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The temporal profile of methane (CH 4) emissions from ruminants is affected by feed composition and forage type. This study aimed to 1) describe and compare the post-feeding pattern of CH 4 emissions from lambs fed fresh ryegrass substituted with graded levels of forage rape, and 2) to evaluate the association between the magnitude of the variation in CH 4 emission patterns and organic fermentation products quantified in pre- and- post- feeding rumen content samples. Methane emissions were measured at approximately 6 min intervals in respiration chambers from 70 lambs (n = 14 per treatment) fed ryegrass only (FR0) or as a proportion, 0.25 forage rape + 0.75 ryegrass (FR25), 0.50 forage rape + 0.50 ryegrass (FR50), 0.75 forage rape + 0.25 ryegrass (FR75), and forage rape only (FR100). The magnitude of the variability in CH 4 emissions was defined as the ratio of maximum to minimum CH 4 emissions in a 24 h period. This ratio was correlated (P < 0.05) with the proportions of major short chain fatty acids, and calculated hydrogen (H 2) available per unit of glucose fermented (H 2 /GEF), quantified in rumen content samples collected pre- and- post- feeding. The CH 4 emission profile after each feeding followed an asymmetrical positively skewed shape for FR0 to FR75, but not in lambs fed FR100. The lowest CH 4 emission rates were observed before morning feeding which was followed by a CH 4 peak within the 2 h after feeding, and then the CH 4 emissions decreased until the next feeding. In FR100 lambs, the CH 4 emission rate was, unexpectedly, relatively constant after feeding, without any clear CH 4 peaks. The magnitude of the variability in the CH 4 emission rate increased when the pH of rumen contents and H 2 /GEF measured in pre-feeding samples decreased. Including forage rape at 0.75, or greater proportion, in the diet of lambs drastically changed the CH 4 emissions pattern, likely due to a continuous low pH in the rumen which is detrimental for methanogenesis. In conclusion, the daily variation in CH 4 emissions decreased with increasing forage rape inclusion in the diet of sheep and this was associated with a decreasing acetate proportion in the rumen liquid. • Lambs fed 100% forage rape had relatively constant CH 4 emissions throughout the day. • Adding increasing pasture to the forage rape increased the variability of CH 4. • H 2 available per unit of glucose fermented was correlated to the variability of CH 4. [ABSTRACT FROM AUTHOR]

Abstract: Studies have shown that thermogravimetric (TG) analysis can highlight differences in the combustion patterns of high, medium and poorly digestible ryegrass samples as measured by pepsin cellulase assay. The samples used in our study were obtained from experiments completed in England and Wales during 1980–1988. The objectives were to develop regression models based on the thermal characteristics of ryegrass and validate the models using 20 samples from two experiments completed in Northern Ireland for in vivo organic matter (OMD) and dry matter digestibility (DMD). Differences in combustion patterns of the samples from 30 to 600°C were compared and four segments of the thermal data were regressed against OMD and DMD by employing the partial least squares regression method in which a number of equations were developed. The best TG models were generated using the 300–1450 (i.e., 133–516.3°C) segment (OMD, R 2 =0.76, standard error of cross validation [SECV]=28.9g/kg DM; DMD, R 2 =0.84, SECV=35.5g/kg DM) and R 2 values for validation of the best models were 0.74 (standard error of prediction [SEP]=28.6g/kg DM) and 0.72 (SEP=28.8g/kg DM) for OMD and DMD respectively using 20 samples of herbage and grass silage from two animal feeding experiments. Thermogravimetry can be used as a rapid quality assessment tool to monitor changes in composition of stem, sheath, young and mature leaves of F2 and F3 progeny with minimal labour cost. The technique has the potential to enhance understanding of ruminant digestion of plant cell wall fractions. [Copyright &y& Elsevier]

Abstract: White and red clover silages have been shown to result in a higher transfer efficiency of polyunsaturated fatty acids (PUFA) to the milk or meat of ruminants compared to ryegrass silages. For red clover this has been related to protein bound phenols formed by polyphenol oxidase (PPO). PPO is typically active in red clover and the protein bound phenols, which are the result of PPO activity, could result in a decrease in PUFA biohydrogenation in the rumen through inhibition of lipolysis in the silage and/or in the rumen, as lipolysis is a prerequisite of biohydrogenation. Higher transfers of white clover PUFA have been associated with increased rumen outflow rates, although lower in silo lipolysis also has been observed. No research on effect of ensiling agricultural practice as dry matter (DM) and using different silage additives on extent of in silo lipolysis has been performed earlier. Therefore, the goal of this experiment was to study the effect of formic acid, an inoculum or a carbonate buffer as a silage additive and DM content of the wilted forages at ensiling on fatty acid (FA) composition and lipolysis in silages of red clover, white clover and ryegrass. Furthermore, it was attempted to link lipase activity measured as the p-nitrophenyl butyrate hydrolyzing activity of a protein extract with in silo lipolysis and to study the correlation of this enzyme activity with the amount of protein bound phenols. Higher DM content at ensiling resulted in lower linolenic acid concentrations, which was suggested to be related to the longer wilting period and more extensive oxidation. Formic acid resulted in a lower lipolysis in all forages compared to the other treatments. The effect of DM content was rather limited, although lipolysis decreased slightly with increasing DM content in ryegrass. Lipolysis was lower in silages of red and white clover compared to ryegrass at 300gDM/kg. At higher DM contents lipolysis was equal or lower in ryegrass silages. Enzyme activity measurements indicated bound phenols could inhibit enzyme activity, both in red and in white clover. However, no direct link between measured plant lipase activity of wilted forages and in silo lipolysis could be found. [Copyright &y& Elsevier]