A 4-unit, dual-flow continuous culture fermentor system was used to assess nutrient digestibility, volatile fatty acids (VFA) production, bacterial protein synthesis, and methane (CH) output of warm-season annual grasses. Treatments were randomly assigned to fermentors in a 4 × 4 Latin square design using 7 d for adaptation to treatment and 3 d for sample collection. Treatments were (1) 100% orchardgrass (Dactylis glomerata L.; ORD); (2) 50% orchardgrass + 50% Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz; MIL]; (3) 50% orchardgrass + 50% brown midrib sorghum × sudangrass (Sorghum bicolor L. Moench × S. bicolor var. sudanense; SSG]; or (4) 50% orchardgrass + 25% millet + 25% sorghum × sudangrass (MIX). Fermentors were fed 60 g of dry matter (DM)/d in equal portions of herbage 4 times daily (0730, 1030, 1400, and 1900 h). To replicate a typical 12-h pasture rotation, fermentors were fed the orchardgrass at 0730 and 1030 h and the individual treatment herbage (orchardgrass, Japanese millet, sorghum × sudangrass, or 50:50 Japanese millet and sorghum × sudangrass) at 1400 and 1900 h. Gas samples for CH analysis were collected 6 times daily at 0725, 0900, 1000, 1355, 1530, and 1630 h. Fermentor pH was determined at the time of feeding, and fermentor effluent samples for NH-N and VFA analyses were taken daily at 1030 h on d 8, 9, and 10. Samples were also analyzed for DM, organic matter (OM), crude protein, and fiber fractions to determine nutrient digestibilities. Bacterial efficiency was estimated by dividing bacterial N by truly digested OM. True DM and OM digestibilities and pH were not different among treatments. Apparent OM digestibility was greater in ORD than in MIL and SSG. The concentration of propionate was greater in ORD than in SSG and MIX, and that of butyrate was greatest in ORD and MIL. Methane output was greatest in MIL, intermediate in ORD, and lowest in SSG and MIX. Nitrogen intake did not differ across treatments, whereas bacterial N efficiency per kilogram of truly digestible OM was greatest in MIL, intermediate in SSG and MIX, and lowest in ORD. True crude protein digestibility was greater in ORD versus MIL, and ORD had lower total N, non-NH-N, bacterial N, and dietary N in effluent flows than MIL. Overall, we detected little difference in true nutrient digestibility; however, SSG and MIX provided the lowest acetate to propionate ratio and lower CH output than MIL and ORD. Thus, improved warm-season annual pastures (i.e., brown midrib sorghum × sudangrass) could provide a reasonable alternative to orchardgrass pastures during the summer months when such perennial cool-season grass species have greatly reduced productivity.

A continuous-culture fermentor study was conducted to assess nutrient digestibilities, volatile fatty acid (VFA) concentrations, microbial protein synthesis, bacterial nitrogen (N) efficiency, and enteric methane (CH 4 ) production of four 50:50 grass-legume diets, randomly assigned in a 4 × 4 Latin square design. Four legumes with different concentrations of condensed tannins (CT) were tested: alfalfa [ALF; Medicago sativa L., non-CT legume]; birdsfoot trefoil [BFT; Lotus corniculatus L., low-CT legume]; crown vetch [CV; Securigera varia (L.) Lassen, moderate-CT legume]; and sericea lespedeza [SL; Lespedeza cuneata (Dum. Cours.) G. Don, high-CT legume]. Orchardgrass (Dactylis glomerata L.) was the common forage used in all diets. Four fermentors were evaluated over four 10-d periods by feeding 82 g of dry matter (DM)/d in 4 equal feedings. Methane output was recorded every 10 min. Effluent samples were collected during the last 3 d of the experiment,composited by fermentor and period, and analyzed for pH and VFA, as well as DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber for determination of apparent and true nutrient digestibilities. Microbial protein synthesis and bacterial efficiency were estimated by analysis of N flows and purines. The CT concentrations were 3, 21, 38 and 76 g/kg of DM for ALF, BFT, CV, and SL diets, respectively. The SL diet had decreased fiber digestibilities and total VFA concentrations compared with the other diets. This resulted in the least total CH 4 production in the SL diet. Bacterial N efficiency per kilogram of organic matter truly digested was lower in the SL diet than in the BFT and CV diets. The lowest CH 4 production per unit of digestible nutrients was also found in the SL diet. Further work should be conducted to find optimal diets (by testing other legumes, rations, and sources of CT) for reducing CH 4 emissions without negatively affecting ruminal digestion to maintain or improve productivity.

Information regarding the susceptibility of currently grown bermudagrass [Cynodon dactylon (L.) Pers.] cultivars to the bermudagrass stem maggot (BSM; Atherigona reversura) could aid forage producers with the implementation of integrated pest management (IPM) strategies to manage this exotic pest. The objectives of this research were to compare the severity of damage among selected cultivars and quantify the phenotypic variation in cultivar response to the BSM among selected bermudagrass cultivars. Eight Cynodon cultivars were used in this study. Flies collected from infested fields were introduced six times throughout the 4‐wk growing period to the cultivars, which were grown in the greenhouse and contained in acetate and mesh enclosures. The number and percent of tillers damaged depended on cultivar in that cultivars with greater tiller density exhibited the greatest damage. When corrected for cultivar differences in the number of total tillers per pot, the stargrass (Cynodon nlemfuensis Vanderyst) cultivars and hybrids had a lower percentage of their tillers damaged (P < 0.10) by the presence of BSMs than the fine‐textured cultivars, except for ‘Russell’ in 2012. Presence of the BSM was coincident with a lower tiller count, increased tiller diameter, and darker leaf color, though no difference in any other physical characteristic was observed. The results showed that stargrass and stargrass hybrids are less susceptible to damage by the BSM and should be employed in IPM strategies wherever these cultivars are adapted.

Core Ideas The accuracy of rising plate meter in multispecies swards has not been tested thoroughly. Forcing X intercept to zero increases the precision of the calibration equations. Higher‐order polynomial regressions do not result in more accurate forage estimates. The rising plate meter (RPM) provides rapid estimates of herbage mass (HM). Accurate calibration of the RPM is difficult due to variability in forage management, growth, and species composition. The RPM is typically calibrated by linear regression of HM and RPM height; however, the r2 is usually low. Curvilinear regression, with the X intercept set to zero, could provide a more robust calibration equation and decrease variability in RPM estimates. Three Pennsylvania organic dairy farms grazing lactating dairy cattle on multispecies pastures were used to determine measured HM and estimated HM using a RPM. Removal of the X intercept increased the adjusted r2 of all equations between 42.8 and 89.0%. Use of quadratic and cubic regression only resulted in 0.01 to 0.02 increase in adjusted r2. Linear regression remains the simplest and preferred method of calibration; however, error can be reduced by setting calibration equations so that zero RPM height is associated with zero HM.

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