Dietary n-3 polyunsaturated fatty acids enhance dry matter intake in transition cows by regulating taste transduction gene expression in the liver associated with rumen microbial alteration

This study explored the effect of supplementing the diet with n-3 polyunsaturated fatty acids (PUFA) on liver gene expression and its contribution to the recovery of cows during the transition phase. A total of 30 multiparous non-lactating Holstein dairy cows (35 d before expected calving) were randomly fed a diet with either 1% dry matter (DM) of hydrogenated fatty acid (FA) (C16:00 enriched; control group [CON]) or 3.5% DM of extruding flaxseed (n-3 enriched; HN3 group). The cows underwent a 7-d adaptation period, followed by a 28-d prepartum period and a 28-d postpartum period. In the beginning of the experiment, parity, body weight (BW), body condition score (BCS) and milk yield were 2.6 ± 1.2, 757.5 ± 65.8 kg, 3.3 ± 0.2 and 10,286.5 ± 1464.8 kg/previous lactation (mean ± SD), respectively. The relative abundances of Bacteroidota (<i>P</i> = 0.047) and Spirochaetota (<i>P</i> = 0.091) were higher and that of <i>Patescibacteria</i> (<i>P</i> = 0.076) was lower in the HN3 group than in the CON group on 4 d before prepartum. The dry matter intake (DMI) of cows was positively correlated with the abundance of bacteria in the rumen (Spirochaetota: <i>r</i> = 0.871, <i>P</i> < 0.001; Bacteroidota: <i>r</i> = 0.896, <i>P</i> < 0.001) and the differential expression of genes involved in taste transduction (<i>ACSL1</i>: <i>r</i> = 0.673, <i>P</i> < 0.001; <i>PLIN4</i>: <i>r</i> = 0.632, <i>P</i> < 0.01; <i>CPT1A</i>: <i>r</i> = 0.694, <i>P</i> < 0.001). These results suggest that dietary n-3 PUFA at an appropriate concentration can promote DMI recovery by upregulating the expression of these genes and maintaining the balance of the rumen microbiota.