A study was undertaken to compare Tifton 85 (T85) and Coastal (CBG) bermudagrasses for effects of cultivar and age at harvest on yields of DM and digestible DM, in vitro digestion, nutrient content, cell wall composition, in situ digestion kinetics, and feed intake and digestion by growing beef steers. 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 bermudagrass 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 Exp. 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 concentrations 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, greater IVDMD, in vitro NDF and ADF disappearances, and higher in situ DM and NDF digestion (P < .05). Coastal bermudagrass had higher concentrations of lignin and lower concentrations of total neutral sugars, arabinose, glucose, 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 forages staged for growth in July 1997 were harvested as hay at 3, 5, and 7 wk from .8-ha pastures and fed to 36 individually penned growing beef steers (initial 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 cellulose than CBG (P < .05). Steers fed T85 had higher (P < .05) digestion of DM, OM, NDF, ADF, hemicellulose, and cellulose than steers fed CBG. Digestion of NDF, ADF, hemicellulose, and cellulose decreased (P < .05) with increased age at harvest for both cultivars. In conclusion, T85 produced more DM 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 cultivar.

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The coastal plain of the southeastern USA lacks a dependable per· ennial cool season forage crop, but tall fescue (Festuca arundinacea Schreb.) gennplasms have been developed which show greater per· sistence and yield than currently marketed cultivars in this region. Since these gennplasms were found to be infected with the tall fescue endophyte (Acremonium coenophialum Morgan-Jones and Gams), the contribution of the endophyte to their perfonnance was unknown. The objective of this study was to compare yield and stand survival of endophyte-infected (EI) and endophyte-free (EF) (achieved by re· mo~·aJ of its endophyte) versions of four persistent gennplasms (GA· 5, GA-Jesup, GA·Jesup Improved, and GA-Ecotype KY31) in clipped small plots at three locations in Georgia (Americus and Tifton in the coastal plain and Watkinsville located in the fescue groWing area of the southern piedmont region) for a 3-yr period. The El version of each gennplasm showed greater stand survival and yield than its EF version at Americus and Tifton, but no differences were recorded for infection status for the same parameters at Watkinsville. These find· ings indicate that endophyte removal greatly reduces the ecological fitness of tall fescue by possibly allowing less tolerance to summer drought. Presently, only El tall fescue can be dependably recom· mended for perennial pasture in the southeastern coastal plain.

A new high-yielding bermudagrass hybrid, Tifton 85, produced 26% higher DM yield (P = .05) with 11% higher IVDMD (P = .05) than Coastal in two 3-yr yield trials. Tifton 78 and Tifton 85 were established in duplicate .81-ha pastures in 1988 and were grazed during 1989, 1990, and 1991 using a variable stocking rate method. Four tester steers per pasture with 269 kg initial BW grazed continuously for 169 d/yr beginning in April. Forage mass, targeted at 2,800 kg of DM/ha, was maintained by adjusting stocking rates at 14-d intervals to correspond with ground-level forage samples taken at 14-d intervals. Pastures received 84 kg of N/ha in March, June, and August of each year. Nutritive value was assessed using whole masticate samples from two esophageal cannulated steers grazing each pasture in late May, mid-July, or early September. The 3-yr mean masticate analyses revealed similar CP for Tifton 78 and Tifton 85 in May and July, but higher (P < .05) CP for Tifton 85 than for Tifton 78 in September. The IVDMD was higher (P < .05) in May and September for Tifton 85 than for Tifton 78; and, mean and medium particle sizes were greater (P < .05) for Tifton 85 than for Tifton 78 in May, July, and September samples.(ABSTRACT TRUNCATED AT 250 WORDS)

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Comparisons of stocking rates across sites can be facilitated by calculating grazing pressure. We used peak standing crop and stocking rates from six studies in the North American Great Plains

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Habitat conservation strategies of the North American Waterfowl Management Plan (NAWMP) are guided by current understanding of factors that limit growth of waterfowl populations. The 1998 implementation plan of the Upper Mississippi River and Great Lakes Region Joint Venture (UMR and GLRJV) assumed that availability of foraging resources during autumn in wetlands actively managed for waterfowl was the primary limiting factor for duck populations during the nonbreeding season. We used multistage sampling during autumn and spring 2001–2004 to estimate energetic carrying capacity (ECC) of actively and passively managed wetlands in Ohio, USA, and examine this assumption. Energetic carrying capacity during autumn was similar between actively and passively managed wetlands each year. Averaged across years, energetic carrying capacity was 3,446 and 2,047 duck energy‐days (DED)/ha for actively and passively managed wetlands, respectively. These estimates exceeded the UMR and GLRJV assumption that 1,236 DED/ha were provided by managed wetland habitats. Energetic carrying capacity declined each year by >80% between autumn and spring migration. Consequently, ECC of actively and passively managed wetlands was low during spring ( = 66–242 DED/ha). These results suggested that duck foraging resources in actively and passively managed wetland habitats are abundant during autumn, but overwinter declines may create food‐limiting environments during spring.