Whole cottonseed supplementation improves performance and reduces methane emission intensity of grazing beef steers

Abstract

<h2>ABSTRACT</h2> The objective of this experiment was to determine the effect of level of whole cottonseed (WCS) supplementation on ADG and enteric CH₄ emissions of steers grazing tallgrass prairie in the summer. Steers (n = 18; initial BW=316 ± 23 kg) were trained for 3 wk to use a portable, automated head-chamber system (GreenFeed; C-Lock Inc., Rapid City, SD). Steers were then offered from 0 to 2.9 kg/d (as fed) WCS in individual feeders for 43 d. Body weight was measured weekly before feeding. Total fat concentration of the diet (supplement + forage) at the greatest supplement intake was estimated to be 8.3% of DM. Body weight gain increased linearly as supplement intake increased (<i>P</i> = 0.01). Because of inadequate use of the automated head-chamber system by steers at the 0-kg WCS level, this level was excluded from further analysis. In supplemented steers, there was a tendency (<i>P</i> = 0.1) for a quadratic relationship between CH₄ emissions (g/animal per d) and supplement intake, with minimum CH₄ at 2.0 kg of supplement (WCS + bait) per day. Emission intensity (g of CH₄/kg of BW gain) also responded quadratically (<i>P</i> < 0.004) and was minimized at approximately 2.2 kg of supplement intake per day. The results of this experiment suggest that if WCS supplementation is used to mitigate CH₄ emission intensity in stocker cattle grazing tallgrass prairie in the early summer, a dose near 2 kg/d is suggested.