The bilateral parotidomegaly (hypertrophy) induced by acorn consumption in pigs is dependent on individual׳s age but not on intake duration

Abstract

Polyphenolic compounds, namely dietary tannins, are biologically active substances capable to induce an increased proline rich proteins (PRPs) content in the salivary secretions of the parotid gland, in different animal species and in man. In general terms, a pulsed increased secretion of salivary PRPs could be observed mainly in browsing animal species and to a lesser extent in grazers, which rely on an evolutionary adaptation to cope with seasonal feeding stuffs, varying in tannin content. Therefore, PRPs secretion might appear to be a first line of defense from severe intoxications, which can occur in animals incapable to code for tannin binding proteins (TBP) in the saliva. Pigs appeared to be tolerant to high intake of raw acorns, known to be rich in hydrolysable tannins. The parotid gland (PG) response to an experimental acorn combined diet (50% inclusion of raw shredded acorns in the diet, as fed, high in hydrolysable tannins: 25g tannic acid equivalents TAE/kg dry matter in the diet) offered to pigs (growing vs. finishing pigs) was studied and compared to the morphometry and functional activity of the PG in pigs fed on a control conventional diet (0% acorns in the diet). A total of 32 cross-bred pigs were involved in two feeding trials (1 vs. 4 weeks of experimental feeding) and divided into groups according to the experimental diets (0% vs. 50% acorns included in the diet). The bilateral parotidomegaly (hypertrophy of the parotid gland) occurred constantly and significantly (p<0.01) in the totality of pigs fed with the acorn combined diets, displaying different extents of hypertrophy, according to the age of the pigs: growers, 2–3 folds of the control PG vs. finishers, 1.30–1.40 folds of the respective control PG, either after an exposure of 1 or 4 weeks. No statistic significance could be pointed out after 1 week vs. 4 weeks of experimental feeding, testing on a tannin concentration of 25g TAE/kg DM from acorns in the diet offered, either to growers and to finishers. The morphometry and functionality of the PG is more strongly stimulated in the growing pigs than observed in the finishing pigs, independently of the duration of consumption of the acorn combined diet, rich in hydrolysable tannins.