% CP, 37% NDF); 3) ground and pelleted dehydrated alfalfa (DEHY; 21% CP, 44% NDF); and 4) longstem alfalfa hay (HAY; 20% CP, 37% NDF). All supplements were from a single cutting of alfalfa and fed at .5% BW (as-fed basis). Supplementing steers with alfalfa increased (P < or = .07) bluestem forage OM intake (FOMI); total OM intake (TOMI); true ruminal OM digestibility; total tract OM digestibility (TTOMD); total N, microbial N, and nonammonia-nonmicrobial N (NANM) flows to the duodenum; ruminal OM and fluid fill; fluid dilution rates; dietary DE concentration; and ruminal total VFA and NH3 N concentrations. Because of the enhanced FOMI and TOMI associated with alfalfa supplementation and the concomitant improvement in TTOMD, digestible OM intake (DOMI) also increased (P < .01) when supplemental alfalfa was fed. Method of processing alfalfa had little impact on forage utilization, except FOMI (P = .11), TOMI (P = .10), and ruminal OM fill (P = .09) tended to be greater when supplemental alfalfa pellets were dehydrated. Similarly, processing method tended to alter the molar proportions of some minor VFA. In conclusion, alfalfa supplementation exerted a dramatic impact on utilization of low-quality forage.