Effects of dietary tannin source on performance, feed efficiency, ruminal fermentation, and carcass and non-carcass traits in steers fed a high-grain diet

The objective of this study, which was part of an integrated project to investigate the antimicrobial effects of dietary tannins on native food borne pathogens in beef cattle, was to examine the effects of source of tannin (condensed, CT, vs. hydrolysable, HT) on performance, feed efficiency, ruminal fermentation parameters, and carcass and non-carcass traits in finishing beef steers. Thirty-six crossbred steers averaging 414±40kg BW were stratified by initial BW and randomly assigned to one of three treatments: control (CN), CT, or HT tannins. Commercially available tannin extracts were added to a high-grain diet (ME=11.9MJ/kg DM) at 14.9g/kg DM. Mimosa and chestnut extracts provided condensed tannin and hydrolysable tannin, respectively. Steers were individually fed using Calan gate feeders a high-grain diet. Rumen fluid was collected on days 0, 21, and 42 via stomach tube and analyzed for VFA and in vitro methane producing activity. Cattle were harvested at the end of the study and carcass data collected 24-h postharvest. There was no effect (P>0.05) of tannin supplementation on animal performance, ruminal fermentation parameters, in vitro methane producing activity, or carcass and non-carcass traits, except for HCW, EBW, and rumen mass and empty GIT (g/kg EBW). Condensed tannin steers had 3.7% lower (P<0.05) HCW compared to CN with HT steers having intermediate HCW. Hydrolysable tannin treated steers had 2.8% lower (P<0.05) EBW compared to CN while CT steers had intermediate EBW; CT treated steers also had 15.2% higher (P<0.05) rumen mass (g/kg EBW) compared to HT with CN steers being intermediate. This resulted in a 10.2% increase (P<0.05) in total empty GIT (g/kg EBW) for HT steers compared to CT steers with CN steers bring intermediate. There was a treatment x day interaction for butyrate concentration. For steers fed CT, there was a linear increase in butyrate while the HT steers remained relatively stable and the control steers had numerically lower butyrate. Despite the significant interaction, treatment means on day 42 were not significantly different. Results indicate that neither source of dietary tannin affected performance and feed efficiency. There were no detrimental effects of tannins on other offal measured indicating that tannins supplementation may be a viable option in finishing beef cattle if bactericidal efficacy is established. More research is needed to further our understanding of how tannin supplementation may fit into real-life feedlot situations.