Energy and nutrient digestibility of degossypolized cottonseed protein and its utilization as a protein source in nursery pigs

Three experiments were conducted to determine the digestible (DE) and metabolizable energy (ME) values, and apparent (AID) and standardized ileal digestibility (SID) of amino acids (AAs) in degossypolized cottonseed protein (DCP), and to evaluate the effects of DCP as a replacement for soy protein concentrate (SPC) or fish meal (FM) on growth performance and diarrhea frequency of nursery pigs. In Exp. 1, 12 barrows (38.5 ± 3.0 kg initial BW) were allotted into 2 dietary treatments to determine the DE and ME values of DCP. In Exp. 2, 12 barrows (31.5 ± 2.2 kg initial BW) fitted with ileal T-cannula were allotted into 2 dietary treatments to determine the AID and SID of AAs in DCP using the exogenous indicator method. In Exp. 3, 144 nursery pigs (7.4 ± 1.1 kg initial BW) were randomly assigned to 1 of 4 treatments, including a control diet with 10% SPC and 4% FM, and 3 experimental diets formulated by replacing SPC with 5% or 10% DCP or replacing FM with 4% DCP, respectively. The results showed that the concentrations of crude protein (CP) and most AAs in DCP were close to those in SPC, but the fiber levels in DCP was greater than that in SPC. The DE and ME values of DCP were 19.11 and 17.77 MJ/kg on dry matter (DM) basis, respectively, and the AID and SID of indispensable AAs were ranged from 0.73 to 0.93 and 0.76 to 0.94, respectively. There were no differences in growth performance, diarrhea frequency and ATTD of gross energy (GE), DM and CP among the 4 treatments during day 0–28 fed to nursery pigs. However, pigs fed diets with 10% DCP had lower (P < 0.01) ADG, FCR, and ATTD of GE, DM and CP and greater (P = 0.03) diarrhea frequency compared to the control group during day 0–14. In conclusion, DCP as an alternative plant protein source could be supplemented in nursery pig diets with a proportion under 5% within the first 2 weeks after weaning, and could be supplemented in diets with a proportion of 10% after day 14 of weaning because of its high fiber content and low AA digestibility.