Preanalytical factors affecting blood inorganic phosphate concentration in dairy cows.

BACKGROUND: Hypophosphatemia is a condition that affects feed intake and milk production in dairy cows, and, to assess it, a precise biological parameter is needed. Plasma inorganic phosphate (Pi) can be used as a potential indicator of bioavailability of feed phosphorus in dairy cows. OBJECTIVE: The purpose of this study was to evaluate the effects of sample type (serum vs. plasma), blood sampling site (jugular vs. coccygeal), and morning feeding on blood Pi concentration in dairy cows. METHODS: Blood samples from 28 clinically healthy multiparous Holstein cows were analyzed for Pi concentration. The animals were sampled twice by coccygeal vessel into Vacutainer tubes both with and without sodium heparin, 3 hours after the morning feeding. In 4 additional cows, the concentration of Pi was measured in blood samples obtained simultaneously by jugular and coccygeal venipuncture into heparinized tubes before the morning feeding and 2, 4, and 6 hours after the feeding. The results were analyzed using parametric statistical tests. RESULTS: Serum and plasma concentrations of Pi were correlated (r(2) = 0.999, P < .0001), but serum Pi concentration was higher than plasma Pi (P < .02). Plasma Pi concentration 2 hours after feeding tended to be higher than that before feeding in jugular samples, but the difference was not significant. There was no significant variation in plasma Pi during the morning postfeeding times, although jugular concentrations were 19% lower than coccygeal (P = .04). CONCLUSION: To increase the precision of plasma Pi measurements as an indicator of bioavailability of feed phosphorus, sample type, sampling time, and site must be taken into account, to correctly interpret plasma Pi concentrations.

Serum biochemical parameters and embryo production during superovulatory treatment in dairy cattle.

The objective of this study was to determine the relationship between the number of transferable embryos (TE) and various blood chemistry parameters as a reflection of the metabolic state of cows after superovulatory treatment. Forty-nine Holstein cows were subjected to superovulatory treatment for commercial embryo production. At the time of embryo harvest, individual blood samples were taken from cows for biochemical analysis. All embryos including dead ones as well as non-fertilized oocytes were counted in uterine lavage. Feed samples collected daily for a period of two weeks before embryo harvest, were analyzed for mycotoxins: vomitoxin, zearalenone and T-2 toxin. On average, cows produced 9.45+/-5.60 embryos and oocytes of which 5.27+/-4.20 were TE, 0.37+/-0.80 were dead embryos and 3.82+/-3.78 were non-fertilized oocytes. Higher concentrations of Mg and K were associated with a higher production of TE (p=0.005 and p=0.043, respectively) and higher activity of creatinine kinase was associated with a lower production of TE (p=0.011).

Evaluation of variation in serum globulin concentrations in dairy cattle.

BACKGROUND: Several factors may influence the concentration of serum globulins in healthy cows and thereby affect clinical interpretation; however, few studies have addressed sources of variation in globulin values. OBJECTIVES: The purpose of this study was to compare colorimetry-based total serum globulin values with electrophoretically-determined serum globulin fractions and with IgG concentration, and to evaluate diurnal and long-term physiological variation and the effects of lactation and venipuncture site on serum globulin concentrations in Holstein dairy cattle. METHODS: Serum total globulin and albumin concentrations were analyzed by colorimetry and electrophoresis in 86 lactating cows; IgG concentrations were determined by radial immunodiffusion in 41 dry and 34 lactating cows. Serum globulins were analyzed hourly for 24 hours in 8 lactating cows and weekly for 15 weeks in 6 additional cows. Globulin concentrations were compared in samples obtained from jugular and coccygeal venipuncture sites in 4 cows. Results were analyzed using parametric statistical tests. RESULTS: Colorimetry-based total serum globulin concentrations correlated well with gamma-globulin fractions (r2 = 0.87) and IgG concentrations (r2 = 0.91). Diurnal variation of total serum globulins concentration was significant (P =.01); however, globulins did not vary significantly over a 15-week period. Mean serum globulins concentration in samples obtained from the jugular vein was 2.35 g/L higher than that in samples obtained by coccygeal venipuncture (P <.0001). CONCLUSIONS: The colorimetric method used widely in routine laboratory analyses remains a useful test for globulins determination in dairy cattle. However, time of sampling and venipuncture site should be considered in the interpretation of serum globulins on serial or interindividual specimens.