Smoothing spline assessment of the accuracy of enteric hydrogen and methane production measurements from dairy cattle using various sampling schemes

• DOI: 10.3168/jds.2022-23207
• Publication Date: 2023-05-18T19:45:51Z
• Authors: Henk J. van Lingen; James G. Fadel; Ermias Kebreab; André Bannink; Jan Dijkstra; Sanne van Gastelen
• Keywords: Methane Emissions; Restricted maximum likelihood

Estimating daily enteric hydrogen (H2) and methane (CH4) emitted from dairy cattle using spot sampling techniques requires accurate schemes. These schemes determine the number of samplings their intervals. This simulation study assessed accuracy H2 CH4 emissions various for gas collection. Gas emission data were available a crossover experiment with 28 cows fed twice at 80% to 95% ad libitum intake, an that used repeated randomized block design 16 libitum. Gases sampled every 12 15 min 3 consecutive days in climate respiration chambers. Feed was 2 equal portions per day both experiments. Per individual cow-period combination, generalized additive models fitted all diurnal profiles. profile, cross-validation, REML, REML while assuming correlated residuals, heteroscedastic residuals. The areas under curve (AUC) these 4 fits numerically integrated over 24 h compute production compared mean points, which considered reference. Next, best evaluate 9 different evaluation determined average predicted values 0.5, 1, intervals starting 0 morning feeding, 1 0.5 6 8 unequally spaced or samples day. Sampling needed obtain productions not selected AUC restricted feeding experiment, whereas less frequent had predictions varying 47% 233% AUC. For 85% 155% corresponding shorter, depending on time after scheme did affect experiment. In conclusion, major impact production, particularly severely affected by scheme.