Comparison of Tifton 85 and Coastal bermudagrasses for yield, nutrient traits, intake, and digestion by growing beef steers

A study was undertaken to compare Tifton 85 (T85) and Coastal (CBG) bermuda grasses for effects of cultivar and age at harvest on yields of DM and dige stible DM, in vitro digestion, nutrient content, cell wall composition, in situ digestion kinetics, and feed intake and digestion by growing beef stee rs. In Exp. 1, T85 and CBG forages staged for growth in May or July of 1993 were harvested at 3, 4, 5, 6, 7, and 8 wk from subplots. Tifton 85 bermuda grass had 7.1% greater DM yield, 18.2% higher (P < .05) digestible DM yield , and 7.1% greater IVDMD than CBG, and, after 5 wk of forage growth, IVDMD of both T85 and CBG decreased with increased age at harvest (P < .05). In E xp. 2, T85 and CBG forages staged for growth in July 1997 were harvested at 2, 3, 4, 5, 6, and 7 wk from subplots. Even though T85 had higher concentr ations of NDF and ADF than CBG, T85 had 34.1% higher DM yield, 47.9% higher digestible DM, 55.0% higher digestible NDF, 91.7% higher digestible ADF, g reater IVDMD, in vitro NDF and ADF disappearances, and higher in situ DM an d NDF digestion (P < .05). Coastal bermudagrass had higher concentrations o f lignin and lower concentrations of total neutral sugars, arabinose, gluco se, and xylose than T85 (P < .05). In vitro digestibilities of DM, NDF, and ADF were lower and concentrations of ADF and lignin were greater for 7- vs 6-wk harvests of both T85 and CBG ( P < .05). In Exp. 3, T85 and CBG forag es staged for growth in July 1997 were harvested as hay at 3, 5, and 7 wk f rom .8-ha pastures and fed to 36 individually penned growing beef steers (i nitial BW = 244 kg) to quantify ad libitum intake without supplementation. Tifton 85 bermudagrass had lower concentrations of lignin and ether-linked ferulic acid and greater concentrations of NDF, ADF, hemicellulose, and cel lulose than CBG (P < .05). Steers fed T85 had higher (P < .05) digestion of DM, OM, NDF, ADF, hemicellulose, and cellulose than steers fed CBG. Digest ion of NDF, ADF, hemicellulose, and cellulose decreased (P < .05) with incr eased age at harvest for both cultivars. In conclusion, T85 produced more D M and had more digestible nutrients in vitro, in situ, and in vivo than CBG , and 3 and 5 wk of growth would be recommended ages to harvest either cult ivar.