Influence of feeding a low-phosphorus diet on leucocyte function in dairy cows

Abstract

Phosphorus depletion and hypophosphatemia have been described to interfere with immune function in rats and humans. In dairy cows, hypophosphatemia has been associated with muscle weakness and recumbency as well as with intravascular hemolysis resulting from increased osmotic fragility of erythrocytes, but so far, the influence of P depletion and hypophosphatemia on immune function has not been studied. Therefore, the aim of this study was to investigate whether P depletion and ensuing hypophosphatemia are associated with impaired granulocyte and lymphocyte function. Eight mid-lactation dairy cows were fed a P-deficient ration (0.2% P/kg of DM) for a period of 4 wk. The depletion phase was preceded by a 2-wk acclimatization period and followed by a 2-wk repletion phase, during which the same ration was supplemented with P to meet or exceed daily requirements. Blood samples were collected at the end of the acclimatization period, after 2 and 4 wk of P depletion, and at the end of the repletion phase. Plasma phosphate concentrations ([Pi]) were determined and white blood cells were counted and isolated. General immune function was investigated by performing a phagocytosis assay with Staphylococcus aureus and a lymphocyte stimulation test (LST) with concanavalin A and pokeweed mitogen. The plasma [Pi] decreased significantly, with the lowest values (mean 0.7 ± 0.2 mmol/L) occurring after 2 wk of depletion, although depletion was continued for another 2 wk. During repletion, plasma [Pi] increased above baseline concentrations. Granulocyte counts changed in parallel with plasma [Pi] over time, decreasing significantly at 2 wk after P depletion and increasing again thereafter. Granulocyte survival after phagocytosis was lowest after 4 wk of P depletion. Phagocytosis activity of surviving granulocytes determined by mean fluorescence intensity was higher, indicating that phagocytosis was not negatively influenced by P depletion. Lymphocyte stimulation showed a similar trend, with a decreasing stimulation index at the end of P depletion, but differences were not statistically significant. Data presented in this study indicate that hypophosphatemia leads to a decrease in granulocyte counts. Chronic P depletion impairs granulocyte survival during phagocytosis but not phagocytosis activity. Lymphocyte function is not influenced by P depletion.

Possibilities of Designating Swards of Grasses and Small-Seed Legumes From Selected Organic Farms in Poland for Feed

“…In the case of beef cattle breeding, phosphorus content above 0.17% should suffice (Mc Dowell, 1996). When phosphorus content in feed is too low, there can be problems with animal health associated with the limited ability to move, osteopathic lesions, and with problems with reproduction (Eisenberg et al 2014). The problem of macro element deficiency in cattle eating feed from one source was emphasized particularly by Mc Dowell (1996) and McNamara et al (2017).…”

Effect of dietary phosphorus deprivation on leukocyte function in transition cows

“…One study conducted in non-periparturient dairy cows and feeding diets with varying amounts of P, covering a range at or above current recommendations for dietary P content for dairy cow rations, did not reveal an effect of the dietary P content on the innate or cell-mediated immune response (Mullarky et al, 2009). A second study conducted in mid-lactating dairy cows and feeding a markedly P-deficient diet reported a negative effect of dietary P deprivation on granulocyte survival but no negative effect on the phagocytic activity of viable granulocytes (Eisenberg et al, 2014).…”

“…Leukocytes were isolated from EDTA blood under sterile conditions using osmotic lysis as described be-fore with slight modification (Eisenberg et al, 2014). Briefly, 18 mL of distilled water was added to 9 mL of EDTA blood and after 30 s iso-osmolarity was restored by adding 2 mL of 10× PBS (Lonza Group AG, Basel, Switzerland) to the sample.…”

“…The phagocytosis assay was performed as described before with slight modifications (Eisenberg et al, 2014). Briefly, 10 µL of S. aureus containing 2 × 10 7 bacteria was added to a well of a 96-well round-bottom plate and diluted with 10 µL of pooled bovine serum.…”

“…After 5 min of incubation, samples were washed twice with FACS buffer and directly measured by using flow cytometry and analyzed by using FlowJo. To determine phagocytosis, FlowJo software was used for selective gating on FSC-SSC as described before (Eisenberg et al, 2014). Briefly, first all live cells were gated on FSC-SSC, then the granulocyte population was gated, and finally the degree of phagocytosis was determined by identifying the relative number of granulocytes with a fluorescent signal produced by digested labeled S. aureus (Supplemental Figure S2; https: / / doi .org/ 10 .3168/ jds .2018 -15417).…”