The effects of milk matrices on the transit and digestion of secretory immunoglobulin A in the gut : a thesis presented in partial fulfilment of requirements for the degree of Masters of Science in Animal Science at Massey University, Palmerston North, New Zealand and AgResearch, Ruakura, Hamilton, New Zealand
Bovine secretory immunoglobulin A (BSIgA) has the potential to provide protective effects to the gastrointestinal tract (GIT) when consumed orally. Oral administration of immunoglobulin (Ig) preparations has been explored and proven satisfactory in defence of a variety of enteric microbial infections in humans. Currently Ig preparations focus on bovine colostrum or whole milk. The effects of different milk matrices and how the overall composition may impact BSIgA transit and digestion have not been explored. In this study, an in vivo experiment was used to demonstrate the transit and digestion of BSIgA in two different milk matrices through the GIT of mice. The milk matrices of interest were whey protein concentrate (WPC) and skim milk powder (SMP). Mice were gavaged with 200 μL of each treatment and groups were culled at four time points; 7 minutes, 20 minutes, 1 hour, and 4 hours. The GIT was dissected into four pieces; stomach, small intestine, large intestine, and caecum. These were flushed with phosphate buffered saline (PBS) and the amount of BSIgA in the washouts was measured on an ELISA. Bovine SIgA survived digestive processes in the GIT of mice in SMP and WPC, as it was detected at all time points. Intestinal washouts from mice that were fed SMP measured at 7 minutes, 20 minutes, 1 hour, and 4 hours detected 66.3%, 22.4%, 0.45%, and 0.97%, of BSIgA respectively. The corresponding values for mice that were fed WPC were 43.8%, 10.2%, 0.12%, and 0.14%, respectively. Overall, the results supported the hypothesis that the milk matrix affected transit and digestion of BSIgA through the GIT of mice. BSIgA was digested 10 fold faster in a WPC matrix than SMP matrix. The BSIgA in SMP appeared more protected from digestion than that in WPC. This is the first study to highlight different milk matrices affecting the transit and digestion of BSIgA. It gives an insight into manufacturing BSIgA into a commercial product and the potential benefits it may provide to the consumer.