Effects of supplement type and forage quality on ruminal metabolism and diet digestibility of cattle

Abstract Text: Objectives were to test the interaction of supplement type, liquid versus dry, and forage type, hay versus corn stover, on diet digestibility and ruminal metabolism of cattle. Rumen fistulated steers were used in a replicated 4×4 Latin square with a 2×2 factorial arrangement of treatments: 1) hay with a liquid supplement (HL), 2) hay with a dry supplement (HD), 3) stover with a liquid supplement (SL), and 4) stover with a dry supplement (SD). Steers were fed once daily for ad-libitum intake. Each period began with 14 d dietary adaptation, followed by 7 d of collections (5 d of fecal and 2 d of ruminal collections). In-situ disappearance was determined by placing dacron bags, containing soybean hulls, in the rumen for 24 h. There were no interactions (P ≥ 0.25) of supplement and forage type on DMI, apparent total tract digestibility, or ruminal pH. Nor were there effects (P ≥ 0.12) of supplement type on DMI, apparent total tract or in situ digestibility, or ruminal pH. However, steers fed hay had increased (P < 0.01) DMI and increased (trend; P = 0.07) apparent total tract NDF digestibility when compared to steers fed stover, regardless of supplement type. Although apparent total tract NDF digestibility was driven by forage type, there was a tendency (P = 0.09) for a forage by supplement type interaction for in situ NDF disappearance (ISNDFD). There were no differences in ISNDFD in steers fed hay; but, liquid supplementation increased ISNDFD in steers fed stover. At 0, 1.5, and 18 h post-feeding, ruminal pH was greater (P ≤ 0.01) in cattle consuming stover when compared to those fed hay, regardless of supplement type. There was a supplement by hour interaction (P = 0.04) on acetate concentrations (Ac). At 0h post-feeding, there was no effect; however, at 3 and 6 h post-feeding Ac were reduced in steers fed liquid when compared to those fed dry supplements. In addition there was a supplement by hour (P = 0.02) interaction for butyrate concentration (Bu); where, at all time points, Bu increased (P ≤ 0.01) in steers fed liquid when compared to those fed dry supplements. Steers fed hay, regardless of supplement, had increased (P < 0.01) concentrations of Ac and total VFA compared to steers fed stover. In the present trial, there tended to be an increase in ISNDFD when steers were fed SL, but this did not affect total tract digestibility.

Keywords: cattle, forage quality, liquid supplement