Effect of dietary phosphorus deprivation during the dry period on the liver transcriptome of high-yielding periparturient dairy cows

While dietary phosphorus (P) deprivation extending from the dry period into early lactation impairs health and productivity of cows, restricting dietary P supply during the dry period not only appears to be innocuous but rather effectively mitigates hypocalcemia during the first wk of lactation. To investigate possible negative metabolic effects of P deprivation during the dry period, the present study tested the hypothesis that restarted dietary P supply during the dry period alters the liver transcriptome of dairy cows during the periparturient period. Thirty late-pregnant multiparous Holstein-Friesian dairy cows entering their 2nd, 3rd or 4th lactation were assigned to either a dry cow ration with low (LP, 0.16% P in DM) or adequate P content (AP, 0.35% in DM) during the last 4 wk of the dry period (n = 15/group). Liver transcriptomics, which was carried out in a subset of 5 2nd parity cows of each group (n = 5), and determination of selected hormones and metabolites in blood of all cows, was performed approximately one wk before calving and on d 3 postpartum. Liver tissue specimens and blood samples were obtained by a micro-invasive biopsy technique from the right 10th intercostal space and puncture of a jugular vein, respectively. 175 hepatic transcripts were expressed differentially between LP vs. AP cows in late pregnancy, and 165 transcripts differed between LP vs. AP cows in early lactation (Fold change >1.3 and < −1.3, P < 0.05). In late pregnancy, the enriched biological processes of the upregulated and the downregulated transcripts were mainly related to immune processes and signal transduction (P < 0.05), respectively. In early lactation, the enriched biological processes of the upregulated and the downregulated transcripts were involved in mineral transport and biotransformation (P < 0.05), respectively. The plasma concentrations of the hormones and acute phase proteins (progesterone, insulin-like growth factor 1, serum amyloid α, haptoglobin, and 17β-estradiol) determined were not affected by P supply. These results suggest that P deprivation during the dry period moderately affects the liver transcriptome of cows in late pregnancy and early lactation, and causes no effects on important plasma hormones and acute phase proteins indicating no obvious impairment of health or metabolism of the cows.