Effect of diet complexity and dietary fish peptide and enzyme complex supplementation on weanling pigs

Two experiments were conducted to assess the potential of replacing complex weanling pig diets with simple corn-soybean meal (SBM) diets by supplementation with a feed additive. The effort was made to determine the optimum inclusion rate of fish peptides in experiment 1 (Exp. 1), whereas the possibility of replacing complex diets with simply corn-SBM diets was investigated in Exp. 2. Ninety six (7.9 ± 0.7 kg) and 48 (7.8 ± 0.8 kg) pigs were used in Exp. 1 and 2, respectively, and pigs were assigned randomly to 6 (Exp. 1) and 3 (Exp. 2) dietary treatments with 4 pens per treatment and 2 gilts and 2 castrated males per pen in both experiments. The phase 1 (d 0 to 14) and 2 (d 14 to 28) complex, positive control diets (POS) were formulated in both experiments. Two simple corn-SBM, negative control (NEG) diets were formulated to be iso-lysinic to the POS diets in Exp. 1, and the NEG diets were supplemented with 0.5, 1.0, 1.5, or 2.0% fish peptides. Similarly, the phase 1 and 2 simple corn-SBM, NEG diets were formulated to be iso-lysinic to the POS diets in Exp. 2. However, the NEG diets contained 1.5% fish peptides, and those diets were supplemented with multienzyme complexes (ALL). During the wk 4, blood sample was collected and analyzed for serum metabolites and cytokines in Exp. 1 and metabolites in Exp. 2. During the last 2 wk of Exp. 1, the intake of feed, Lys, and digestible energy (DE) increased (cubic, P < 0.026) as fish peptides increased from 0 to 2%. Dietary treatments had no effect on gain to feed (G:F), gain to Lys (G:Lys), or gain to DE (G:DE) intake. Although there were some differences in serum total protein, urea N, and triglycerides, dietary treatments seemed to have no clear effect on serum metabolites or cytokines. Pigs seemed to respond to the diets containing 1.5% fish peptides, and it was used as the basis for the dietary treatments in Exp. 2. From wk 0 to 2 in Exp. 2, pigs fed the NEG and ALL diets had greater G:F, G:Lys intake, and G:DE intake (P < 0.004) than those fed the POS diet. In addition, G:F and G:Lys intake tended to be greater (P = 0.095) and G:DE intake was greater (P = 0.009) in pigs fed the ALL diet than those fed the NEG diet. Dietary treatments had no clear effect on the growth performance during the phase 2 or overall. Serum total protein and globulin were greater (P < 0.007) in pigs fed the NEG and ALL diets than those fed the POS diets because of the greater values in pigs fed the ALL diets, but those metabolites were not different between pigs fed the NEG and ALL diets. The results indicated that a complex diets can be replaced with a simple corn-SBM diet by supplementing the weanling pig diet with fish peptides and multienzyme complexes during the phase 1 (d 0 to 14).