Tryptophan (Trp) can produce bioactive compounds for appetite regulation, calcium mobilization, and mammary gland homeostasis via a serotonin pathway. This study evaluated the effects of Trp supplementation on the reproduction performance, milk yield, and composition of lactating sows, growth performance of their piglets, and the secretion function of porcine mammary epithelial cells (PMECs). The infrared emulsion analyzer and ELISA analyses revealed that feeding sows with a 0.12% Trp addition increased ( P < 0.05) sow average daily feed intake, milk yield, milk calcium concentration, average daily gain of piglets, fatty acid synthase (FAS) and lactose synthase (LS), β-casein secretion, intracellular Ca2+ level, the expression of calcium binding protein CaM, and the activity of CaMKII. In a cellular experiment of PMECs treated with Trp, ELISA and flow cytometry analyses revealed that the pretreatment of a Trp hydroxylase inhibitor reduced ( P < 0.05) FAS and LS synthesis, the intracellular Ca2+ level, and the activity of CaMKII. In conclusion, Trp supplementation at 0.12% increased sows' reproductive performance, milk yield, and calcium concentration and piglets' growth performance. Milk yield increased by Trp was linked to 5-hydroxytryptamine-mediated synthesis of FAS, LS, and β-casein in PMECs, while the increase in calcium concentration was attributed to increasing CaM expression and CAMKII activity.
Keywords: 5-hydroxytryptamine; calcium concentration; growth performance; lactating sows; milk yield; tryptophan.