Effects of a flaxseed and pea matrix on in vitro ruminal fermentation, nutrient degradability, and methane emissions

Abstract

The objective of this study was to determine the impacts of feeding a rumen-protected matrix of fat and protein from flaxseed and peas (LinPRO-R [LIN]; ∼21% fat, 24% CP, and 10.07% n-3 FA; % of DM) on ruminal fermentation, nutrient degradability, and methane emissions, in vitro. Treatments were: 0% (0P), 2.5% (2.5P), 5% (5P), and 7.5% (7.5P) of DM inclusion of LIN, with LIN replacing portions of dried distillers grains and calcium salts of long-chain fatty acids in the diet to maintain similar levels of CP and ether extract (EE). In experiment 1, we used 3 independent runs with 4 replicates per treatment, and 0.5 g of each TMR (16% CP, 33% NDF, 28% starch, 4.2% EE; as % of DM) was incubated in buffered ruminal content for 24 and 48 h, for a total of 6 runs, in glass serum bottles. Gas pressure was measured at 0, 3, 6, 9, 12, 24, and 48 h to estimate total gas and methane productions in the headspace and VFA and lactate concentrations in the fermentation liquid phase. Furthermore, OM degradation was measured at 24 and 48 h after bottles were opened. For experiment 2, twice daily, 53 g of DM of the same treatments was provided to each fermentor. The treatments were arranged in a replicated 4 × 4 Latin square using 8 fermenters. Four 10-d experimental periods (7 d adaptation and 3 d sample collection) were done. Samples were collected from fermentor effluents at 3, 6, 9, and 24 h after morning feeding and composited to determine lactate and VFA concentrations and nutrient degradation. Experiment 1 data were analyzed using PROC GLIMMIX of SAS where treatment was a fixed effect and run was a random effect. Experiment 2 data were analyzed similarly, with square, fermentor within square, period, and the fermentor by treatment interaction being random effects. For experiment 1 with increasing LIN, total gas volume and methane produced per gram of OM degraded decreased linearly, whereas lactate concentration and OM degradability linearly increased. We found no effect of LIN inclusion level on any VFA proportion. For experiment 2 Butyrate and isobutyrate proportions linearly decreased, and NDF degradation quadratically increased, with increasing inclusion of LIN. We found no differences for any other VFA proportions, the total concentration of all VFA, lactate concentration, or the degradation of DM, OM, or CP. Thus, inclusion of LIN, with its higher concentration of n-3, can occur without impairing ruminal fermentation and nutrient degradation; it alters the fermentation profile to reduce total gas volume and methane produced per gram of OM degraded, favors other VFA rather than butyrate or isobutyrate, and increases fiber degradation.