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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]

This study focuses on calibrating and validating models for hyperspectral canopy reflectance data that are useful to predict the nutritive value of ryegrass-white clover mixed herbage available to the grazing cow. Hyperspectral measurements and herbage cuts were collected from 286 sampling plots from a dairy farm from July 2017 to May 2018. Hyperspectral data were pre-treated by applying a Savitzky-Golay filter followed by a Gap-segment derivative algorithm. Herbage samples were analyzed for determination of herbage nutritive value traits, digestible organic matter in dry matter (DOMD), metabolizable energy (ME), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF). Partial least squares regression was performed to calibrate the spectra against the five nutritive value traits. Results indicate that accuracy was moderately high for the CP model (R2 = 0.78) and moderate for the DOMD, ME, NDF and ADF models (0.54 < R2 < 0.67). The possibility of being able to use proximal sensing for the estimation of herbage nutritive value in the field could potentially contribute to more efficient grazing management with potential economic benefits for the farm business. [ABSTRACT FROM AUTHOR]