|dc.description.abstract||Teff grass (Eragrostis tef [Zucc.] Trotter) was fed to beef steers either alone or in combination with crude protein supplements in order to evaluate forage DMI, animal growth performance, grass production attributes, water usage, and animal digestion characteristics. In trial 1, four adjacent sub-surface irrigated paddocks (experimental unit, 2.66 ha each) were seeded in ‘Tiffany’ teff grass (Eragrostis tef [Zucc.] Trotter) and continuously-grazed for 63 d by beef steers (n = 5, initial BW = 289 ± 30, yr 1; n = 6, initial BW = 286 ± 23, yr 2) receiving one of two CP supplements during 2 consecutive growing seasons. Each year, daily supplements (0.45 kg hd·d-1 cottonseed meal, CSM; 0.50% µ paddock BW hd·d-1 dried distillers grains, DDGS) were assigned at random to 2 paddocks each. Total plant and canopy DM, OM, NDF, ADF, and volumetric soil water content were quantified at 7-d intervals. Measures of CP, in vitro true dry matter digestibility (IVTDMD), and available forage mass were recorded at 14-d intervals. Shrunk body weights of steers were obtained prior to grazing and following each subsequent 21-d period. In trial 2, six ruminally-cannulated beef steers (experimental unit, 304 ± 11 kg) were fed either ‘WW-B. Dahl’ Old World bluestem [Bothriochloa bladhii (Retz) S.T. Blake; WWBD or Eragrostis tef (Zucc.) Trotter; TEFF alone or in combination with DDGS supplementation (0.5% kg BW hd·d-1) in a 4 × 6 unbalanced Latin square design (6 steers and 4 diets: WWBD or TEFF, with or without DDGS). Each period consisted of a 14-d adaptation and 7-d collection. Steers were fed once daily at 1000 h. Data were analyzed using the GLIMMIX procedures of SAS with year as a random effect in trial 1 and steer within sequence a random effect in year 2.
In trial 1, teff ADF was greater (P ≤ 0.05) in the whole plant relative to the canopy on d 49 and 56. Crude protein was greater (P < 0.01) in the canopy relative to the entire sward. Supplement type did not influence NDF, ADF, CP, or IVTDMD or in vitro true OM digestibility (P ≥ 0.39). Total nutrient yield did not differ (P ≥ 0.43) by supplement over the course of the grazing season. Steers supplemented with DDGS had higher (P = 0.01) shrunk ADG relative to CSM. Predicted teff DMI (P < 0.01), NEm (P = 0.02), and NEg (P = 0.03) were greater with CSM. Total DMI was similar (P = 0.14) between treatments although predicted dietary NEm, NEg, gain:feed, and BW gain per ha were greater (P ≤ 0.02) with DDGS. Estimates of DM, OM, NDF, and ADF consumed were greater (P ≤ 0.05) for CSM. Nutrient yield of teff remaining on d 56 was similar (P = 0.33) between treatments. Crude protein yield per m3 water tended (P = 0.09) to be higher for CSM with no other differences (P = 0.24). Neither stocking rate nor unit of water received per stocking rate differed (P ≥ 0.32) by treatment. Soil water content differed (P < 0.01) by grazing day and depth but not by supplement (P = 0.40). In trial 2, total daily DMI was greater with TEFF and DDGS (both, P = 0.04) relative to WWBD and no supplement, respectively. Daily digestible intake of all nutrients measured (DM, OM, CP, NDF, ADF, and hemicellulose) were greater (P < 0.01) with TEFF. Chewing activity per kg NDF or kg peNDF intake did not differ by hay type (P ≥ 0.54). Non-supplemented steers spent more time (min/d) eating hay (P < 0.01) than steers fed DDGS. Average ruminal pH of TEFF (6.32) was lower (P > 0.01) than WWBD (6.56). Non-supplemented steers produced less total gas and methane (both, P = 0.02) per g rumen fluid DM. Neither total VFA nor acetate:propionate were affected by hay type (P ≥ 0.45) or supplement (P = 0.92). Mean ruminal NH3-N was greater for TEFF (P = 0.02) and with DDGS (P = 0.03). Mean ruminal NH3-N did not differ by time post-feeding (P = 0.66). Daily fecal output and apparent total-tract digestibility of all nutrients were greater (P < 0.01) with TEFF. Non-supplemented steers tended (P = 0.09) to have greater fecal output. Apparent total-tract digestibility of hemicellulose was reduced by 7% (P = 0.03) with DDGS. A hay type × incubation time interaction resulted in a greater ruminal disappearance of all nutrients (P < 0.01). Greater nutrient disappearances with TEFF were observed beginning at h 6, 6, 24, 24, 36, and 12 for DM, OM, CP, NDF, ADF, and hemicellulose, respectively. Following 96 h incubation, ruminal disappearance rates of DM, CP, and NDF were 26.6, 61.7, and 24.6% greater, respectively, for TEFF relative to WWBD.
Supplementing teff forage is expected to reduce level of teff forage intake. This reduction may be of greater magnitude when compared to some perennial forages such as WW-B. Dahl. Despite reduced forage intake, animal performance is likely to be greater when a supplement contains additional energy, such as that in dried distillers grains, relative to cottonseed meal. Regardless of supplement type, total forage and forage nutrient yields should not be affected. The difference in animal growth performance in conjunction with similar yield of forage nutrients equates to improved use of water resources with an energy-containing supplement. When assessed relative to both perennial and teff forages alone, a dried distillers grains supplement increased total dry matte intake while imposing no negative effects on ruminal digestion.||