Relationship between sainfoin proanthocyanidins and in vitro fermentation depending on time of harvest and level of inclusion in the diet

The aim of the current study was to evaluate the effect of the presence of active proanthocyanidins (PAC) from sainfoin, either fresh or dehydrated included in the finishing concentrate of lambs, on in vitro ruminal fermentation parameters, by including polyethylene glycol to block PAC. Total gas and methane productions, ammonia (NH₃-N), and volatile fatty acids (VFA) were analyzed in fresh and in dehydrated sainfoin included in concentrates for finishing lambs at different rates (0 %, 20 % and 40 %), and ruminal biohydrogenation (BH) only in the latter. Under the conditions of the present in vitro study, active PAC from fresh and dehydrated sainfoin reduced the production of gas and methane (P < 0.01), with no effect on total VFA (P > 0.05). The presence of active PAC reduced NH₃-N content in fresh sainfoin (P < 0.01), whereas the lower PAC contents in concentrates including dehydrated sainfoin only elicited a tendency (P = 0.06). The presence of sainfoin PAC in the concentrate decreased the BH extent and promoted the trans-11 BH pathway (P < 0.05). The inclusion of sainfoin in the diet of lambs produced a nonlinear effect concerning gas production, with a decrease only when dehydrated sainfoin was included in the concentrate at 20 %. In contrast, a reduction in methane production was only obtained with a 40 % sainfoin addition. The inclusion of dehydrated sainfoin in the concentrate decreased the ruminal percentage of branched-chain fatty acids (FA; P < 0.01) and increased most of the trans-monounsaturated FA, C18:3 n-3, and BH intermediates (P < 0.05).