Cattle grazing wheat pasture in the southern Great Plains are sometimes fed an energy supplement; however, the benefits of supplementation on nutrient balance, energy metabolism, and greenhouse gas emissions have not been elucidated. Therefore, we used 10 British crossbred steers (206 ± 10.7 kg initial BW) in a respiration calorimetry study to evaluate the effects of energy supplementation on energy losses, N balance, and nutrient digestibility of steers fed green-chopped wheat forage. The study design was an incomplete replicated 4 × 4 Latin square with treatments in a 2 × 2 factorial arrangement. Steers ( = 8) were assigned to 1 of 2 BW blocks (4 steers per block) with dietary factors consisting of 1) no supplementation (CON) or supplemented with a steam-flaked corn-based energy supplement (that also contained monensin sodium) at 0.5% of BW daily (SUP) and 2) NEm intakes of 1 times (1x) or 1.5 times (1.5x) maintenance. Wheat forage was harvested daily and continuously fed as green-chop to steers during the 56-d study. There were no differences ( ≥ 0.32) between CON and SUP for OM (78.3 vs. 80.7%, respectively) or NDF (68.3 vs. 64.8%, respectively) digestibility. At the 1.5x level of intake, there was no difference ( ≥ 0.16) in energy lost in feces (4.27 vs. 3.92 Mcal/d) or urine (0.58 vs. 0.55 Mcal/d), heat production (8.69 vs. 8.44 Mcal/d), or retained energy (3.10 vs. 3.46 Mcal/d) between supplementation treatments. Oxygen consumption (1,777 vs. 1,731 L/d; = 0.67) and CO production (1,704 vs. 1,627 L/d; = 0.56) of CON and SUP steers, respectively, were not different; however, SUP steers tended to have ( = 0.06) lower CH production (115 vs 130 L/d) than CON steers. Methane, as a proportion of GE intake, was similar for CON (6.87%) and SUP (6.07%; = 0.18), as was the ME:DE ratio ( = 0.24; 86.3% for CON and 87.9% for SUP). Fractional N excretion in urine and feces, as a proportion of total N excreted ( ≥ 0.84) or N intake ( ≥ 0.63), was not different between treatments. Calculated NEm and NEg values for CON were 1.76 and 1.37 Mcal/kg DM, respectively, whereas the NEm and NEg values for the SUP treatment were 2.32 and 1.61 Mcal/kg DM, respectively. Calculated NE values for steers fed additional energy were approximately 17.5% greater than the expected difference in energy content. This was probably the result of the inconsistent response at the 1x DMI level. Under these circumstances, energy supplementation did appear to enhance NEm and NEg value of the supplemented wheat forage diet.

Condensed tannins (CT) may decrease greenhouse gas emissions and alter the site of N excreted by ruminants. We evaluated the effect of top-dressing a steam-flaked corn-based finishing diet (14.4% CP and NEg 1.47 Mcal/kg) for beef cattle with a commercially available CT extract at 3 levels (0, 0.5, and 1.0% of diet, DM basis). Angus-crossbred steers ( = 27; 350 ± 32 kg initial BW) were individually fed via Calan gates for 126 d. Diet digestibility and N balance were estimated after 34 and 95 d on feed (Phase 1 and Phase 2, respectively) using titanium dioxide as a marker of fecal output and the creatinine:BW ratio as a marker for urine output. Ruminal CH and metabolic CO fluxes were measured using a GreenFeed system (C-Lock Inc., Rapid City, SD) for 2 sampling periods that coincided with fecal and urine sampling. Urine energy loss was estimated from urine N excretion, assuming all excreted N was urea. Oxygen consumption was estimated from CO production assuming a respiratory quotient of 1.05. Average daily gain (2.08, 2.14, and 2.08 kg/d for 0, 0.5, and 1.0% CT, respectively) and G:F did not differ ( = 0.88) among treatments. Starch intake and OM intake did not differ ( ≥ 0.42) among treatments during each phase. Apparent total tract starch digestibility during Phase 1 linearly decreased ( = 0.04) with inclusion of CT. Apparent total tract digestibility of OM and starch were not different among treatments ( ≥ 0.13) during Phase 2. Nitrogen intake did not differ ( ≥ 0.16) among treatments during each phase, but fecal N excretion linearly increased ( = 0.05) with inclusion of CT during Phase 1. Urinary N excretion was not different ( ≥ 0.39) among treatments during both phases, but urinary N as a proportion of total N excretion linearly decreased ( = 0.01) when CT was included in the diet during Phase 1. Retained N was not different ( ≥ 0.27) among treatments during each phase. Fluxes of CO were similar ( ≥ 0.37) among treatments during both phases. No differences ( ≥ 0.23) were observed for percentage of GE intake lost as CH (2.99, 3.12, and 3.09% in Phase 1 and 3.54, 3.55, and 4.35% in Phase 2) for 0, 0.5, and 1.0% CT, respectively. No difference ( ≥ 0.42) was observed for heat production lost as a percent of GE intake during both phases. Growth performance, gas emissions, and energetic losses were not affected by the inclusion CT in a steam-flaked corn-based finishing diet.

Concurrent experiments were conducted to evaluate the effect of protein supplementation to beef cattle grazing warm-season shortgrass forage during the late growing season. Cattle in all experiments grazed adjacent shortgrass pastures dominated by Buffalograss (Buchloe dactyloides) and Blue Grama (Bouteloua gracilis). Stocking rates (≥ 2.3 ha/animal) were maintained such that forage availability was not limiting throughout the experiment. Precipitation in the area during the experiment was 176% of normal. For all Exp., treatments consisted of a supplemented group (1.32 kg per head of a 39% CP range cube fed 3 times a week) and a non-supplemented control group. Supplemented animals were fed a daily average of 0.22 kg of CP. In Exp. 1, 45 multiparous cow-calf pairs (initial BW 646 ± 13 kg) were individually weighed and body condition scored every 14 d. Forage clippings were taken simultaneously with BW measurements. Cow measurements and forage clippings began July 6 and concluded September 28. Cow final BW (P = 0.24) and ADG (P = 0.38) were not affected by treatment. There was no difference (P = 0.97) in cow final BCS regardless of treatment. Calf ADG (P = 0.54) and weaning weight (P = 0.45) were not affected by treatment. In Exp. 2, 26 primiparous cows (initial BW 546 ± 12 kg) were supplemented and measurements obtained in the same manner as Exp.1. Cow final BW (P = 0.39) and final BCS (P = 0.81) did not differ between treatments. Cow ADG (P = 0.07) tended to be greater when supplemented with 0.22 kg CP per day. Calf ADG (P = 0.50) and weaning weight (P = 0.11) did not differ between treatments. In Exp. 3, 25 replacement heifers (initial BW 412 ± 9 kg) were observed for BW and forage clippings were obtained every 14 d. Heifer final BW (P = 0.17) was not different between treatments. Heifer ADG (P = 0.02) was greater for supplemented heifers. Supplementing protein to cattle grazing late season medium quality forage is advantageous for increasing ADG in replacement heifers and potentially beneficial to improve condition in lactating primiparous cows. Repeating this experiment under varied precipitation patterns, as is normal for short-grass regions, would be beneficial to further examine the impact of late growing season protein supplementation on cow-calf pair/replacement heifer performance.

Journal Article 1665 WS Effect of corn-based supplementation on gas emissions, performance, and energetic losses of steers grazing wheat pasture Get access P. Ebert, P. Ebert 1Department of Agricultural Sciences, West Texas A&M University, Canyon, TX Search for other works by this author on: Oxford Academic PubMed Google Scholar E. A. Bailey, E. A. Bailey 1Department of Agricultural Sciences, West Texas A&M University, Canyon, TX Search for other works by this author on: Oxford Academic PubMed Google Scholar A. L. Shreck, A. L. Shreck 2USDA-ARS Conservation and Production Research Laboratory, Bushland, TX Search for other works by this author on: Oxford Academic PubMed Google Scholar N. A. Cole, N. A. Cole 2USDA-ARS Conservation and Production Research Laboratory, Bushland, TX Search for other works by this author on: Oxford Academic PubMed Google Scholar J. S. Jennings J. S. Jennings 3Texas A & M AgriLife Research and Extension Center, Amarillo Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Animal Science, Volume 94, Issue suppl_5, October 2016, Pages 811–812, https://doi.org/10.2527/jam2016-1665 Published: 01 October 2016