PSXII-3 Impact of a fibrolytic enzyme additive on digestibility and performance in the grower and early finisher phases of feedlot cattle

Abstract

Abstract The objective of this study was to examine if a fibrolytic enzyme feed additive would improve animal performance and apparent total tract digestibility of fibre in feedlot rations. To meet these objectives 54 steers were assigned to one of three pens by weight and fed a corn-based grower (78.7% corn-silage and 20% dried distillers grains plus solubles, DM basis) diet for 80 days, followed by a finisher diet (60% high moisture corn, 20% DDGS, and 17% alfalfa haylage, DM basis) for 60 days. Steers were randomly assigned to control (CON; n = 27) or enzyme (ENZ; n = 27) treatments, with ENZ steers receiving 0.75 ml/kg DM of the enzyme additive. Every 28 days body weight, ultrasound measures of back and rump fat depths were recorded, and blood was collected via jugular venipuncture. Ruminal pH was monitored using a reticulo-ruminal in-dwelling probe and recorded at five minutes intervals over three weeks each in the grower phase and through the transition. Apparent total tract digestibility was measured using acid-insoluble ash as an internal marker. Data were analyzed as a complete randomized block design using PROC GLIMMIX in SAS, with treatment as a fixed effect, and block as a random effect. Adding ENZ during the grower and early finisher phases did not impact (P ≥ 0.05) animal performance traits (gains, feed intake, feed conversion), blood metabolites, or ruminal pH in grower or finisher periods. However, ENZ significantly (P ≤ 0.05) improved digestibility of dry matter, crude protein, sugar, and net energy of gains. This study has demonstrated that the use of this fibrolytic enzyme in a corn-based feedlot diet improved digestibility of some nutrients, but this did not result in improved steer performance.