Dietary n-3 PUFA enhances DMI in transition cows by regulating taste transduction gene expression in liver associated with rumen microbial alteration

We hypothesised that the addition of n-3 polyunsaturated fatty acids (PUFAs) in the diet could affect gene expression in the liver and have beneficial effects on the recovery of cows in the transition phase. A total of 30 multiparous non-lactating Holstein dairy cows (35 days before expected calving) were randomly fed a diet with either 1% dry matter (DM) of hydrogenated fatty acid (C16:00 enriched; CON) or 3.5% DM of extruding flaxseed (n-3 enriched; HN3). 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/d (mean ± SD), respectively, at the beginning of the experiment. The relative abundance of Bacteroidota ( P = 0.047) and Spirochaetota ( P = 0.091) was higher and that of Patescibacteria ( P = 0.076) was lower in the HN3 group than in the CON group on prepartum day 4. The DMI of cows was positively correlated with the abundance of bacteria in the rumen ( Spirochaetota : r = 0.871, P < 0.001; Bacteroidota : r = 0.896, P < 0.001) and the differential expression of genes involved in taste transduction (ACSL1: r = 0.673, P < 0.001; PLIN4: r = 0.632, P < 0.01; CPT1A: r = 0.694, P < 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.