Comparative study of proteins, peroxidase activity and N-acetyl-β-D-glucosaminidase activity in llama milk

Abstract

Increased rearing of llamas in the USA has been associated with a need to supplement milk to orphaned or undernourished llama neonates. Ruminant milks and milk replacers are used, but there are few data comparing the nutrient composition and protective factors of llama milk to those of ruminant milks. We compared proteins in llama milk with those in cow, sheep, and human milks. Proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by Coomassie blue. Caseins were the predominant proteins in llama milk, as in cow and sheep milks. A considerably lower proportion of casein was identified in human milk. α-Lactalbumin was present in similar amounts in llama, sheep, and cow milks, with proportionately more α-lactalbumin in human milk. β-Lactoglobulin, the major whey protein of cows and sheep, was not detectable by this method in either llama or human milk. Gel profiles of llama milk contained a relatively higher proportion of a protein band co-migrating with lactoferrin compared with cow or sheep milk, but not as much as in human milk. We also compared the activities of peroxidase and N-acetyl-β-D-glucosaminidase in milks of the four species. Peroxidase activity in llama milk was more than ten times less than in cow or sheep milk. Activity of N-acetyl-β-D-glucosaminidase was more than 20-fold higher in llama milk than in milks of the ruminants. Activities of both enzymes in llama milk more closely resembled activities in human milk. Results of this study suggest that llama milk differs from cow and sheep milk in protein composition, and that the relative importance of protective factors, such as lactoferrin, peroxidase, and N-acetyl-β-D-glucosaminidase, in milk may be different for llamas compared with ruminants.