The objective of this study was to investigate the effect of the degree and duration of early dietary AA restrictions on subsequent and overall pig performance and physical and sensory characteristics of pork. For the grower (G) and finisher-1 (F1) phases, 3 corn-soybean meal diets were formulated to contain 100, 80, or 60% of the 1998 NRC total Lys recommendations (100G, 80G, or 60G, and 100F1, 80F1, or 60F1, for the G and F1 phases, respectively). For the finisher-2 (F2) phase, a common corn-soybean meal diet was formulated to satisfy the 1998 NRC total Lys recommendation. Thirty gilts and 30 castrated males (2 gilts or 2 castrated males/pen) were randomly assigned to 5 dietary treatments (100G-100F1, 80G-100F1, 80G-80F1, 60G-100F1, and 60G-60F1) when BW was 22.7 +/- 0.3 kg. Pigs were switched to F1 and F2 diets at 50.7 +/- 0.4 and 79.9 +/- 0.5 kg of BW, respectively. Pigs had ad libitum access to feed and water. All pigs were slaughtered at 110.7 +/- 0.5 kg of BW, and LM samples were collected. Pigs fed the 60G diet had less (P < or = 0.05) ADG during the G phase and greater (P < or = 0.05) ultrasound backfat (UBF) at the end of the G phase than those fed the 100G diet. The ADG decreased linearly (R(2) = 0.70; P < 0.001) as the degree of AA restrictions became more severe. Although serum total protein (TP) and albumin concentrations in pigs fed the 60G-100F1 diets were less (P < or = 0.05) than those fed the 100G-100F1 diets at the end of the G phase, TP concentration was similar between the 2 groups at the end of the F1 phase. Likewise, ADG during the F1 phase and UBF at the end of the F1 phase in pigs fed the 60G-100F1 diets were similar to those fed the 100G-100F1 diets. Feeding the 80G diet resulted in numerically decreased ADG during the G phase, but there was no difference in ADG during the F1 and F2 phases or UBF at the end of F1 and F2 phases between pigs fed the 80G and 100G diets. Overall, pigs fed the 80G-80F1 diets had similar ADG, but less (P < or = 0.05) fat-free lean gain (LG) than those fed the 100G-100F1 diets. These pigs also had less (P < or = 0.05) serum TP and albumin concentrations than pigs fed the 100G-100F1 diets throughout the study. Pigs fed the 60G-60F1 diets had less (P < or = 0.05) overall ADG and G:F and less (P < or = 0.05) LM area and LG than those fed the 100G-100F1 diets. However, they had a greater (P < or = 0.05) subjective marbling score than those fed the 100G-100F1 diets. The results indicated that pigs fed the 80G-80F1 diets may have exhibited compensatory growth in BW gain, but not in terms of lean accretion. Growth performance and carcass traits of pigs fed the 60G-60F1 diets were reduced, indicating that the restriction may have been too severe or too long or both. Early dietary AA restrictions had no clear effect on physical and sensory characteristics of pork.

The objective of this study was to determine the possibility of replacing soybean meal (SBM) in finisher pig diets completely with hydrolyzed feather meal (FM). Forty-five gilts and 45 castrated males (57.8+/-0.8 kg of BW; 3 gilts or 3 castrated males/pen) were randomly assigned to 5 finisher-1 diets with 6 pens per diet. At an average pen BW of 81.0+/-1.4 kg, pigs were offered finisher-2 diets. Corn-SBM, finisher-1 and finisher-2 positive control (PC) diets were formulated to contain 6.1 and 4.7 g of apparent ileal digestible (AID) Lys/kg, respectively. Corn-FM negative control (NC) diets were formulated to be iso-N to the PC diets. The NC diets were supplemented with Lys and Trp (NRC; NC + Lys and Trp) to alleviate apparent deficiencies based on AID AA in FM reported by the 1998 NRC. In addition, the NC diets were supplemented further with the third limiting AA, Thr (40+3AA; NC + Lys, Trp, and Thr), and fourth and fifth limiting AA, His and Ile (40+5AA; NC + Lys, Trp, Thr, His, and Ile), based on the assumption that the apparent ileal digestibility of all indispensable AA in FM is 40%. Pigs had ad libitum access to feed and water. At the end of the study (112.1+/-1.8 kg), blood samples were collected from all pigs before slaughter. As expected, overall ADFI, AID Lys (representing indispensable AA) intake (LysI), ADG, and G:F were greater and BW gain:LysI (G:LysI) was less in pigs fed the PC diet than those fed the NC diet (P<0.001). Pigs fed the NRC diet grew slower than those fed the PC diet (P=0.004), and their G:LysI tended to be less than those fed the PC (P=0.083) or the 40+3AA and 40+5AA diets (P=0.094). Greater fat-free lean percentage (P=0.005), fat-free lean gain (LG; P<0.001), and LG:F (P<0.001) were observed in pigs fed the PC diet compared with those fed the NC diet, but their LG:F or LG:LysI was similar to those fed the NRC diet. However, LG:F (P=0.030) and LG:LysI (P=0.028) were greater in pigs fed the 40+3AA and the 40+5AA diets than those fed the NRC diet. Pigs fed the 40+5AA diet tended to utilize AID Lys more efficiently for LG than those fed the 40+3AA diet (P=0.068). Subjective meat color (P<0.001), firmness (P=0.004), and marbling (P<0.001) scores were greater in pigs fed the 40+5AA diet than those fed the 40+3AA diet. Diets seemed to have no clear effect on the weight of liver, kidney, and heart or serum urea N and triacylglycerides. Pigs fed the PC diet had more serum albumin and total protein (P<0.001), but less glucose (P=0.031) and cholesterol (P<0.001) than those fed the NC diet. Serum total protein was greater (P=0.031) in pigs fed the 40+5AA diet than those fed the 40+3AA diet. The results indicated that the corn-FM diets were not as effective as the corn-SBM diet in supporting BW gain of finisher pigs. However, the results seemed to indicate that pigs fed the corn-FM diet supplemented with the necessary AA can utilize feed and AA for BW gain and lean gain as efficiently as those fed the corn-SBM diet. Further research is needed to explore fully the optimal AA supplementation strate...