Effects of feeding ensiled spearmint (Mentha spicata) byproduct on nutrient utilization and ruminal fermentation of steers

Two studies were conducted to determine the feeding value of ensiled spearm int byproduct (mint silage) for beef steers. Six ruminally fistulated steer s were used in a completely randomized design to determine the effects of f eeding mint silage or barley silage on ruminal fermentation and nutrient ut ilization. Ruminal nutrient degradbilities of mint silage relative to barle y silage were determined in a randomized complete block design using two ru minally fistulated steers. Relative to barley silage, mint silage contained 17, 180, 20 and 330% more neutral detergent fiber (NDF), acid detergent li gnin (ADL), crude protein (CP), and acid detergent insoluble protein, respe ctively. Steers fed mint silage consumed less (P < 0.05) dry matter (DM) th an those fed barley silage. Ruminal pH was higher (P < 0.05) while concentr ations of volatile fatty acids (VFA) were lower (P < 0.05) for mint silage- fed steers than for barley silage-fed steers. Ruminal degradability of DM, CP and acid detergent fiber (ADF) was 46, 62 and 11% higher (P < 0.05), res pectively, for barley silage than for mint silage. Total tract digestibilit y of CP (290 versus 648 g kg(-1)), NDF (312 versus 471 g kg(-1)), ADF (300 versus 454 g kg(-1)), and gross energy (463 versus 654 J kJ(-1)) were lower (P < 0.05) for steers fed mint silage than for those fed barley silage. Mi nt silage had a lower (P < 0.05) digestible energy content (7.79 MJ kg(-1)) than barley silage (11.01 MJ kg(-1)). It was concluded that mint: silage w as poorly utilized by steers largely because of its high ADL and acid deter gent insoluble protein contents. <(c)> 2001 Elsevier Science B.V. All right s reserved.