Relationship between passive immune transfer and a simplified score system for diagnosis of respiratory diseases in dairy calves

Abstract

The objectives of the present study were to determine the effect of passive immune transfer on growth, morbidity and mortality, and to evaluate a simplified score system for diagnosis of respiratory disease in dairy calves housed in groups. After calving, all calves (n= 275) ingested 4 L of stored colostrum which was assessed by refractometry (Brix scale). The cut point used as Indicative of good quality colostrum was ≥ 22%. A blood sample was taken from the jugular vein of Holstein dairy calves at 1-7 days of ages to determine serum total protein concentration by refractometry. The cut point used as indicative of failure of passive transfer (FPT) was <5.2 g/dL. Subsequently, all calves were evaluated once a week for 8 weeks using heart-girth measuring tape and two clinical scores. The first clinical score (CS1) included the following signs and assigned them a value (0 to 3): nasal discharge, ocular discharge, coughing, ear position and fever (Calf Health Scoring Chart, University of Wisconsin). Calves were considered positive when the total score was ≥ 5. The second clinical score (CS2, simplified score) did not include fever and calves were considered positive when the score was ≥ 4. Data about deaths were recorded during the visits. Statistical analyses were performed by logistic regression and by Kappa?s coefficient analysis. The prevalence of FPT was 21.22 % (59/278). Duringsummer, the FPT was higher than during the rest of the seasons (P= 0.02). Colostrum quality had an important effect on FPT. Calves that ingested 4 L of bad colostrum quality had 3.67 times greater odds of having FPT than calves that ingested 4 L of good colostrum quality (P=0.002). The average of weight gain at 8 weeks of ages was 73.09 Kg and 69.01 Kg for calves with a successful passive transfer of immunity and with FPT, respectively (P<0.001). Thus, calves that had FPT weighted 4.20 Kg less at weaning compared to their mates. On the other hand, calves with FPT had 2.5 (P= 0.09) times greater odds of having respiratory disease using CS1 and 3.6 (P= 0.03) using CS2 but had no effect on the incidence of diarrhea (P= 0.43). Calves that had FPT had 2.74 times greater odds of death that their mates (P= 0.10). Finally, the two scores had good agreement (Kappa`s coefficient of 0.73). In conclusion, a successful passive transfer of immunity improves the development of the calves, has a protective effect against respiratory disease and decreases the odds of death. The simplified CS2 is a useful method that could be use in calves housed in groups because does not include the measuring of rectal temperature.