The effects of conjugated linoleic acid on growth performance, carcass traits, meat quality, antioxidant capacity, and fatty acid composition of broilers fed corn dried distillers grains with solubles Wen Jiang, Shaoping Nie, Zhe Qu, Chongpeng Bi, and Anshan Shan1 Institute of Animal Nutrition, Northeast Agricultural University, Harbin, 150030, China fatty acids but increased the proportion of polyunsaturated fatty acids of the thigh meat (P < 0.05). Diets supplemented with 1% CLA significantly decreased the abdominal fat percentage (P < 0.05). Supplementation with 1% CLA increased the crude fat content and decreased the color (b*) value and shear force value of the breast meat (P < 0.05). Diets supplemented with 1% CLA increased the total superoxide dismutase activity of the serum, breast meat, and liver, and decreased the malondialdehyde content of the serum and breast meat (P < 0.05). Supplementation with 1% CLA decreased the proportion of monounsaturated fatty acids and increased the proportion of saturated fatty acids (P < 0.05). Accumulation of CLA in the thigh meat was significantly increased (P < 0.05) with increasing CLA level in the diet. In conclusion, dietary supplementation with 1% CLA had positive effects on meat quality, antioxidant capacity, and fatty acid composition of broilers, although it had no significant effect on growth performance.
Key words: conjugated linoleic acid, corn dried distillers grains with solubles, meat quality, antioxidant capacity, broiler 2014 Poultry Science 93:1202–1210 http://dx.doi.org/10.3382/ps.2013-03683
INTRODUCTION Corn dried distillers grains with solubles (DDGS) is a coproduct of ethanol production from corn, produced through the dry grind process. Corn dried distillers grains with solubles is recognized as a valuable source of energy, amino acids, water-soluble vitamins, linoleic acid, and minerals for poultry diets (Jensen, 1978, 1981; Parsons and Baker, 1983; Wang et al., 2007c; Salim et al., 2010). The increasing supply of DDGS from the modern ethanol industry has resulted in the encouragement of its use in higher proportions in poultry diets than has been used previously (Renewable Fuels ©2014 Poultry Science Association Inc. Received October 11, 2013. Accepted February 8, 2014. 1 Corresponding author: [email protected]
Association, 2011). At the same time, feeding greater quantities of DDGS could have a significant impact on feed costs for poultry producers due to the current price fluctuations of feed ingredients such as corn and soybean meal (Deniz et al., 2013). Therefore, using a higher level of DDGS in broiler diets formulation is economically justifiable. Previous researchers reported that broilers can be fed 6% DDGS during the starter period (Lumpkins et al., 2004) and 12 to 15% DDGS during the finishing stage without affecting carcass traits or growth performance (Lumpkins et al., 2004; Wang et al., 2007b,c). Corzo et al. (2009) reported that 8% DDGS in broiler diets did not diminish breast meat quality, as determined by pH value at 15 min and 24 h postmortem, instrumental color (L*), cooking loss, and shear force. However, recent studies indicated that including up to 24% DDGS in broilers diets affected the meat qual-
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ABSTRACT This study investigated the effects of dietary supplementation with conjugated linoleic acid (CLA) on the growth performance, carcass traits, meat quality, antioxidant capacity, and fatty acid composition of broilers fed corn dried distillers grains with solubles (DDGS). Four hundred eighty 1-d-old broilers were randomly assigned to 4 groups, consisting of 6 replicates with 20 broilers each. Broilers were allocated 1 of 4 diets and fed for 49 d in a 2 × 2 factorial design. The dietary treatments consisted of 2 levels of DDGS (0 or 15%) and 2 levels of CLA (0 or 1%). The results of growth performance analyses showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on ADG, ADFI, and feed/gain (P > 0.05). Dietary supplementation with 15% DDGS did not significantly affect meat color values, drip loss percentage, pH value at 15 min, crude fat content, or shear force value (P > 0.05). Diets supplemented with 15% DDGS decreased the proportions of saturated fatty acids (P < 0.05) and monounsaturated
RESEARCH NOTE
MATERIALS AND METHODS Experimental Materials The DDGS were purchased from Fuel Alcohol Limited of Jilin in China. The CLA (80% purity) was purchased from Auhai Biotechnology Limited in Qingdao, China. The basal level of 1% soybean oil in the diet was replaced by commercial 1% CLA.
Birds and Experimental Design A total of 480 one-day-old Arbor Acres broilers were randomly assigned into 4 treatment groups. Each treatment group comprised 6 replicates with 20 broilers each. The broiler groups were allocated to diets 1 through 4 and were fed for 49 d in a 2 × 2 factorial design. The dietary treatments included 2 levels of DDGS (0 or 15%) and 2 levels of CLA (0 or 1%). The diets were a corn-soybean meal basal feed with or without 15% DDGS, formulated to meet the nutrient requirements for broilers (NRC, 1994). Zeolite was used as
filler when necessary. The compositions of the diets are listed in Table 1.
Management The birds were housed in wire cages in temperaturecontrolled (26 ± 1°C) and artificially lighted rooms on a 12L:12D cycle (0700–1900 h). The birds had free access to feed and water. The experimental protocol was approved by the Northeast Agricultural University Ethics Committee on the Use and Care of Animals. These guidelines are similar to those of the US National Institute of Health.
Data and Sample Collection Growth Performance. On d 21, 42, and 49 of the experiment, the BW and feed consumption of the broilers were recorded to calculate ADG, ADFI, and feed/gain. Carcass Traits. At 49 d of age, the broilers were fasted for 12 h and then killed. Each carcass was dissected into deboned skinless thighs and breasts immediately after slaughter. The weights of each carcass (with feet and head) and its breast, thigh, and abdominal fat were recorded. Meat Quality. Breast meat pH values were recorded 15 min after slaughter using a DSH-2F pH meter. Objective color measurements were determined using an automatic Minolta Chroma Meter II. Mean CIEL* (lightness), a* (redness), and b* (yellowness) values were collected from 3 locations on the surface of each breast meat. Water-holding capacity was determined in accordance with the NY/T1333–2007 method (Liu et al., 2007) for livestock and poultry. Samples were placed into sealed drip loss tubes such that the cut surface of the meat was perpendicular to the long axis of the tube. Drip loss analyses were evaluated in triplicate from the core samples. After 24 h at 4°C, the drip loss containers (plus sample) were reweighed. The meat samples were removed and discarded, and the containers were reweighed with the exudates only. The percent drip loss was calculated and recorded. At 24 h after slaughter, the breast muscles were heated in a water bath at 80°C for 5 min. After cooling at room temperature, the cooked breasts were cut into strips parallel to the direction of the muscle fibers. Samples were sheared perpendicular to the muscle fibers using a C-LM3 instrument (Heilongjiang Tianli Technology Development Co. Ltd., Harbin, China). The crude fat content of the breast meat was determined using the diethyl ether extraction-submersion method (AOAC International, 2005). Antioxidant Capacity. Total superoxide dismutase (T-SOD) activity of the serum, liver, and breast meat was determined using the xanthine oxidase method. Malondialdehyde (MDA) content of the serum, liver, and breast meat was determined using the sulfur generation barbituric acid method. Test reagent kits (JianCheng Bioengineering Institute, Nanjing, China) and
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ity, which may be due to its higher polyunsaturated fatty acid (PUFA) content, which is deposited preferentially in adipose tissue (Schilling et al., 2010). The increase in PUFA has a detrimental effect on the meat quality and shelf life of chicken because unsaturated fats are more vulnerable to lipid oxidation. Conjugated linoleic acid (CLA) refers to a mixture of positional and geometric isomers of linoleic acid with 2 conjugated double bonds at various carbon positions in the fatty acid chains. The interest in CLA studies stems from its well-documented health-enhancing functions, including its anti-cancer, anti-atherogenic, anti-diabetic, antiobesity, and immunomodulatory properties (Khanal, 2004; Salas-Salvadó et al., 2006). Conjugated linoleic acid consisting of a group of geometric and positional isomers of linoleic acid (cis-9, cis-12-18:2) has a positive influence on pork and chicken quality and fat deposition because it is a repartitioning agent (Sirri et al., 2003; Cordero et al., 2010). Dietary supplementation with CLA improved the oxidative stability of chicken meat and decreased the TBA reactive substance value and hexanal content of meat patties after storage under aerobic conditions (Du et al., 2001). Dietary supplementation with 2 or 4% CLA in broilers decreased the content of monounsaturated fatty acid (MUFA; oleic and palmitoleic acids) of breast and drumstick meat (Sirri et al., 2003). Martin et al. (2008) obtained results that indicated that dietary CLA modified the fatty acid profile of pig meat tissue by increasing the ratio of saturated fatty acids (SFA) to unsaturated fatty acids. The hypothesis of this study was that CLA could improve the growth performance, carcass traits, meat quality, antioxidant capacity, and fatty acid composition of broilers fed high levels of DDGS, which contains high concentrations of PUFA that are susceptible to oxidation.
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Table 1. Composition of experimental diets1
Item
Grower phase (22–42 d)
Finisher phase (43–49 d)
0% DDGS
15% DDGS
0% DDGS
0% DDGS
15% DDGS
60 30 0 4 2.4 0.08 0.2 1.1 1.5 0.3 0.07 0.3 0.03 0.02 100 12.54 20.97 1 0.45 1.17 0.5 89.48 21.87 1.36 0.75 6.55
54.3 21.5 15 4 2 0.14 0.13 0.78 1.45 0.3 0.07 0.3 0.03 0 100 12.53 20.97 1 0.45 1.17 0.5 89.57 21.63 1.47 0.71 6.48
68.3 23.5 0 3 2.5 0 0.04 0.8 1.16 0.3 0.07 0.3 0.03 0 100 13.26 18.04 0.81 0.35 0.88 0.34 88.99 18.07 1.03 0.63 5.37
61.7 15.3 15 3 2.5 0.05 0.01 0.37 1.34 0.3 0.07 0.3 0.03 0.03 100 13.26 18.06 0.81 0.35 0.88 0.34 88.81 19.29 1.12 0.64 5.59
63.2 27.5 0 4 2.2 0.08 0.09 0.8 1.4 0.3 0.07 0.3 0.03 0.03 100 13.05 20.06 0.9 0.4 1.07 0.40 89.40 20.58 1.21 0.65 5.86
15% DDGS
56.5 19.5 15 4 2.2 0.1 0.04 0.5 1.37 0.3 0.07 0.3 0.03 0.09 100 13.05 20.07 0.9 0.41 1.07 0.41 89.35 21.06 1.18 0.69 5.61
1DDGS: dried distillers grains with solubles. Analyzed composition of DDGS used in the experiment analyzed according to AOAC International (1990) was as follows (%): DM, 89.19; CP, 32.9; crude fat, 8.3; crude fiber, 11.2; crude ash, 5.06; calcium, 0.15; phosphorus, 0.74; lysine, 0.87; methionine, 0.61; cysteine, 0.53; threonine, 1.08; tryptophan, 0.23; histidine, 0.77; isoleucine, 1.02; leucine, 2.95; phenylalanine, 1.62; valine, 1.44; and arginine, 1.09. 2CLA diet: 1% soybean oil was replaced by commercial 1% CLA. 3The mineral premix contained (per kg of diet): manganese, 120 mg; zinc, 100 mg; iron, 100 mg; copper, 8 mg; iodine, 0.7 mg; and selenium, 0.46 mg. 4The vitamin premix contained (per kg of diet): vitamin A, 15,000 IU; vitamin D , 4,050 IU; vitamin E, 20 IU; vitamin K , 2.4 mg; vitamin B , 3 3 12 0.03 mg; vitamin B1, 2.4 mg; vitamin B2, 6.6 mg; vitamin B6, 2.4 mg; folic acid, 1.5 mg; d-pantothenic acid, 12 mg; riboflavin, 5.0 mg; niacin, 33 mg; thiamine, 1.54 mg; and d-biotin, 0.12 mg.
an UV-visible spectrophotometer UV-2401PC (Shimadzu Co., Kyoto, Japan) were used. Fatty Acid Composition. For fatty acid analysis, thigh meat was extracted with chloroform/methanol (2:1, vol/vol; Folch et al., 1957). The fatty acid methyl esters were separated on a gas chromatograph (GC2010, Shimadzu Co.) equipped with a flame ionization detector. A volume of 1 μL of sample was injected into the chamber and split (split ratio, 100:1) with a SP-2560 capillary column (100 m × 0.25 mm × 0.20 μm, Supelco Inc., Bellefonte, PA) using nitrogen as the carrier gas. An initial oven temperature of 140°C was maintained for 5 min and then increased by 4°C min−1 to a final temperature of 240°C. The injector and detector temperatures were 260°C. The carrier gas was delivered at a flow rate of 1.04 mL∙min−1, with a linear velocity of 20 cm/s. Fatty acid identification was achieved by comparison of their retention times with Supelco 37 component FAME standard mix (SigmaAldrich Co., St. Louis, MO). Results were expressed as area percentages of each fatty acid methyl ester relative to the total detected.
Statistical Analysis Data were analyzed using the GLM procedure of SPSS 20.0 for 2-way ANOVA to assess the main effects of DDGS and CLA and their interactions. Significant differences between treatments were determined at P < 0.05 using Duncan’s new multiple range tests. The values given in the tables are means values and pooled SEM.
RESULTS AND DISCUSSION Growth Performance There were no significant interaction effects between DDGS and CLA levels for growth performance (Table 2). The results of growth performance showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on ADG, ADFI, and feed/gain (P > 0.05). Our results were similar to previous reports (Youssef et al., 2008; Zhang et al., 2013). Zhang et al. (2013) found that increasing
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Ingredient (%) Corn Soybean meal DDGS Fish meal Soybean oil2 l-Lysine·HCl l-Methionine Dicalcium phosphate Limestone Sodium chloride Choline chloride Mineral premix3 Vitamin premix4 Zeolites Total Calculated composition ME (MJ/kg) CP (%) Calcium (%) Available phosphorus (%) Lys (%) Met (%) Analyzed composition (%) DM CP Calcium Total phosphorus Ash
Starter phase (0–21 d)
0.36 0.14 0.98 0.024 1DDGS:
dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 20 birds each.
0.78 0.22 0.81 0.038 0.75 0.28 0.89 0.015 0.48 0.49 0.63 0.021 0.070 0.41 0.95 0.599 0.52 0.50 0.87 2.927 0.33 0.80 0.76 0.983 0.27 0.57 0.85 0.753 0.19 0.097 0.93 0.418 0.41 0.72 0.47 0.215
0.12 0.052 0.73 0.215
0.079 0.23 0.97 0.711
1.93 1.86 2.31 2.22 1.99 1.96 105 104 73.1 74.5 38.3 38.4
66.8 67.6
54.4 56.2
56.3 55.4
133 133
169 165
1.47 1.44
1.88 1.92 2.27 2.25 1.98 1.97 106 103 74.4 73.3
Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
38.5 38.2
67.5 66.9
56.6 54.0
56.7 55.0
134 132
169 165
1.47 1.44
Finisher phase Grower phase All phases Finisher phase Grower phase Finisher phase Item
Starter phase
Grower phase
All phases
Starter phase
ADFI (g) ADG (g)
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levels of DDGS from 0 to 20% for broilers did not negatively affect growth performance. Good-quality DDGS could be used in broiler diets at levels of 15 to 20% with few adverse effects on growth performance (Wang et al., 2007b). Although DDGS is traditionally regarded as having limited usefulness as a feed ingredient due to its high concentrations of fibrous constituents, the use of this nutrient-rich material has increased recently due to improved animal production methodologies (Shurson et al., 2003). Feeding broilers with 1% CLA had no significant effects on growth performance. These results were consistent with the findings of Sirri et al. (2003) and Zhang et al. (2008) in broiler experiments. However, some researchers found that dietary supplementation with CLA at levels greater than 10 g/kg decreased the growth rate of broilers (Badinga et al., 2003; Suksombat et al., 2007). West et al. (1998) noted that the decreased growth performance of mice accompanied by high doses (above 10 g/kg) of dietary CLA was due to the acceleration of fatty acid oxidation and the enhancement of the metabolic rate. Therefore, the use of CLA in broiler diets has been kept low to avoid adverse effects on growth performance.
Carcass Traits There were no significant interaction effects between DDGS and CLA levels for carcass traits. The results in Table 3 showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on percentages of eviscerated carcass yield, breast meat, and thigh meat. Our results agreed with Wang et al. (2007a), who found that increasing levels of DDGS from 0 to 30% for male broilers did not negatively affect carcass traits. However, the broilers fed diets containing 1% CLA had decreased abdominal fat percentage (P < 0.05), consistent with a previous report (Zhang et al., 2007), most likely because the increase in dietary CLA may enhance the metabolic rate and stimulate fatty acid oxidation in animals (West et al., 1998; Szymczyk et al., 2001).
Meat Quality There were no significant interaction effects between DDGS and CLA levels for meat quality. The pH value at 15 min, the color values (L*, a*, b*), crude fat content, and shear force value of the breast meat were not significantly influenced by 15% DDGS (Table 4). These results were consistent with the findings reported by Zhang et al. (2013). Our result showed that drip loss percentage was not significantly influenced by dietary 1% CLA, 15% DDGS, or both. This result was consistent with the findings by Sun et al. (2007) and Zhang et al. (2013). The drip loss is a very important factor in meat because of its financial implications; usually, meat with a high drip loss percentage has an unattractive ap-
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Table 2. Effect of conjugated linoleic acid on growth performance of broilers fed dried distillers grains with solubles (DDGS)1
Starter phase
Feed/gain
All phases
RESEARCH NOTE
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Jiang et al. Table 3. Effect of conjugated linoleic acid on carcass traits of broilers fed dried distillers grains with solubles (DDGS)1 Carcass trait (%) Eviscerated carcass yield
Item Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
Breast meat
Thigh meat
Abdominal fat
85.2 85.0
9.79 10.3
7.92 7.99
1.54 1.60
85.1 85.0
9.96 10.1
7.78 8.13
1.65a 1.49b
0.67 0.052 0.80 0.087
0.32 0.012 0.89 0.031
0.50 0.74 0.75 0.140
0.13 0.66 0.43 0.151
a,bMeans
pearance and therefore has a low consumer acceptance, which leads to loss of sales. The addition of 1% CLA significantly increased the crude fat content, and reduced the b* value and shear force value of the breast meat (P < 0.05). Our result was similar to that of Zhang et al. (2007), who found that supplementation with a small amount of CLA increased the crude fat content of the broiler breast meat. However, previous studies showed that feeding broilers a diet containing 1% CLA had no effect on crude fat content (Suksombat et al., 2007). This may be associated with the purity of CLA and the breed of chicken. The broilers fed diets containing 1% CLA showed no significant effect on pH value at 15 min, consistent with the reports of Zhang et al. (2007) and Wiegand et al. (2001, 2002) in broilers and pigs, respectively. Table 4 shows that breast meat shear force value decreased as the CLA intake increased, consistent with the report of Zhang et al. (2007). The L*, a*, and b* values for all treatments were characteristic of normal broiler breast meat (L* < 55; Battula et al., 2008; Corzo et al., 2009). Dietary supplementation with 1% CLA sig-
nificantly reduced the b* value (P < 0.05), which was a result similar to that found by Zhang et al. (2007). The improvement of meat color stability in CLA-fed chickens indicated that CLA might play a crucial role in the prevention of lipid peroxidation in tissues (Du and Ahn, 2002). Joo et al. (2002) reported that dietary supplementation with CLA decreased lipid peroxidation of pork meat might be associated with the reduced the total content of unsaturated fatty acids. Thus, a beneficial effect of CLA-mediated antiperoxidation was involved in the improvement of meat quality.
Antioxidant Capacity There were no significant interaction effects between DDGS and CLA levels for antioxidant capacity of the serum, liver, and breast meat. Table 5 shows that dietary supplementation with 1% CLA decreased MDA content of the serum and breast meat (P < 0.05), and increased T-SOD activity of the serum, liver, and breast meat (P < 0.05). However, the broilers fed diets containing 15% DDGS increased MDA content of
Table 4. Effect of conjugated linoleic acid on breast meat quality of broilers fed dried distillers grains with solubles (DDGS)1 Breast meat quality Item Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM a,bMeans
Drip loss (%)
Crude fat (%)
Shear force (kg/cm2)
16.2 15.4
8.62 7.80
4.19 4.05
2.00 2.10
16.5a 15.0b
8.22 8.20
3.95b 4.29a
2.15a 1.96b
0.15 0.97 0.36 0.279
0.35 0.031 0.44 0.075
0.098 0.002 0.88 0.028
pH
L*
a*
b*
6.44 6.36
52.6 51.8
11.7 11.9
6.39 6.41
52.5 51.9
11.5 12.0
0.16 0.68 0.39 0.029
0.28 0.51 0.31 0.387
0.62 0.28 0.11 0.218
0.27 0.045 0.51 0.366
with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 2 samples each. 1DDGS:
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with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 2 samples each. 1DDGS:
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RESEARCH NOTE
Fatty Acid Composition There were no significant interaction effects between DDGS and CLA levels for fatty acid composition of the thigh meat. The dietary DDGS clearly affected the fatty acid composition of the thigh meat (Table 6).
The proportions of palmitic acid (C16:0), stearic acid (C18:0), SFA, and MUFA decreased with increased level of DDGS in the diets (P < 0.05). In contrast, dietary supplementation with 15% DDGS increased the proportions of linoleic (18:2n-6) and PUFA (P < 0.05). These results were consistent with previous reports (Schilling et al., 2010; Jiang et al., 2013). It is evident from literature that fatty acid composition of the feed is the most important determinant of the fatty acid composition in the resulting meat (Su et al., 2013). Because an increased proportion of PUFA is an indicator of increased susceptibility to oxidation (Faustman, 1994), increasing the level of DDGS in the diets could make thigh meat more susceptible to oxidation. Therefore, the use of DDGS in poultry diets has been low to avoid adverse effects on the quality of animal products. The effect of CLA supplementation on fatty acid composition of the thigh meat is given in Table 6. The CLA could deposit in the muscle tissues and affect fatty acid composition of the thigh meat. Previously, Suksombat et al. (2007) investigated the effects of increasing CLA concentrations (0, 0.5, 1.0, and 1.5%) in grower diet in Arbor Acres chickens and found a linear increase of CLA in tissue samples associated with CLA supplementation and no CLA in the control group. Supplementation of the diet with 1% CLA significantly decreased the proportions of oleic acid (C18:1n-9), linoleic (C18:2n-6), MUFA, and increased the proportions of palmitic acid (C16:0) and SFA (P < 0.05), in agreement with Badinga et al. (2003) and Sirri et al. (2003). These results we obtained indicate that dietary supplementation with 1% CLA in corn DDGS diet can decrease the unsaturation of the thigh meat, and improve the increase of fat unsaturation caused by feeding corn DDGS to broilers. Therefore, the results suggested that dietary CLA changed fatty acid composition and enhanced antioxidant capacity of chicken meat and broilers.
Table 5. Effect of conjugated linoleic acid on antioxidant capacity of broilers fed dried distillers grains with solubles (DDGS)1 Antioxidant capacity MDA
Item Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM a,bMeans
T-SOD
Serum (nmol/mL)
Liver (nmol/mg of protein)
Breast meat (nmol/mg of protein)
4.21b 4.82a
1.12 1.28
1.51b 1.64a
116 114
206 208
194 188
4.81a 4.22b
1.30 1.10
1.63a 1.51b
108b 122a
191b 223a
185b 196a
0.037 0.039 0.96 0.140
0.17 0.087 0.91 0.057
0.009 0.019 0.37 0.024
Serum (U/mL)
0.69 0.038 0.64 3.273
Liver (U/mg of protein)
0.84 0.001 0.24 4.549
Breast meat (U/mg of protein)
0.30 0.043 0.89 2.626
with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 2 samples each. MDA = malondialdehyde; T-SOD = total superoxide dismutase. 1DDGS:
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the serum and breast meat (P < 0.05). The MDA is one of the end products of lipid peroxidation, and its contents reflect the lipid peroxidation degree of body, indirectly reflect the degree of cell damage. Our results agreed with Li et al. (2012), who found that the double bonds in unsaturated fatty acid of corn DDGS are easily attacked by free radicals and cause lipid peroxidation. The antioxidant capacity of CLA was first recognized in 1990 from in vitro experimental results (Ha et al., 1990). They reported that CLA is an effective antioxidant, more potent than α-tocopherol and almost as effective as butylated hydroxytoluene. Our results suggested that dietary CLA enhances the capacity of scavenging free radicals and decreases the damages to tissues or cells. Similar to our results, it was reported that CLA enhanced the oxidative stability of the longissimus dorsi meat in rabbit (Corino et al., 2002) and broilers given 0 to 10 g of CLA/kg due to an ameliorated antioxidant balance and improved the quality of poultry meat during oxidative stress (Zhang et al., 2008). Broilers are prone to lipid peroxidation is mainly due to the fatty acid composition of broiler carcass, which may due to its higher PUFA, deposited preferentially in adipose and muscle tissue. Therefore, our results showed that dietary supplementation with 1% CLA in broilers resulted in an elevated oxidative stability of meat by increasing T-SOD activity and decreasing MDA content of the meat, which suggests that dietary CLA may improve the meat quality and prolong the shelf life of chicken meat.
30.3a 27.6b 0.087 0.005 0.32 0.441
29.7 28.1
C18:1n-9
0.74 0.73 0.12b 1.35a 0.91 0.000 0.69 0.047
0.18b 2.01a 0.52 0.000 0.56 0.040
trans-10, cis-12
7.30 7.26 0.040 0.92 0.89 0.202
1.17 1.11
cis-9, trans-11
3.61 3.42 0.34 0.58 0.53 0.168
25.7b 26.9a 0.003 0.012 0.082 0.206
0.60 0.67 0.68 0.31 0.93 0.031
7.72a 6.83b
C18:0
3.68 3.35
C16:1
27.0a 25.6b
C16:0
0.62 0.65
C14:0
35.9b 37.2a 0.002 0.046 0.16 0.300
37.6a 35.4b
SFA
24.1a 21.9b 0.027 0.010 0.94 0.378
22.2b 24.0a
C18:2n-6
24.8b 26.5a 25.2 26.1 0.043 0.24 0.84 0.404
34.2a 31.2b 0.027 0.001 0.19 0.399
0.29 0.25 0.79 0.21 0.56 0.013
33.7a 31.8b
2.26 2.37 0.68 0.50 0.70 0.085
0.37 0.37 0.91 0.99 0.65 0.021
0.27 0.27
PUFA
2.28 2.35
0.37 0.38
C20:1
MUFA
C21:0
C18:3n-6
1DDGS:
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0.34 0.33 0.82 0.81 0.82 0.016
0.34 0.33
C20:5
with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA, SFA: saturated fatty acids, MUFA: monounsaturated fatty acids, PUFA: polyunsaturated fatty acids. Data are the mean of 6 replicates of 2 samples each.
a,bMeans
Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
Item
Table 6. Effect of conjugated linoleic acid on fatty acid composition in the thigh meat of broilers fed dried distillers grains with solubles (DDGS)1
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RESEARCH NOTE
Conclusions The results showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on growth performance. Dietary supplementation with 15% DDGS increased the proportion of PUFA and decreased the proportions of SFA and MUFA. However, dietary supplementation with 1% CLA had positive effects on meat quality, antioxidant capacity, and fatty acid composition of broilers.
ACKNOWLEDGMENTS
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Jensen, L. S. 1981. Value of distillers dried grains with solubles in poultry feeds. Proc. Distillers Res. Conf. 36:87–93. Cincinnati, OH. Jiang, W., L. C. Zhang, and A. S. Shan. 2013. The effect of vitamin E on laying performance and egg quality in laying hens fed corn dried distillers grains with solubles. Poult. Sci. 92:2956–2964. Joo, S. T., J. I. Lee, Y. L. Ha, and G. B. Park. 2002. Effects of dietary conjugated linoleic acid on fatty acid composition, lipid oxidation, color, and water-holding capacity of pork loin. J. Anim. Sci. 80:108–112. Khanal, R. C. 2004. Potential health benefits of conjugated linoleic acid (CLA): A review. Asian-australas. J. Anim. Sci. 17:1315– 1328. Li, G. L., X. Wang, M. X. Lin, Z. F. Lu, and W. Yao. 2012. Effects of corn DDGS in combination with compound enzymes on growth performance, carcass fat quality, and plasma and tissue redox homeostasis of growing-finishing pigs. Livest. Sci. 149:46–52. Liu, S. Y., H. You, Y. J. Liu, Y. H. Cai, and Y. H. Li. 2007. NY/ T1333. Determination of livestock and poultry meat quality. China Agriculture Press, Chaoyang District of Beijing. Lumpkins, B. S., A. B. Batal, and N. M. Dale. 2004. Evaluation of distillers dried grains with solubles as a feed ingredient for broilers. Poult. Sci. 83:1891–1896. Martin, D., E. Muriel, E. Gonzalez, J. Viguera, and J. Ruiz. 2008. Effect of dietary conjugated linoleic acid and monounsaturated fatty acids on productive, carcass and meat quality traits of pigs. Livest. Sci. 117:155–164. NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. Parsons, C. M., and D. H. Baker. 1983. Distillers dried grains with solubles as a protein source for the chick. Poult. Sci. 62:2445– 2451. Renewable Fuels Association. 2011. Industry Resources: Co-products. Accessed Mar. 2011. http://www.ethanolrfa.org/pages/ industry-resources-coproducts. Salas-Salvadó, J., F. Marquez-Sandoval, and M. Bullo. 2006. Conjugated linoleic acid intake in humans: A systematic review focusing on its effect on body composition, glucose, and lipid metabolism. Crit. Rev. Food Sci. Nutr. 46:479–488. Salim, H. M., Z. A. Kruk, and B. D. Lee. 2010. Nutritive value of corn distillers dried grains with solubles as an ingredient of poultry diets: A review. World’s Poult. Sci. J. 66:411–432. Schilling, M. W., V. Battula, R. E. Loar, V. Jackson, S. Kin, and A. Corzo. 2010. Dietary inclusion level effects of distillers dried grains with solubles on broiler meat quality. Poult. Sci. 89:752– 760. Shurson, J., M. Spiehs, J. Wilson, and M. Whitney. 2003. Value and use of ‘new generation’ distillers dried grains with solubles in swine diets. Pages 223–235 in Nutritional Biotechnology in the Feed and Food Industries, Proceedings of Alltech’s 19th International Symposium. T. P. Lyons and K. A. Jacques, ed. Nottingham University Press, Nottingham, UK. Sirri, F., N. Tallarico, A. Meluzzi, and A. Franchini. 2003. Fatty acid composition and productive traits of broiler fed diets containing conjugated linoleic acid. Poult. Sci. 82:1356–1361. Su, B. C., L. S. Wang, H. Wang, B. M. Shi, A. S. Shan, and Y. Z. Li. 2013. Conjugated linoleic acid and betain prevent pork quality issues from diets containing distillers dried grains with solubles. Can. J. Anim. Sci. 93:477–485. Suksombat, W., T. Boonmee, and P. Lounglawan. 2007. Effects of various levels of conjugated linoleic acid supplementation on fatty acid content and carcass composition of broilers. Poult. Sci. 86:318–324. Sun, J. H., G. B. Park, and S. T. Joo. 2007. A comparison of the effects of dietary conjugated linoleic acid contents, cholesterol, lipid oxidation and drip loss in pork loin and chicken breast. J. Muscle Foods 18:264–275. Szymczyk, B., P. M. Pisulewski, W. Szczurek, and P. Hanczakowski. 2001. Effects of conjugated linoleic acid on growth performance, feed conversion efficiency, and subsequent carcass quality in broiler chickens. Br. J. Nutr. 85:465–473. Wang, Z., S. Cerrate, C. Coto, F. Yan, and P. W. Waldroup. 2007a. Effect of rapid and multiple changes in level of distillers dried
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This work was supported by the National Natural Science Foundation of China (No. 31272453, No. 31072046) and the Program for Innovative Research Team of Universities in Heilongjiang Province.
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grain with solubles (DDGS) in broiler diets on performance and carcass characteristics. Int. J. Poult. Sci. 6:725–731. Wang, Z., S. Cerrate, C. Coto, F. Yan, and P. W. Waldroup. 2007b. Use of constant or increasing levels of distillers dried grains with solubles (DDGS) in broilers diets. Int. J. Poult. Sci. 6:501–507. Wang, Z., S. Cerrate, C. Coto, F. Yan, and P. W. Waldroup. 2007c. Utilization of distillers dried grains with solubles (DDGS) in broiler diets using a standardized nutrient matrix. Int. J. Poult. Sci. 6:470–477. West, D. B., J. P. Delany, P. M. Camet, F. Blohm, A. A. Truett, and J. Scimeca. 1998. Effects of conjugated linoleic acid on body fat and energy metabolism in the mouse. Am. J. Physiol. 275:R667–R672. Wiegand, B. R., F. C. Parrish, J. E. Swan, S. T. Larsen, and T. J. Baas. 2001. Conjugated linoleic acid improves feed efficiency, decreases subcutaneous fat, and improves certain aspects of meat quality in stress-genotype pigs. J. Anim. Sci. 79:2187–2195. Wiegand, B. R., J. C. Sparks, F. C. Parrish, and D. R. Zimmerman. 2002. Duration of feeding conjugated linoleic acid influences
growth performance, carcass traits, and meat quality of finishing barrows. J. Anim. Sci. 80:637–643. Youssef, I. M. I., C. Westfahl, A. Sünder, F. Liebert, and J. Kamphues. 2008. Evaluation of dried distillers’ grains with solubles (DDGS) as a protein source for broilers. Arch. Anim. Nutr. 62:404–414. Zhang, G. M., J. Wen, J. L. Chen, G. P. Zhao, M. Q. Zheng, and W. J. Li. 2007. Effect of conjugated linoleic acid on growth performances, carcase composition, plasma lipoprotein lipase activity and meat traits of chickens. Br. Poult. Sci. 48:217–223. Zhang, H. J., Y. M. Gao, Y. D. Tian, and J. M. Yuan. 2008. Dietary conjugated linoleic acid improves antioxidant capacity in broiler chicks. Br. Poult. Sci. 49:213–221. Zhang, Y., A. S. Shan, W. Jiang, C. P. Bi, and Z. Y. Li. 2013. The effect of vitamin E on growth performance and meat quality in broilers given diets containing distillers dried grains with solubles (DDGS). Br. Poult. Sci. 54:138–143.
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Key words: conjugated linoleic acid, corn dried distillers grains with solubles, meat quality, antioxidant capacity, broiler 2014 Poultry Science 93:1202–1210 http://dx.doi.org/10.3382/ps.2013-03683
INTRODUCTION Corn dried distillers grains with solubles (DDGS) is a coproduct of ethanol production from corn, produced through the dry grind process. Corn dried distillers grains with solubles is recognized as a valuable source of energy, amino acids, water-soluble vitamins, linoleic acid, and minerals for poultry diets (Jensen, 1978, 1981; Parsons and Baker, 1983; Wang et al., 2007c; Salim et al., 2010). The increasing supply of DDGS from the modern ethanol industry has resulted in the encouragement of its use in higher proportions in poultry diets than has been used previously (Renewable Fuels ©2014 Poultry Science Association Inc. Received October 11, 2013. Accepted February 8, 2014. 1 Corresponding author: [email protected]
Association, 2011). At the same time, feeding greater quantities of DDGS could have a significant impact on feed costs for poultry producers due to the current price fluctuations of feed ingredients such as corn and soybean meal (Deniz et al., 2013). Therefore, using a higher level of DDGS in broiler diets formulation is economically justifiable. Previous researchers reported that broilers can be fed 6% DDGS during the starter period (Lumpkins et al., 2004) and 12 to 15% DDGS during the finishing stage without affecting carcass traits or growth performance (Lumpkins et al., 2004; Wang et al., 2007b,c). Corzo et al. (2009) reported that 8% DDGS in broiler diets did not diminish breast meat quality, as determined by pH value at 15 min and 24 h postmortem, instrumental color (L*), cooking loss, and shear force. However, recent studies indicated that including up to 24% DDGS in broilers diets affected the meat qual-
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ABSTRACT This study investigated the effects of dietary supplementation with conjugated linoleic acid (CLA) on the growth performance, carcass traits, meat quality, antioxidant capacity, and fatty acid composition of broilers fed corn dried distillers grains with solubles (DDGS). Four hundred eighty 1-d-old broilers were randomly assigned to 4 groups, consisting of 6 replicates with 20 broilers each. Broilers were allocated 1 of 4 diets and fed for 49 d in a 2 × 2 factorial design. The dietary treatments consisted of 2 levels of DDGS (0 or 15%) and 2 levels of CLA (0 or 1%). The results of growth performance analyses showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on ADG, ADFI, and feed/gain (P > 0.05). Dietary supplementation with 15% DDGS did not significantly affect meat color values, drip loss percentage, pH value at 15 min, crude fat content, or shear force value (P > 0.05). Diets supplemented with 15% DDGS decreased the proportions of saturated fatty acids (P < 0.05) and monounsaturated
RESEARCH NOTE
MATERIALS AND METHODS Experimental Materials The DDGS were purchased from Fuel Alcohol Limited of Jilin in China. The CLA (80% purity) was purchased from Auhai Biotechnology Limited in Qingdao, China. The basal level of 1% soybean oil in the diet was replaced by commercial 1% CLA.
Birds and Experimental Design A total of 480 one-day-old Arbor Acres broilers were randomly assigned into 4 treatment groups. Each treatment group comprised 6 replicates with 20 broilers each. The broiler groups were allocated to diets 1 through 4 and were fed for 49 d in a 2 × 2 factorial design. The dietary treatments included 2 levels of DDGS (0 or 15%) and 2 levels of CLA (0 or 1%). The diets were a corn-soybean meal basal feed with or without 15% DDGS, formulated to meet the nutrient requirements for broilers (NRC, 1994). Zeolite was used as
filler when necessary. The compositions of the diets are listed in Table 1.
Management The birds were housed in wire cages in temperaturecontrolled (26 ± 1°C) and artificially lighted rooms on a 12L:12D cycle (0700–1900 h). The birds had free access to feed and water. The experimental protocol was approved by the Northeast Agricultural University Ethics Committee on the Use and Care of Animals. These guidelines are similar to those of the US National Institute of Health.
Data and Sample Collection Growth Performance. On d 21, 42, and 49 of the experiment, the BW and feed consumption of the broilers were recorded to calculate ADG, ADFI, and feed/gain. Carcass Traits. At 49 d of age, the broilers were fasted for 12 h and then killed. Each carcass was dissected into deboned skinless thighs and breasts immediately after slaughter. The weights of each carcass (with feet and head) and its breast, thigh, and abdominal fat were recorded. Meat Quality. Breast meat pH values were recorded 15 min after slaughter using a DSH-2F pH meter. Objective color measurements were determined using an automatic Minolta Chroma Meter II. Mean CIEL* (lightness), a* (redness), and b* (yellowness) values were collected from 3 locations on the surface of each breast meat. Water-holding capacity was determined in accordance with the NY/T1333–2007 method (Liu et al., 2007) for livestock and poultry. Samples were placed into sealed drip loss tubes such that the cut surface of the meat was perpendicular to the long axis of the tube. Drip loss analyses were evaluated in triplicate from the core samples. After 24 h at 4°C, the drip loss containers (plus sample) were reweighed. The meat samples were removed and discarded, and the containers were reweighed with the exudates only. The percent drip loss was calculated and recorded. At 24 h after slaughter, the breast muscles were heated in a water bath at 80°C for 5 min. After cooling at room temperature, the cooked breasts were cut into strips parallel to the direction of the muscle fibers. Samples were sheared perpendicular to the muscle fibers using a C-LM3 instrument (Heilongjiang Tianli Technology Development Co. Ltd., Harbin, China). The crude fat content of the breast meat was determined using the diethyl ether extraction-submersion method (AOAC International, 2005). Antioxidant Capacity. Total superoxide dismutase (T-SOD) activity of the serum, liver, and breast meat was determined using the xanthine oxidase method. Malondialdehyde (MDA) content of the serum, liver, and breast meat was determined using the sulfur generation barbituric acid method. Test reagent kits (JianCheng Bioengineering Institute, Nanjing, China) and
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ity, which may be due to its higher polyunsaturated fatty acid (PUFA) content, which is deposited preferentially in adipose tissue (Schilling et al., 2010). The increase in PUFA has a detrimental effect on the meat quality and shelf life of chicken because unsaturated fats are more vulnerable to lipid oxidation. Conjugated linoleic acid (CLA) refers to a mixture of positional and geometric isomers of linoleic acid with 2 conjugated double bonds at various carbon positions in the fatty acid chains. The interest in CLA studies stems from its well-documented health-enhancing functions, including its anti-cancer, anti-atherogenic, anti-diabetic, antiobesity, and immunomodulatory properties (Khanal, 2004; Salas-Salvadó et al., 2006). Conjugated linoleic acid consisting of a group of geometric and positional isomers of linoleic acid (cis-9, cis-12-18:2) has a positive influence on pork and chicken quality and fat deposition because it is a repartitioning agent (Sirri et al., 2003; Cordero et al., 2010). Dietary supplementation with CLA improved the oxidative stability of chicken meat and decreased the TBA reactive substance value and hexanal content of meat patties after storage under aerobic conditions (Du et al., 2001). Dietary supplementation with 2 or 4% CLA in broilers decreased the content of monounsaturated fatty acid (MUFA; oleic and palmitoleic acids) of breast and drumstick meat (Sirri et al., 2003). Martin et al. (2008) obtained results that indicated that dietary CLA modified the fatty acid profile of pig meat tissue by increasing the ratio of saturated fatty acids (SFA) to unsaturated fatty acids. The hypothesis of this study was that CLA could improve the growth performance, carcass traits, meat quality, antioxidant capacity, and fatty acid composition of broilers fed high levels of DDGS, which contains high concentrations of PUFA that are susceptible to oxidation.
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Table 1. Composition of experimental diets1
Item
Grower phase (22–42 d)
Finisher phase (43–49 d)
0% DDGS
15% DDGS
0% DDGS
0% DDGS
15% DDGS
60 30 0 4 2.4 0.08 0.2 1.1 1.5 0.3 0.07 0.3 0.03 0.02 100 12.54 20.97 1 0.45 1.17 0.5 89.48 21.87 1.36 0.75 6.55
54.3 21.5 15 4 2 0.14 0.13 0.78 1.45 0.3 0.07 0.3 0.03 0 100 12.53 20.97 1 0.45 1.17 0.5 89.57 21.63 1.47 0.71 6.48
68.3 23.5 0 3 2.5 0 0.04 0.8 1.16 0.3 0.07 0.3 0.03 0 100 13.26 18.04 0.81 0.35 0.88 0.34 88.99 18.07 1.03 0.63 5.37
61.7 15.3 15 3 2.5 0.05 0.01 0.37 1.34 0.3 0.07 0.3 0.03 0.03 100 13.26 18.06 0.81 0.35 0.88 0.34 88.81 19.29 1.12 0.64 5.59
63.2 27.5 0 4 2.2 0.08 0.09 0.8 1.4 0.3 0.07 0.3 0.03 0.03 100 13.05 20.06 0.9 0.4 1.07 0.40 89.40 20.58 1.21 0.65 5.86
15% DDGS
56.5 19.5 15 4 2.2 0.1 0.04 0.5 1.37 0.3 0.07 0.3 0.03 0.09 100 13.05 20.07 0.9 0.41 1.07 0.41 89.35 21.06 1.18 0.69 5.61
1DDGS: dried distillers grains with solubles. Analyzed composition of DDGS used in the experiment analyzed according to AOAC International (1990) was as follows (%): DM, 89.19; CP, 32.9; crude fat, 8.3; crude fiber, 11.2; crude ash, 5.06; calcium, 0.15; phosphorus, 0.74; lysine, 0.87; methionine, 0.61; cysteine, 0.53; threonine, 1.08; tryptophan, 0.23; histidine, 0.77; isoleucine, 1.02; leucine, 2.95; phenylalanine, 1.62; valine, 1.44; and arginine, 1.09. 2CLA diet: 1% soybean oil was replaced by commercial 1% CLA. 3The mineral premix contained (per kg of diet): manganese, 120 mg; zinc, 100 mg; iron, 100 mg; copper, 8 mg; iodine, 0.7 mg; and selenium, 0.46 mg. 4The vitamin premix contained (per kg of diet): vitamin A, 15,000 IU; vitamin D , 4,050 IU; vitamin E, 20 IU; vitamin K , 2.4 mg; vitamin B , 3 3 12 0.03 mg; vitamin B1, 2.4 mg; vitamin B2, 6.6 mg; vitamin B6, 2.4 mg; folic acid, 1.5 mg; d-pantothenic acid, 12 mg; riboflavin, 5.0 mg; niacin, 33 mg; thiamine, 1.54 mg; and d-biotin, 0.12 mg.
an UV-visible spectrophotometer UV-2401PC (Shimadzu Co., Kyoto, Japan) were used. Fatty Acid Composition. For fatty acid analysis, thigh meat was extracted with chloroform/methanol (2:1, vol/vol; Folch et al., 1957). The fatty acid methyl esters were separated on a gas chromatograph (GC2010, Shimadzu Co.) equipped with a flame ionization detector. A volume of 1 μL of sample was injected into the chamber and split (split ratio, 100:1) with a SP-2560 capillary column (100 m × 0.25 mm × 0.20 μm, Supelco Inc., Bellefonte, PA) using nitrogen as the carrier gas. An initial oven temperature of 140°C was maintained for 5 min and then increased by 4°C min−1 to a final temperature of 240°C. The injector and detector temperatures were 260°C. The carrier gas was delivered at a flow rate of 1.04 mL∙min−1, with a linear velocity of 20 cm/s. Fatty acid identification was achieved by comparison of their retention times with Supelco 37 component FAME standard mix (SigmaAldrich Co., St. Louis, MO). Results were expressed as area percentages of each fatty acid methyl ester relative to the total detected.
Statistical Analysis Data were analyzed using the GLM procedure of SPSS 20.0 for 2-way ANOVA to assess the main effects of DDGS and CLA and their interactions. Significant differences between treatments were determined at P < 0.05 using Duncan’s new multiple range tests. The values given in the tables are means values and pooled SEM.
RESULTS AND DISCUSSION Growth Performance There were no significant interaction effects between DDGS and CLA levels for growth performance (Table 2). The results of growth performance showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on ADG, ADFI, and feed/gain (P > 0.05). Our results were similar to previous reports (Youssef et al., 2008; Zhang et al., 2013). Zhang et al. (2013) found that increasing
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Ingredient (%) Corn Soybean meal DDGS Fish meal Soybean oil2 l-Lysine·HCl l-Methionine Dicalcium phosphate Limestone Sodium chloride Choline chloride Mineral premix3 Vitamin premix4 Zeolites Total Calculated composition ME (MJ/kg) CP (%) Calcium (%) Available phosphorus (%) Lys (%) Met (%) Analyzed composition (%) DM CP Calcium Total phosphorus Ash
Starter phase (0–21 d)
0.36 0.14 0.98 0.024 1DDGS:
dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 20 birds each.
0.78 0.22 0.81 0.038 0.75 0.28 0.89 0.015 0.48 0.49 0.63 0.021 0.070 0.41 0.95 0.599 0.52 0.50 0.87 2.927 0.33 0.80 0.76 0.983 0.27 0.57 0.85 0.753 0.19 0.097 0.93 0.418 0.41 0.72 0.47 0.215
0.12 0.052 0.73 0.215
0.079 0.23 0.97 0.711
1.93 1.86 2.31 2.22 1.99 1.96 105 104 73.1 74.5 38.3 38.4
66.8 67.6
54.4 56.2
56.3 55.4
133 133
169 165
1.47 1.44
1.88 1.92 2.27 2.25 1.98 1.97 106 103 74.4 73.3
Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
38.5 38.2
67.5 66.9
56.6 54.0
56.7 55.0
134 132
169 165
1.47 1.44
Finisher phase Grower phase All phases Finisher phase Grower phase Finisher phase Item
Starter phase
Grower phase
All phases
Starter phase
ADFI (g) ADG (g)
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levels of DDGS from 0 to 20% for broilers did not negatively affect growth performance. Good-quality DDGS could be used in broiler diets at levels of 15 to 20% with few adverse effects on growth performance (Wang et al., 2007b). Although DDGS is traditionally regarded as having limited usefulness as a feed ingredient due to its high concentrations of fibrous constituents, the use of this nutrient-rich material has increased recently due to improved animal production methodologies (Shurson et al., 2003). Feeding broilers with 1% CLA had no significant effects on growth performance. These results were consistent with the findings of Sirri et al. (2003) and Zhang et al. (2008) in broiler experiments. However, some researchers found that dietary supplementation with CLA at levels greater than 10 g/kg decreased the growth rate of broilers (Badinga et al., 2003; Suksombat et al., 2007). West et al. (1998) noted that the decreased growth performance of mice accompanied by high doses (above 10 g/kg) of dietary CLA was due to the acceleration of fatty acid oxidation and the enhancement of the metabolic rate. Therefore, the use of CLA in broiler diets has been kept low to avoid adverse effects on growth performance.
Carcass Traits There were no significant interaction effects between DDGS and CLA levels for carcass traits. The results in Table 3 showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on percentages of eviscerated carcass yield, breast meat, and thigh meat. Our results agreed with Wang et al. (2007a), who found that increasing levels of DDGS from 0 to 30% for male broilers did not negatively affect carcass traits. However, the broilers fed diets containing 1% CLA had decreased abdominal fat percentage (P < 0.05), consistent with a previous report (Zhang et al., 2007), most likely because the increase in dietary CLA may enhance the metabolic rate and stimulate fatty acid oxidation in animals (West et al., 1998; Szymczyk et al., 2001).
Meat Quality There were no significant interaction effects between DDGS and CLA levels for meat quality. The pH value at 15 min, the color values (L*, a*, b*), crude fat content, and shear force value of the breast meat were not significantly influenced by 15% DDGS (Table 4). These results were consistent with the findings reported by Zhang et al. (2013). Our result showed that drip loss percentage was not significantly influenced by dietary 1% CLA, 15% DDGS, or both. This result was consistent with the findings by Sun et al. (2007) and Zhang et al. (2013). The drip loss is a very important factor in meat because of its financial implications; usually, meat with a high drip loss percentage has an unattractive ap-
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Table 2. Effect of conjugated linoleic acid on growth performance of broilers fed dried distillers grains with solubles (DDGS)1
Starter phase
Feed/gain
All phases
RESEARCH NOTE
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Jiang et al. Table 3. Effect of conjugated linoleic acid on carcass traits of broilers fed dried distillers grains with solubles (DDGS)1 Carcass trait (%) Eviscerated carcass yield
Item Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
Breast meat
Thigh meat
Abdominal fat
85.2 85.0
9.79 10.3
7.92 7.99
1.54 1.60
85.1 85.0
9.96 10.1
7.78 8.13
1.65a 1.49b
0.67 0.052 0.80 0.087
0.32 0.012 0.89 0.031
0.50 0.74 0.75 0.140
0.13 0.66 0.43 0.151
a,bMeans
pearance and therefore has a low consumer acceptance, which leads to loss of sales. The addition of 1% CLA significantly increased the crude fat content, and reduced the b* value and shear force value of the breast meat (P < 0.05). Our result was similar to that of Zhang et al. (2007), who found that supplementation with a small amount of CLA increased the crude fat content of the broiler breast meat. However, previous studies showed that feeding broilers a diet containing 1% CLA had no effect on crude fat content (Suksombat et al., 2007). This may be associated with the purity of CLA and the breed of chicken. The broilers fed diets containing 1% CLA showed no significant effect on pH value at 15 min, consistent with the reports of Zhang et al. (2007) and Wiegand et al. (2001, 2002) in broilers and pigs, respectively. Table 4 shows that breast meat shear force value decreased as the CLA intake increased, consistent with the report of Zhang et al. (2007). The L*, a*, and b* values for all treatments were characteristic of normal broiler breast meat (L* < 55; Battula et al., 2008; Corzo et al., 2009). Dietary supplementation with 1% CLA sig-
nificantly reduced the b* value (P < 0.05), which was a result similar to that found by Zhang et al. (2007). The improvement of meat color stability in CLA-fed chickens indicated that CLA might play a crucial role in the prevention of lipid peroxidation in tissues (Du and Ahn, 2002). Joo et al. (2002) reported that dietary supplementation with CLA decreased lipid peroxidation of pork meat might be associated with the reduced the total content of unsaturated fatty acids. Thus, a beneficial effect of CLA-mediated antiperoxidation was involved in the improvement of meat quality.
Antioxidant Capacity There were no significant interaction effects between DDGS and CLA levels for antioxidant capacity of the serum, liver, and breast meat. Table 5 shows that dietary supplementation with 1% CLA decreased MDA content of the serum and breast meat (P < 0.05), and increased T-SOD activity of the serum, liver, and breast meat (P < 0.05). However, the broilers fed diets containing 15% DDGS increased MDA content of
Table 4. Effect of conjugated linoleic acid on breast meat quality of broilers fed dried distillers grains with solubles (DDGS)1 Breast meat quality Item Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM a,bMeans
Drip loss (%)
Crude fat (%)
Shear force (kg/cm2)
16.2 15.4
8.62 7.80
4.19 4.05
2.00 2.10
16.5a 15.0b
8.22 8.20
3.95b 4.29a
2.15a 1.96b
0.15 0.97 0.36 0.279
0.35 0.031 0.44 0.075
0.098 0.002 0.88 0.028
pH
L*
a*
b*
6.44 6.36
52.6 51.8
11.7 11.9
6.39 6.41
52.5 51.9
11.5 12.0
0.16 0.68 0.39 0.029
0.28 0.51 0.31 0.387
0.62 0.28 0.11 0.218
0.27 0.045 0.51 0.366
with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 2 samples each. 1DDGS:
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with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 2 samples each. 1DDGS:
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RESEARCH NOTE
Fatty Acid Composition There were no significant interaction effects between DDGS and CLA levels for fatty acid composition of the thigh meat. The dietary DDGS clearly affected the fatty acid composition of the thigh meat (Table 6).
The proportions of palmitic acid (C16:0), stearic acid (C18:0), SFA, and MUFA decreased with increased level of DDGS in the diets (P < 0.05). In contrast, dietary supplementation with 15% DDGS increased the proportions of linoleic (18:2n-6) and PUFA (P < 0.05). These results were consistent with previous reports (Schilling et al., 2010; Jiang et al., 2013). It is evident from literature that fatty acid composition of the feed is the most important determinant of the fatty acid composition in the resulting meat (Su et al., 2013). Because an increased proportion of PUFA is an indicator of increased susceptibility to oxidation (Faustman, 1994), increasing the level of DDGS in the diets could make thigh meat more susceptible to oxidation. Therefore, the use of DDGS in poultry diets has been low to avoid adverse effects on the quality of animal products. The effect of CLA supplementation on fatty acid composition of the thigh meat is given in Table 6. The CLA could deposit in the muscle tissues and affect fatty acid composition of the thigh meat. Previously, Suksombat et al. (2007) investigated the effects of increasing CLA concentrations (0, 0.5, 1.0, and 1.5%) in grower diet in Arbor Acres chickens and found a linear increase of CLA in tissue samples associated with CLA supplementation and no CLA in the control group. Supplementation of the diet with 1% CLA significantly decreased the proportions of oleic acid (C18:1n-9), linoleic (C18:2n-6), MUFA, and increased the proportions of palmitic acid (C16:0) and SFA (P < 0.05), in agreement with Badinga et al. (2003) and Sirri et al. (2003). These results we obtained indicate that dietary supplementation with 1% CLA in corn DDGS diet can decrease the unsaturation of the thigh meat, and improve the increase of fat unsaturation caused by feeding corn DDGS to broilers. Therefore, the results suggested that dietary CLA changed fatty acid composition and enhanced antioxidant capacity of chicken meat and broilers.
Table 5. Effect of conjugated linoleic acid on antioxidant capacity of broilers fed dried distillers grains with solubles (DDGS)1 Antioxidant capacity MDA
Item Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM a,bMeans
T-SOD
Serum (nmol/mL)
Liver (nmol/mg of protein)
Breast meat (nmol/mg of protein)
4.21b 4.82a
1.12 1.28
1.51b 1.64a
116 114
206 208
194 188
4.81a 4.22b
1.30 1.10
1.63a 1.51b
108b 122a
191b 223a
185b 196a
0.037 0.039 0.96 0.140
0.17 0.087 0.91 0.057
0.009 0.019 0.37 0.024
Serum (U/mL)
0.69 0.038 0.64 3.273
Liver (U/mg of protein)
0.84 0.001 0.24 4.549
Breast meat (U/mg of protein)
0.30 0.043 0.89 2.626
with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA. Data are the mean of 6 replicates of 2 samples each. MDA = malondialdehyde; T-SOD = total superoxide dismutase. 1DDGS:
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the serum and breast meat (P < 0.05). The MDA is one of the end products of lipid peroxidation, and its contents reflect the lipid peroxidation degree of body, indirectly reflect the degree of cell damage. Our results agreed with Li et al. (2012), who found that the double bonds in unsaturated fatty acid of corn DDGS are easily attacked by free radicals and cause lipid peroxidation. The antioxidant capacity of CLA was first recognized in 1990 from in vitro experimental results (Ha et al., 1990). They reported that CLA is an effective antioxidant, more potent than α-tocopherol and almost as effective as butylated hydroxytoluene. Our results suggested that dietary CLA enhances the capacity of scavenging free radicals and decreases the damages to tissues or cells. Similar to our results, it was reported that CLA enhanced the oxidative stability of the longissimus dorsi meat in rabbit (Corino et al., 2002) and broilers given 0 to 10 g of CLA/kg due to an ameliorated antioxidant balance and improved the quality of poultry meat during oxidative stress (Zhang et al., 2008). Broilers are prone to lipid peroxidation is mainly due to the fatty acid composition of broiler carcass, which may due to its higher PUFA, deposited preferentially in adipose and muscle tissue. Therefore, our results showed that dietary supplementation with 1% CLA in broilers resulted in an elevated oxidative stability of meat by increasing T-SOD activity and decreasing MDA content of the meat, which suggests that dietary CLA may improve the meat quality and prolong the shelf life of chicken meat.
30.3a 27.6b 0.087 0.005 0.32 0.441
29.7 28.1
C18:1n-9
0.74 0.73 0.12b 1.35a 0.91 0.000 0.69 0.047
0.18b 2.01a 0.52 0.000 0.56 0.040
trans-10, cis-12
7.30 7.26 0.040 0.92 0.89 0.202
1.17 1.11
cis-9, trans-11
3.61 3.42 0.34 0.58 0.53 0.168
25.7b 26.9a 0.003 0.012 0.082 0.206
0.60 0.67 0.68 0.31 0.93 0.031
7.72a 6.83b
C18:0
3.68 3.35
C16:1
27.0a 25.6b
C16:0
0.62 0.65
C14:0
35.9b 37.2a 0.002 0.046 0.16 0.300
37.6a 35.4b
SFA
24.1a 21.9b 0.027 0.010 0.94 0.378
22.2b 24.0a
C18:2n-6
24.8b 26.5a 25.2 26.1 0.043 0.24 0.84 0.404
34.2a 31.2b 0.027 0.001 0.19 0.399
0.29 0.25 0.79 0.21 0.56 0.013
33.7a 31.8b
2.26 2.37 0.68 0.50 0.70 0.085
0.37 0.37 0.91 0.99 0.65 0.021
0.27 0.27
PUFA
2.28 2.35
0.37 0.38
C20:1
MUFA
C21:0
C18:3n-6
1DDGS:
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0.34 0.33 0.82 0.81 0.82 0.016
0.34 0.33
C20:5
with different superscripts within each column are significantly different (P < 0.05). dried distillers grains with solubles, CLA: conjugated linoleic acid, DDGS × CLA: interaction of DDGS and CLA, SFA: saturated fatty acids, MUFA: monounsaturated fatty acids, PUFA: polyunsaturated fatty acids. Data are the mean of 6 replicates of 2 samples each.
a,bMeans
Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
Main effect mean for DDGS 0% DDGS 15% DDGS Main effect mean for CLA 0% CLA 1% CLA P-value DDGS CLA DDGS × CLA SEM
Item
Table 6. Effect of conjugated linoleic acid on fatty acid composition in the thigh meat of broilers fed dried distillers grains with solubles (DDGS)1
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RESEARCH NOTE
Conclusions The results showed that dietary supplementation with 1% CLA, 15% DDGS, or both in broilers had no significant effects on growth performance. Dietary supplementation with 15% DDGS increased the proportion of PUFA and decreased the proportions of SFA and MUFA. However, dietary supplementation with 1% CLA had positive effects on meat quality, antioxidant capacity, and fatty acid composition of broilers.
ACKNOWLEDGMENTS
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This work was supported by the National Natural Science Foundation of China (No. 31272453, No. 31072046) and the Program for Innovative Research Team of Universities in Heilongjiang Province.
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