Growth of parotid glands in pigs experimentally exposed to different tannin containing diets at different ages

Objectives: Phenolic compounds, in particular dietary tannins, are responsible of inducing a hyperfunctionality of parotid glands. Aim of this study was to follow the pattern of parotid gland’s growth in pigs exposed to conventional complete diets vs high tannins from fresh ripe acorns diet to quantify the adaptation of parotid glands in pigs (different dosage and exposures) that tolerate high intakes of acorns. Methods: The trial included 32 cross-bred pigs at different ages exposed to experimental diets differing in tannins content expressed as Tannic Acid Equivalents (TAE: 25.8 g/kg DM= 50% acorns shred in the diet; TAE: 36.1 g/kg DM= 70% acorns shred in the diet), for 1 and 4 weeks. Each growth category was fed according to the feeding plan reported into details in the Table (top). Pigs were sacrificed and fresh weight, length and width of parotid glands were recorded. Furthermore, microscopic analyses (HE and PAS staining) considered number, volume, cytoplasm/nucleus ratio of cells (hypertrophy vs hyperplasia). Results: Enlargement (hypertrophy) of parotid glands occurred in all of the pigs fed the combined diet with acorns. Features and folds of relative weights of parotid glands are reported in the Table. Conclusions: Combined diets with ripe acorns (50% and 70%) induce reactions of parotid glands against dietary tannins at all growth phases, both after 1 week and 4 weeks of exposure. The stronger modification of parotids in weanling piglets is pointed out as far as a possible age dependence of the folded relative weights.