Fig. 1: Formula feeding trial design, and the whey protein composition and tryptophan content of the diets.

A Differences in α-lactalbumin, β-lactoglobulin, tryptophan content, and the tryptophan to other large neutral amino acid (LNAA) ratio among the α-lactalbumin-enriched formula (ALAC formula), the formula predominantly high in β-lactoglobulin (WPI formula), and sow milk. Detailed nutritional composition of the ALAC formula, the WPI formula, and sow milk is presented in Supplementary Tables 2–4. LNAA includes isoleucine, leucine, valine, phenylalanine, and tyrosine. B Overview of the 10-day formula-feeding study design. The study enrolled 30 piglets who suckled from their sows until postnatal Day 6. These piglets were then randomized into three groups: the ALAC group, which received the ALAC formula (n = 12); the WPI group, which received the WPI formula (n = 12); and a sow-fed reference group (n = 6). From Day 6 to 16, the ALAC and WPI groups were bottle-fed every 3 h, while the sow-fed group remained with the sow. On Days 11 and 12, postprandial blood measurements were collected from the ALAC and WPI piglets, with half of the piglets in each group being tested each day. On Day 16, the piglets were anesthetized and sacrificed ~1 h after their last meal. Blood, urine, liver, and brain samples were then collected for analysis. Of the total 30 piglets, one piglet was euthanized 2 days after the start of the feeding intervention due to an accidental injury caused by the sow.