Olive pomace oil and acid oil as alternative fat sources in growing-finishing broiler chicken diets a-Oriol ,*,1 A. Tres ,y M. Verd G. Verge-Merida ,* D. Sol u,z G. Farre,z C. Garces-Narro ,x and A. C. Barroeta * * Animal Nutrition and Welfare Service, Department of Animal and Food Sciences, Universitat Aut onoma de Barcelona, 08193 Bellaterra, Spain; yNutrition, Food Science and Gastronomy Department INSA-XIA, Universitat de Barcelona, 08921 Santa Coloma de Gramenet, Spain; zDepartment of Animal Nutrition and Feed Industry,  bonArea Agrupa, 25210 Guissona, Spain; and xDepartment of Animal Production and Health, Universidad CEU Cardenal Herrera, CEU Universities, 46115 Alfara de Patriarca, Valencia, Spain ABSTRACT The aim of the present study was to showed higher values than PO for all FA in both appar- investigate the effect of dietary supplementation of olive ent ileal digestibility (AID) and apparent total tract pomace oil and olive pomace acid oil, which are rich in digestibility. Comparing the AID between O and OA, no monounsaturated fatty acids (FA) but differ in free FA differences were observed for total FA, monounsaturated content, on growth performance, digestibility and FA FA, or polyunsaturated FA, but animals fed OA showed profile of abdominal fat and breast meat. A total of 3,048 lower AID values for saturated FA than those fed O (P < one-day-old mixed-sex broiler chickens (Ross 308) were 0.001). The FA profile of abdominal fat and breast meat randomly distributed into 24 pens and 3 dietary treat- reflected that of the diet, with higher monounsaturated ments (8 replicates per treatment). Experimental diets FA and lower saturated FA in animals fed O and OA were administered for growing (from 22 to 29 d) and fin- compared to those fed PO. In sum, the inclusion of both ishing (from 30 to 39 d) periods, consisting of a basal olive pomace oil and acid oil in growing-finishing broiler diet supplemented with 6% (as-fed basis) palm oil (PO), chicken diets led to great performance parameters and olive pomace oil (O), or olive pomace acid oil (OA). Ani- high FA digestibility values, together with an enrich- mals fed O achieved the lowest feed conversion ratio ment with monounsaturated FA in abdominal fat and (P < 0.01), together with the highest AME value breast meat compared to the use of palm oil. However, a (P = 0.003), but no differences were observed between better AID of saturated FA and feed conversion ratio is OA and PO. Regarding FA digestibility, O and OA achieved with O compared to OA. Key words: olive pomace oil, acid oil, digestibility, fatty acid, by-product 2022 Poultry Science 101:102079 https://doi.org/10.1016/j.psj.2022.102079 INTRODUCTION unsaturated FA (UFA) are known to be better absorbed than saturated FA (SFA; Ravindran et al., Fats and oils are widely included in broiler chicken 2016). Moreover, the inclusion of olive-derived oils in diets due to their high energy content and supply of broiler chicken diets could enrich the FA profile in meat essential fatty acids (FA). However, the need for more and deposition fat with UFA (Skrivan et al., 2018). efficient and sustainable animal production necessitates In terms of molecular structure, olive pomace oil is a continuous search for alternative fat sources to achieve mainly composed of triacylglycerols, while olive pomace these goals. In this regard, olive pomace oil and olive acid oil, a by-product generated from the chemical refin- pomace acid oil could be 2 potential alternative fat sour- ing of olive pomace oil, accumulates a high content of ces for use in broiler chicken diets. Both are rich in free FA (FFA, 40−60%; Varona et al., 2021a). There monounsaturated FA (MUFA), and particularly in are controversial results in the literature regarding the oleic acid (C18:1 n-9), which is of special interest since effects of dietary FFA content on fat utilization and AME. Some authors have reported a decrease in the Ó 2022 The Authors. Published by Elsevier Inc. on behalf of Poultry AME value and lower digestibility values when dietary Science Association Inc. This is an open access article under the CC BY FFA content increases (Wiseman and Salvador, 1991; license (http://creativecommons.org/licenses/by/4.0/). Received May 7, 2022. Blanch et al., 1995,1996; Wiseman et al., 1998), while Accepted July 19, 2022. other studies observed no negative impact on perfor- 1 Corresponding author: david.sola@uab.cat mance or feed efficiency (Zumbado et al., 1994; Vilarrasa 1 2 VERGE-MeRIDA ET AL. et al., 2015; Rodriguez-Sanchez et al., 2019a,2021; Jime- Table 1. Composition of experimental fats included in the nez-Moya et al., 2021a). In this regard, and according to grower and finisher diets of broiler chickens. the results of previous studies, it may be better to use Experimental fats acid oils from unsaturated sources and include them in Item1 POO OO OAO growing-finishing broiler chicken diets rather than in Fatty acid composition, % earlier stages, as age has a positive effect on FFA absorp- C 14:0 0.96 0.03 0.06 tion and fat utilization (Tancharoenrat et al. 2013; Roll C 16:0 42.56 12.66 12.43 et al. 2018; Rodriguez-Sanchez, et al. 2019b; Vi~ nado et C16:1 n-7 0.16 0.91 1.04 C 18:0 4.53 2.69 2.69 al. 2019; Jimenez-Moya et al. 2021a). Additionally, the C18:1 n-9 40.80 70.06 63.24 inclusion of olive pomace acid oil, a food-chain by-prod- C18:1 n7 0.61 1.59 1.68 uct, could help to reduce feeding costs as it is usually C18:1 trans 0.02 0.12 0.43 C18:2 n-6 9.50 10.09 15.83 competitively priced, and its direct application might C18:3 n-3 0.30 0.68 0.90 contribute to a circular bioeconomy system and more C20:0 0.40 0.48 0.52 sustainable production compared to other uses of these C20:1 n-9 0.15 0.35 0.28 C22:0 - 0.23 0.46 by-products that require further processing. Therefore, C24:0 - 0.11 0.44 olive pomace oil and acid oil, which are rich in MUFA SFA 48.61 16.20 16.60 but differ in FFA content, could be suggested as feeding MUFA 41.59 73.03 66.67 PUFA 9.80 10.77 16.73 fats for growing-finishing broilers. However, before rec- UFA:SFA 1.06 5.17 5.02 ommending them, it is essential to evaluate their effects n-6:n-3 31.89 14.73 17.61 to assure suitable animal production performance, espe- Lipid class composition, % TAG 87.98 91.09 24.47 cially under commercial production practices. DAG 8.67 8.38 18.60 Therefore, the aim of the present study was to investi- MAG 0.05 0.32 2.34 gate the potential use of olive pomace oil and olive pom- FFA 3.31 0.21 54.59 MIU, % ace acid oil as fat sources in growing-finishing broiler Moisture - - 0.73 diets. This was assessed by studying the effect of dietary Impurities 0.49 0.28 1.37 supplementation of olive pomace oil and olive pomace Unsaponifiable 0.22 1.44 4.53 acid oil on the growth performance, carcass parameters, Abbreviations: POO, palm oil; OO = olive pomace oil; OAO, olive digestibility, abdominal fat deposition, and FA profile of pomace acid oil; SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; UFA, unsaturated abdominal fat and breast meat. fatty acids; TAG, triacylglycerols; DAG, diacylglycerols; MAG, monoa- cylglycerols; FFA, free fatty acids; MIU, moisture, impurities and unsaponifiable. MATERIALS AND METHODS 1 All samples were analyzed in duplicate. Experimental Fats libitum throughout the study. Environmental conditions The chemical composition of experimental fats is were automatically controlled, following the recommen- shown in Table 1. Olive pomace oil and olive pomace dations and specifications of the Ross 308 management acid oil were supplied by RIOSA S.A. (Jaen, Spain), and handbook (Aviagen, 2018).  palm oil was provided by bonArea Agrupa (Guissona, A 4-phase feeding program was used, consisting of a Spain). All samples were analyzed in duplicate for FA pre-starter diet from 0 to 7 d, a starter diet from 8 to composition, lipid class composition, moisture, impuri- 21 d, a grower diet from 22 to 29 d and a finisher diet ties, and unsaponifiable matter as described by Varona from 30 to 39 d, all in pelleted form. The ingredients of et al. (2021b). the experimental diets are shown in Table 2, and these were formulated to meet or exceed requirements (FEDNA, 2018). Pre-starter and starter diets were com- Experimental Design and Diets mon to all animals. For grower and finisher diets, 3 The study was conducted on the experimental facili- experimental treatments were obtained as the result of  ties of bonArea Agrupa (Nial Farm, Guissona, Spain). adding 6% (as-fed basis) of different fat sources: palm oil All animal housing and husbandry was in accordance (PO), olive pomace oil (O), and olive pomace acid oil with the European Union Guidelines (2010/63/EU), (OA). Silicate (Ibersil D-100M; IQESIL S.A., Zaragoza, and all management practices and procedures were Spain) was added to the finisher diets (1.00% as-fed approved by the Animal Ethics Committee (CEEAH) basis) to increase the amount of HCl-insoluble ash as an of the Universitat Autonoma de Barcelona (code num- inert digestibility marker. ber: 3938). A total of 3,048 newly hatched mixed-sex broiler chickens (Ross 308; 40.9 § 0.26 g of BW, mean § Controls and Sampling SD) were obtained from the commercial hatchery of  bonArea Agrupa. On arrival, birds were distributed into Feed consumption and BW (pen-basis) were recorded 24-floor pens (12 m2, 127 animals per pen), balanced by at 7, 21, 29, and 39 d of age. This was used to calculate body weight and assigned to 1 of the 3 dietary treat- the ADG, the ADFI and the feed conversion ratio ments (8 replicates per treatment). Each pen was pro- (FCR) for each period and for the overall study. Mortal- vided with feed and water that could be accessed ad ity was recorded and weighed to adjust and correct these ALTERNATIVE FAT SOURCES IN BROILER DIETS 3 Table 2. Ingredient composition of the pre-starter, starter, Chemical Analyses grower and finisher diets (as-fed basis) for broiler chickens. The composition of feeds is shown in Table 3. Analyti- Common period Experimental period cal determinations of the feeds were performed accord- Ingredients, % Pre-Starter Starter Grower Finisher ing to AOAC International (2005) methods: dry matter Corn 24.01 35.07 35.11 34.99 (Method 934.01), ash (Method 942.05), crude protein Soybean meal 47% 36.20 30.38 23.79 19.74 (Method 954.01), ether extract (Method 920.39), and Wheat 30.04 24.86 10.85 15.01 Sorghum - - 10.00 10.00 crude fiber (Method 962.09). The gross energy was Sunflower meal - - 10.00 10.00 determined with an adiabatic calorimeter (Parr 6300 Soybean oil 4.69 4.72 - - Calorimeter, Parr Instrument Company, Moline, IL) Experimental fat1 - - 6.00 6.00 Silicate 1.00 1.00 1.00 1.00 according to the Standard UNE-EN ISO 9831:2004. Dicalcium phosphate 1.36 1.12 0.98 0.73 Lipid class composition was analyzed by size exclusion Calcium carbonate 1.04 1.12 0.69 1.02 HPLC with refractive index detection, following the Vit-Min. premix2 0.45 0.45 0.45 0.45 Sodium chloride 0.32 0.30 0.29 0.28 method described by Varona et al. (2021b). The FA con- DL-Methionine3 0.36 0.34 0.28 0.24 tent of feed, ileal content and excreta were analyzed fol- L-Lysine4 0.39 0.46 0.46 0.45 lowing the method described by Sukhija and Palmquist L-Threonine 0.12 0.14 0.09 0.08 L-Valine 0.02 0.04 0.01 0.01 (1988). Abdominal fat pad and breast meat FA were 1 analyzed following the method described by Carrapiso Palm oil, olive pomace oil or olive pomace acid oil. 2 Provides, per kg of feed: vitamin A (retinyl acetate), 10,000 IU; vita- et al. (2000). Nonadecanoic acid (C19:0, Sigma Aldrich min D, 4,700 IU; vitamin E (dl-alpha-tocopheryl acetate), 100 IU; vitamin Chemical Co.; St. Louis, MO) was added as an internal K, 4 mg; vitamin B1, 4 mg; vitamin B2, 8 mg; vitamin B6, 5 mg; vitamin standard. The FA composition of the final extract was B12, 18 mg; biotin, 0.25 mg; Cu, 13.12 mg (from CuSO4); I, 1.25 mg (from KI); Mn, 121.5 mg (from MnO2); Se, 0.3 mg (from Na2SeO3); Zn, 67.5 mg injected in a gas chromatograph (HP6890, Agilent Tech- (from ZnO); Fe, 141.75 mg (from FeSO4); phytase, 1,500 FYT (Ronozyme nologies; Waldbronn, Germany) following the method Trade mark; DSM, Herleen, The Netherlands). conditions described by Cortinas et al. (2004). HCl- 3 DL-2-hydroxy-4-methylthiobutanoic acid (HMTBa), the hydroxyl analogue of DL-methionine. insoluble ash was determined in feeds, ileal content and 4 L-Lysine sulphate. feces according to the methods of European Commission Regulation n° 152/2009(“European Commission Regula- tion No 152/2009 of 27 January 2009. Laying down the parameters. The digestibility balance was determined methods of sampling and analysis for the official control from 30 to 36 d of age in a subset of 144 animals (n = 48 of feed - Publications Office of the EU,”). animals/treatment). Animals selected for the digestibil- ity balance were closer to the average BW (mean § 0.5 Calculations SD) of each sex within each pen (3 males and 3 females were selected from each pen). At d 36, excreta samples The apparent digestibility of a particular FA (X) was were collected from selected animals by abdominal-mas- calculated as follows: sage stimulation and then these animals were electrically stunned (Reference: 105523; FAF, Saint-Sernin-sur- % apparent digestibility of X Rance, France) and immediately exsanguinated to obtain ileal content. The ileal digestive contents (from ¼ f1  ½ðXf =Mf Þ = ðXd=Md Þg  100 the junction with Meckel's diverticulum to a point 1 cm proximal to the iliocecal junction) of samples from each where Xf is the concentration of a particular FA in sex group in each pen were pooled, homogenized, freeze excreta or ileal content, Mf is the concentration of the dried (LyoAlpha 10/15; Telstar, Barcelona, Spain), inert marker in excreta or ileal content, Xd is the concen- ground (1 mm screen diameter) and kept at 5°C until tration of a particular FA in the diet, and Md is the con- further analyses. Animals euthanized for digestibility centration of the inert marker in the diet. The ileal balance were adjusted as mortality for the performance digestible energy and AME of feeds was calculated from parameters calculations. the product of energy apparent digestibility and its cor- At d 39, animals were fasted for 10 h and slaughtered responding feed gross energy.  at the bonArea Agrupa commercial slaughterhouse (Guissona, Spain). All carcasses were processed (blood, Statistical Analysis feathers, viscera, head, and feet were removed) and weighed to obtain the carcass yield. Breast meat and The normality of the data and homogeneity of vari- abdominal fat pad were obtained from the 5 female ance were verified using the CAPABILITY procedure of broilers per pen (n = 40 animals/treatment) that were SAS (version 9.4, SAS Inst. Inc.; Cary, NC). All data closest to the average BW (mean § 0.5 SD). Samples of were analyzed using the GLM procedure of SAS. For breast meat were homogenized, minced, pooled for each performance, carcass parameters and FA profile of pen, freeze-dried, ground (1-mm screen diameter), and breast meat and abdominal fat pad, diet was defined as kept at 5°C until further analyses. Samples of abdominal the main factor. For digestibility balance, diet and sex fat pad were homogenized, pooled for each pen and kept were defined as the main factors. No interactions were at 20°C until further analyses. found between diet and sex for any of the variables 4 VERGE-MeRIDA ET AL. Table 3. Macronutrient and energy content, fatty acid, and lipid class composition of the diets fed to broiler chickens. Grower diets Finisher diets Item1 Pre-starter diet Starter diet PO O OA PO O OA Macronutrient and energy content, % Dry matter 89.19 89.42 89.70 90.14 89.77 90.27 90.34 90.36 Crude protein 20.15 20.16 18.98 19.11 19.68 18.53 18.19 18.45 SID Methionine* 0.65 0.61 0.56 0.56 0.56 0.51 0.51 0.51 SID Lysine* 1.24 1.13 1.04 1.04 1.04 0.94 0.94 0.94 Ether extract 5.91 5.40 7.71 7.76 7.49 8.06 7.71 8.07 Crude fiber 3.24 3.09 4.47 4.48 4.98 5.06 4.43 4.6 Ash 6.13 5.45 5.38 5.17 5.46 5.62 5.54 5.81 Calcium* 1.08 1.04 0.85 0.85 0.85 0.90 0.90 0.90 Phosphorus* 0.63 0.56 0.60 0.60 0.60 0.54 0.54 0.54 Digestible phosphorus* 0.48 0.43 0.42 0.42 0.42 0.37 0.37 0.37 Chloride* 0.24 0.23 0.24 0.24 0.24 0.23 0.23 0.23 Gross energy, kcal/kg 4,059 4,162 4,231 4,243 4,203 4,232 4,221 4,225 Fatty acid composition, % C16:0 15.99 20.03 30.62 13.67 15.49 30.89 13.89 17.50 C18:0 3.75 3.73 3.87 2.81 3.25 3.81 2.82 3.34 C18:1 n-9 18.65 24.41 33.93 51.42 43.80 34.71 51.72 43.44 C18:1 n-7 1.35 1.22 1.06 1.91 1.67 1.06 1.56 1.83 C18:2 n-6 54.12 45.71 27.71 27.14 32.25 26.84 26.72 30.42 C18:3 n-3 5.46 4.20 1.32 1.51 1.68 1.19 1.42 1.50 Minor fatty acids 0.69 0.69 1.50 1.53 1.86 1.50 1.87 1.96 SFA 20.59 24.67 36.22 17.21 19.94 36.21 17.46 22.43 MUFA 19.83 25.42 34.75 54.14 46.13 35.75 54.40 45.64 PUFA 59.58 49.91 29.03 28.65 33.93 28.03 28.14 31.93 UFA:SFA 3.86 3.05 1.76 4.81 4.02 1.76 4.73 3.46 Lipid class composition, % TAG 58.93 70.04 82.54 84.14 54.84 84.21 84.98 56.38 DAG 15.85 12.18 8.83 9.17 13.19 8.27 8.84 12.69 MAG 1.99 1.14 0.43 0.58 1.27 0.45 0.13 1.10 FFA 23.23 16.64 8.19 6.11 30.70 7.08 0.18 29.83 Abbreviations: DAG, diacylglycerols; FFA, free fatty acids; MAG, monoacylglycerols; MUFA, monounsaturated fatty acids; O, olive pomace oil diet; OA, olive pomace acid oil diet; PO, palm oil diet; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; TAG, triacylglycerols; UFA, unsatu- rated fatty acids. * Calculated values from the theoretical formulation of the diets 1 All samples were analyzed in duplicate. studied. For all analyses, the experimental unit was the values for moisture, impurities, and unsaponifiable pen (n = 8 for each treatment), and differences between (MIU) were found for olive pomace acid oil (6.63%), means were tested using Tukey’s adjust correction for while olive pomace (1.72%) and palm oil (0.71%) had multiple comparisons. The results in the tables are lower values. The composition of experimental diets is reported as least square means. For all statistical analy- shown in Tables 2 and 3. The gross energy and all mac- ses, significance was declared at P < 0.05 and tendencies ronutrient content values were similar among dietary were discussed at 0.05 < P < 0.10. treatments. The FA and lipid class composition mir- rored that of the added experimental oils, the O and OA diets being richer in MUFA while PO was richer in SFA. RESULTS Also, the OA diet showed a higher content in FFA. Characterization of Experimental Oils and Diets Growth Performance and Feed Intake The composition of the experimental oils is presented The effects of the dietary experimental oils on growth in Table 1. Regarding the FA composition, olive pomace performance and feed intake are shown in Table 4. No oil, and olive pomace acid oil were rich in monounsatu- differences were found between OA and PO in any per- rated FA (73.03 and 66.67%, respectively), while palm formance parameter (P > 0.10). Considering the grower oil was rich in saturated FA (48.45%). Of the experimen- period, from d 22 to 29, animals fed O had a higher tal oils, olive pomace acid oil had the highest content of ADG than those fed OA (P = 0.017) and the lowest polyunsaturated FA (PUFA; 16.73%). The main FA FCR among dietary treatments (P = 0.004). No differ- was oleic acid in the cases of olive pomace oil and olive ences were observed in BW at d 29 or in ADFI during pomace acid oil (70.06 and 63.24%, respectively), while this period. For the finishing period, from d 30 to 39, ani- for palm oil, palmitic (42.56%), and oleic (40.80%) mals fed O had the lowest ADFI and FCR among die- appeared in similar proportions. Both olive pomace oil tary treatments (P < 0.05) and showed a tendency to and palm oil were composed mainly of triacylglycerols reach a higher BW at d 39 than those fed OA. Concern- (» 90%), while olive pomace acid oil had a higher ing the entire production cycle, animals fed O had the amount of free FA (54.59%). Additionally, the highest lowest FCR among dietary treatments (P = 0.016) and ALTERNATIVE FAT SOURCES IN BROILER DIETS 5 Table 4. Growth performance and carcass parameters of broiler Table 5. Feed apparent digestible and metabolizable energy chickens fed different dietary fat sources. (kcal/kg) and fatty acid apparent ileal and total tract digestibility in 36-day-old broiler chickens fed different dietary fat sources. Common diets Item1 Mean SD Dietary treatments Item PO O OA SEM1 P-value2 From 0 to 21 d BW 0 days, g 40.85 0.26 AID, % BW 7 days, g 181.88 3.33 Apparent ileal 3,024.97b 3,288.03a 3,052.98b 45.96 0.003 ADFI, g/d 59.0 1.82 digestible ADG, g/d 43.0 0.56 energy, kcal/kg FCR, g/g 1.370 0.04 Total FA 85.92b 95.75a 93.88a 0.64 < 0.001 SFA 71.74c 89.75a 84.75b 1.43 < 0.001 MUFA 92.61b 96.44a 95.25a 0.44 < 0.001 Dietary treatments PUFA 95.88b 97.88a 97.81a 0.20 < 0.001 PO O OA SEM2 P-value C16:0 72.82b 90.50a 86.31a 1.33 < 0.001 C18:0 66.04c 86.31a 79.94b 1.59 < 0.001 From 22 to 29 d C18:1 n-9 93.27b 96.44a 95.31a 0.38 < 0.001 BW 21 days, g 944.3 945.3 944.4 4.44 0.985 C18:1 n-7 89.37b 95.88a 94.44a 0.64 < 0.001 BW 29 days, g 1,679 1,692 1,670 7.73 0.161 C18:2 n-6 95.67b 97.75a 97.69a 0.20 < 0.001 ADFI, g/d 135.2 133.6 134.8 1.11 0.577 C18:3 n-3 97.73b 99.56a 100.00a 0.47 0.028 ADG, g/d 91.8ab 93.3a 90.7b 0.67 0.017 ATTD, % FCR, g/d 1.478a 1.432b 1.487a 0.012 0.004 AME, kcal/kg 3,087.56b 3,281.07a 3,153.88b 39.25 0.003 From 30 to 39 d Total FA 85.06c 95.25a 93.06b 0.47 < 0.001 BW 39 days, g 2,674 2,701 2,647 15.68 0.071 SFA 70.69c 90.75a 85.59b 0.95 < 0.001 ADFI, g/d 189.0ab 183.2b 191.5a 1.81 0.013 MUFA 92.25c 95.56a 93.81b 0.36 < 0.001 ADG, g/d 100.2 101.0 98.9 0.95 0.296 PUFA 93.94b 96.88a 97.19a 0.26 < 0.001 FCR, g/g 1.897 a 1.815b 1.935a 0.019 < 0.001 C16:0 71.81c 91.69a 87.25b 0.88 < 0.001 From 0 to 39 d C18:0 63.00c 87.25a 79.44b 1.28 < 0.001 ADFI, g/d 112.6 110.6 111.8 0.99 0.385 C18:1 n-9 92.25c 95.56a 93.81b 0.36 < 0.001 ADG, g/d 67.5 68.2 66.8 0.40 0.071 a b a C18:1 n-7 88.63c 94.63a 92.06b 0.45 < 0.001 FCR, g/g 1.668 1.622 1.673 0.012 0.016 C18:2 n-6 94.13b 96.88a 97.19a 0.24 < 0.001 Carcass parameters C18:3 n-3 93.00b 99.00a 99.75a 0.38 < 0.001 Carcass weight, g 2,016 2,007 1,968 20.15 0.210 Carcass yield, % 75.42 74.29 73.72 0.61 0.154 Abbreviations: AID , apparent ileal digestibility; ATTD, apparent total tract digestibility; MUFA, monounsaturated fatty acids; O, olive Abbreviations: ADFI, average daily feed intake; ADG, average daily pomace oil diet; OA, olive pomace acid oil diet; PO, palm oil diet; PUFA, gain; BW, body weight; FCR, feed conversion ratio; O, olive pomace oil polyunsaturated fatty acids; SEM, standard error of the mean; SFA, satu- diet; OA, olive pomace acid oil diet; PO, palm oil diet; SEM, standard rated fatty acids. error of the mean. 1 1 n = 16 for each treatment (8 replicates £ 2 sex). Values of ADFI and ADG are expressed as-fed basis. 2 2 No effect of sex or interactions between diet and sex were detected for n = 8. a-b any of the variables studied and therefore, only diet effects are presented. Values within a row with different superscripts differ significantly at a-c Values within a row with different superscripts differ significantly at P < 0.05. P < 0.05. Fatty Acid Composition of Abdominal Fat Pad and Breast Meat a tendency to have a higher ADG than those fed OA (P = 0.071). No differences were found in carcass weight The FA composition of abdominal fat pad and breast or carcass yield among dietary treatments (P > 0.10). meat are presented in Tables 6 and 7, respectively. The FA profiles of abdominal fat pad and breast meat resem- bled that of the diet. Animals fed O had a higher abdom- Digestibility Balance inal fat deposition than those fed OA (P = 0.023). In relation to abdominal fat pad, O had the highest MUFA The ileal apparent digestible energy, AME and appar- content and the highest UFA:SFA ratio, together with ent ileal (AID), and total tract (ATTD) FA digestibil- the lowest PUFA content among dietary treatments ity of the feeds are presented in Table 5. No effect of sex (P < 0.01). Also, O had the lowest SFA content while or interactions between diet and sex were detected for PO had the highest (P < 0.001). For individual FA, oleic any of the variables studied and therefore, only diet acid showed the highest values for O while palmitic acid effects are presented. For apparent ileal digestible did for PO (P < 0.001). Moreover, O had the lowest energy and AME, O showed the highest values among content in linoleic acid among dietary treatments (P < dietary treatments, while no differences were observed 0.001). In relation to breast meat, differences were simi- between OA and PO (P < 0.01). Considering the digest- lar to those obtained for abdominal fat pad. Breast meat ibility of FA, O and OA showed higher values than PO from animals fed O was the richest in MUFA, while for all analyzed FA in both AID and ATTD (P < 0.001). that from animals fed OA was richest in PUFA and that When comparing O and OA, no differences were from animals fed PO was richest in SFA (P < 0.001). observed for the AID of total FA, MUFA, and PUFA, Hence, both O and OA had a higher unsaturated-to- but O had higher values for SFA than OA (P < 0.001). saturated FA (UFA:SFA) ratio than PO (P < 0.001). For ATTD, O showed higher values for total FA, SFA In terms of individual FA, palmitic acid showed the and MUFA than OA (P < 0.001), and no differences highest values for PO, oleic acid did for O and linoleic were observed for PUFA. acid did for OA (P < 0.001). 6 VERGE-MeRIDA ET AL. Table 6. Fatty acid composition (%) of abdominal fat pad from with the present results, Crespo and Esteve-Garcia female broiler chickens according to different dietary fat sources. (2001) reported an increase in feed efficiency in growing- Dietary treatments finishing broilers fed olive oil, which has a similar FA profile to olive pomace oil, compared to those fed tallow, Item PO O OA SEM1 P-value ab a b which is rich in SFA. However, Zhang et al. (2013) did Abdominal fat pad, % 1.31 1.44 1.25 0.05 0.023 Sum of FA, mg/g 717.80 744.85 708.91 13.28 0.150 not observe differences in broilers fed olive oil compared SFA 30.73a 25.64c 27.90b 0.50 < 0.001 to those fed tallow. The improved feed efficiency in ani- MUFA 47.38c 54.78a 49.71b 0.64 < 0.001 mals fed O compared to those fed PO may be explained PUFA 21.89a 19.58b 22.40a 0.53 0.002 UFA:SFA 2.26c 2.90a 2.60b 0.06 < 0.001 by the higher degree of unsaturation, since many n-6:n-3 19.53b 17.91a 18.82ab 0.61 0.049 authors have reported that digestibility increases as the C16:0 24.44a 20.13c 21.85b 0.48 < 0.001 degree of unsaturation does (Tancharoenrat et al., 2014; C16:1 4.00 3.73 3.96 0.18 0.507 C18:0 5.02 4.76 5.11 0.13 0.157 Rodriguez-Sanchez et al., 2019a,2021; Jimenez-Moya et C18:1 n-9 41.44c 48.17a 43.61b 0.58 < 0.001 al., 2021b). In contrast, OA performed more poorly than C18:1 n-7 1.60b 1.97a 1.74b 0.05 < 0.001 O despite having a similar FA composition. This could C18:2 n-6 20.14a 18.21b 20.57a 0.49 0.005 C18:3 n-3 1.07 1.07 1.13 0.04 0.464 be related either to the higher FFA or MIU content, or Minor FA 2.21a 1.86b 2.04ab 0.06 0.001 both. It has been described that high FFA content could Abbreviations: FA, fatty acids; SFA, saturated fatty acids; MUFA, lead to a lower AME (Wiseman et al., 1992; Powles et monounsaturated fatty acids; O, olive pomace oil diet; OA, olive pomace al., 1993), which is in agreement with the present results acid oil diet; PO, palm oil diet; PUFA, polyunsaturated fatty acids; SEM, as OA showed a lower AME than O. Similarly, a higher standard error of the mean; UFA, unsaturated fatty acids. 1 n = 8. MIU content also dilutes the energy content of the a-c Values within a row with different superscripts differ significantly at added fat source (Varona et al., 2021a). Hence, the P < 0.05. higher OA FFA and MIU contents than O could explain the lower AME values. In turn, this could be related to DISCUSSION the higher ADFI found in the finishing period (from 30 to 39 d) for animals fed OA in comparison to O, since Growth Performance and Feed Intake broilers tend to vary their feed intake in order to cover The present results show that the inclusion of olive their energy requirements (NRC, 1994). pomace oil, which is rich in monounsaturated FA and mainly composed of triacylglycerols, improved perfor- mance parameters and feed efficiency in both growing Digestibility Balance (from d 22 to 29) and finishing (from d 30 to 39) periods, which resulted in a better FCR when considering each In the present study, O and OA showed higher FA period and the overall trial. As far as we know, no other digestibility than PO, both in AID and ATTD. This was studies have assessed the effects of olive pomace oil or expected because, as mentioned earlier, digestibility olive pomace acid oil in broiler chickens. In agreement increases as the degree of unsaturation does. When com- paring FA AID of OA with O, similar results were obtained for total and UFA. However, for SFA and stea- Table 7. Fatty acid composition (%) of breast meat from female ric acid, lower AID values were obtained in OA com- broiler chickens according to different dietary fat sources. pared to O. The lower digestibility of SFA in OA could be explained by the higher content of FFA. Some Dietary treatments authors agree that the explanation for the different fat PO O OA SEM1 P-value utilization in diets rich in FFA is found in the absorption Sum of FA, mg/g 13.63 13.53 13.52 1.06 0.994 processes (Rodriguez-Sanchez et al., 2019a; Jimenez- SFA 32.49a 27.03c 28.92b 0.24 < 0.001 Moya et al., 2021a). First, due to a lower monoacylgly- MUFA 41.92c 48.47a 44.42b 0.37 < 0.001 PUFA 25.58b 24.50c 26.65a 0.23 < 0.001 cerol content and bile acid secretion in the duodenum UFA:SFA 3.68b 4.89a 4.39a 0.19 < 0.001 (Sklan, 1979; Atteh and Leeson, 1985), which are consid- n-6:n-3 14.37a 19.94b 16.46a 0.10 < 0.001 ered essential for the formation of mixed micelles and C16:0 23.83a 18.85c 20.30b 0.13 < 0.001 C16:1 3.09a 2.50b 2.68b 0.10 0.002 hence the absorption of lipolysis end-products (Krog- C18:0 8.07 7.82 8.16 0.19 0.433 dahl, 1985; Ravindran et al., 2016). On the other hand, C18:1 n-9 36.26c 42.84a 38.93b 0.33 < 0.001 FFA can interact with ionized minerals, forming insolu- C18:1 n-7 2.18c 2.64a 2.40b 0.06 < 0.001 C18:2 n-6 19.33b 18.30c 20.24a 0.19 < 0.001 ble soaps that are unavailable for absorption (Small C18:3 n-3 0.74b 0.82a 0.86a 0.02 < 0.001 1991; Jimenez-Moya et al., 2021a). Concretely, and in C20:1 n-9 0.39c 0.48a 0.42b 0.01 < 0.001 accordance with the present results, this effect has been C20:4 n-6 4.08 3.98 4.11 0.20 0.888 Minor FA 2.04a 1.77b 1.91ab 0.05 0.004 found to be much more pronounced in SFA rather than UFA (Atteh and Leeson, 1985; Wiseman and Salvador, Abbreviations: FA, fatty acids; SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; O, olive pomace oil diet; OA, olive pomace 1991). In agreement with this, other studies in broiler acid oil diet; PO, palm oil diet; PUFA, polyunsaturated fatty acids; SEM, chickens have found that the ileal digestibility of SFA standard error of the mean; UFA, unsaturated fatty acids. decreases as dietary FFA content increases (Rodriguez- 1 n = 8. a-c Values within a row with different superscripts differ significantly at Sanchez et al., 2019a). However, although absorption of P < 0.05. SFA could have been compromised by the presence of ALTERNATIVE FAT SOURCES IN BROILER DIETS 7 FFA in OA, the values obtained for these animals were and other confounding factors such as endogenous losses much higher than those obtained for PO. These results are thus avoided (Stein, 2017). suggest that the saturation degree had more influence on FA digestibility than the dietary FFA content did, which is in agreement with other previous studies (Vilar- Fatty Acid Composition of Abdominal Fat rasa et al., 2015; Rodriguez-Sanchez et al., 2019a; Jime- and Breast Meat nez-Moya et al., 2021a; Rodriguez-Sanchez et al., 2021). The present study showed that when acid oils are In the present study, animals fed O showed a higher included in growing-finishing diets (from 22 to 39 d) abdominal fat deposition than those fed OA. In fact, olive only SFA is affected, and no changes in TFA, MUFA or pomace acid oil used in this study had a higher content in PUFA AID are observed, which may be explained by PUFA, which previous studies have associated with a the fact that saturated FFA are more prone than unsat- decrease in abdominal fat deposition (Crespo and Esteve- urated FFA to form insoluble soaps. In agreement with Garcia, 2002a,b; Ferrini et al., 2008; Vilarrasa et al., the present results, recent studies showed that adding a 2015). Preferential b-oxidation of PUFA with respect to moderate content of dietary FFA does not negatively SFA or MUFA and a decreased rate of FA synthesis affect TFA digestibility. Rodriguez-Sanchez et al. could explain this (Crespo and Esteve-Garcia, 2002c). (2021) and Jimenez-Moya et al. (2021a) did not find Moreover, dietary PUFA seem to reduce serum levels of negative effect on the digestibility of TFA in growing- insulin and of very low density lipoproteins (Crespo and finishing broiler chickens that were fed diets containing Esteve-Garcia, 2003), which also limits fat deposition. up to 35% and 30% of FFA, respectively. Furthermore, The FA profile of both abdominal fat pad and breast the use of olive pomace acid oil (38.6% of dietary FFA) meat reflected that of the diet, depending on the added fat in growing-finishing pigs did not affect the digestibility source, which is in agreement with the results reported in of TFA compared to olive pomace oil (Verge-Merida et the literature (Ferrini et al., 2008; Vilarrasa et al., 2015; al., 2021). In fact, other authors have found that the Skrivan et al., 2018; Vi~ nado et al., 2020). Concretely, in O effect of dietary FFA is limited to SFA, and especially in and OA treatments, SFA were reduced in both tissues, young animals, that have lower production and secre- increasing the content in MUFA and the UFA:SFA ratio tion of bile acids, which hinders their dietary fat assimi- when compared to PO. The reduction of SFA in breast lation (Wiseman et al., 1991; Rodriguez-Sanchez et al., meat contributes to the global trend towards producing 2019a; Jimenez-Moya et al., 2021a). Hence, in agree- healthy meat products, since consumption of saturated fat ment with previous studies, the present results suggest have been related to many health concerns (Islam et al., that acid oils could be included in growing-finishing diets 2019; Lopez-Pedrouso et al., 2021). without major impairment of FA digestibility, at least In conclusion, the inclusion of olive pomace oil at 6% when dietary FFA content does not exceed 30% and the in growing finishing broiler diets achieved better perfor- dietary UFA:SFA ratio is above 3.46. mance, feed efficiency, and digestibility compared to a In general, similar values were obtained for ATTD to conventional source such as palm oil. On the other hand, those obtained for AID. This was expected since the when olive pomace acid oil (fat by-product rich in FFA) absorption of fat is practically negligible in the hindgut of is used instead of palm oil, no negative effect was poultry (Renner, 1965; Ravindran et al., 2016). However, observed in performance or feed efficiency. However, in contrast to what was observed in the AID of FA, values olive pomace acid oil showed lower digestibility of SFA for ATTD were lower in OA when compared to O for than olive pomace oil, although no changes in TFA, most of the FA, with the exception of PUFA. This is in MUFA, or PUFA ileal digestibility were observed. Addi- accordance with other studies that described how high die- tionally, the inclusion of olive pomace oil or olive pomace tary FFA has negative effects on fat digestibility measured acid oil leads to a reduction in saturated fatty acids in at fecal level (Blanch et al., 1995,1996; Vila and Esteve- both abdominal fat and breast meat compared to palm Garcia, 1996; Wiseman et al., 1998). This effect could be oil. Hence, the present results suggest that olive pomace caused by bacterial activity, mainly in the cecum. In this oil and acid oil are interesting sources for inclusion in regard, bacteria biohydrogenation of oleic, linoleic, and growing-finishing broiler chicken diets, which may linolenic acids would convert them into stearic acid and potentially reduce feeding costs and contribute to more other FA that originate from this activity (Duran-Montge efficient production and the circular economy. et al., 2007; Rodriguez-Sanchez et al., 2019a, 2021), which therefore affects the ATTD values, especially those of SFA ACKNOWLEDGMENTS and MUFA. Previous studies (Rodriguez-Sanchez et al. 2019a; Rodriguez-Sanchez et al. 2021) found increasing The authors acknowledge the staff at Nial farm facili- concentrations of FA produced by bacterial activity (cap-  ties and bonArea Agrupa (Guissona, Spain) for all sup- ric acid, C10:0; margaric acid, C17:0; trans C18:1; and vac- port. The authors are also grateful to RIOSA S.A. cenic acid, C18:1 n-7) as dietary FFA content increased, (Jaen, Spain) for providing the experimental oils. In suggesting that the higher the dietary FFA content, the addition, students and colleagues at the Universitat de greater the bacterial activity. These results indicate that Barcelona (Barcelona, Spain) and Servei de Nutrici o i AID data are more accurate and should be used instead of Benestar Animal (SNiBA; Cerdanyola del Valles, Spain) ATTD data for FA digestibility, since the microbial effect who helped during the experiment are acknowledged. 8 VERGE-MeRIDA ET AL. This work was carried out thanks to the financial sup- fat as well as abdominal fat in broiler chickens. Poult. Sci. 87:528– port provided by Ministerio de Economía y Competitivi- 535. Fundaci on Espa~ nola para el Desarrollo de la Nutrici on Animal dad of the Spanish Government (project AGL2015- (FEDNA). 2018. Necesidades nutricionales para avicultura: Nor- 64431-C2-1-R, funded by MCIN/AEI/ 10.13039/ mas FEDNA. FEDNA, Madrid, Spain. 501100011033 and by “ERDF A way of making Europe”; Islam, M. A., M. N. Amin, S. A. Siddiqui, M. P. Hossain, F. Sultana, the grant RYC-2017-23601 funded by MCIN/AEI/ and M. R. Kabir. 2019. Trans fatty acids and lipid profile: a serious risk factor to cardiovascular disease, cancer and diabetes. Diabetes 10.13039/501100011033 and by “ESF Investing in your Metab. Syndr. 13:1643–1647.  future”), by bonArea AGRUPA and a pre-doctoral Jimenez-Moya, B., A. C. Barroeta, A. Tres, M. D. Soler, and research grant from the Ministerio de Ciencia, R. Sala. 2021. Soybean oil replacement by palm fatty acid distillate Innovacion y Universidades of the Spanish Government in broiler chicken diets: fat digestibility and lipid-class content along the intestinal tract. Animals 11:10–35. (Ref. FPU17/02263). David Sola-Oriol is supported by Jimenez-Moya, B., D. Martin, C. Soler-Rivas, A. C. Barroeta, the UAB-Banco de Santander Talent Programme. A. Tres, and R. Sala. 2021. Acid versus crude oils for broiler chicken diets: in vitro lipid digestion and bioaccessibility. Anim. Feed Sci. Technol. 276:114926. DISCLOSURES Krogdahl, A. 1985. Digestion and absorption of lipids in poultry. J. Nutr. 115:675–685. The authors declare that they have no known compet- Lopez-Pedrouso, M., J. M. Lorenzo, B. Gull on, P. C. B. Campagnol, ing financial interests or personal relationships that and D. Franco. 2021. Novel strategy for developing healthy meat products replacing saturated fat with oleogels. Curr. Opin. Food could have appeared to influence the work reported in Sci. 40:40–45. this paper. National Research Council (NRC). 1994. Nutrient Requirements of Poultry. 9th ed Natl. Acad. Press, Washington, D.C. Powles, J., J. Wiseman, D. J. A. Cole, and B. Hardy. 1993. 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