Spot measurements of methane emission rate (n = 18 700) by 24 Angus steers fed mixed rations from GrowSafe feeders were made over 3-to 6-min periods by a GreenFeed emission monitoring (GEM) unit. The data were analysed to estimate daily methane production (DMP; g/day) and derived methane yield (MY; g/kg dry matter intake (DMI)). A one-compartment dose model of spot emission rate v. time since the preceding meal was compared with the models of Wood (1967) and Dijkstra et al. (1997) and the average of spot measures. Fitted values for DMP were calculated from the area under the curves. Two methods of relating methane and feed intakes were then studied: the classical calculation of MY as DMP/DMI (kg/day); and a novel method of estimating DMP from time and size of preceding meals using either the data for only the two meals preceding a spot measurement, or all meals for 3 days prior. Two approaches were also used to estimate DMP from spot measurements: fitting of splines on a 'per-animal per-day' basis and an alternate approach of modelling DMP after each feed event by least squares (using Solver), summing (for each animal) the contributions from each feed event by best-fitting a one-compartment model. Time since the preceding meal was of limited value in estimating DMP. Even when the meal sizes and time intervals between a spot measurement and all feeding events in the previous 72 h were assessed, only 16.9% of the variance in spot emission rate measured by GEM was explained by this feeding information. While using the preceding meal alone gave a biased (underestimate) of DMP, allowing for a longer feed history removed this bias. A power analysis taking into account the sources of variation in DMP indicated that to obtain an estimate of DMP with a 95% confidence interval within 5% of the observed 64 days mean of spot measures would require 40 animals measured over 45 days (two spot measurements per day) or 30 animals measured over 55 days. These numbers suggest that spot measurements could be made in association with feed efficiency tests made over 70 days. Spot measurements of enteric emissions can be used to define DMP but the number of animals and samples are larger than are needed when day-long measures are made.

The effects of 5 endpoint temperatures for cooked, internal color were determined for boneless pork longissimus muscle from 4 treatment groups: normal, normal-injected, PSE, and DFD. Visual and instrumental color, myoglobin denaturation, and acid phosphatase (ACP) of raw and cooked samples were evaluated. Visual internal color became (P < 0.05) less pink as endpoint temperature increased; however, DFD chops were more pink (P < 0.05) and PSE chops were less pink (P < 0.05) than other treatments at most endpoint temperatures. Cooked color was similar (P > 0.05) for chops from normal and normal-injected groups. Myoglobin denaturation increased as endpoint temperature increased. ACP activity in raw chops was not affected by treatment group and it was a good indicator of doneness at 71.1 °C.

The aim of the present experiment was to evaluate the utility of carbon dioxide production rate (CPR; g CO2/day) and animal weight (WT) data as proxies for feed intake to adjust methane production rate (MPR; g CH4/day) in situations where dry-matter intake (DMI) is not known. This experiment measured individual-animal DMI, MPR and CPR in the feedlot, and then again on restricted quantities of grain and roughage diets in open-circuit respiration chambers. Of the 59 cattle tested in the feedlot, 41 had MPR and CPR recorded, and 59 and 57 had test results on the restricted grain and roughage rations. Methane production relative to DMI by individual animals was calculated as CH4 yield (MY; MPR/DMI) and as residual CH4 production (RMPDMI; calculated as MPR less predicted MPR based on DMI). A second form of RMP: RMPCO2, was calculated by regressing MPR against CPR to determine whether animals were producing more or less CH4 than predicted for their CPR. Carbon dioxide production rate was positively associated with DMI in all three test phases (R2 = 0.25, 0.45 and 0.47; all P < 0.001). The associations for MY with MPR : CPR were moderate and positive, as follows: R2 = 0.49 in the feedlot test; R2 = 0.37 in the restricted-grain test; and R2 = 0.59 in the restricted-roughage test, and with RMPCO2, values of R2 were 0.57, 0.34 and 0.59 in the three test phases (all P < 0.001). The R2 for RMPDMI with MPR : CPR in all three tests were 0.50, 0.79 and 0.69, and with RMPCO2, values of R2 were 0.68, 0.79 and 0.68 (all P < 0.001). The high R2 for MY with MPR : CPR and RMPCO2 and even higher R2 for RMPDMI with MPR : CPR and RMPCO2 in all three test phases showed that CPR can be used to adjust MPR data for DMI when DMI is not recorded. In the feedlot test, where animal WT data were recorded over 70 days, MPR adjusted for WT and WT gain had R2 with MY and RMPDMI of 0.60 and 0.83, respectively (P < 0.001), offering the possibility that animal WT data determined over an extended time period could also be used as a proxy for DMI in adjustment of MPR.

Nitrate may serve as a non-protein nitrogen (NPN) source in ruminant diets while also reducing enteric methane emissions. A study was undertaken to quantify methane emissions of cattle when nitrate replaced urea in a high concentrate diet. Twenty Angus steers were allocated to two treatment groups and acclimated to one of two iso-energetic and iso-nitrogenous finisher rations (containing NPN as urea or as calcium nitrate), with all individual feeding events recorded. A single methane measurement device (C-lock Inc., Rapid City, SD, USA) was exchanged weekly between treatments (2 × 1-week periods per treatment) to provide estimations of daily methane production (DMP; g CH4/day). A 17% reduction in estimated DMP (P = 0.071) resulted from nitrate feeding, attributed to both a tendency for reduced dry matter intake (DMI; P = 0.088) and H2 capture by the consumed nitrate. NO3-fed cattle consumed a larger number of meals (14.69 vs 7.39 meals/day; P < 0.05) of smaller size (0.770 vs 1.820 kg/meal) each day, so the average interval between a feeding event and methane measurement was less in NO3-fed cattle (3.44 vs 5.15 h; P < 0.05). This difference could potentially have skewed the estimated DMP and contributed to the tendency (P = 0.06) for NO3-fed cattle to have a higher methane yield (g CH4/kg DMI) than urea-fed cattle. This study found short-term methane emission measurements made over 2 weeks (per treatment group) were adequate to show dietary nitrate tended to reduce emission and change the feeding pattern of feedlot cattle. Changes in feeding frequency may have confounded the ability of short-term methane measurements to provide data suitable for accurately estimating methane per unit feed intake.