http:// www.jstage.jst.go.jp / browse / jpsa doi:10.2141/ jpsa.0120112 Copyright Ⓒ 2013, Japan Poultry Science Association. Combination of Linseed and Palm Oils is a Better Alternative than Single Oil for Broilers Exposed to High Environmental Temperature Jianjun Wang, Qiufeng Zhu, Hussain Ahmad, Xuhui Zhang and Tian Wang College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, P.R. China This study was conducted to investigate the effects of combination of linseed oil (rich in omega 3 polyunsaturated fatty acid, ω3 PUFA) and palm oil (rich in saturated fatty acid, SFAs) on the growth performance, meat quality, and fatty acid composition of birds under high environmental temperature. Experiment was conducted in summer (average high temperature 31℃). Birds in the positive temperature control group (PTC) and negative temperature control group (NTC) were fed with maize-soybean meal-maize gluten basal diet, the other 4 experimental groups were fed with basal diets containing linseed oil (LO), palm oil (PO), or their combination at the ratio of 3:2 (linseed oil/palm oil, w/w, group LPI) or 2:3 (group LPII), respectively. Results showed that the NTC deleteriously affect the growth performance, carcass quality and fatty acid composition of chickens than PTC group. The growth performance of birds under high environmental temperature was improved by oil supplementation. Furthermore, the combination of both oils achieved a better growth performance than the single oil during 22 to 42 d. Compared with NTC group, the yields of breast, leg and carcass were significantly improved in group LPI. Fatty acid composition of meat was significantly modified by dietary oil, and PUFA, especially ω3 PUFA in meat was increased by linseed oil (P<0.05). However, the MUFA and SFA contents in meat were not positively correlated with their contents in diet. Birds fed with combined oil at the ratio of 2:3 (w/w) achieved better economic results. It was concluded that the combination of linseed and palm oils at 2:3 (w/w) in chicken diets had more positive effect on growth performance, enhanced the n-3 PUFA content in meat, and economically better than single dietary oil. Key words: broiler, fatty acid composition, high environmental temperature, linseed oil, palm oil J. Poult. Sci., 50: 332-339, 2013 Introduction Ambient temperature is an important factor in poultry production. The harmful effects of high ambient temperatures on the performance, carcass characteristics, and meat quality of broilers have been well documented (Temim et al., 2000; Lu et al., 2007; Mujahid et al., 2007; Ghazalah et al., 2008; Dai et al., 2009). When chicks were exposed to temperatures exceeding 30℃ from 4 weeks of age up to marketing, the resulting feed intake, growth rate, and feed utilization were reduced significantly (Cooper and Washburn 1998; Yalcin et al., 2001; Olanrewaju et al., 2010). Moreover, carcass yield and meat quality were deteriotated due to high temperature (Mendes et al., 1997; Lu et al., 2007). Several nutritional strategies have been proposed to alleviate the adverse effects of high ambient temperatures (Ahmad et Received: July 27, 2012, Accepted: February 11, 2013 Released Online Advance Publication: March 25, 2013 Correspondence: Prof. T. Wang, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, P.R. China. (E-mail: tianwangnjau@163.com) al., 2009; Dai et al., 2009; Mujahid 2011). At present, it has been widely accepted that dietary metabolic energy increased by adding oil or fat in the poultry diets improved the growth performance of chicks exposed to high environmental temperature (Al-Batshan 1999; Gous and Morris 2005). Researchers have been concerned over the recent years to find out new strategies in poultry nutrition that can improve the growth performance and meat quality of broiler chickens. Single poultry fat (Ghazalah et al., 2008), olive oil (Mujahid et al., 2009) , and other oils (An et al., 2001; Zulkifli et al., 2007) have been used to resist the side effects of high environmental temperature. In poultry production, addition of fat from different sources is not only important for chicken production but also very critical for human health. There is, indeed, a potential possibility of designing the profile of fatty acid in the carcass of poultry by a suitable composition of poultry diet. Palm oil is rich in saturated fatty acid (SFAs), which resist against high environmental temperature, but it also led to the meat of an undesirable composition of fatty acid. Linseed oil is rich in poly unsaturated fatty acid (PUFA), especially ω3 PUFA, Wang et al.: Dietary Oil for Heat Stress which produced the meat of more favorable balanced fatty acid (Ferrer et al., 2001). However, previous study indicated that the mechanism by which PUFA aggravating heat stress by inducing more heat increment (Brue and Latshaw 1985) or higher body temperature (Zulkifli et al., 2007) in chickens. Limited information is reported on the influence of the blended oil of linseed oil and palm oil on the performance and meat quality of chicks under high environmental temperature. The objectives of this present study were to achieve not only better growth performance but also produce chicken meat with favorable fatty acid under high environmental temperature. Therefore, the present study was conducted to investigate the effects of dietary linseed oil and palm oil, either alone or in their combination on the performance, carcass quality, and fatty acid composition in broilers under high environmental temperature. Materials and Methods Animal Treatments and Diets This work was conducted at the college of Animal Science and Technology, Nanjing Agricultural University. The birds were reared during the summer season (July and August). The ambient temperature ranged between 28℃ and 35℃. The average ambient temperature was 31℃ while the average relative humidity was 80% during the experiment. The minimum and maximum temperatures were recorded daily at morning and noon (6 AM and 12 AM). A total of 720 oneday-old commercial Arbor Acres (AA) broilers obtained from a local commercial hatchery (Hewei, Anhui, China) were randomly allocated to 6 treatment groups consisting of 6 replicates of 20 unsexed birds. All birds were placed in Table 1. wire cages in a 3-level battery and housed in an environmentally controlled room maintained at 35℃ during the first 3 days and at 32℃ during the subsequent 4 days, and then 120 birds in positive temperature control group (PTC) were still raised on thermonertral temperature with environmental control system (reduce temperature by 2℃ every week until 26℃, and then keep the temperature at 26℃). The other 600 birds were exposed to the natural environment during the whole period of experiment. The birds in the negative temperature control group (NTC) and PTC group were given the corn-soybean meal-maize gluten basal diet for the respective growth stage. The other 4 experimental groups were given experimental diets based on the basal diets, containing an additional of linseed oil (LO group), palm oil (PO group), or their combination with the ratio of 3:2 (linseed oil/palm oil, w/w) (LPI group) or 2:3 (LPII group). The inclusion levels of oil in the experimental diets were 4% (w/w) in starter diet (1 to 21 d) and 5% (w/w) in finisher diet (22 to 42 d). All the diets were formulated to meet the nutrient requirements of the broiler (Commercial recommendation). The birds were fed a starter diet until 21 d of age followed by a finisher diet from 22 to 42 d. Each diet was isocaloric and isonitrogenous (regardless the ether extracts and fatty acid composition). Ingredients and nutritional contents of diets were showed in Table 1, and the fatty acid profiles of starter and finisher diets were summarized in Table 2. The light regimen was 24 h light. Birds were allowed to consume both feed and water ad libitum. Fresh diets were prepared once a week and were stored in sealed bags at room temperature (24℃). All the procedures were approved by the Institutional Animal Care and Use Committee of the Nanjing Agri- Feed composition and nutrient contents of broiler diets Start diets Start diets Finisher diets Ingredient1 Basal diets6 Test diets6 Basal diets Maize Soybean meal MGM2 L-Lysine DL-Methionine Stone power CaHPO4 Sodium chloride Premix3 DDGS4 Oil5 62 . 13 15 . 03 17 . 84 0 . 43 0.1 1 . 36 1 . 81 0.3 1 0 0 52 . 23 37 . 14 2 0 0 . 19 1 . 26 1 . 88 0.3 1 0 4 66 . 47 10 . 74 11 . 64 0 . 45 0 . 03 1 . 69 0 . 95 0.3 1 6 . 72 0 1 333 Finisher diets Test diets Nutrients7 Basal diets Test diets Basal diets Test diets 49 . 75 18 . 99 2 0 . 26 0 . 04 1 . 89 0 . 55 0.3 1 20 . 22 5 ME CP EE CF Ca P Lys Met Arg Tyr Met+Cys 3002 22 . 39 3 . 01 3 . 81 0 . 98 0 . 43 1 . 07 0 . 54 1 . 12 0 . 54 0 . 88 3002 22 . 37 6 . 98 3 . 75 1 . 00 0 . 44 1 . 08 0 . 54 1 . 13 0 . 55 0 . 89 3017 19 . 95 3 . 05 3 . 86 0 . 97 0 . 40 0 . 93 0 . 34 0 . 95 0 . 32 0 . 72 3017 19 . 94 7 . 93 3 . 90 0 . 99 0 . 39 0 . 92 0 . 34 0 . 96 0 . 31 0 . 71 The composition of nutrients in Table 1 was base on determined, and expressed as weight percentage. MGM, Maize gluten meal. 3 Provided for kg feed: iron, 60 mg; copper, 7.5 mg; zinc, 65 mg; manganese, 110 mg; iodine, 1.1 mg; selenium, 0.4 mg; Bacitracin Zinc, 30 mg; Vitamin A, 4500 IU; Vitamin D3, 1000 IU; Vitamin E, 20 mg; Vitamin K, 1.3 mg; Vitamin B1, 2.2 mg; Vitamin B2, 10 mg; Vitamin B3, 10 mg; choline chloride, 400 mg; Vitamin B5, 50 mg; Vitamin B6, 4 mg; Biotin, 0.04 mg; Vitamin B11, 1 mg; Vitamin B12, 1.013 mg. 4 DDGS, Dried distillers grains with solubles. 5 Vitamin E was added by 0.03% in oil to prevent oxidation. 6 Basal diets for PTC and NTC groups, Test diets for LO, PO and combined oil groups. 7 ME expressed as kcal/kg, other nutrient contents expressed as weight percentage in the feed. 2 Journal of Poultry Science, 50 (4) 334 Table 2. Fatty acid profile of the starter and finisher diets with different oil types Starter diets2 Fatty acid Finisher diet2 profile1, % Cont. LO PO LPI LPII Cont. LO PO LPI LPII C12:0 C14:0 C16:0 C16:1 ω7 C18:0 C18:1 ω9 C18:2 ω6 C18:3 ω3 C20:0 C20:4 ω6 C22:5 ω3 C22:6 ω3 SFA3 MUFA3 PUFA3 P:S3 ω6:ω33 0 . 29 0 . 65 13 . 66 0 . 11 2 . 50 27 . 88 52 . 86 1 . 48 0 . 57 0 . 15 ND4 ND 17 . 67 27 . 99 54 . 34 3 . 08 35 . 72 ND 0 . 15 9 . 63 0 . 23 3 . 47 36 . 93 35 . 48 13 . 39 0 . 73 0 . 12 ND ND 13 . 98 37 . 15 48 . 87 3 . 50 2 . 65 1 . 16 0 . 96 28 . 10 0 . 13 4 . 25 33 . 84 28 . 65 2 . 21 0 . 70 0 . 14 ND ND 35 . 16 33 . 97 30 . 86 0 . 88 12 . 99 0 . 54 0 . 48 17 . 99 0 . 19 3 . 66 36 . 29 31 . 37 8 . 79 0 . 69 0 . 13 ND ND 23 . 36 36 . 48 40 . 16 1 . 72 3 . 57 0 . 80 0 . 67 21 . 42 0 . 12 4 . 05 35 . 24 30 . 67 6 . 64 0 . 39 0 . 12 ND ND 27 . 32 35 . 37 37 . 31 1 . 37 4 . 62 0 . 16 0 . 18 14 . 79 0 . 15 2 . 37 30 . 06 49 . 12 2 . 39 0 . 57 0 . 16 ND ND 18 . 07 30 . 21 51 . 72 2 . 86 20 . 61 0 . 04 1 . 03 10 . 63 0 . 34 1 . 23 37 . 24 34 . 36 14 . 45 0 . 53 0 . 14 ND ND 13 . 47 37 . 58 48 . 96 3 . 63 2 . 39 1 . 02 0 . 86 27 . 88 0 . 34 1 . 30 38 . 06 27 . 87 2 . 05 0 . 50 0 . 11 ND ND 31 . 56 38 . 40 30 . 03 0 . 95 13 . 64 0 . 46 0 . 97 19 . 28 0 . 36 1 . 30 36 . 46 30 . 90 9 . 61 0 . 53 0 . 13 ND ND 22 . 54 36 . 81 40 . 64 1 . 80 3 . 23 0 . 60 0 . 96 20 . 60 0 . 36 1 . 34 38 . 40 29 . 69 7 . 42 0 . 50 0 . 12 ND ND 24 . 00 38 . 76 37 . 24 1 . 55 4 . 02 1 All values are means as weight percentages of total fatty acid methyl esters. Cont., without additional oil for PTC and NTC groups; LO, added with linseed oil; PO, added with palm oil; BOI, linseed oil/palm oil (w/w) at the ratio 3/2; BOII, linseed oil/palm oil (w/w) at the ratio 2/3. 3 SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; P:S, PUFA: SFA; ω6: ω3, ω6 PUFA /ω3 PUFA. 4 ND, Not detectable. 2 cultural University, China. Sample Collection and Procedures Body weights (BW) were recorded for each replicate at 1, 21 and 42 days of age. Feed intake was measured over these feeding periods. At 42 d, 2 birds per replicate were randomly selected and weighed, then killed by exsanguinations and necropsies immediately. After decapitation, the carcasses were opened, separated, and weighed. Samples of muscle were then rapidly excised and stored at −20℃ until for further analysis. Carcass Quality Assay After the birds were manually eviscerated, the eviscerated carcass, abdominal fat, breast meat (including pectoralis major and pectoralis minor), and leg meat (including thigh and drumstick) were measured. The weight percentages of eviscerated carcass, breast meat, leg meat, and abdominal fat were calculated as a percentage of live BW after fasting at the end of finisher period. Fatty Acid Profiles Total lipid was extracted from 3 g feed or homogenized breast muscle (left side) with chloroform -methanol (2:1, v/v) according to method of Folch (1957). Extracted lipids were transmethylated with boron trifluoride and methanolic KOH (Morrison and Smith 1964). The methylic esters of fatty acid were analyzed by gas chromatography (Shimadzu GC-14B) over a CP-Sil88-fames column (50 m×0.25 mm×0.2 um; Varian, Palo Alto, CA, USA) with a Hewlett-Packard. Hydrogen was used as carrier gas at a constant flow rate of 1/50. The oven temperature was programmed as follows: 160℃, held for 4 min; from 160℃ to 220℃ at a rate of 3℃/min. The injector port and detector temperature were 280℃. Samples were injected with an auto-sampler. Output signals were identified and quantified from the retention times and peak areas of known calibration standards. Economic Evaluation Feed cost and total costs per replicate were calculated. Feed cost was calculated as average feed expenditure (USA dollar, USD) divided by average body weight gain (kg) for each bird during the period of 1-21 d, 22-42 d and 1-42 d. Total costs were calculated as the total expenditure (USD) of individual bird divided by average body weight gain (kg) at the end of experiment. The total expenditure of individual bird included the money used for purchasing feed, medicine, day old chicken, labor, and the depreciation of fixed asset during the experiment. Data Analysis Data for performance and fatty acid composition in breast were analyzed by One-Way ANOVA (SPSS, 16.0). The percentages of carcass, breast, leg, and abdominal fat were transformed by the arcsine square root before analysis. Data of carcass traits were determined by General Linear Model (GLM, SPSS 16.0), and the treatments and sex were set as fixed factors. Differences between treatments means were tested by Tukey’s Multiple Range Test. Significance was evaluated at the level of P≤0.05. Results Growth Performance As shown in Table 3, there was no significant difference of initial body weight (BW) at 1 d age between treatments, and Wang et al.: Dietary Oil for Heat Stress Table 3. perature 335 Effect of dietary oil types on growth performance of broilers exposed to high environmental tem- Items BW2, g/bird/period 1d 21 d 42 d FI2, g/bird/period 1 to 21 d 22 to 42 d 1 to 42 d FCR2, g:g 1 to 21 d 22 to 42 d 1 to 42 d Treatments1 PTC NTC LO PO LPI LPII SEM P 40 . 0 504 . 1c 1748 . 0d 40 . 3 400 . 5a 1234 . 9a 40 . 7 439 . 0ab 1424 . 6b 40 . 4 474 . 0bc 1553 . 4c 39 . 9 473 . 3bc 1685 . 7d 40 . 1 483 . 4bc 1710 . 9d 0 . 57 17 . 33 41 . 14 0 . 763 0 . 001 0 . 001 757 . 4c 2394 . 4d 3175 . 2d 603 . 4a 1716 . 8a 2319 . 8a 641 . 9ab 1975 . 1b 2617 . 3b 683 . 9abc 2123 . 8bc 2807 . 7bc 671 . 6ab 2256 . 8cd 2928 . 8c 688 . 4bc 2273 . 3cd 2966 . 1cd 27 . 39 55 . 17 72 . 91 0 . 001 0 . 001 0 . 001 1 . 55a 1 . 85a 1 . 77a 0 . 03 0 . 02 0 . 02 0 . 001 0 . 001 0 . 001 1 . 63ab 1 . 92bc 1 . 86b 1 . 68b 2 . 06e 1 . 94c 1 . 61ab 2 . 00de 1 . 89bc 1 . 58a 1 . 97cd 1 . 86b 1 . 55a 1 . 86ab 1 . 78a a-d Means within the same row that do not share a common superscript are significantly different (P<0.05). n=6. PTC, under thermonertral environmental temperature, NTC, LO, PO, TC, LPI and LPII, exposed to high environmental temperature. PTC and NTC, without additional oil; LO, linseed oil; PO, palm oil; LPI, linseed oil and palm oil at the ratio 3/2 (w/w); LPII, linseed oil and palm oil at the ratio 2/3 (w/w). 2 BW, body weight; FI, feed intake; FCR, feed conversion ratio. 1 the mean BW at 1 day was 40.2 g. Feed intake (FI), BW and feed conversion ratio (FCR) were significantly (P<0.05) affected by treatments. FI, BW in every period and FCR in 1-41 d and 22-42 d were significantly lowered in NTC than PTC group. Compared with NTC group, dietary oil alleviated the side effect of high environmental temperature on birds’ performance. FI in high environmental temperature was significantly increased in group LPII during 1 to 21d and in all the 4 oil added groups during 22 to 42 d and 1 to 42 d than NTC group. Among the oil added groups, there was a significant increase of FI in LPII in 1-21 d and in LPI and LPII groups in 1-42 d and 22-42 d than LO group. Compared with NTC group, BW was significantly increased in PO, LPI and LPII groups in 1-21 d and in all oil added groups in 22-42 d and 1-42 d. Among the oil added groups, BW was significantly increased by adding oil in combination than single oil during 22-42 d and 1-42 d. FCR was significantly improved in PO, LPI and LPII groups in every period than NTC group. Among the oil added groups, combined oil significantly improved FCR than single oil during 22-42 d and 1-42 d. Compared the effect of 2 combined oil groups on growth performance, no significantly difference was observed in chickens. Carcass Quality Carcass traits of chicken were summarized in Table 4. Live BW and the percentages of carcass, leg and breast were significantly affected by treatments. The effect of different oils alone or in combination on carcass traits was significantly varied with sex of chicks, male broiler chickens tended to achieve better carcass traits than female chickens. Our data showed that the percentages of breast, leg, abdominal fat, and carcass were decreased in NTC group than PTC group. Dietary oils improved carcass traits of birds under high temperature, and some carcass traits were significantly increased by dietary oil, e.g. BW in PO and LPI groups, carcass percentage in LPI and LPII groups, breast percentage in all oil added groups, leg percentage in group LPI. While the effect of different oils alone or in combination in chickens varied in both sex significantly affected BW and the percentage of carcass, and male birds showed a high BW and carcass percentage. The interaction between sex and treatments did not significantly affect carcass traits. Among the oil added groups, combined oil exerted a significant increase of BW in LPI, carcass percentage in the two combined oil groups, leg percentage in LPI group than LO group. Dietary oil did not significantly affect abdominal fat percentage, but linseed oil added groups had a tendency to decrease abdominal fat deposit than PO group. Fatty Acid Profiles of Meat Data of breast fatty acid composition were summarized in Table 5. Except of C12:0, C14:0 and C20:0, all other fatty acid contents were significantly affected by treatments. Compared the fatty acid composition between NTC and PTC groups, which showed that high environmental temperature significantly increase the contents of C18:0, C18:1, while decreased the contents of C18:2, C20:4; in other words NTC group resulted with significant increase of SFA and MUFA contents, and an decrease of PUFA contents than PTC group. Compared with NTC and PO group, groups (LO, LPI, and LPII) supplemented with linseed oil significantly decreased the contents of SFA and MUFA, and the ratio of ω6:ω3, while increased PUFA contents, and the ratio of P:S. However, the contents of MUFA and SFA in the breast were not positively correlated to their content in diet. The desired ω3 PUFA (C18:3 ω3) in breast was increased according the increasing supplementation of linseed oil. In brief, the quality of fatty acid composition was according this order: LO>LPI> LPII >PO>PTC>NTC. Journal of Poultry Science, 50 (4) 336 Effect of dietary oil types on carcass traits of broilers exposed to high environmental temperature Table 4. Treatments1 BW2, g Carcass3, % Breast3, % Leg3, % AF2, % PTC NTC LO PO LPI LPII SEM P (Treatments) Male Female SEM P (Sex) P (Sex*Treatments) 1678ab 1435a 1600ab 1768b 1789b 1701ab 107 0 . 033 1731 1593 62 0 . 036 NS4 87 . 40ab 84 . 14a 86 . 39ab 88 . 54ab 89 . 31b 89 . 06b 1 . 45 0 . 013 88 . 81 86 . 13 0 . 84 0 . 004 NS4 16 . 79c 12 . 46a 14 . 53b 15 . 61bc 15 . 04b 15 . 64bc 0 . 55 0 . 001 15 . 32 14 . 7 0 . 32 NS4 NS4 16 . 26c 13 . 48a 14 . 05ab 14 . 37ab 15 . 48bc 14 . 53ab 0 . 53 0 . 001 15 . 09 14 . 3 0 . 31 NS4 NS4 2 . 80b 2 . 12a 2 . 21a 2 . 33a 2 . 26a 2 . 26a 0 . 07 0 . 001 2 . 34 2 . 32 0 . 04 NS4 NS4 a-c Means within the same line that do not share a common superscript are significantly different (P<0.05). n=6. 1 PTC, under thermonertral environmental temperature; NTC, LO, PO, TC, LPI and LPII, exposed to high environmental temperature. PTC and NTC, without additional oil; LO, linseed oil; PO, palm oil; LPI, linseed oil and palm oil at the ratio 3/2 (w/w); LPII, linseed oil and palm oil at the ratio 2/3 (w/w). 2 BW, live body weight; AF, abdominal fat. 3 Calculated as a percentage of live BW. 4 NS, not significant. Effect of dietary oil types on fatty acid profiles of chicken breast under high environmental temperature Table 5. Treatments1 Fatty acid profile2, % PTC NTC LO PO LPI LPII C12:0 C14:0 C16:0 C16:1 ω7 C18:0 C18:1 ω9 C18:2 ω6 C18:3 ω3 C20:0 C20:4 ω6 C22:5 ω3 C22:6 ω3 SFA3 MUFA3 PUFA3 P:S3 ω6:ω33 0 . 04 0 . 47 24 . 53d 4 . 32d 7 . 54b 39 . 07c 20 . 90b 0 . 85a 0.1 2 . 01b ND4 ND4 32 . 69d 43 . 39c 23 . 82b 0 . 73b 27 . 07d 0 . 04 0 . 47 24 . 70d 4 . 12d 7 . 94c 40 . 40d 19 . 68a 0 . 83a 0 . 09 1 . 73a ND4 ND4 33 . 24e 44 . 52d 22 . 24a 0 . 70a 25 . 80d 0 . 03 0 . 46 19 . 27a 2 . 81a 7 . 87c 37 . 69b 23 . 39d 6 . 68d 0 . 09 1 . 71a ND4 ND4 27 . 72a 40 . 50b 31 . 78d 1 . 15e 3 . 76a 0 . 04 0 . 46 25 . 52e 3 . 72c 7 . 32a 40 . 07d 19 . 21a 0 . 98a 0.1 2 . 55c ND4 ND4 33 . 44e 43 . 80c 22 . 75a 0 . 68a 22 . 14c 0 . 04 0 . 48 21 . 54b 3 . 03b 7 . 58b 37 . 84b 22 . 55c 4 . 78c 0 . 11 2 . 07b ND4 ND4 29 . 75b 40 . 86b 29 . 40c 0 . 99d 5 . 16b 0 . 04 0 . 47 23 . 65c 2 . 82ab 7 . 62b 36 . 10a 22 . 85cd 3 . 92b 0.1 2 . 38c ND4 ND4 31 . 88c 38 . 92a 29 . 15c 0 . 91c 6 . 44b a-e SEM P 0 . 00 0 . 01 0 . 15 0 . 07 0 . 07 0 . 23 0 . 20 0 . 07 0 . 01 0 . 01 NS5 NS5 0 . 12 0 . 21 0 . 25 0 . 01 0 . 46 NS NS 0 . 001 0 . 001 0 . 001 0 . 001 0 . 001 0 . 001 NS 0 . 001 NS5 NS5 0 . 001 0 . 001 0 . 001 0 . 001 0 . 001 Means within the same row that do not share a common superscript are significantly different (P<0.05). n=6. 1 PTC, under thermonertral environmental temperature, NTC, LO, PO, TC, LPI and LPII, exposed to high environmental temperature. PTC and NTC, without additional oil; LO, linseed oil; PO, palm oil; LPI, linseed oil and palm oil at the ratio 3/2 (w/w); LPII, linseed oil and palm oil at the ratio 2/3 (w/w). 2 All values are means as weight percentages of total fatty acid methyl esters. 3 SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; P: S, PUFA: SFA; ω6:ω3, ω6 PUFA /ω3 PUFA. 4 ND, not detectable. 5 NS, not significant. Wang et al.: Dietary Oil for Heat Stress Table 6. perature Effect of dietary fat types on cost of broilers exposed to high environmental tem- Cost, USD/kg BW Feed cost 1 to 21 22 to 42 1 to 42 Total cost2 337 d d d (1 to 42d) Treatments1 PTC NTC LO PO LPI LPII 0 . 82a 0 . 88a 0 . 87a 1 . 26a 0 . 84a 0 . 94b 0 . 91b 1 . 48c 1 . 00d 1 . 16d 1 . 12e 1 . 61d 0 . 86ab 0 . 95b 0 . 93bc 1 . 38b 0 . 91c 1 . 00c 0 . 98d 1 . 39b 0 . 89bc 0 . 97bc 0 . 95c 1 . 36b SEM P 0 . 02 0 . 01 0 . 01 0 . 02 0 . 001 0 . 001 0 . 001 0 . 001 a-e Means within the same row that do not share a common superscript are significantly different (P<0.05). n=6. PTC, under thermonertral environmental temperature, NTC, LO, PO, TC, LPI and LPII, exposed to high environmental temperature. PTC and NTC, without additional oil; LO, linseed oil; PO, palm oil; LPI, linseed oil and palm oil at the ratio 3/2 (w/w); LPII, linseed oil and palm oil at the ratio 2/3 (w/w). 2 Total cost, including the costs of feed, medicine, baby chicken, labor, and depreciation of fixed asset. 1 Economic Evaluation Feed cost and total cost of per kg body weight gain was shown in Table 6. Heat stress significantly (P<0.05) increased the feed cost and total cost. However, the oil supplementation did not decrease the feed cost in high temperature than NTC group, while we took the total cost into consideration, the situation was different, then palm oil and combined oil significantly decreased the total cost than NTC group, and the combined oil (LO/PO, 2/3) achieved the best economic results. Discussion Previous studies reported that high environmental temperature suppressed birds performance (Temim et al., 2000; Lu et al., 2007; Ghazalah et al., 2008; Dai et al., 2009). The results of our present study were similar with the previous studies that high environmental temperature reduced the growth performance of broiler chickens. Fat and oil have been widely used in poultry diets to increase dietary energy concentration and promote performance of birds exposed to high environmental temperature (Dale and Fuller 1980; Mujahid et al., 2009). Several experiments indicated that single fat or oil, such as poultry fat (Ghazalah et al., 2008), olive oil (Mujahid et al., 2009), coconut oil and canola oil (Ben-Hamo et al., 2011) improved the performance of broiler chicks under high environmental temperature. The results of our present study are in agreement with the results of previous studies that diets supplemented with linseed oil, palm oil and blended oil improved growth performance of broiler chicks exposed to high environmental temperature. This might be the result of lower heat increment induced by dietary oil, and then alleviated the side effect of high environmental temperature. Chen and Chiang (2005) and Buckingham (1985) reported that dietary P/S (polyunsaturated/ saturated) ratio did not affect heat increment in birds and rats under high environmental temperature, while Ben-Hamo et al. (2011) suggested that fatty acid composition in muscle and liver was associated with thermoregulation. In the current experiment, the effect of linseed oil on performance was not as good as those with palm oil or combined oil, which maybe a result of heat increment induced by the high content PUFA in the linseed oil. Qi et al. (2010) reported that substituted ω3 for ω6 C18 fatty acid in the diets of chickens tended to improve feed conversion and survival, though there was no effects on growth performance. In the current experiment, the combined oils obtained better performance than single oil, and the possible reason is that both palm and linseed oils have their disadvantages. Dietary oil including linseed oil could alleviate the side effects of heat stress on birds but the influence was not as good as other oils that are rich in SFA. The possible reason of this low efficiency of linseed oil is its high heat increment as compared to other oils that are enriched in SFA (Ben-Hamo et al., 2011), while palm oil is insufficient in essential fatty acid (Ramos et al., 2009). The combined oil reduced their disadvantages and obtained better performance. The better performance was achieved by combined oil in 22-42 d, but not in 1-21 d. The difference of performance between starter and finisher periods may be due to the difference in deleterious effect of high environmental temperature in different growth period. In the starter period, the birds need higher temperature than finisher period, and the environmental temperature keep similar in the two periods, so the side effect of high temperature in starter period was not serious as finisher period, and then the improvement of performance with combined oil was not as good as finisher period. The bird’s physical function was not well developed in the starter period, so the combined oil did not show better performance in starter period. Briefly, dietary oil alleviated the side effect of high environmental temperature on performance. However, combined oil showed better performance than single oil, while palm oil showed better performance than linseed oil. As a consequence of chronic heat exposure generally involved a reduction of meat quality, such as more abdominal fat deposited, less carcass yield obtained (Baziz et al., 1996; Geraert et al., 1996; Mendes et al., 1997; Lu et al., 2007). Same results showed in the current experiment. Carcass traits in NTC were deteriorated than PTC group, except abdominal fat was decreased by NTC than PTC. Because of the less heat increment induced by dietary oil, then it could 338 Journal of Poultry Science, 50 (4) improve birds’ carcass quality under high environmental temperature, which also showed in the current experiment. Dietary oil resource played an important role in regulating fat deposition due to the composition of fatty acid. For example, SFAs are easier to be deposited in the body, and PUFAs are easier to be oxidized for energy (Baião and Lara 2005). The current experiment showed that abdominal fat of birds under high environmental temperature was not significantly affected by dietary oil sources. However, the oil supplementation increased abdominal deposit than NTC group, similar results showed in Esmail’s (1987) report, he found that there was a tendency for dietary energy derived from fat to be deposited more fat in the body. Among the oil added groups, linseed oil tended to decrease abdominal fat deposit more than palm oil did, which was in accordance with previous report (Ferrini et al., 2008) indicating that it is because of the higher PUFA in linseed oil than palm oil. Qi et al. (2010) added linseed oil to the diets of broiler chickens, and found no effects on most slaughter traits, which also showed in the current experiment. In the current experiment, NTC produced lower P:S meat than PTC group, which means that birds under high temperature environmental tended to deposit more SFA and MUFA rather than PUFA. In other words, high environmental temperature aggravated the unbalance of fatty composition in breast. Similar results were reported by Sonaiya (1988), birds reared in high temperature (30℃) had a significantly lower proportion of P:S in their abdominal fat between 34 and 54 d than birds in low temperature (17℃). Previous studies reported that the fatty acid composition of meat was a mirror of dietary fatty acid composition in monogastric animal (Kouba and Mourot 2011). Ferrer et al. (2001) and Qi et al. (2010) increased the dietary ω3 PUFA content due to dietary supplementation of fish oil or linseed oil, which increased the deposition of desirable ω3 PUFA in the edible tissue, thereby, achieving nutritionally enriched meat. Similar result was achieved in the present experiment, ω3 PUFA enriched chicken meat was produced in broiler chickens supplemented with linseed oil, and the ω3 PUFA content was positively related to its content in diet. The contents of PUFA, especially ω3 PUFA were increased by linseed oil. However, SFA and MUFA contents in breast were not related to their contents in diet. The variations of MUFA and SFA contents in breast were affected by the exact quantity of PUFA rather than by ratio of PUFA in total fatty acid. The results suggested that the contents of PUFA in diet regulate all the fatty acid deposit in muscle. The possible reason is that PUFA is more active in biologic functions than MUFA and SFA, since more unsaturated bonds exist in PUFA. Our data showed that combined oil was better for the performance, carcass quality and fatty acid profile of birds under high temperature environment. However, economic factor must be taken into consideration in practical use of combined oil. Indeed linseed oil is more expensive than palm oil. When single linseed oil was used, we couldn’t achieve good profit even if better fatty acid profile was obtained. However, taking the total cost of per kg weight gain into consideration, the combined oil (linseed oil/palm oil, 2/3, w/w) obtained better profit than linseed and palm oil, because the combined oil (linseed oil/palm oil, 2/3, w/w) obtained more body weight than single oil. And then, the fixed costs (costs of medicine, baby chicken, labor, and depreciation of on fixed asset) of per kg body weight were decreased in combined oil added group. In addition, n-3 PUFA enhanced chicken meat was produced with combined oil instead of palm oil, and the meat rich in n-3 PUFA could sell at a better price (Mapiye et al., 2012), so the combined oil at the ratio of 2 to 3 would obtain better profit than linseed or palm oil. In conclusion, the present study showed that, performance of birds was deteriorated under high environmental temperature, which could be improved by dietary oil, and the combined oil was better than single oil. Linseed oil, either in its single form or in combination with palm oil, improved carcass quality and fatty acid composition, while the effect of linseed oil on performance of birds under high environmental temperature was not as good as palm oil and combined oil. 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