Abstract
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 (P = 0.047) and Spirochaetota (P = 0.091) were higher and that of Patescibacteria (P = 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: 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.