Effect of quebracho condensed tannin extract on fecal gas flux in steers.

Naturally occurring gaseous by-products of ruminant production-carbon dioxide (CO2 ), methane (CH4 ), and nitrous oxide (N2 O)-can negatively affect the environment. Along with enteric fermentation, manure on pasture is among the most significant contributors to non-CO2 emissions. Condensed tannins, a group of naturally occurring phenolic compounds, can alter the route of nutrient excretion and interact with microbes, suggesting they are a plausible feed additive for reducing excreta gas emissions. We evaluated how quebracho (Schinopsis balansae) tannin extract fed at 0, 15, 30, and 45 g kg-1 of dry matter (DM) within a roughage-based diet affected fecal gas emissions at multiple locations (College Station and Stephenville, TX) during two periods corresponding to winter and spring. During both periods, CO2 , CH4 , and N2 O fluxes were determined using the vented-static chamber methodology over 39 d, and cumulative emissions were calculated. A random coefficients model with animal nested within dietary treatment and period as the random factor was analyzed by location due to the presence of collinearity with soil parameters within periods. Daily CO2 flux was influenced by soil moisture and temperature (r = .34; P < .01), whereas CH4 and N2 O were associated with soil moisture. Cumulative gas production confirmed a dietary effect for CO2 and gross CO2 equivalent at the College Station site (P ≤ .001), demonstrating a linear reduction as quebracho inclusion increased. Variance partitioning indicated that dietary treatment and seasonal period likely influenced animal digestive and metabolic parameters. Within specific environments, quebracho supplementation may assist in reducing fecal gas emissions.

Effects of energy supplementation on energy losses and nitrogen balance of steers fed green-chopped wheat pasture I: Calorimetry.

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.