|Hales Paxton, Kristin|
|Wells, James - Jim|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2015
Publication Date: 5/1/2015
Publication URL: https://handle.nal.usda.gov/10113/60916
Citation: Freetly, H.C., Lindholm-Perry, A.K., Hales, K.E., Brown-Brandl, T.M., Kim, M.S., Myer, P.R., Wells, J. 2015. Methane production and methanogen levels in steers that differ in residual gain. Journal of Animal Science. 93(5):2375-2381.
Interpretive Summary: Methane is produced as a product of fermentation in the digestive tract of cattle. Methane released by cattle represents a loss of feed energy. The methane is produced by a specific group of bacteria (methanogens). Steers vary in the amount of weight they gain on a given amount of feed. We found that steers that differed in their weight gain did not differ in their potential to produce methane. We also determined that the total level of methanogens did not differ between the two groups of steers. Methanogens were identified in both the upper (reticulum-rumen complex) and lower digestive tract (colon). The potential to produce methane was greater in the reticulum-rumen complex than the colon.
Technical Abstract: Methane gas released by cattle is a product of fermentation in the digestive tract. The two primary sites of methane fermentation in ruminants are the reticulum-rumen complex, and the cecum. Methane release from cattle represents a 2 to 12% loss of the energy intake. Reducing the proportion of feed energy lost as methane (CH4) has the potential of improving feed efficiency as well as decreasing the contribution of cattle to greenhouse gas production. Feed intake and growth were measured on 132 fall-born steers for 70 d. Seven steers with extreme positive residual gain (RG) and 7 steers with extreme negative RG whose dry DMI was within 0.32 STD of the mean DMI were selected for subsequent measurements. Enteric methane production was measured via indirect calorimetry. Rumen, cecum, and rectal contents were obtained from steers at slaughter for measurement of in vitro methane production and methanogen levels. Enteric methane production did not differ (P = 0.11) between the positive RG (628 ± 73 mol/6 h) and the negative RG (415 ± 73 mol/6 h) steers. In vitro rumen methane production did not differ between steers with different RG (P = 0.98). In vitro methane production was greater in the rumen (0.510 ± 0.051 CH4 nmol·DM g-1·min-1) than cecum (0.036 ± 0.051 CH4 nmol·DM g-1·min-1; P < 0.001). Methanogens as a percentage of the total bacteria did not differ between RG groups (P = 0.18). The percentage of methanogens in rumen content (5.3 ± 3.1%) did not differ from the cecum content (11.8 ± 3.1%; P = 0.14). The percentage in the rectum content (0.7 ± 3.1%) was not different than the rumen content (P = 0.29), and was lower than the cecum content (P = 0.01). The order Methanomicrobiales as a percentage of total methanogens did not differ across sample sites (P = 0.81); however, steers with negative RG (8.3 ± 2.5%) had more compared to steers with positive RG (3.5 ± 2.5%). Cattle that differ in RG at the same DMI do not differ in characteristics associated with methane production.