INTRODUCTION
Chicken meat has lower cholesterol and saturated fatty acid content than other meats, but there have been many attempts to produce beneficial fatty acids for human body and produce chicken with less cholesterol and saturated fatty acids. In particular, as the effect of omega-3-unsaturated fatty acids on lowering blood lipid concentration and reducing the incidence of circulatory diseases have been reported [1,2], many researchers have been a great interest in the production of livestock containing omega-3-polysaturated fatty acids. Although attempts to lower cholesterol levels in eggs and meat have not been successful [3], however, many studies reported that the fatty acids composition in these poultry products is influenced by the dietary feed such as fish oil and fish meal [4,5], sesame oil and sesame meal [6,7]. For this reason, we consider feedstuff rich in omega-3-unsaturated fatty acids.
Perilla seed meal (PSM) is known to be enriched in compositions of omega-3 polysaturated fatty acids and bioactive compounds such as phytic acid, polysaccharides, phenolic compounds, and protein as a by-product made after extracting oil from perilla seeds [8]. The rich nutrient content and the use of by-product have received much attention recently to increase profitability [9,10]. In our analysis, PSM has been shown to be a potential protein (39.01%) source of feed. The use of PSM as feedstuff can be an alternative to soybean meal whose cost has increased in recent years [11]. However, studies on the use of PSM as a feedstuff in livestock are insufficient. Therefore, the aim of this experiment was to evaluate effects of replacing soybean meal with perilla seed meal on growth performance, and meat quality in ROSS 308 broilers.
MATERIALS AND METHODS
Experimental protocols describing the management and care of animals were reviewed and approved by the Animal Care and Use Committee of Chungbuk National University.
A total of 60 healthy mixed sex 1-day-old ROSS 308 broilers with an initial body weight (BW) of 44.8 ± 0.4 g were used in a 5-week experiment. Broilers were randomly blocked based on their initial BWs to four treatment groups. Each treatment group had fifteen replicate cages (1 broilers per cage). Water and feed were available ad libitum. The experiment was divided into two periods: a starter period (0 to 2 weeks of age) and a finishing period (2 to 5 weeks of age). Table 1 shows nutrient compositions of the perilla seed meal used in this study. Dietary treatments included a control (CON) corn-soybean meal based diets (basal diet) and three test diets in which perilla seed meal (Table 1) was included at 0.5% (T1), 1% (T2), and 2% (T3) to gradually replace soybean meal (Tables 2 and 3). To meet amino acid requirements, diets in the finishing period were supplemented with L-lysine and corn gluten meal. All diets were formulated to meet or exceed National Research council (NRC) [12] nutrient requirements for poultry.
Provided per kg of complete diet: 12,000 IU of vitamin A; 2,500 IU of vitamin D3; 25 mg of vitamin E; 0.7 mg of vitamin K3; 1 mg of tdiamin, 12 mg of riboflavin; 2 mg of pyridoxine; 0.03 mg of vitamin B12; 35 mg of niacin; 10 mg of Ca-pantotdenate; 0.5 mg of folic acid and 0.085 mg of biotin; 1,700 mg of etdoxyquin.
Provided per kg of complete diet: 12,000 IU of vitamin A; 2,500 IU of vitamin D3; 25 mg of vitamin E; 0.7 mg of vitamin K3; 1 mg of tdiamin, 12 mg of riboflavin; 2 mg of pyridoxine; 0.03 mg of vitamin B12; 35 mg of niacin; 10 mg of Ca-pantotdenate; 0.5 mg of folic acid and 0.085 mg of biotin; 1,700 mg of etdoxyquin.
Individual broilers’ BWs were recorded at the end of weeks 0, 2, and 5, and feed intake were recorded every day to determine weight gain (WG), feed intake (FI), and feed conversion ratio (FCR). All broilers of each treatment were selected at the end of the 5th week to collect breast and leg meat. Aponeuroses and skin were removed from breast and leg samples. They were then homogenized and submitted for proximate analysis. Moisture, fat, and ash contents were analyzed in triplicate. All analyses were carried out according to AOAC method [13]. Water holding capacity (WHC) was determined following the method of Laakkonenen et al. [14]. The pH values of breast meat were determined by using glass-eletrode pH meter (WTH Measurement System, Ft. Myers, Florida, FL, USA). Drip loss, cooking loss, and shear force after cooking were measured according to the guide of Sirri et al. [15]. The breast meat color value was analyzed by using a reflectance spectrometry chroma meter (Yasuda Seiko, Minolta, Japan) to measure lightness (L*), redness (a*) and yellowness (b*).
Lipids were analyzed from thigh meat according to the method of Folch et al. [16]. Thigh meat (30 g) was blended with 150 mL of solution (chloroform : methanol = 2 : 1) and added 0.88% KOH. The solution was kept at room temperature for 2 hours and the upper phase was extracted. Then chloroform was evaporated using 99.9% N2 gas and cooling. 1 mL of BF3-Methanol (Sigma Chemical, St. Louis, MO, USA) was added to the sample and heated at 70 °C for 30 min. After samples were cooled, 2 mL of Hexan (HPLC grade) and 5 mL of distilled water were added to the solution. The upper phase is rolled out after vortexing the samples. Fatty acid methyl ester dissolved in hexane was transferred to a GC vial and the fatty acids were analyzed using a capillary column (30 mm × 0.32 mm × 0.25 μm film thickness, Omegawax 320, Supelco, Bellefonte, PA, USA) of GC (Shimadzu Gas Chromatography 17-A, Tokyo, Japan).
The oven temperature was set to 200 °C and helium was divided by a 100:1 split ratio to serce as a carrier gas at linear flow of 0.79 mL/min. Fatty acids were determined by comparison with standard retention times and the relative amounts were identicated in weight percent of total fatty acids.
All data were subjected to statistical analysis as a randomized complete block design using GLM procedures of SAS version 9.4 (SAS Inst., Cary, NC, USA). Differences in means among treatment groups were determined using Duncan’s multiple range test with a p < 0.05 indicating statistical significance.
RESULTS
At 2 and 5 weeks, broilers fed with T2 or T3 had significantly (p < 0.05) higher BW than broilers fed with CON or T1 (Table 4). From 0 to 2 weeks, WG of broilers fed with T2 or T3 diet was increased (p < 0.05) compared to that of broilers fed with CON or T1 diet. Moreover, broilers in T2 treatment group had significantly (p < 0.05) higher WG than those fed with T3. FCR was significantly (p < 0.05) decreased for broilers fed with T2 or T3 diet. There was no significant difference in FI among groups. From 2 to 5 weeks, WG of broilers fed with T2 or T3 diet was increased. Regarding FI, broilers fed with T1 or T3 had significantly higher FI than those fed with T2 or CON. FCR was significantly increased for broilers fed with T1 or T2 diet.
In the overall period, broilers fed with T2 or T3 diet had significantly (p < 0.05) higher WG than broilers fed with CON or T1 diet. FI was increased (p < 0.05) for broilers fed with T3 diet while broilers fed with T2 diet had lower (p < 0.05) FI than those in other treatment groups. FCR was significantly decreased in broilers fed with T2 diet.
There was no significant (p > 0.05) difference in moisture or ash composition of breast meat from broilers (Table 5). However, broilers fed with T2 or T3 diet had higher (p < 0.05) fat composition in breast meat than broilers fed with CON or T1 diet.
| Item (%) | CON | T1 | T2 | T3 | SE | p-value |
|---|---|---|---|---|---|---|
| Moisture | 75.9 | 75.9 | 74.9 | 75.5 | 1.1 | 0.613 |
| Fat | 1.53b | 1.55b | 1.75a | 1.74a | 0.05 | 0.025 |
| Ash | 1.99 | 2.11 | 2.14 | 1.88 | 0.19 | 0.349 |
WHC was significantly (p < 0.05) increased in broilers fed with T2 or T3 diet (Table 6). However, there was no significant difference in other characteristics among groups.
Regarding fatty acids composition of thigh meat from broilers, linolenic acid content was increased (p < 0.05) in broilers fed with T3 diet (Table 7).
DISCUSSION
In the present study, PSM showed potential as an alternative feedstuff for soybean meal. Moreover, it improved growth performance of broilers. In particular, FCR and WG were significantly increased when 1%–2% soybean meal was replaced by PSM. Perilla is a rich source of polyunsaturated fatty acids such as omega-6-fatty acids and omega-9-fatty acids (ω-9). It can be the best feedstuff for additional omega-3 polyunsaturated fatty acids [17]. Omega-3-fatty acids (ω-3) are a series of fatty acids, including eicosapentaenoic acid (EPA), α-linolenic acid, and docosahexaenoic acid (DHA) [18]. Shin et al. [19] have found that supplementation ω-3 and ω-9 fatty acid blends does not affect the accumulation of liver fat or the ratio of live weight to broiler liver weight. However, unlike results of our study, Oh et al. [20] have reported that supplementation of 10% PSM to 45-d Korean native chickens does not affect the growth performance in a 21-day experiment period. In addition, many studies have found that ω-3 and ω-9-enriched feedstuffs (full-fat flaxseed meal, canola seed meal, fish oil, etc.) do not affect the growth performance of broilers [19–23], although some studies have shown that sesame meal can replace soybean meal to improve the growth performance of broilers [24,25]. More research is needed to determine whether a seed meal is suitable for broiler diets. Based on results of this study, we can see a lot of potential of replacing soybean meal with PSM.
Regarding proximate composition of breast meat from broiler, many researchers have reported that increase of fat content in broilers is associated with the composition of dietary fatty acids. Hadi [26] have reported that 5% PSM supplementation in duck diet can improve the fat content of meat. Similarly, the supplementation of ω-3 and ω-9 in diet can improve the fat composition of breast meat in broiler [4,21,23,27,28].
In present study, the pH of the breast meat from broiler fed with PSM as a replacement was not significantly affected by such replacement. However, water holding capacity was significantly increased after soybean meal was replaced with PSM at 1% or 2%. Huff-Lonergan and Lonergan [29] and Jung et al. [30] have reported that WHC could be inactivated by oxidation not only by pH, but also by post-protein degradation initiated by the activation of μ-capain. In the current study, the antioxidative effect was not tested, although the substitution of PSM could improve breast meat quality of broilers.
Based on results of fatty acids composition of meat analysis in this study, the content of linolenic acid was increased after soybean meal was replaced with PSM at 1% or 2%. Such results are similar to previous studies showing that higher percentage of ω-3 can improve meat quality [23,31]. Hulan et al. [4] have reported that ω-3 in broiler meat can be improved by increasing levels of ω-3 in broiler diets. Feeding fat or vegetable seeds containing α-LNA can increase the absorption of linolenic acids, EPA, and DHA in poultry and chick tissues [32,33]. Oh et al. [20] have reported that the ratio of α-LNA in broiler’s breast meat is increased more than three times in 10% PSM supplementation treatment compared to basal diet. Thus, PSM could be used as a feedstuff for the production of polyunsaturated fatty acid-enriched poultry meat.
