To study the effects of soybean small peptides (SSP) on nitrogen balance, nutrient digestibility and concentrations of glucose, ammonia and amino acids (AA) in portal veinous plasma (PVP) of goats, eight Xiangdong black goats were used in a 4 x 4 Latin square design. Goats were divided at random into four groups (two goats per group). Each group received the following four treatments in a different order over four treatment periods: SSP in the basic diet by feeding (SSPF), free AA (FAA) in the basic diet by feeding (FAAF), SSP by infusing through the duodenum fistula (SSPI), or FAA by infusing...
