Digestion of plant proteins and gut hypersensitivity in the preruminant calf

Abstract

The recent developments of studies on digestion of plant protein sources by the preruminant calf, and on immune-mediated gut hypersensitivity reactions are reviewed. The immuno-chemical determination of the antigenic activity of soyabean products should involve hyperimmune sera rather than monoclonal antibodies, and the data should be expressed quantitatively (mg antigen / g crude protein). Equations based on analytical criteria, particularly beta-conglycinin levels and antitryptic activities, have been set up ; they could accurately predict the faecal digestibility of soyabean nitrogen in vivo. When antigenic soya was consumed, substantial amounts of immunoreactive soyabean globulins escaped small intestinal digestion, of which intact basic polypeptides of glycinin and intact alpha-conglycinin.

Most soyabean antinutritional factors, including glycinin and beta-conglycinin, were shown to be implicated as allergens in both antibody- and cell-mediated reactions in sensitive calves. Intestinal hyper-secretion and motor disorders associated with these adverse reactions were mediated mainly by histamine release. Increased densities of helper (CD4+) T lymphocytes in the lamina propria and of suppressor-cytotoxic (CD8+) T lymphocytes in the epithelium may probably account for intestinal damage due to chronic antigenic soya consumption.

Other plant protein sources, in particular wheat and lupin, proved to be well digested and tolerated by calves.