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Title: Rumen and cecum methane emissions between steers that are either negative or positive for residual gain

Author
item Freetly, Harvey
item Hales Paxton, Kristin
item Wells, James - Jim

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2012
Publication Date: 7/2/2012
Citation: Freetly, H.C., Hales, K.E., Wells, J. 2012. Rumen and cecum methane emissions between steers that are either negative or positive for residual gain [abstract]. Journal of Animal Science. 90(Suppl. 3):478.

Interpretive Summary:

Technical Abstract: Cattle produce CH4 in the rumen and the cecum, and it represents a loss of feed energy. A possible cause of variation in feed efficiency may be differences in capacity to produce CH4. We hypothesized that cattle with a higher residual gain (RG) would have a decreased capacity to produce CH4. Individual DMI and BW gain were determined on crossbred steers (n = 132, initial age = 348 ± 1 d and BW 444 ± 4 kg) for 56 d. Steers were offered feed ad libitum and intake was measured using an Insentec RIC Feeding System (Insentec B.V., Marknesse, The Netherlands). The diet consisted of 82.75% rolled corn, 12.75% corn silage, and 4.5% Biegerts supplement (Bradshaw, NE; contains 0.066% monensin, 51% CP). On d 0, 1, 21, 42, 56, 62, and 63 BW was measured, and BW gain was calculated using the regression coefficient. Residual gain was calculated from the regression of BW on DMI; f(x) = (0.1262 ± 0.0128)x + (25.7 ± 9.9), R2 = 0.43. The 7 animals with the most extreme positive and negative RG that were within 32% of the STD of the mean DMI (772 ± 90 kg) were sampled. Steers received the diet until they were slaughtered. One positive and negative RG steer were slaughtered at 12, 13, 14, 15, 19, 20, and 21 d after the end of the feeding period. At slaughter, rumen fluid was filtered and placed in a flask in a 39°C waterbath and allowed to settle. Samples were taken from the center layer. Cecum contents were placed directly into an incubation flask. For each sample site, 10 gm of sample was anaerobically transferred to incubation bottles (110 mL) that contained 70 mL of buffer (4 replicates/steer). Bottles received 40 mL of hydrogen gas and were incubated in a 39°C shaking waterbath. Gas volume and CH4 concentrations were determined at 2, 4, 6, and 8 h. Rate of CH4 production was the average of replicate bottles within steer. Data were analyzed as a 2 × 2 factorial with sample site and RG as fixed effects. Methane production per unit DM (mmol·g-1·min-1) was greater in rumen 0.000510 ± 0.000051 than cecum 0.000036 ± 0.000051 samples (P < 0.001). Methane production did not differ between high and low RG (P = 0.98).