Changes of protein fractions, lipoproteins, ceru- loplasmin and urea nitrogen in serum of peri- parturient cows receiving dietary monensin

SUMMARY Monensin was added into diet of dairy cows (n=7) from about 20 days before predicted calving date to 45 days after parturition. Serum concentrations of total proteins, albumin, α, β, and γ globulins, VLDL, LDL, HDL, ceruloplasmin and BUN of treated cows were compared with those of untreated cows (n=6, control group). Blood samples were obtained on days 20 and 10 before predicted calving (prepartum phase), and on days 4, 15, 25 (phase I), and days 35 and 45 (phase II) postcalving. Concentration of serum total proteins increased in the treated group (P=0.007) but not in control cows (P=0.259) in phase II postcalving. Concentrations of β globulins tend to be more stable in the treated group (P=0.681) than in the control group in which they tend to decrease (P=0.100) in phase II postpartum. Concentrations of ceruloplasmin increased after parturition in the treated group (P=0.006) and not in the control group (P= 0.674) in phase I postpartum. Concentrations of VLDL (P=0.017) and LDL (P=0.046) were higher in the cows received monensin than in control cows in phase I postpartum. General comparison of the groups during the entire period of the experiment revealed significantly higher concentrations of VLDL (P=0.009) in the treated group. On the other hand, the concentrations of BUN did not vary significantly between treated and untreated cows. Although the concentrations of some specific proteins may be increased by monensin treatment, liver protein metabolism appears to be weakly affected and changes observed in this study would be related to improvement of energy status and liver functions.