Saliva as a potential non-invasive fluid for passive immune transfer surveillance in calves

Abstract

Passive immune transfer (PIT) is detrimental to the calf’s welfare. PIT is currently assessed by immunoglobulins or total proteins concentration (TP) in blood. Blood collection has some constraints, ergo, a simple and non-invasive alternative method is of great interest. This study aimed to evaluate the potential use of saliva as a non-invasive fluid to assess PIT. A total of eighty saliva and blood samples were taken from twenty calves at 4 time points: at birth (approximately 30 min before colostrum consumption), at 24h, 48h and at day 7, for total protein and IgG levels concentration assessment. A hand-held refractometer was used for serum samples and the Bradford method for total protein determination in both saliva and serum samples. Dot-blot analysis was performed in a sub-sample to check for IgG in saliva and serum (n=5 calves). With both methods, TP in serum at 24h, 48h and at day 7 was significative higher than TP at birth (P<0.001). A tendency for elevated TP at 24h (P<0.1) was found in saliva samples. A significant Pearson’s positive correlation was found between TP in saliva and in serum by refractometer at 48h (r=0.45; P=0.0474). Dot-blot analysis showed an increase in IgG from birth to following phases in blood and saliva. These results suggest that saliva can be used for PIT surveillance, highlighting the importance of further studies.