Methane prediction based on individual or groups of milk fatty acids for dairy cows fed rations with or without linseed

Abstract

Milk fatty acids (MFA) are a proxy for the prediction of CH 4 emission from cows, and prediction differs with diet. Our objectives were (1) to compare the effect of diets on the relation between MFA profile and measured CH 4 production, (2) to predict CH 4 production based on 6 data sets differing in the number and type of MFA, and (3) to test whether additional inclusion of energy-corrected milk (ECM) yield or dry matter intake (DMI) as explanatory variables improves predictions. Twenty dairy cows were used. Four diets were used based on corn silage (CS) or grass silage (GS) without (L0) or with linseed (LS) supplementation. Ten cows were fed CS-L0 and CS-LS and the other 10 cows were fed GS-L0 and GS-LS in random order. In feeding wk 5 of each diet, CH 4 production (L/d) was measured in respiration chambers for 48 h and milk was analyzed for MFA concentrations by gas chromatography. Specific CH 4 prediction equations were obtained for L0-, LS-, GS-, and CS-based diets and for all 4 diets collectively and validated by an internal cross-validation. Models were developed containing either 43 identified MFA or a reduced set of 7 groups of biochemically related MFA plus C16:0 and C18:0. The CS and LS diets reduced CH 4 production compared with GS and L0 diets, respectively. Methane yield (L/ kg of DMI) reduction by LS was higher with CS than GS diets. The concentrations of C18:1 trans and n-3 MFA differed among GS and CS diets. The LS diets resulted in a higher proportion of unsaturated MFA at the expense of saturated MFA. When using the data set of 43 individual MFA to predict CH 4 production (L/d), the cross-validation coefficient of determination (R 2 CV ) ranged from 0.47 to 0.92. When using groups of MFA variables, the R 2 CV ranged from 0.31 to 0.84. The fit parameters of the latter models were improved by inclusion of ECM or DMI, but not when added to the data set of 43 MFA for all diets pooled. Models based on GS diets always had a lower prediction potential (R 2 CV = 0.31 to 0.71) compared with data from CS diets (R 2 CV = 0.56 to 0.92). Models based on LS diets produced lower prediction with data sets with reduced MFA variables (R 2 CV = 0.62 to 0.68) compared with L0 diets (R 2 CV = 0.67 to 0.80). The MFA C18:1 cis-9 and C24:0 and the monounsaturated FA occurred most often in models. In conclusion, models with a reduced number of MFA variables and ECM or DMI are suitable for CH 4 prediction, and CH 4 prediction equations based on diets containing linseed resulted in lower prediction accuracy.

Methane Emissions and Milk Fatty Acid Profiles in Dairy Cows Fed Linseed, Measured at the Group Level in a Naturally Ventilated Housing and Individually in Respiration Chambers

“…The two intermediates mentioned, but not the terminal product C18:0, are considered valuable to human health. Linseed has been reported to enhance both the n-3 FA and biohydrogenation intermediates [8,10,11]. The effects of linseed on the FA profile of milk fat in our study were similar at both the individual and group levels (bulk milk), indicating that changes can be clearly recovered in a few bulk milk samples obtained from linseed-fed herds of dairy cattle.…”

“…This difference in response to extruded linseed could have resulted from the different forage type (corn vs. grass silage) and the forage-to-concentrate ratio used in the experiments. Accordingly, the effect of moderate levels of linseed on CH 4 were weaker in the studies of Engelke et al [10] and Martin et al [6], when exchanging corn silage with grass silage and when reducing the concentrate proportion from 50% to 40%, respectively. This is consistent with the findings of Machmüller et al [35], who found that using a lower forage-to-concentrate proportion led to lower methane-mitigating effects of medium-chain FA.…”

“…This lipid supplementation did not cause more than a trend for a CH 4 mitigation effect, although clear effects could have been expected based on the results reported in earlier studies. For example, Martin et al [6]), Engelke et al [10], and Focant et al [11] supplemented extruded linseed at a similar moderate level (26-36 g lipids•kg −1 diet DM) and found CH 4 suppression by approximately 10-20%. This difference in response to extruded linseed could have resulted from the different forage type (corn vs. grass silage) and the forage-to-concentrate ratio used in the experiments.…”

“…At supplementation levels of ≤20 g linseed lipids per kg feed DM, there was no reduction in the CH 4 emissions [7][8][9]. Thus, supplementing feed with moderate levels ranging from 26-36 g linseed lipids kg −1 feed DM appears to be the most promising approach to achieve a clear CH 4 reduction with marginal effects on digestion and intake [6,10,11]. In addition, extruded linseed increases the proportion of n-3 polyunsaturated fatty acids (FAs) in milk fat, which is considered beneficial to human health (e.g., [12]).…”

Mogelijke risico's nieuwe emissie-reducerende producten voor herkauwers

“…Via vetzuurprofielen van de melk blijkt een voorspelling van de methaanuitstoot mogelijk te zijn (Dijkstra et al, 2011). Dit is ook afhankelijk van de samenstelling van het voer (Engelke et al, 2019).…”