Peculiarities in the Amino Acid Composition of Sow Colostrum and Milk, and Their Potential Relevance to Piglet Development

Simple Summary Sow's milk, serving as the primary nutrient source, contributes to the morphological and functional maturation of piglets' gastrointestinal tract. The abrupt diet transition at weaning has required piglets to familiarize a solid diet earlier through supplementation with creep feed apart from milk during the suckling period. We assume that the composition of sow milk is the gold standard and could inspire the optimization of creep feed for suckling piglets. Therefore, in this study, we investigated how conserved and variable the amino acid profile of sow colostrum and milk is, compared with other literature and species. The amino acid profile of sow milk is conserved compared to actual content throughout the lactation period and is rich in glycine, valine, and proline compared to other species. Similarities with characteristic differences were observed within these comparisons, which may reflect the nutritional requirements for preweaning piglets. The composition of mother's milk is considered the ideal diet for neonates. This study investigated how conserved or variable the amino acid profile of sow colostrum and milk is throughout lactation, compared with other studies in sows and other species. Twenty-five sows (parity one to seven) from one farm with gestation lengths of 114 to 116 d were sampled on d 0, 3, and 10 after parturition. The total amino acid profile of the samples was analyzed through ion-exchange chromatography, and the results were displayed as the percentage of total amino acid and compared with literature data. Most of the amino acid concentrations in sow milk decreased significantly (p < 0.05) throughout the lactation period, while the amino acid profile generally showed a conserved pattern, especially from d 3 to d 10, and was rather similar across different studies. Glutamine + glutamate was the most abundant amino acid in milk at all sampling moments, accounting for 14-17% of total amino acids. The proportions of proline, valine, and glycine in sow milk nearly accounted for 11%, 7%, and 6% respectively, and were higher compared to human, cow, and goat milk, while the methionine proportion was less than the other three. Compared to the large variations often reported in macronutrient concentrations, the amino acid profile of sow milk in the present study, as well as in others, seems well conserved across the lactation period. Similarities with characteristic differences were also observed between sow milk and piglet body composition, which might reflect the nutrition requirements of preweaning piglets. This study warrants further research exploring the link between the whole amino acid profile and the particular amino acids for suckling piglets and could facilitate insight for optimizing creep feed.