The acquisition of immunity by neonatal calves is highly dependent on the ingestion and absorption of colostrum since the bovine placenta does not allow the transfer of immune molecules and cells. Failure of passive transfer (FPT) occurs when these immune molecules, especially immunoglobulins (Ig), do not reach satisfactory levels in the neonate. Several methods are used to evaluate this failure, either by direct Ig determination or indirectly by other parameters. However, most of the reference values come from the international literature and have restricted applicability at the national level, mainly due to different management conditions, racial patterns and environmental pathogens. Therefore, the objective of this work is the evaluation of methods to determine FPT in neonatal calves and to correlate maternal parameters with those of calves, trying to determine an alternative method applicable to the field for FPT evaluation. It will be used 40 cows with their respective calves, from which will be collected colostrum and blood to obtain serum. IgG levels will be determined from cows, calves, and colostrum by the turbidity test with zinc sulfate in photocolorimeter from known concentrations of bovine IgG. Total protein, albumin, and GGT levels will be determined in the blood serum of cows and calves and colostrum in photocolorimeters using commercial reagents. Total protein levels will also be obtained by optical refractometry and colostrum will also be evaluated by the Brix refractometer. The variables will be tested for normality by the Shapiro-Wilk test and the comparison of calves before and after colostrum ingestion will be performed by the paired t-test or the Wilcoxon test, the associations between the qualitative variables will be performed by the Chi-square and the correlations between numerical quantitative variables will be performed by the Pearson or Spearman tests, always considering significant when p<0.05.
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