FREE AND PROTEIN-BOUND AMINO-ACIDS IN SOWS COLOSTRUM AND MILK

The changes in the concentrations of free and protein-bound amino acid s in sow's colostrum and milk were quantified in this study. in sow's colostrum, taurine and histidine were the most abundant free amino aci ds (1 mmol/L of defatted milk). The concentrations of free histidine d ecreased, whereas those of other free amino acids increased, as lactat ion progressed. Milk free glutamine concentrations increased to the gr eatest extent among all free amino acids during the 29-d lactation per iod, and became the most abundant free amino acid in the milk (1.9 and 3.4 mmol/L of defatted milk) on d 22 and 29 of lactation. Sow's matur e milk was rich in free taurine, glycine and glutamate (1-1.4 mmol/L o f defatted milk). In contrast to free amino acids, the concentrations of milk protein and protein-bound amino acids decreased during the fir st 8 d of lactation and then leveled off. In colostrum and milk, gluta mine plus glutamate were the most abundant protein-bound amino acids, whereas histidine and cystine were the least abundant. Leucine was the second and fourth most abundant protein-bound amino acid in colostrum and milk, respectively, with proline and lysine being the second most abundant ones on d 8 to 29 of lactation. Both colostrum and milk cont ained large amounts of urea (4.8-1.7 mmol/L of defatted milk) and ammo nia (1.1-2 mmol/L of defatted milk), with ammonia concentration decrea sing with advancing lactation stages in a pattern similar to that of m ilk protein. Thus, this study demonstrates the abundance of free gluta mine, taurine, glycine and histidine in sow's milk relative to other f ree amino acids, as well as the changes in free and protein-bound amin o acids in sow's milk during the 29-d lactation period. In light of th e present findings, the nutritional importance of amino acids in milk for the growth and development of suckling piglets,merits further stud ies.