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.