Effects of a dietary antioxidant blend on growth performance, liver function, oxidative stress, and meat and fat quality in pigs and broiler chickens fed diets high in oxidants
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High feed ingredient prices have increased the use of by-products containing a high proportion of polyunsaturated fatty acids (PUFA) in pig and chicken feeds. This can increase the oxidation of other feed nutrients as well as causing oxidative stress in animals. Two studies were conducted to evaluate the effects of a dietary antioxidant blend (AOX, ethoxyquin and propyl gallate) in pigs and broiler chickens fed a diet high in oxidants. The objective of the first study was to evaluate the antioxidant blend on growth performance, meat quality, liver function, oxidative status, carcass characteristics, meat quality, and fatty acid profile in pigs. Crossbred barrows (n = 100, 10.91 ± 0.65 kg, 36 ± 2 d of age, Landrace × Duroc) were allotted to 5 treatments based on body weight (BW, 5 replicate pens per treatment, 4 pigs per pen). Treatments included: 1) HO: high oxidant diet containing 5% oxidized soy oil and 10% PUFA source (containing docosahexaenoic acid, DHA, 3.7% of diet); 2) VE: the HO diet with 11 IU/kg of added vitamin E; 3) AOX: the HO diet with AOX (135 mg/kg); 4) VE+AOX: the HO diet with both vitamin E and AOX; and 5) SC: a standard corn-soy control diet. The trial lasted for 118 d; on d 83, the HO diet pigs were switched to the SC diet because the animals were displaying very poor health. Compared with SC pigs, HO pigs had decreased average daily gain (ADG) and average daily feed intake (ADFI) from d 26 to 82 (P < 0.05). However, after switching the HO pigs to the SC diet, the VE treatment became the most stressed treatment with the poorest performance from d 83 to 118 (P < 0.05). The AOX restored pig performance to a level similar to pigs fed the SC diet (P > 0.05) with greater gain to feed ratio (G:F) for the entire period (P < 0.05). The AOX added treatments also attenuated the enlarged liver symptoms and reduced markers of liver stress including total bilirubin and aspartate transaminase, thiobarbituric acid reactive substances (TBARS) and carbonyl concentrations. In addition, the AOX addition in the high oxidant diet restored the lighter carcass weight, less back fat, less lean body mass and smaller loin eye area, decreased dressing percentage and intensive lipofuscin deposition induced by the high oxidant diet. However, the traits of loin muscle redness and belly firmness were not fully corrected by AOX. The second study was to investigate the antioxidant blend and vitamin E on growth performance, oxidative status, meat quality, fatty acid profile, liver function and inflammatory response in broiler chickens. Cobb 500 male broilers (n = 1200, 44.7 ± 0.8 g, d 0) were randomly distributed into 60 floor pens across 6 treatments with 10 replicate pens of 20 chicks each. Treatments included: 1) HO: high oxidant diet with vitamin E at 10 IU/kg, 3% oxidized oil, 3% PUFA source; 2) VE: the HO diet with vitamin E at 200 IU/kg; 3) AOX: the HO diet with AOX at 135 mg/kg, 4) VE+AOX: the HO diet with both vitamin E at 200 IU/kg and AOX at 135 mg/kg, 5) SC: standard control, a corn soy diet with vitamin E at 10 IU/kg, 3% non-oxidized soybean oil, no PUFA source, and 6) PC: positive control, the SC diet with AOX at 135 mg/kg. Compared to the SC birds, the PUFA added treatments (HO, VE, AOX, VE+AOX) groups had greater body weight, ADG and ADFI from d 0 through d 21 (P < 0.05). However, the growth of birds fed the VE treatment fell behind that of other treatments (P < 0.05) during the last 21 d of the trial. Compared to the HO birds, the AOX birds had lower TBARS and greater uric acid concentrations in the plasma, greater gene expression of superoxide dismutase and less drip loss, suggesting enhanced systematic antioxidant capability. In addition, dietary addition of AOX or AOX plus VE moderately improved liver function and reduced inflammation in fat tissue to a level similar to control groups. In both studies, the AOX supplement was effective in preserving PUFA, especially DHA deposition in the back fat of pigs and abdominal fat of chickens. These results suggest that feeding the high oxidant diet caused a series of changes in growth performance, liver function, oxidative status, carcass characteristics and meat quality in pigs, and AOX addition attenuated many of these. The supplementation of AOX also showed some effects on reducing oxidative stress in chickens. However, the effects were not as profound as the pig study.
- Doctoral Dissertations