Animal 15 (2021) 100389 Contents lists available at ScienceDirect Animal The international journal of animal biosciences Crude and acid oils from olive pomace as alternative fat sources in growing-finishing pigs G. Verge-Mèrida a, A.C. Barroeta a, F. Guardiola b, M. Verdú c, M. Balart c, M. Font-i-Furnols d, D. Solà-Oriol a,⇑ a Animal Nutrition and Welfare Service, Department of Animal and Food Sciences, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain b Nutrition, Food Science and Gastronomy Dept. INSA-XIA, Universitat de Barcelona, 08921 Santa Coloma de Gramenet, Spain c Department of Animal Nutrition and Feed Industry, bonÀrea Agrupa, 25210 Guissona, Spain d Food Quality and Technology Program, IRTA, 17121 Monells, Spain a r t i c l e i n f o a b s t r a c t Article history: The inclusion of crude and acid oils from olive pomace can lead to more unsaturated meat products and, Received 11 May 2021 especially in the case of olive pomace acid oil, achieve a more economically and environmentally sustain- Revised 21 September 2021 able swine production. The objective of this trial was to study the effect of dietary supplementation with Accepted 27 September 2021 crude and acid oils from olive pomace, which are rich in monounsaturated fatty acids (FAs) and have dif- Available online 27 November 2021 fering free FA content, on growth performance, digestibility, carcass parameters and FA profile of Longissimus muscle (LM) and backfat in growing-finishing pigs compared to the conventional crude palm Keywords: oil. A total of 224 male and female pigs [(Landrace  Large White)  Duroc] were randomly distributed Crude olive pomace oil Digestibility into 48 pens according to initial BW (58.7 ± 9.71 kg, mean ± SD) and sex. Four experimental treatments Fatty acid were randomly assigned (n = 12 pens/treatment; 4–5 pigs/pen) for the growing (0–42 days) and finishing Meat composition (40–62 days) phases. Treatments consisted of a basal diet supplemented with 5% (as-fed basis) palm oil Olive pomace acid oil (PO), olive pomace oil (O), olive pomace acid oil (OA) or a mixture (M) of PO and OA at 50/50. No differ- ences were found in the growth performance results between PO, O or M, but animals fed OA showed a lower gain to feed ratio than M (P = 0.008). No differences were found in apparent ileal digestibility among treatments, however, animals fed O and OA showed the highest values of total FA apparent total tract digestibility, while those fed PO had the lowest values, and M had intermediate values (P < 0.001). No differences were observed in carcass composition among treatments. In relation to backfat and the LM FA profile, O and OA treatments led to a higher unsaturated FA to saturated FA ratio and a lower content in saturated FA than PO. Moreover, O showed a higher intramuscular fat (IMF) content in LM than PO (P = 0.037). It is concluded that olive pomace oil is an interesting alternative fat source that can be included at 5% in growing-finishing pig diets, leading to meat products with more IMF, rich in monoun- saturated FA, reaching high FA digestibility values and good pig performance parameters. Alternatively, olive pomace acid oil blended with conventional palm oil did not negatively impact fat utilisation nor performance. Including these fat by-products reduced feeding costs and led to a more efficient and envi- ronmentally sustainable production. Ó 2021 The Author(s). Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Implications palm oil. Moreover, including olive pomace oil may be a good nutritional strategy to both increase intramuscular fat content in The use of crude and acid oils from olive pomace can increase Longissimus muscle and achieve good performance. the ratio of monounsaturated to saturated fatty acids in meat prod- ucts. Moreover, the inclusion of olive pomace acid oil, by-product from the refining industry, in swine diets results in a more efficient Introduction and environmentally sustainable swine production. Our results indicate that crude and acid oils from olive pomace may be suitable The inclusion of fats and oils in monogastric animal feeding is a alternative fat sources to commonly used saturated fats, such as widespread practice due to their high energetic input and their supply of essential fatty acids (FAs), which contribute to efficient ⇑ Corresponding author. production. Moreover, dietary fat modifies lipid quality, and the E-mail address: david.sola@uab.cat (D. Solà-Oriol). nutritional and organoleptic properties of meat, which is of partic- https://doi.org/10.1016/j.animal.2021.100389 1751-7311/Ó 2021 The Author(s). Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 ular interest in high-fat content crossbred pigs, such as those fin- Table 1 ished with Duroc lines. Ingredient composition of the experimental diets (as-fed basis) for growing-finishing pigs. Crude olive pomace oil is obtained by extraction from olive pomace, and olive pomace acid oil is a by-product generated from Experimental period the soapstocks obtained during the chemical refining of the crude Diet composition Grower (from 0 to Finisher (from 41 to olive pomace oil. The FA profile of these two oils is rich in monoun- 40 days) 62 days) saturated FA, particularly in oleic acid (C18:1 n-9; 55–83%), which Ingredients, % consumption has been widely linked to many beneficial health Corn meal 30.00 17.98 traits (Isabel et al., 2004; Foscolou et al., 2018). The growing trend Barley 8.00 18.07 Sorghum 11.70 16.15 towards healthy meat products makes olive oil and its by-products Wheat 10.00 10.00 interesting for use in pig feeding, as they can lead to high quality Soybean meal 47% 15.95 10.96 meat products, such as loin or cured ham with a lower saturated Wheat bran 5.75 8.00 fat content and enriched in oleic acid. Olive pomace acid oil is rich Experimental fat1 5.00 5.00 Silicate 2.74 2.74 in free FA (50–70%). Although it is well known that the degree of Cane molasses 2.00 – saturation, chain length and positional distribution in the triglyc- Sunflower meal 30% 5.00 7.04 erides of the dietary FA affect their digestibility (Cho and Kim, Calcium carbonate 0.90 1.12 2012; Vilarrasa et al., 2015), there is some controversy in relation Di-calcium phosphate 0.65 0.64 to the effects of dietary free FA content. Thus, while some authors Sodium chloride 0.55 0.60 Vitamin and mineral 0.61 0.61 have reported negative effects of free FA on digestible energy, premix2 which can impair performance (Powles et al., 1993; Wiseman DL-Methionine3 0.17 0.13 et al., 1998; Jørgensen and Fernández, 2000), other authors have L-Lysine4 0.73 0.74 observed no effects on either digestible energy, FA digestibility or L-Tryptophan 0.02 0.02 the performance of pigs (DeRouchey et al., 2004; Rojas-Cano L-Threonine 0.19 0.18 L-Valine 0.04 0.02 et al., 2014; Vilarrasa et al., 2015) when including sources rich in free FA in pigs’ diets. Predicted values5 Net energy, MJ/kg 10.21 10.13 Current animal production is expected to be efficient and envi- CP, % 15.81 15.12 ronmentally sustainable. In this context, using food-chain fat by- Standardised ileal 0.99 0.92 products as alternative fat sources in swine feeding could be a good digestible lysine, % opportunity to reduce both the feeding costs and the environmen- Ca, % 0.74 0.81 P, % 0.50 0.52 tal impact. Therefore, the aim of the present study was to research the potential of using crude and acid oils from olive pomace, rich in 1 Crude palm oil (PO), crude olive pomace oil (O), olive pomace acid oil (OA) or a monounsaturated FA and differing in free FA content, as fat sources mixture (M) of PO + OA at 50/50. 2 Provides per kg of feed: vitamin A, 5 995 IU; Vitamin D3, 1 497 IU; Vitamin E, in growing-finishing pig diets. This was assessed by studying the 15 ppm; Fe, 100 ppm (FeSO4H2O); I, 0.3 ppm (KI); Cu, 18 ppm (CuSO45H2O); Mn, effect of dietary supplementation with crude olive pomace oil 40 ppm (MnO2); Zn, 94 ppm (ZnO); Se, 0.34 ppm (Na2SeO3). and olive pomace acid oil on growth performance, digestibility, 3 DL-2-hydroxy-4-methylthiobutanoic acid (HMTBa), the hydroxy analogue of carcass parameters and the FA profile of the Longissimus muscle DL-methionine. 4 (LM) and backfat in growing-finishing pigs compared to conven- L-Lysine sulphate. 5 Ted values from the theoretical formulation of the diets. tional crude palm oil as a conventional dietary fat. amount of hydrochloric acid-insoluble ash as an inert digestibility Material and methods marker. Four experimental treatments were obtained as the result of adding, to the same basal diet, 5% (as-fed basis) of different fat Experimental fats sources: crude palm oil (PO), crude olive pomace oil (O), olive pomace acid oil (OA) and a mixture (M) of PO + OA 50/50. Thus, Crude olive pomace oil and olive pomace acid oil were supplied 12 replicates per treatment were obtained, six per sex and four by RIOSA S.A. (Jaén, Spain), and crude palm oil was provided by per block of BW. bonÀrea Agrupa (Guissona, Spain). All samples were analysed in A total of 224 boars and gilts [(Landrace  Large duplicate for FA composition, lipid class composition, moisture, White)  Duroc] were obtained from the swineherd of the same impurities and unsaponifiable matter as described by Varona facility. Pigs (age of 103 ± 3 days) were individually weighed (58. et al. (2021a). 7 ± 9.71 kg of BW, mean ± SD) and randomly allocated to 48 pens and two different barns according to four dietary treatments and Experimental design and diets sex. There were a total of 12 pens per treatment, six for males and six for females. Pens were classified in one of three BW blocks The study was performed at the animal experimental facilities (light 48.4 ± 8.19 kg, medium 60.2 ± 6.18 kg, and heavy 68.3 ± 5. of bonÀrea AGRUPA (Nial farm, Guissona, Lleida, Spain). All animal 91 kg BW, mean ± SD, respectively) balanced within sex (boars housing and husbandry were in accordance with the European 59.0 ± 9.39 kg and gilts 59.7 ± 8.27 kg) and treatment (PO 59.0 ± 8 Union Guidelines (2010/63/EU). The experiment was planned to .43 kg, O 59.4 ± 9.35 kg, OA 58.7 ± 8.43 kg, and M 59.3 ± 9.82 kg cover the BW range from 60 to 130 kg BW. Therefore, the feeding BW, mean ± SD, respectively; according to two pens of light, med- programme consisted of two diets (in pelleted form): a grower diet ium and heavy BW per sex within each treatment). There were four (from 60 to 103 kg average BW; from 0 to 40 days of the exper- pigs per pen for heavy animals and five pigs per pen for medium imental period) and a finisher diet (from 103 to 130 kg BW; from and light animals. Each pen (1.13 m2 per animal for heavy pigs 41 to 62 days of the experiment). The ingredients of the experi- and 0.91 m2 per animal for medium and light pigs) had a half slat- mental diets are shown in Table 1. Basal diets were formulated ted concrete floor, a feeder and a nipple waterer. All the animals to meet or exceed requirements (FEDNA, 2013) and to minimise had ad libitum access to feed and water during the entire trial. basal fat levels. Silicate (Ibersil D-100 M; IQESIL S.A., Zaragoza, No mortality or sick animals were observed throughout the exper- Spain) was added to the diets (2.74% as-fed basis) to increase the imental period. 2 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 Controls and sampling and homogenised samples was determined by near infrared trans- mittance spectroscopy (FoodScan TM; Foss Analytical, Hillerød, Feed consumption (pen basis) and individual BW of the animals Denmark), previously validated (Font-i-Furnols et al., 2012), at were recorded at days 0, 40 and 62 of the experiment. This was wavelengths between 850 and 1048 nm. Hydrochloric acid- used to calculate the average daily feed intake, average daily gain insoluble ash was determined in feeds, ileal content and faeces and gain to feed ratio per pen for each period and for the overall according to the methods of the European Commission Regulation study. The digestibility balance was determined from day 40 to no. 152/2009. day 62 in a subset of 64 pigs (n = 16 animals/treatment). Animals selected for the digestibility balance were those closest to the aver- Calculations age BW for each group of each sex within each treatment (at least one pig from each pen). Faecal samples were collected on the last The apparent digestibility of a particular FA (X) was calculated two days of the study (days 61 and 62) from selected animals (av- as follows: erage marketing weight of 130.00 ± 16.73 kg BW, mean ± SD) by rectal stimulation and samples were pooled immediately after % apparent digestibility of X ¼ f1  ½ðXf =Mf Þ=ðXd=MdÞg  100 the second day of collection. Then, all the animals were slaugh- tered (same day, at 166 ± 3 days of age), and the ileal content where Xf is the concentration of a particular FA in faeces or ileal was collected at the slaughterhouse from the same selected ani- content, Mf is the concentration of the inert marker in faeces or ileal mals for faces collection. All samples were immediately homoge- content, Xd is the concentration of a particular FA in the diet, and nised, freeze-dried (LyoAlpha 10/15; Telstar, Barcelona, Spain), Md is the concentration of the inert marker in the diet. The digesti- ground (1 mm screen diameter) and kept at 5 °C until further ble energy of feeds was calculated from the product of energy analysis. apparent digestibility and its corresponding feed gross energy. Backfat thickness was individually measured by ultrasound (Future-1; Inserbo, Lleida, Spain) at the midline between the last Statistical analysis thoracic and first lumbar vertebrae (P2) at the start (5.49 ± 1.09 mm) and at the end of the study. In addition, carcass quality The normality of the data and homogeneity of variance were parameters were monitored in a subset of 100 pigs at the slaugh- verified using the CAPABILITY procedure of SAS (version 9.4, SAS terhouse. Animals selected for carcass quality assessment were Inst. Inc.; Cary, NC, USA). Performance parameters were analysed those closest to the average BW within each group of BW (eight using the MIXED procedure of SAS. Diet, block and sex were heavy, nine medium and eight light) for each treatment, equally defined as the main factors and room was defined as a random for each pen (two animals per pen) and sex (in medium block of effect. Digestibility coefficients, FA composition of LM and backfat, BW, five males and four females were selected). Pigs were fasted carcass composition and IMF were analysed by using the GLM pro- (deprived of feed but not water) for 20 h (except in pigs selected cedure of SAS. For digestibility balance, diet and sex were defined for digestibility balance, which were not fasted), and weighed the as the main factors. For carcass composition and IMF, diet, sex and following morning to obtain the fasted live weight. Animals were block were defined as the main factors. For FA composition of LM stunned with 85% CO2 for 120 s and immediately exsanguinated and backfat, diet was defined as the main factor. No interactions at the commercial slaughterhouse of bonÀrea Agrupa (La Closa; between diet, sex and block were observed for any of the variables Guissona, Spain). Ham fat thickness and lean meat percentage studied. For the performance parameters, the experimental unit were obtained with an AutoFom III ultrasonic system (Frontmatec was the pen. For digestibility balance, FA composition, carcass A/C; Herlev, Denmark). Backfat and LM samples were obtained parameters and IMF, the experimental unit was the individual. (n = 18 samples/treatment) from the dorsal midline between the For all statistical analyses, differences between means were tested last rib and the first lumbar vertebrae. Animals selected for backfat using Tukey’s adjust correction for multiple comparisons. The and muscle sampling were the 18 females that were closest to the results in the tables are reported as least square means. For all sta- average BW within each treatment (at least one from each pen). tistical analyses, significance was declared at P < 0.05 and tenden- Samples were homogenised and stored at 20 °C until the chemi- cies were discussed at 0.05 > P > 0.10. cal analyses were performed. Results Chemical analysis Experimental fats and diets Analytical determinations of the feeds were performed accord- ing to AOAC International (2005) methods: DM (Method 934.01), Composition of the experimental fats is presented in Table 2. ash (Method 942.05), CP (Method 954.01), ether extract (Method Crude olive pomace oil and olive pomace acid oil were rich in 920.39) and crude fibre (Method 962.09). The gross energy was monounsaturated FA, in particular in oleic acid (70.5 and 65.0%, determined with an adiabatic calorimeter (Parr 6300 Calorimeter, respectively), while crude palm oil was composed mainly of palmi- Parr Instrument Company, Moline, IL, USA) according to the Stan- tic (42.4%) and oleic (41.6%) acids in similar proportions. Both dard UNE-EN ISO 9831:2004. Lipid class composition was analysed crude palm oil and crude olive pomace oil, as crude oils, were com- by size exclusion HPLC with refractive index detection, following posed of triacylglycerols (>80%). In contrast, olive pomace acid oil, the method described by Varona et al. (2021a). The FA content of a by-product of the olive pomace oil refining process, had the high- feed, ileal content and faeces were analysed following the method est amount of free FA (53.98%). Olive pomace acid oil had the high- described by Sukhija and Palmquist (1988). Backfat and LM FAs est moisture, impurities and unsaponifiable values (MIU; 12.67%), were analysed by gas chromatography following the method while crude olive pomace oil (4.65%) and crude palm oil (0.49%) described by Carrapiso et al. (2000). Nonadecanoic acid (C19:0; had the lowest values. Composition of the experimental diets is Sigma-Aldrich Chemical Co.; St. Louis, MO, USA) was added as presented in Table 3. All diets showed a similar content in gross internal standard. The final extract obtained was injected in a gas energy and all macronutrients analysed. The fatty acid and lipid chromatograph (HP6890, Agilent Technologies; Waldbronn, Ger- class composition of the experimental diets resemble those of many) following the method conditions described by Cortinas the added fats, and M was at the midpoint between PO and OA et al. (2004). The intramuscular fat content (IMF) of the LM minced for all analysed parameters. 3 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 Table 2 those fed OA (P = 0.005). Concerning the entire experimental per- Composition of experimental fats1 included in the diets of growing-finishing pigs. iod (from 0 to 62d), animals fed OA showed a lower average daily Experimental fats gain than those fed M or PO (P = 0.006). In addition, the gain to feed Item PO O OA ratio in animals fed OA was lower than in those fed M (P = 0.008), and tended to be lower than in those fed O (P = 0.074) or PO Fatty acid composition (g/100 g of FA) C14:0 0.85 – – (P = 0.076). No differences were observed in the final BW or in C16:0 42.43 12.95 13.59 the global average daily feed intake among treatments (P > 0.10). C18:0 4.57 2.60 3.62 Regarding sex, gilts showed a lower BW, average daily gain and C18:1 n-9 41.62 70.47 64.97 gain to feed ratio than boars considering the entire experimental C18:2 n-3 0.28 0.89 0.97 period (P < 0.001). Concerning block of BW, differences between C18:2 n-6 9.73 12.03 15.03 C20:0 0.32 0.41 0.56 heavy, medium and light animals were maintained throughout C20:1 n-9 0.13 0.32 0.29 the experimental period for BW, average daily feed intake and gain C22:0 – – 0.45 to feed ratio (P < 0.001). However, no differences between blocks of C24:0 – – 0.44 BW were observed on the average daily gain when considering the Saturated FA 48.25 16.14 18.67 Monounsaturated FA 41.75 70.79 65.25 entire experimental period (P = 0.807) although heavy animals Polyunsaturated FA 10.01 12.93 16.00 showed a higher average daily gain than light animals in the grow- Unsaturated FA to Saturated FA ratio 1.07 5.19 4.35 ing period (from 0 to 40 days; P = 0.022). Lipid class composition (g/100 g of FA) Triacylglycerols 86.67 82.36 23.98 Diacylglycerols 8.36 8.25 19.76 Digestibility balance Monoacylglycerols 0.63 0.56 2.29 Free FA 4.34 8.82 53.98 Feed digestible energy and FA apparent ileal (AID) and total MIU (g/100 g of fat) tract (ATTD) digestibility values are presented in Table 5. Regard- Moisture 0.14 0.28 1.27 ing dietary treatments, no significant differences were observed Impurity 0.13 0.79 7.84 in AID (P > 0.10); however, pigs fed O showed a tendency to have Unsaponifiable 0.22 3.58 3.56 higher values than PO in the AID of total FA (P = 0.078), monoun- Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace saturated FA (P = 0.066) and oleic acid (P = 0.071). In addition, M acid oil; FAs = fatty acids; MIU = moisture, impurities and unsaponifiable. 1 showed a tendency to have higher values than PO in the AID of pal- All samples were analysed in duplicate. mitic acid (P = 0.092). Regarding ATTD, OA and M showed a higher DE than PO (P = 0.001). In addition, O and OA showed the highest Performance and feed intake values for total FA (P < 0.001). OA had the highest values in the ATTD of monounsaturated FA and polyunsaturated FA, while PO The effects of the dietary fat sources on growth performance are had the lowest (P < 0.001). M showed higher values for saturated shown in Table 4. No differences were observed among dietary FA ATTD than O (P = 0.032). Concerning individual FA, OA showed treatments during the grower period (from day 0 to day 40 of the highest ATTD values for palmitic, oleic and linoleic acids the experiment; 59.3 ± 8.74–104 ± 10.92 kg BW) in any perfor- (P < 0.001). However, very low values were obtained in the ATTD mance parameter (P > 0.10). During the finishing period (from of stearic acid, which were even negative in the case of O and day 40 to day 62 of the experiment; 104 ± 10.92–131.7 ± 12.67 k OA. In terms of sex, no differences were obtained in the AID g BW), animals fed M showed a higher average daily gain than (P > 0.10), but higher values were obtained for ATTD of monounsat- Table 3 Analysed1 macronutrient content and fatty acid and lipid class composition of the experimental diets of growing-finishing pigs. Grower diets Finisher diets Item PO O OA M PO O OA M Macronutrient content (g/100 g of feed) DM 88.43 87.28 87.75 87.40 89.25 88.85 89.07 89.04 CP 16.05 15.53 15.61 16.65 15.60 15.33 15.11 15.45 Ether extract 6.55 6.32 6.63 6.43 6.79 6.29 6.44 6.44 Crude fibre 4.45 4.15 4.13 4.31 4.65 4.84 4.33 4.67 Ash 6.38 6.66 7.06 6.77 6.59 6.74 6.10 6.67 Gross energy (MJ/kg) 17.28 16.97 16.89 17.03 17.18 17.12 17.33 17.27 Fatty acid composition (g/100 g of FA) C16:0 30.02 13.68 13.24 23.07 30.56 15.11 14.40 24.27 C18:0 4.05 2.74 2.99 3.60 3.86 2.78 2.97 3.55 C18:1 n-9 35.21 46.51 46.00 39.03 34.10 45.94 44.96 38.86 C18:2 n-6 27.43 31.62 32.33 29.97 27.83 30.58 31.91 28.59 C18:3 n-3 1.42 1.87 1.86 1.66 1.66 2.04 2.09 1.72 Minor fatty acids 1.87 3.58 3.58 2.67 1.99 3.55 3.67 3.01 Saturated FA 34.97 17.50 17.55 27.71 35.38 18.93 18.72 29.19 Monounsaturated FA 36.19 49.01 48.26 40.65 35.14 48.45 47.28 40.50 Polyunsaturated FA 28.85 33.49 34.19 31.64 29.49 32.62 34.00 30.31 Lipid class composition (g/100 g of FA) Triacylglycerols 83.69 70.72 49.26 68.21 81.19 67.13 44.77 64.37 Diacylglycerols 8.89 11.12 14.90 11.77 9.55 11.91 15.05 12.39 Monoacylglycerols 0.93 1.27 1.66 1.27 1.09 1.40 1.63 1.54 Free FA 6.49 16.88 34.19 18.75 8.17 19.56 38.55 21.70 Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace acid oil; M = mixture of PO + OA at 50/50; FAs = fatty acids. 1 All samples were analysed in duplicate. 4 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 Table 4 Performance parameters in growing–finishing pigs fed different dietary fat sources. Dietary treatments P-values 1 2 Item PO O OA M SEM Diet Sex3 Block4 From 0 to 40 days BW at 0d (kg) 59.0 59.4 58.7 59.3 0.89 0.942 0.175 <0.001 Average daily feed intake (g) 2 593 2 561 2 594 2 581 37.00 0.930 0.487 <0.001 Average daily gain (g) 1 151 1 130 1 098 1 121 28.79 0.257 <0.001 0.022 Gain to feed ratio (g/kg) 444 443 424 436 1.19 0.178 <0.001 <0.001 From 40 to 62 days BW at 40d (kg) 105.1 104.5 102.6 104.1 1.69 0.633 0.009 <0.001 Average daily feed intake (g) 3 168 3 115 3 045 3 114 170.70 0.491 0.016 0.002 Average daily gain (g) 1 235ab 1 185ab 1 155b 1 273a 51.53 0.005 <0.001 0.056 Gain to feed ratio (g/kg) 391 386 380 412 0.96 0.110 <0.001 <0.001 From 0 to 62 days BW at 62d (kg) 133.0 131.5 128.8 133.5 4.69 0.119 <0.001 <0.001 Average daily feed intake (g) 2 802 2 737 2 785 2 768 72.53 0.748 0.352 <0.001 Average daily gain (g) 1 181a 1 154ab 1 119b 1 186a 51.18 0.006 <0.001 0.807 Gain to feed ratio (g/kg) 422ab 423ab 403b 429a 1.02 0.008 <0.001 <0.001 Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace acid oil; M = mixture of PO + OA at 50/50. a,b Values within a row with different superscripts differ significantly at P < 0.05. 1 Values of average daily feed intake and gain to feed ratio expressed as-fed basis. 2 n = 12. 3 Boars vs gilts. 4 Three blocks of BW: light 48.37 ± 8.19 kg, medium 60.22 ± 6.18 kg, and heavy 68.33 ± 5.91 kg BW, mean ± SD of initial BW. Table 5 Feed digestible energy (MJ/kg) and fatty acid apparent digestibility (%, ileal and total tract) in finishing pigs fed different dietary fat sources. Dietary treatments P-values Item PO O OA M SEM1 Diet Sex2 Apparent ileal digestibility Digestible energy, MJ/kg 12.55 12.32 11.82 12.04 0.34 0.319 0.489 Total FA 76.21 83.07 81.56 82.50 2.11 0.078 0.922 Saturated FA 54.19 58.50 60.63 66.94 4.27 0.177 0.926 Monounsaturated FA 85.56 90.29 89.38 90.06 1.50 0.066 0.991 Polyunsaturated FA 80.56 86.36 82.19 87.01 3.13 0.336 0.749 C16:0 61.13 68.93 70.25 71.33 3.36 0.092 0.866 C18:0 22.64 23.69 19.44 41.96 8.62 0.236 0.405 C18:1 n-9 86.13 90.43 89.56 90.30 1.40 0.071 0.964 C18:2 n-6 82.38 87.14 83.56 87.63 2.85 0.421 0.685 C18:3 n-3 87.25 92.25 88.29 89.69 1.19 0.233 0.997 Apparent total tract digestibility Digestible energy, MJ/kg 13.88b 12.32ab 14.20a 14.20a 0.06 0.001 0.097 Total FA 79.63c 87.94a 89.31a 85.26b 0.54 <0.001 0.237 Saturated FA 51.81ab 50.56b 54.19ab 58.81a 2.08 0.032 0.222 Monounsaturated FA 93.81c 95.94b 96.94a 94.63c 0.25 <0.001 0.031 Polyunsaturated FA 96.66c 97.56b 98.19a 97.50b 0.12 <0.001 0.026 C16:0 60.75c 73.50b 81.13a 69.31b 1.37 <0.001 0.003 C18:0 2.31a 26.79b 49.31b 0.94a 6.56 <0.001 0.551 C18:1 n-9 94.13d 96.19b 97.19a 95.06c 0.24 <0.001 0.045 C18:2 n-6 96.50c 97.44b 98.13a 97.50b 0.12 <0.001 0.002 C18:3 n-3 100.00 100.00 100.00 100.00 . . . Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace acid oil; M = mixture of PO + OA at 50/50; FAs = fatty acids. a–d Values within a row with different superscripts differ significantly at P < 0.05. 1 n = 16. 2 Boars vs gilts. urated FA and polyunsaturated FA in females (P < 0.05). When con- in carcass weight, yield and lean percentage or ham and backfat sidering individual FA, females had a higher ATTD for palmitic acid thickness among dietary treatments (P > 0.10). However, some dif- (C16:0; P = 0.003), oleic acid (C18:1 n-9; P = 0.045) and linoleic acid ferences were found in terms of BW block. As expected, heavy ani- (C18:2 n-6, P = 0.002). mals (140.8 ± 15.5 kg BW) had the highest carcass weight while light animals (119.2 ± 12.0 kg BW) had the lowest (111.2 vs 90.0 kg carcass weight for heavy and light animals, respectively; Carcass quality and intramuscular fat P < 0.001). Moreover, in contrast to light animals, heavy animals showed a greater ham fat thickness (13.29 vs 10.93 mm of ham The effects of dietary treatments on carcass yield, composition fat thickness for heavy and light animals, respectively; P = 0.004) and LM IMF are shown in Table 6. No differences were observed 5 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 Table 6 Carcass yield, composition and Longissimus muscle intramuscular fat of fattening pigs according to different dietary fat sources. Dietary treatments P-values 1 Item PO O OA M SEM Diet Sex Block Carcass weight (kg) 101.7 99.9 100.4 102.2 2.52 0.900 0.230 <0.001 Carcass yield (%) 73.59 73.95 73.90 72.71 0.91 0.743 0.109 0.555 Carcass lean percentage (%) 60.26 60.78 61.45 61.06 0.57 0.495 0.734 0.916 Backfat thickness2 (mm) 10.85 10.77 9.93 10.80 0.72 0.198 0.223 0.053 Ham fat thickness (mm) 12.84 11.95 11.80 12.18 0.58 0.585 0.845 0.004 Intramuscular fat3 (%) 1.78b 2.21a 2.15ab 2.07ab 0.107 0.037 <0.001 0.844 Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace acid oil; M = mixture of PO + OA at 50/50. a,b Values within a row with different superscripts differ significantly at P < 0.05. 1 n = 25. For intramuscular fat, n = 18. 2 Backfat thickness measurement made by ultrasound between the last thoracic and first lumbar vertebrae (P2) in live pigs. 3 Measured by near infrared transmittance spectroscopy (FoodScan TM; Foss Analytical, Hillerød, Denmark). and tended to have a thicker backfat thickness (11.10 vs 10.03 mm higher values of palmitic acid than OA (P = 0.026) and higher val- of backfat thickness for heavy and light animals, respectively; ues of stearic acid than O (P = 0.001). Animals fed O had a higher P = 0.053). Animals fed O showed a higher IMF value than those monounsaturated FA content, in particular oleic acid, than those fed PO (P = 0.037). In addition, a sex effect was observed, since fed PO (P = 0.003). No differences were observed for linoleic or females showed a higher IMF level (2.27 mm) than males linolenic acids. In terms of unsaturated FA to saturated FA ratio, (1.88 mm; P < 0.001). the highest values were obtained with the O and OA diets, while the lowest value was obtained with the PO diet (P = 0.001). Fatty acid composition of backfat and Longissimus muscle Discussion The fatty acid composition of backfat and LM are presented in Tables 7 and 8, respectively. The FA profiles of backfat and LM Performance and feed intake resemble the profile of the fat sources supplemented in the feed. Animals fed O or OA had a higher unsaturated FA to saturated FA The study results show that including crude olive pomace oil, ratio than animals fed PO. In relation to backfat, animals fed PO rich in monounsaturated FA and triacylglycerols, as an alternative had the highest level of saturated FA while those fed O or OA fat source to conventional crude palm oil did not modify the per- had the lowest (P = 0.034). Animals fed O had the highest monoun- formance parameters in any phase or in the overall trial. On the saturated FA levels and those fed PO had the lowest (P < 0.001). other hand, the biological response obtained regarding the effects Therefore, animals fed O had the highest unsaturated FA to satu- of sex and block of BW were as expected. These results are in rated FA ratio while animals fed PO had the lowest, and diets OA agreement with previous studies that include olive oil in the diets and M presented intermediate values (P < 0.001). In terms of indi- of growing-finishing pigs, which are similar in FA composition to O, vidual FA, oleic acid showed the highest values for O or OA and and which did not find differences in growth performance com- linolenic acid showed the highest values for O, OA or M. Palmitic pared to other commonly used fat sources, such as tallow or soy- and stearic acid showed the highest values for PO (P < 0.001). No bean oil (Park et al., 2012). Other studies have reported no differences were observed for linoleic acid. negative effects on growth performance when olive pomace cake In relation to LM, the lowest levels of saturated FA (P < 0.001) (with an approximate content of 28% fat) was added to growing- were observed in animals fed O or OA. Moreover, PO showed finishing pig diets (Ferrer et al., 2020). Table 7 Fatty acid composition (g/100 g of FA) of backfat from finishing pigs according to different dietary fat sources. Dietary treatments Item PO O OA M SEM1 P-value C14:0 1.11 1.05 1.11 1.09 0.03 0.212 C16:0 22.71a 19.82c 20.25c 21.20b 0.22 <0.001 C16:1 1.51 1.56 1.62 1.44 0.06 0.159 C17:0 0.22 0.20 0.23 0.22 0.23 0.093 C18:0 12.56a 10.39c 10.96bc 11.64b 0.20 <0.001 C18:1 n-9 42.20c 46.31a 44.12a 43.33bc 0.36 <0.001 C18:1 n-7 1.93b 2.31a 2.26a 1.99b 0.04 <0.001 C18:2 n-6 15.06 15.29 16.22 16.16 0.43 0.117 C18:3 n-3 0.67b 0.80a 0.83a 0.79a 0.02 <0.001 C20:0 0.19 0.15 0.19 0.19 0.01 0.060 C20:1 n-9 0.73 0.79 0.80 0.76 0.03 0.289 C20:2 0.58 0.62 0.65 0.63 0.02 0.096 C20:4 n-6 0.23b 0.25ab 0.28a 0.28a 0.01 0.007 Saturated FA 37.14a 31.67c 32.79c 34.41b 0.39 0.034 Monounsaturated FA 46.37c 51.24a 48.78b 47.58bc 0.43 <0.001 Polyunsaturated FA 16.12 16.47 17.50 17.38 0.46 0.083 Unsaturated FA to Saturated FA ratio 1.68c 2.14a 2.01b 1.89b 0.04 <0.001 Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace acid oil; M = mixture of PO + OA at 50/50; FAs = fatty acids. a–c Values within a row with different superscripts differ significantly at P < 0.05. 1 n = 18. 6 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 Table 8 Fatty acid composition (g/100 g of FA) of Longissimus muscle from finishing pigs according to different dietary fat sources. Dietary treatments Item PO O OA M SEM1 P-value C14:0 1.05 1.06 1.06 1.06 0.03 0.988 C16:0 22.57a 21.70ab 21.60b 22.17ab 0.25 0.026 C16:1 2.50 2.68 2.57 2.58 0.10 0.642 C17:0 0.13 0.13 0.20 0.15 0.02 0.131 C18:0 12.51a 11.58b 11.99ab 12.04ab 0.15 0.001 C18:1 n-9 38.41b 41.32a 39.64ab 40.17ab 0.53 0.003 C18:1 n-7 3.18b 3.48a 3.30ab 3.27ab 0.07 0.024 C18:2 n-6 14.32 13.31 14.30 13.55 0.61 0.531 C18:3 n-3 0.38 0.41 0.41 0.39 0.02 0.485 C20:0 0.13 0.14 0.08 0.13 0.02 0.249 C20:1 n-9 0.62 0.63 0.63 0.64 0.01 0.687 C20:2 0.54 0.51 0.56 0.54 0.02 0.320 C20:4 n-6 3.13 2.81 3.19 2.99 0.19 0.487 C21:0 0.35 0.34 0.36 0.35 0.02 0.836 Saturated FA 36.75a 34.70b 35.32b 35.74ab 0.33 <0.001 Monounsaturated FA 44.71b 48.10a 46.16ab 46.69ab 0.66 0.006 Polyunsaturated FA 18.00 16.52 17.96 16.85 0.80 0.442 Unsaturated FA to Saturated FA ratio 1.71b 1.86a 1.82a 1.79ab 0.03 0.001 Abbreviations: PO = crude palm oil; O = crude olive pomace oil; OA = olive pomace acid oil; M = mixture of PO + OA at 50/50; FAs = fatty acids. a–b Values within a row with different superscripts differ significantly at P < 0.05. 1 n = 18. However, these results showed that including olive pomace Digestibility balance acid oil, rich in monounsaturated FA and free FA, at 5% in the growing-finishing diets decreased the average daily gain and In the present study, OA and M diets showed higher digestible therefore reduced the gain to feed ratio. Despite this, there are energy at the faecal level than the PO diet. However, this effect few studies that assess the effect of including fat by-products rich was not observed in the dietary digestible energy determined at in free FA on the growth performance of growing pigs. DeRouchey ileal level. The different results between the digestible energy mea- et al. (2004) observed a linear increase in average daily feed sured in faeces or in ileum could be explained by the effect of intake as the free FA concentration increased (up to 53% free microbiota present in the hindgut (Stein, 2017); therefore, the FA; MIU < 3.3) when choice white grease was included in wean- results obtained at ileal level are more representative. Although ing pigs’ diets. Rojas-Cano et al. (2014) did not find an improve- no statistical differences were observed in this study, a numerical ment in the performance of growing pigs when the dietary energy reduction of digestible energy at ileal level for OA and M could level was increased by including increasing levels of olive acid oil be explained by the higher MIU content in these fat sources. Study- up to 75 g/kg. However, Vilarrasa et al. (2015) observed no differ- ing the effect of dietary treatments on digestibility of FA, and con- ences in the growth performance of growing pigs fed palm fatty cerning ATTD, the present results showed that PO had the lowest acid distillates (53% of free FA) in contrast to palm oil added at FA digestibility among the dietary treatments under study. As 4%. The inconsistent results among studies that include free FA expected, as dietary unsaturation increases, digestibility also rich sources in swine diets might be explained by the high vari- increases (Cho and Kim, 2012; Duran-Montgé et al., 2007). Other- ability in the composition and quality of available fat by- wise, no differences were observed between O and OA in total FA, products. It has been stated that the MIU value of the added acid despite the higher free FA content in the latter. There are contro- oils and fatty acid distillates could lead to a decrease in the DE of versial results in the literature about the effects of free FA on FA pigs (Wiseman et al., 1992; Varona et al., 2021b). In agreement digestibility. The results from the present study are in agreement with this, the present study found the highest MIU values for with those found by DeRouchey et al. (2004), who observed no dif- olive pomace acid oil (12.67%), while crude olive pomace oil or ferences in FA digestibility when free FA levels were increased in crude palm oil had values of 4.64 and 0.49%, respectively. choice white grease fed to weaning pigs. In addition, Vilarrasa Although most of the studies available in the literature did not et al. (2015) did not obtain different results in FA digestibility report values of MIU, it is important to highlight the significance when they compared palm fatty acid distillates with crude palm of knowing the non-energetic fraction of dietary added fats for a oil in growing-finishing pigs. On the contrary, Powles et al. correct assessment of their DE value. (1993) concluded that the level of free FA in the diet of growing The present results also show that including olive pomace acid pigs appeared to be determinant for the digestible energy value oil at 2.5% in a blend with 2.5% crude palm oil achieved similar of fats. It has been proposed that the negative effects of free FA growth performance results as PO or O. It is well established that on FA digestibility are related to its reaction with ionised minerals, blending different fats and oils with different chemical composi- such as calcium and magnesium, which form insoluble soaps that tions (differing in saturation degree, chain length or molecular cause both the free FA and the mineral to become unavailable for structure) produces positive interactions in terms of energy and absorption (Small, 1991). However, this effect is mainly related FA utilisation (Zumbado et al., 1999; Roll et al., 2018). Moreover, to long-chain saturated FA rather than to unsaturated FA, as the blending olive pomace acid oil with a high quality fat source with former has a greater ability to form insoluble soaps than the latter low MIU content, such as crude palm oil, dilutes the final MIU con- (Atteh and Leeson, 1985). This suggests that the negative effect of tent of the blend. With this, the use of the fat blend did not impair free FA on FA digestibility is restricted to saturated sources of free performance parameters, so our results suggest that olive pomace FA (Wiseman and Salvador, 1991). acid oil can be included in growing-finishing swine diets, blended Blending 2.5% olive pomace acid oil and 2.5% crude palm oil is a with conventional crude palm oil, achieving a combination of tria- suitable option in terms of FA utilisation. In general, M showed AID cylglycerols and free FA and a moderate level of MIU. and ATTD values above the arithmetically predicted values 7 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 obtained from the two individual fats. This phenomenon is fre- wet weight; Cagnazzo et al., 2006). Higher IMF content levels have quently referred to as synergism (Powles et al., 1993; Wiseman been linked with a better sensory quality of pork (Font-i-Furnols et al., 1998). First, a synergic effect occurs when unsaturated and et al., 2012). The use of Duroc-finished lines in a commercial envi- saturated fats are blended, since long-chain unsaturated FAs are ronment is an alternative for obtaining meat products with a more able to form mixed micelles than long-chain saturated FAs higher IMF content and therefore fulfilling sensory acceptance by are. Therefore, the presence of unsaturated FA can increase the consumers. capacity to take up saturated FA in the core of mixed micelles, Our results confirm that the IMF content can be modified improving their absorption (Vilarrasa et al., 2015; Rodriguez- through changes in the fat source added to growing-finishing pig Sanchez et al., 2019). Second, it has been suggested that increasing diets, as supplementation of crude olive pomace oil increased the amounts of diacylglycerols or monoacylglycerols have a positive IMF content above the other diets of the study. Present results effect on free FA digestibility because their emulsifying effect were consistent with data reported by Miller et al. (1990), who enhances the inclusion of free FA in mixed micelles (Roll et al., observed higher IMF levels in pigs fed diets rich in oleic acid. In 2018). In agreement with our results, Zumbado et al. (1999) addition, Isabel et al. (2004) found a higher IMF content in described a synergistic effect on digestibility and dietary apparent growing-finishing pigs when the monounsaturated FA to polyun- metabolisable energy values of broiler chickens when unsaturated saturated FA ratio was increased. In the work of Gerfault et al. and saturated fats rich in free FA were blended. The synergic effect (2000), higher concentrations of oleic acid and lower of linoleic observed between 2.5% olive pomace acid oil and 2.5% crude palm acid (therefore, a higher monounsaturated FA to polyunsaturated oil could be due to it being an adequate unsaturated FA to satu- FA ratio) in porcine skeletal muscle and adipose tissue had been rated FA ratio, with the presence of monounsaturated FA from associated with higher lipogenic enzyme activity. In agreement OA and a high proportion of monoacylglycerols from the lipolysis with this, in the present study, O had the highest monounsaturated of palm triacylglycerols, capable of better solubilising free FA in FA to polyunsaturated FA ratio both in the diet (1.46) and in LM the mixed micelle and facilitating its absorption. (2.91) among treatments, while PO had the lowest (1.25 in the In our study, ATTD showed higher values than AID for digestible diet; 2.48 in LM), and hence the lowest IMF values. Alternatively, energy and for all FA except for saturated FA, which means that other nutritional strategies have been applied to reach high IMF energy and unsaturated FA that were not absorbed at the end of levels in pork. Some authors have observed an increase in IMF the ileum disappeared in the hindgut. Duran-Montgé et al. levels when the protein to digestible energy ratio is decreased; (2007) also reported higher values for unsaturated FA ATTD than however, this also may have a negative effect on performance the corresponding AID, and lower values for saturated FA. This (Kerr et al., 1995; D’Souza et al., 2003). Higher IMF content effect may be explained by a biohydrogenation of oleic, linoleic (+53%) has been reported when growing-finishing pigs are fed a and linolenic acids that are saturated by the microflora and, in part, diet deficient in vitamin A, as retinoic acid, a derivative of vitamin converted into stearic acid (Jørgensen and Fernández, 2000; A, could inhibit the terminal differentiation of intramuscular adi- Duran-Montgé et al., 2007). Thus, the low values (or even negative pose tissue (D’Souza et al., 2003). However, although these nutri- for O and OA) obtained in the ATTD of stearic acid could be tional manipulations increased the IMF content, they also led to explained due to this microbial activity. Moreover, C15:0 and other detriments and disadvantages in the pigs’ performance, C17:0, which were not present in the diet, were observed in faecal which made their application unviable in a commercial environ- samples, and were probably generated by microbial synthesis. In ment. Alternatively, the work of Katsumata et al. (2005) showed relation to this, the differences between sexes in the ATTD of FA that a defined lysine deficiency (about a 40% of reduction in recom- obtained in the present study may be affected by these effects, mended dietary lysine levels) in finishing pigs’ diets was an effec- since no differences were observed in any FA in the AID. Although tive way of increasing IMF without affecting performance. Our it is generally accepted to report digestibility of fat as total tract results suggest that increasing dietary monounsaturated FA by digestibility, these findings suggest that using ileal digestibility is including crude olive pomace oil may be another good nutritional more accurate for the FA digestibility and estimates the nutritive strategy to both increase IMF content in the LM of pigs and achieve value of fats better than faecal digestibility. Moreover, the interac- a good performance. tion generated by microbial biohydrogenation of unsaturated FA in the hindgut can be avoided in this way (Stein, 2017). Fatty acid composition of backfat and Longissimus muscle Carcass quality and intramuscular fat The FA profile of both the backfat and LM was affected by the dietary fat, which is in agreement with the literature (Miller The dietary supplementation of crude and acid oils from olive et al., 1990; Vilarrasa et al., 2015). In particular, the use of O or pomace oils did not modify carcass weight, yield and lean percent- OA as an alternative to PO reduced saturated FA and increased age, or ham fat and backfat thickness. However, supplementation the unsaturated FA to saturated FA in both the backfat and LM. with crude olive pomace oil lead to an increase in IMF content in Other studies have reported that reducing saturated FA while the LM. Although there is a relationship between loin and ham fat- increasing monounsaturated FA content in meat has health bene- ness and IMF content, the correlation is not very high, varying fits for consumers (Mateos et al., 2019). Specifically, it has been between 0.28 and 0.49 (Font-i-Furnols et al., 2019). Generally, a observed that including olive pomace cake in growing-finishing 5% increase in carcass fat corresponds only to a 1% increase in pig diets makes it possible to reduce saturated FA in porcine adi- IMF (Hocquette et al., 2010) due to the lower proliferative potential pose tissue (Ferrer et al., 2020). Overall, animals fed O lead to meat or low activity levels of lipogenesis enzymes in intramuscular pre- products with more IMF, rich in monounsaturated FA, with high FA adipocytes compared to subcutaneous adipocytes (Gardan et al., digestibility values and good performance parameters. Thus, this 2006). Consequently, changes in IMF content are difficult to note, pork should result in both better sensory-perceived and healthier especially in commercial lean breeds such as Landrace or Pietrain. products. Similar effects were obtained when OA was used blended However, in high-fat content crossbreed pigs such as Duroc, with a common saturated fat source such as PO. In addition, it is changes in IMF content may be accentuated. Samples of LM from important to note that the use of fat by-products could also reduce the present study (Duroc-finished pigs) showed a higher IMF con- feeding costs, as they usually have competitive prices. tent (an average of 2.05 ± 0.65%) than other values recorded in In conclusion, crude olive pomace oil can be included at 5% in commercial lean breeds such as Landrace or Pietrain (0.5–2.5% of growing-finishing pig diets to obtain a meat rich in monounsatu- 8 G. Verge-Mèrida, A.C. Barroeta, F. Guardiola et al. Animal 15 (2021) 100389 rated FA and low in saturated FA content with high fatty acid Financial support statement digestibility values and performance. Moreover, the inclusion of crude olive pomace oil lead to a higher IMF content in the Longis- This work was carried out thanks to the financial support pro- simus muscle. Another dietary strategy is to include olive pomace vided by the Ministerio de Economía y Competitividad of the Span- acid oil blended with crude palm oil in feed formulation, which ish Government (project AGL2015-64431-C2-1-R, MINECO/FEDER, did not negatively impact fat utilisation or performance. In addi- UE), by bonÀrea AGRUPA and a pre-doctoral research grant from tion, including this by-product reduced feed costs, resulting in a the Ministerio de Ciencia, Innovación y Universidades of the Span- swine production of high-fat content crossbreeds that is more effi- ish Government (Ref. FPU17/02263). cient and environmentally sustainable. 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