Rumen Fermentation and Fatty Acid Composition of Milk of Mid Lactating Dairy Cows Grazing Chicory and Ryegrass

SIMPLE SUMMARY: Enhancing the concentration of individual fatty acids (FA) in milk has been, for a long time, a major aim for researchers because certain FAs are linked with several health benefits in humans as well as improving the processing quality of milk products. It is well documented that diet, management regime, and extent of biohydrogenation in the rumen are critical in determining the composition of FA in the milk of dairy cows. This study investigated the effects of including chicory into the traditional feeding regime of ryegrass/white clover, and time of its allocation on milk production, rumen fermentation, and FA composition of milk and rumen digesta of dairy cows. Our findings show that allocation of mature chicory herbage to dairy cows at 50% of their ration modified rumen fermentation and improved both milk yield and the FA profile of the milk. Allocating chicory herbage during the afternoon is a useful strategy that can translate to improved milk production and quality. These findings reflect not just the feasibility of including chicory as part of a feeding regime, but also the role of chicory in rumen fermentation and biohydrogenation. ABSTRACT: The goals of the current study were to investigate the effects of including chicory (Cichorium intybus L.) into the traditional feeding regime of ryegrass/white clover (Lolium perenne L./Trifolium repens L.), and time of its allocation on milk production, rumen fermentation, and FA composition of milk and rumen digesta of dairy cows. Nine groups of four cows were allocated one of three replicated feeding regimes: (1) ryegrass/white clover only (RGWC), (2) ryegrass/white clover + morning allocation of chicory (CHAM), and (3) ryegrass/white clover + afternoon allocation of chicory (CHPM). One cow per group had a rumen cannulae fitted. Treatment did not affect total grazing time or estimated dry matter intake, but cows ruminated more when fed RGWC than chicory. Allocating chicory in the afternoon elevated milk production compared with RGWC and CHAM. Milk from cows grazing chicory contained greater concentrations of polyunsaturated FA (PUFA) such as C18:3 c9, 12, 15 and C18:2 c9, 12 than those on RGWC. As with milk, rumen digesta concentration of PUFA increased when cows grazed on chicory rather than RGWC, which corresponded with lower concentrations of intermediate vaccenic and biohydrogenation end-product stearic acid for cows grazing on chicory. Mean ruminal pH was lower for cows offered chicory than those on RGWC, reflecting greater rumen concentrations of volatile fatty acids (VFA) for cows fed chicory. Allocating chicory during the afternoon is a useful strategy that can translate to improved milk production. The lower rumen pH, lower concentration of vaccenic and stearic acids, and elevated concentration of PUFA in the rumen of cows fed chicory suggest reduced biohydrogenation and may explain the elevated concentration of PUFA in the milk of cows fed chicory compared with those fed RGWC.