Fecal and saliva IgA secretion when feeding a concentrated mannan oligosaccharide to neonatal dairy calves

The influence of supplementing milk replacer with a mannan-rich fraction (MRF) on adaptive immunity and growth of neonatal dairy calves was investigated using 2 groups of 30 heifer calves. In conjunction, the potential of measuring salivary and fecal IgA as an indicator of mucosal health was studied. Milk replacer was supplemented with 0 or 1 g/d of yeast-derived MRF (Actigen; Alltech Inc., Nicholasville, KY) and fed through weaning at 6 wk of age. Average daily gain tended to be greater for calves fed MRF (517 vs. 411 g/d; P < 0.07), but no effects were observed in measures of skeletal growth. Calves fed MRF in milk replacer had fewer days with high scour scores compared with control calves, and salivary and fecal IgA were elevated earlier in life for MRF-fed calves. No differences were observed in respiratory illness between treatments. In conclusion, salivary IgA was found to be an indicator of fecal IgA; however, it was not as sensitive a measurement of scours because it parallels what is happening in feces. In addition, MRF-fed calves had improved fecal scores compared with control calves in this study where all calves had some level of cryptosporidium infection that was a direct cause of scours.