Can maternal Immunoglobulin G be quantified in calf saliva?

Good colostrum management and prevention of Failure of Passive Transfer (FPT; serum IgG at 24-28 h < 10g/L), is of major importance for calf welfare. To enable surveillance of FPT prevalence in herds, serum has been used, in spite of blood sampling being a relatively invasive technique which in some countries must be done by a veterinarian. Given that maternal immunoglobulin G (IgG) transfers from serum into calf saliva and its levels correspond to that of serum, saliva may represent a non-invasive medium from which FPT-status of calves could be evaluated. To investigate this, we used 20 Norwegian Red dairy calves (age 1-3 d) that were housed in single pens and fed 4 L of colostrum within 4 hours after birth using a teat bottle. We used cotton swabs held into the calves’ mouth for 1 minute to obtain saliva and a syringe to compress the saliva into tubes for storage. Milk feeding was retained at least for two hours prior to sampling. After collection of saliva, blood was drawn from the jugular vein. IgG was determined with Single Radial Immunodiffusion. Mean (±SD) serum and saliva IgG was 32.1 ±11.94 g/l, and 0.2 ± 0.11 g/l respectively. Of the saliva samples, 6 had levels below the lowest detection limit (0.1 g/L). Spearman Rank correlation revealed a strong positive correlation (r=0.7, p<0.001) between IgG in serum and saliva. The results encourage further studies on the reliability of saliva IgG to detect calves with FPT.