Effects of dietary protein sources on growth performance and immune response of weanling pigs

A total of 320 piglets (body weight, 7.0 +/- 0.19 kg) were used to examine the effects of dietary protein sources on growth performance and immune response. Following the weaning at 22( +/- 1) d of age, the pigs were allocated randomly to 4 treatments, with 5 replicates per treatment and 16 pigs per replicate, receiving 4 experimental diets for initial 10 d and then all pigs were offered the common diet for further 22 d. The experimental diets were formulated to contain the same amounts of DE, CP. Lys and Met on an iso-nitrogenous basis derived from different protein supplements, including 4.00% spray dried porcine plasma (SDPP) (control), 4.88% soy protein concentrate (SPC), 9.18% whey protein concentrate (WPC) and 6.50% spray-dried whole egg (SDE), respectively. From day 1 to 10 after weaning, pigs fed SDPP had a significantly higher ADG and consequently a lower feed:gain ratio than those offered SPC or SDE diet. However, all dietary treatments did not affect feed intake and ADG during the period from day 11 to 32 or from day 1 to 32 after weaning. There were no significant treatment effects on villous height to crypt depth ratio (VCR) in ileum measured on day 10 after weaning, whereas this variable in duodenum and jejunum was significantly lower with pigs offered SPC diet than those given SDPP diet. Furthermore, in comparison with pigs offered SDPP diet, pigs fed SPC diet had significantly lower levels of classical swine fever virus (CSFV)-specific antibody titer and unspecific immune molecules (IgG, IgA, C-3), and significantly higher levels of IL-10 and cortisol. Although WPC and SDE diets also affected these variables when compared with SDPP diet, the magnitudes of their effects were much smaller than those derived from SPC diet. Our results suggest that WPC and SDE can be used to replace SDPP as protein supplements for weanling pigs with little adverse effects on feed intake, ADG or development of the immune system. The SPC supplement can influence growth rates and immune response of weanling pigs during initial adaptation period. (C) 2012 Elsevier B.V. All rights reserved.