In vitro assessment of ruminal biohydrogenation of polyunsaturated fatty acids in diets with different types and levels of protected fat and diverse sources of fibre

Abstract

Abstract The objective was to assess in vitrorumen fermentation characteristics, methane production and biohydrogenation of unsaturated fatty acids of diets based on maize silage with two sources of protected fat (PF) from soybean (S) or linseed (L) oil, two levels of PF (0 and 6%) and two forage sources: canola silage (CS) or alfalfa hay (AH); in a factorial 2x2x2 completely randomised design. The highest (P<0.05) amount of C18:2 at the end of incubation was in the S6AH treatment (4.41mg/g DM) and of C18:3 in L6CS (1.98mg/g DM). The AH 6% PF showed the highest concentration of C18:2 cis-9 trans-11 (308 mg/g DM; P<0.05). C18:1 trans-11 was higher with 6% PF than without PF (13.41 vs 7.89 mg/g DM). Cumulative methane production was not affected by treatments (0.9973 ± 0.1549 mmol/g DM; P>0.05). Gas production (GY) was lower with PF at 6% L vs S (150.97 vs 160.88 ml; P<0.05), and IVDMD was higher (P<0.05) with AH without PF than with 6% PF (85.04 vs 78.54%), and IVNDFD was lower with 6% L than with 6% S (62.89 vs 69.28%; P<0.05). L had the highest NH3-N concentration with CS than with AH with the same type of PF (41.27 vs 27.95 mg/dL; P<0.05). In conclusion, although methane production was not affected and in vitro digestibility and GY were reduced with linseed PF supplementation, the concentration of C18:3 and C18:1 trans-11 was increased, which could improve the lipid profile of milk. The negative effects on digestibility were improved with AH instead of CS regardless of PF type and level.