Complete replacement of soybean meal in pig diets with hydrolyzed feather meal with blood by amino acid supplementation based on standardized lleal amino acid digestibility

The current study was conducted to determine the possibility of replacing soybean meal (SBM) in finisher pig diet completely with hydrolyzed feather meal (FM) with blood by supplementing with appropriate amino acids (AA) based on standardized ileal digestible (SID) AA in FM. Corn–SBM, positive control (POS) diets were formulated to contain 6.6 and 5.2 g true ileal digestible (TID) Lys/kg to satisfy the requirements during the finisher-1 and finisher-2 phases, respectively. Corn–FM negative control (NEG) diets were formulated to be iso-N and iso-caloric to the POS diets. The NEG diets were supplemented with Lys and Trp to alleviate AA deficiencies based on TID AA values in FM reported by the NRC in 1998 (NRC). In addition, the NEG diets were supplemented with Lys and Trp to alleviate AA deficiencies based on the determined SID AA in FM (SID). When pigs weighed 50.0±2.9 kg, 32 gilts and 32 castrated males (2 gilts or 2 castrated males/pen) were randomly assigned to 1 of 4 finisher-1 diets with 4 gilt pens and 4 castrated male pens/diet, and they were switched to finisher-2 diets when the average pen weight reached 79.0±2.0 kg. Pigs had ad libitum access to feed and water throughout the study. At the end of the finisher-2 phase (107.7±3.3 kg), blood samples were collected to determine serum metabolite profile and pigs were slaughtered to assess carcass characteristics. Pigs fed the POS diets ended to have greater overall average daily feed intake (ADFI; P = 0.083) and had greater total Lys intake (P = 0.029) than those fed the SID diets, which may have resulted in a tendency for slightly greater average daily gain (ADG; P = 0.094) in pigs fed the POS diets. However, there was no difference in the efficiency of feed or Lys utilization. Pigs fed the SID diets tended to have greater gain:feed (G:F; P = 0.057) and had greater gain:total Lys intake (P<0.001) than those fed the NRC diets. Pigs fed the POS diets tended to have greater ADFI (P = 0.079) and had greater ADG (P<0.001) and G:F (P<0.001) than those fed the NEG diets, but, as expected, they had lower gain:total Lys intake (P<0.001) mostly because of the increased total Lys intake (P<0.001). Serum glucose was not affected by dietary treatments. Pigs fed the POS diets had greater urea-N (P = 0.003) and lower cholesterol (P = 0.002) than those fed the SID diets. As expected, pigs fed the NEG diet had reduced total protein (P<0.001) and increased urea-N (P = 0.001), triglyceride (P<0.001), and cholesterol (P<0.001) compared with those fed the POS diets. Pigs fed the POS diets had greater fat-free lean gain (P = 0.020) that those fed the SID diets, but similar loin muscle area, fat-free carcass percentage, and efficiency of fat-free lean gain. Results indicated that pigs fed the SID diets utilized feed and Lys as efficiently as those fed the POS diets, but they had slightly reduced body weight and fat-free lean gain, perhaps, because of slightly reduced intake of feed and total Lys, as well as other AA.