Short communication: Effect of tannic acid on composition and ruminal degradability of bermudagrass and alfalfa silages

We measured the effects of the addition of tannic acid on chemical composit ion and crude protein (CP) ruminal degradability of bermudagrass, cv, coast cross (Cynodon dactylon L.) and alfalfa (Medicago sativa L.) silages with nylon bags incubated in the rumen of two fistulated lactating cows. Silage pH was greater for alfalfa than for bermudagrass. The addition of tannic ac id had no effect on silage pH. Ammonia N was greater in alfalfa than in ber mudagrass silage. Treated and control silages had similar ammonia N concent rations. The percentage of CP that was solubilized at time 0 was lower for alfalfa than for bermudagrass silage. The addition of tannic acid decreased the portion of CP solubilized at time 0 and increased the potentially degr adable fraction of CP. The potentially degradable fraction of CP was greate r for alfalfa than for bermudagrass. There was an interaction of species an d treatment; the disappearance rate of CP increased with tannic acid treatm ent of alfalfa but decreased with acid treatment of bermudagrass. The effec tive degradability of CP was similar for control and treated alfalfa but lo wer for treated than for control bermudagrass. Tannic acid treatment is eff ective in decreasing the rapidly soluble fraction of alfalfa and bermudagra ss silages, which could be beneficial to the animal because it would decrea se the excess of N in the rumen after feeding. Tannic acid treatment decrea sed CP degradability of bermudagrass silage but had no effect on alfalfa si lage, suggesting that tannic acid concentration required to effectively dec rease CP degradability differs among forages.