Effects of phosphorus deprivation during the periparturient period on the phospholipid composition of erythrocyte membranes in dairy cows.

Previous studies have shown that insufficient phosphorus supply in dairy cows during the transition period can lead to postparturient hemoglobinuria, which is associated with the development of anemia and is presumably a consequence of increased osmotic fragility of erythrocytes. The exact causes of this condition remain unknown. The present study investigated the hypothesis that phosphorus depletion in dairy cows during the transition phase leads to changes in the phospholipid composition of the erythrocyte membrane, which may contribute to increased osmotic fragility. To test this hypothesis, an experiment with 18 healthy, multiparous, pregnant cows was conducted, in which cows received either a control diet with adequate phosphorus content (0.28% and 0.44% phosphorus in DM during the dry period and lactation, respectively, control group) or a diet with reduced phosphorus content (0.15% and 0.20% phosphorus in DM during the dry period and lactation, respectively, phosphorus depletion group) from 4 wk before expected calving until 4 wk postpartum. Blood samples were collected 2 wk before the expected calving date, as well as 1 and 4 wk postpartum. Erythrocyte membranes were isolated, and lipids were extracted for quantitative analysis of individual phospholipid species using liquid chromatography-MS. Phospholipid class contents (sphingomyelin, phosphatidylserine, phosphatidylethanolamine [PE], phosphatidylinositol, phosphatidylcholine [PC], lyso-PC, and lyso-PE) were not affected by the treatment. Similarly, the mean carbon atom chain length and the mean number of double bonds in individual phospholipids were not affected by treatment. There were very few changes of the percentages of individual phospholipid species. The time of sampling had only minimal effect on phospholipid composition and the proportions of individual phospholipid species. In conclusion, these results indicate that moderate and transient dietary phosphorus deprivation does not alter the phospholipid composition of the erythrocyte membrane. This suggests that phosphorus deprivation-induced periparturient hemoglobinuria is not caused by alterations in erythrocyte membrane lipid composition.