An experiment was conducted to test the hypothesis that reducing crude protein (CP) in starter diets for pigs reduces post-weaning diarrhea and improves intestinal health. One hundred eighty weanling pigs were allotted to 3 diets containing 22, 19, or 16% CP. Fecal scores were visually assessed every other day. Blood samples were collected from 1 pig per pen on d 1, 6, 13, 20, and 27, and 1 pig per pen was euthanized on d 12. Results indicated that reducing dietary CP reduced (P < 0.01) overall average daily gain, gain to feed ratio, final body weight, and fecal scores of pigs. Pigs fed the 16% CP diet had reduced (P < 0.01) serum albumin compared with pigs fed other diets. Blood urea nitrogen, haptoglobin, interleukin-1β, and interleukin-6 concentrations in serum were greatest (P < 0.01) on d 13, whereas tumor necrosis factor-α and interleukin-10 concentrations were greatest (P < 0.01) on d 6. Villus height in the jejunum increased (P < 0.05) and crypt depth in the ileum was reduced (P < 0.01) if the 19% CP diet was fed to pigs compared with the 22% CP diet. A reduction (P < 0.05) in mRNA abundance of interferon-γ, chemokine ligand 10, occludin, trefoil factor-2, trefoil factor-3, and mucin 2 was observed when pigs were fed diets with 16% CP. In conclusion, reducing CP in diets for weanling pigs reduces fecal score and expression of genes associated with inflammation.
Two experiments were conducted to determine standardized ileal digestibility (SID) of amino acids (AA) and the concentration of metabolizable energy (ME) in non-heat-treated and heat-treated soybean expellers (L-0, L-12, and L-48). L-0 underwent short-term steam conditioning for 60 s, whereas L-12 and L-48 underwent short-term steam conditioning for 60 s and long-term steam conditioning for 12 or 48 min. All heat-treated soybean expellers were expander processed. In experiment 1, 10 ileal-cannulated barrows (54.22 ± 4.54 kg) were allotted to a replicated 5 × 4 Youden square design with eight replicate pigs per diet. Each source of soybean expellers was included in one diet, and a nitrogen-free diet was also used. Results indicated that the SID of AA in non-heat-treated soybean expellers was less (P < 0.01) than in heat-treated soybean expellers. In experiment 2, 40 barrows (17.52 ± 1.63 kg) housed in metabolism crates were allotted to a corn-based diet or four corn–soybean expellers diets. Feces and urine were collected with 5 d adaptation and 4 d collection periods. The ME in non-heat-treated soybean expellers was less (P < 0.01) compared with L-0, L-12, or L-48. In conclusion, the SID of AA and the ME in heat-treated soybean expellers were greater than in non-heat-treated soybean expellers.
Two experiments were conducted to test the hypothesis that different combinations of conditioning and expansion of soybean expellers increases nutritional value. Non-heat-treated soybean expellers (L-1) and soybean expellers conditioned for 60 s at 90ºC followed by expansion at 110ºC (L-2) were used. Two additional sources of soybean expellers (L-3 and L-4) were processed as L-2 with the exception that the initial conditioning was followed by long-term conditioning for 12 or 48 min at 100ºC before expansion. Analyzed trypsin inhibitor activity in L-1, L-2, L-3, and L-4 was 34.0, 23.1, 4.2, and 2.4 mg/g, respectively. In experiment 1, 10 cannulated barrows (54.22 ± 4.54 kg) were allotted to a replicated 5 × 4 Youden square with 5 diets and 4 periods and 8 replicates per diet. Each source of soybean expellers was included in one diet, and a N-free diet was also used. Data were analyzed by ANOVA using the Mixed Procedure of SAS. The standardized ileal digestibility (SID) of all amino acids (AA) in L-1 was less (P < 0.01) compared with L-2, L-3, and L-4 (Table 1), and SID of all AA in L-2 was less (P < 0.01) than in L-3 or L-4. In experiment 2, 40 barrows (17.52 ± 1.63 kg) were housed in metabolism crates and fed a corn diet or 4 diets based on corn and each source of soybean expellers. Feces and urine were collected using the marker-to-marker approach with 5-d adaptation and 4-d collection periods. Data were analyzed as in Exp. 1. The metabolizable energy (ME) in L-1 was less (P < 0.01) than in L-2, L-3, and L-4 (Table 1). In conclusion, the SID of AA in soybean expellers was maximized if 12 or 48 min of conditioning at 100ºC was used before expansion, but long-term conditioning did not increase ME.
Reducing dietary CP with crystalline AA supplementation has been proposed as a nutritional strategy to control post-weaning diarrhea in response to global concerns about negative effects of sub-therapeutic use of antibiotics. One hundred eighty weaned pigs (5.53 ± 0.88 kg) were randomly allotted to 3 treatments with 12 replicate pens per treatment for 28 d. Treatments included antibiotic-free, corn-soybean meal diets containing 22% and 19% CP, adequate in AA, and a 16% CP diet that provided AA below the requirement. Daily feed provisions and pig weights were recorded weekly. Fecal scores were assessed every other day. Blood samples were collected on d 1, 6, 13, 20, and 27 and 1 pig per pen was euthanized on d 12. Data for growth performance, fecal scores, and intestinal pH were analyzed by contrast statements and data for blood characteristics were analyzed using repeated measures. Results indicated that reducing dietary CP linearly (P ≤ 0.05) reduced overall ADG, G:F, body weight, and fecal scores of pigs. Reduction in dietary CP resulted in greater reduction in BUN after d 13 (treatment × day interaction, P ≤ 0.05). Total protein, albumin, and vitamin A and E in serum were lowest (P ≤ 0.05) on d 13, and pigs fed 16% CP had reduced (P ≤ 0.05) albumin compared with pigs fed other diets. The pH in the ileum was reduced (P ≤ 0.05) as dietary CP decreased but pH in the colon of pigs fed 19% CP was the lowest (P < 0.05) at d 13. In conclusion, reducing CP to 19% and 16% in antibiotic-free diets for weanling pigs reduces fecal score without impairing the growth performance during the first 14 d after weaning. However, additional strategies are needed to maintain growth performance during the next two weeks.
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