Soybean lecithin as an alternative energy source for grower and finisher broiler chickens: impact on performance, fatty acid digestibility, gut health, and abdominal fat saturation degree A. Viñado, L. Castillejos,1 and A. C. Barroeta Animal Nutrition and Welfare Service, Department of Animal and Food Science, Facultat de Veterin a ria, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain ABSTRACT An experiment was performed to assess and histomorphometry. No effects were associated with the inclusion of soybean lecithin (SL) in the replacement of SO replacement by SL on performance (P . 0.05), ileal soybean oil (SO), for grower and finisher broiler chicken digestibility of total, saturated and monounsaturated FA diets (up to 15 d of life), and its effects on performance, (P . 0.05), nor jejunal morphology (P . 0.05). Total fatty acid (FA) absorption, gut health, and saturation replacement of SO by SL reduced ileal absorption of degree of the abdominal fat pad (AFP). A total of 1,440 polyunsaturated FA (P , 0.02) and increased jejunal female Ross-308 chickens were distributed in 60 pens and Lactobacillus spp. counts (P 5 0.049). Higher levels of SL were fed 5 experimental diets. The control diet (T1) was inclusion (T4 and T5) lowered polyunsaturated FA supplemented with SO (grower and finisher diets at concentration of the AFP (P 5 0.002) and, thus, slightly 2.00%), and 4 levels of SL were included in replacement: reduced its unsaturated-to-saturated FA ratio T2 (0.25% in grower and 0.50% in finisher diets), T3 (P 5 0.005). Soybean lecithin inclusion did not modify (0.50% in grower and 1.00% in finisher diets), T4 (0.75% in performance parameters, total FA absorption, nor jejunal grower and 1.50% in finisher diets), and T5 (1.00% in morphology, however caused changes on polyunsaturated grower and 2.00% in finisher diets). At day 39, titanium FA absorption, jejunal microbiota, and saturation degree dioxide was added to finisher diets at 5 g/kg to perform a of the AFP. The study demonstrates that soybean lecithin digestibility balance. At day 46, AFP, tissue, and gut can be included, in combination with or in replacement digesta samples were collected to characterize FA of soybean oil, as an alternative energy source for grower digestibility, adipose saturation degree, microbial groups, (up to a 1%) and finisher broiler diets (up to 2%). Key words: soybean lecithin, soybean oil, fatty acid, phospholipid, free fatty acid 2020 Poultry Science 99:5653–5662 https://doi.org/10.1016/j.psj.2020.06.050 INTRODUCTION (Thormar et al., 2006; Khatun et al., 2018), and carcass quality parameters (Smink et al., 2008; Gonzalez-Ortiz Fats and oils are commonly included in broiler feeds to et al., 2013). increase the energetic density of the diets; however, their Currently, there is a growing interest in the search and inclusion is highly dependent on their chemical composi- use of alternative energy sources in broiler feeding. In tion and economic cost. It has been demonstrated that this context, coproducts derived from the soybean oil the saturation degree and composition in different lipid (SO) refinement process represent an economic alterna- molecular structures have an important influence on per- tive and permit giving an added value to residual prod- formance parameters (Vieira et al., 2006; Ferrini et al., ucts. Soybean lecithin (SL), which is extracted from 2008), fatty acid (FA) absorption (Tancharoenrat et al., the SO degumming process, is mainly composed of polar 2013; Roll et al., 2018), gastrointestinal health lipids (.60%), especially of phospholipids (PL), but also contains an important amount of neutral lipids (30– 40%), as triacylglycerols and free fatty acids (FFAs) Ó 2020 The Authors. Published by Elsevier Inc. on behalf of Poultry (van Nieuwenhuyzen and Tomas, 2008; Bueschelberger Science Association Inc. This is an open access article under the CC BY- et al., 2015; EFSA, 2016). Furthermore, SL represents NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Received February 24, 2020. a good source of phosphorus, choline, and energy for Accepted June 17, 2020. broiler chickens (Mateos et al., 2012; Borsatti et al., 1 Corresponding author: lorena.castillejos@uab.cat 2018), and its combination with other fats and oils could 5653 5654 VIñADO ET AL. be interesting to exploit positive synergies on lipid utili- and 1.00% in finisher diets), T4 (0.75% in grower and zation (Jones et al., 1992; Ravindran et al., 2016). 1.50% in finisher diets), and T5 (1.00% in grower and Available literature indicates that SO replacement by 2.00% in finisher diets). SL, in starter broiler diets, impairs growth performance Broiler BW and feed intake were recorded for the pen (Azman and Ciftci, 2004), reduces feed apparent metab- (24 birds) at day 14, 28, and 39. The data were used to olizable energy content (Huang et al., 2007; Viñado measure BW and calculate the average daily gain et al., 2019), and lowers the total tract apparent digest- (ADG), average daily feed intake, and the feed conver- ibility of the polyunsaturated FA (PUFA; Viñado et al., sion ratio (FCR) of each period and the overall results. 2019). On the contrary, in grower-finisher diets, a few re- Mortality was daily recorded to adjust average daily searchers have indicated that SL can partially replace feed intake and ADG. At day 39, three animals of each SO without modifying energy utilization (Huang et al., pen (6 replicates per treatment) were chosen based on 2007; Viñado et al., 2019) and total-tract apparent FA pen mean BW (a total of 90 animals) and received the digestibility (Viñado et al., 2019). finisher diet with titanium dioxide (TiO2) at 5 g/kg Therefore, the present study was designed with the from day 40 to day 46. The rest of the animals were aim to evaluate increasing rates of SO replacement by slaughtered in a commercial abattoir. At day 46, broiler SL in grower and finisher diets, assessing its effects on chickens were euthanized with the aim to collect sam- growth performance, ileal FA absorption, jejunal ples. The ileal content (from Meckel’s diverticulum to morphology, jejunal microbiota, and the FA profile of a point 1 cm proximal to the ileocecal junction) of all the abdominal fat pad (AFP). birds within a pen was pooled, homogenized, freeze- dried, ground, and kept at 4 C until laboratory analysis. MATERIALS AND METHODS A representative sample of the AFP (from the proven- triculus surrounding the gizzard down to the cloaca) of Experimental Diets, Animal Husbandry and each bird was taken, pooled by replicate, frozen at Sampling 220 C, and analyzed to determine the FA profile. Finally, jejunum tissue and digesta content from T1 This experiment was in accordance with the European and T5 animals were collected to evaluate the effect of Union guidelines for the care and use of animals in using either SO or SL as added fats on jejunal research (European Parliament, 2010) and was approved morphology and microbiota. by the Animal Ethics Committee of the Universitat Autonoma de Barcelona. Laboratory Analyses The experiment was performed in a farm under controlled conditions (Granja Sole, Vila-Rodona, Regarding experimental oil characterization, SO and Spain). A total of 1,440 newly hatched Ross 308 female SL were analyzed in duplicate for FA composition, by broiler chickens were obtained from a local hatchery gas chromatography, according to the methylation (Pondex S.A.U., Juneda, Spain). On arrival, the animals method described by Guardiola et al. (1994). In addition, were weighed and randomly distributed in 60 pens with the acid value was determined according to ISO 660 24 birds per pen. Replicates were allocated for a homoge- (2009), and the acidity was indicated as the FFA percent- neous distribution of treatments and started with a age of oleic acid. The acetone insoluble determination was similar BW mean. Each pen was equipped with a pan performed following the Ja-4-46 analytical method from feeder and a bell waterer, and both, experimental feed American Oil Chemist’s Society (2017), and PL composi- and water, were provided ad libitum throughout the tion was determined by HPLC following Helmerich and whole trial. Temperature, humidity level, and light pro- Koehler (2003) methodology. Experimental feed samples gram used were according to the specifications in the were taken at the beginning and end of each experimental Ross 308 lineage management handbook (Aviagen, period and were ground and kept at 4 C until further 2014). Twice daily, animals and housing facilities were analysis. Diet proximate analysis was performed accord- inspected for general health status, constant feed, dead ing to the methods of AOAC International (2005): ether birds, and water supply, as well as temperature and extract (Method 920.39), crude protein (Method 968.06), ventilation. and crude fiber (Method 962.09). Furthermore, feed and The feeding program was divided into 3 phases: starter excreta samples analysis included ash determination (from 0–14 d), grower (from 15–28 d), and finisher (from (Method 942.05), dry matter (Method 934.01), and GE 29 d to the end of the experiment). All experimental diets content by adiabatic bomb calorimeter (IKA-Kalorime- were based on wheat and soybean meal and formulated to ter system C4000; Staufen, Germany). FA content was meet or exceed Fundacion Española Desarrollo Nutricion analyzed adding nonadecanoic acid (Sigma-Aldrich, St. Animal (2008) requirements, as is seen in Table 1. Ani- Louis, MO) as an internal standard and following the mals were fed 5 experimental treatments (12 replicates method described by Sukhija and Palmquist (1988) in per treatment) during grower and finisher phases, as is feed and ileal content, whereas in the case of AFP, the detailed in Table 2. The control diet (T1) was supple- method described by Carrapiso et al. (2000) was per- mented with SO at 2% (grower and finisher diets), and formed. The final extract obtained was injected in a gas 4 levels of SL were included replacing SO: T2 (0.25% in chromatograph following the method conditions grower and 0.50% in finisher diets), T3 (0.50% in grower described by Cortinas et al. (2004). TiO2 was analyzed SOYBEAN LECITHIN AS ENERGY SOURCE 5655 Table 1. Ingredient composition of experimental basal diets (%, as fed basis). Ingredients (%) Starter diet (0–14 d) Grower diet (15–28 d) Finisher diet (from 29 d) Wheat 29.75 49.37 46.06 Soybean meal 47% 27.40 23.65 22.82 Corn 15.10 0.00 0.00 Barley 9.78 11.74 17.62 Extruded full-fat soybean 9.17 4.58 0.00 Added fats 2.00 3.25 4.50 Rapeseed meal 00 0.0 1.52 3.43 Sepiolite 1.99 1.99 1.99 Trace mineral-vitamin premix1 1.43 1.13 1.15 Calcium carbonate 1.23 1.05 0.93 Monocalcium phosphate 0.96 0.64 0.49 Salt 0.35 0.21 0.23 L-lysine 0.30 0.31 0.29 DL-methionine 0.30 0.25 0.22 Sodium bicarbonate 0.09 0.16 0.12 L-threonine 0.08 0.08 0.08 Choline chloride 75% 0.07 0.07 0.07 1 Provides per kg feed: vitamin A (from retinol), 13,500 IU; vitamin D3 (from cholecalciferol), 4,800 IU; vitamin E (from alfa-tocopherol), 49.5 IU; vitamin B1, 3 mg; vitamin B2, 9 mg; vitamin B6, 4.5 mg; vitamin B12, 16.5 mg; vitamin K3, 3 mg; calcium pantothenate, 16.5 mg; nicotinic acid, 51 mg; folic acid, 1.8 mg; biotin, 30 mg; Fe (from FeSO4$7H2O), 54 mg; I [from Ca(I2O3)2], 1.2 mg; Co (from 2CoCO3$3Co(OH)2$H2O), 0.6 mg; Cu (from CuSO4$5H2O), 12 mg; Mn (from MnO), 90 mg; Zn (from ZnO), 66 mg; Se (from Na2SeO3), 0.18 mg; Mo [from (NH4)6Mo7O24], 1.2 mg; b-glucanase 350 IU; xylanase 1,125 IU; Organic acids (starter diets at 4 g/kg; grower and finisher diets at 3 g/kg). on finisher diets and ileal digesta following the methodol- perform microbiota counts. Diluted digesta samples ogy described by Short et al. (1996). were inoculated on azide glucose, MacConkey, and MRS (de Man, Rogosa and Sharpe) agar (Oxoid Limited, Jejunal Histomorphometry and Microbial Hampshire, United Kingdom) for microbial counts of Counts of Digesta Enterococcus faecium, Enterobacteria, and Lactobacillus spp., respectively. Counts were manually read after 24-h A distal jejunum segment of 5 cm (close to Meckel’s incubation at 37 C. diverticulum) was excised, flushed with sterile PBS, and fixed by immersion in a 3.7 to 4.0% neutral buffered Calculations and Statistical Analysis formaldehyde solution (PanReac AppliChem, Castellar del Valles, Spain). Once fixed, 6 cross sections were ob- The FA apparent ileal digestibility coefficients were tained from each jejunum, embedded in paraffin, and calculated as follows: ileal digestibility coefficient 5 1- prepared and stained with hematoxylin/eosin for further {(TiO2/FA)d/(TiO2/FA)i}, where (TiO2/FA)d is the observations in a light microscope (BHS-Olympus, concentration of the inert marker and the FA in the diet, Tokyo, Japan). The histomorphometric indexes evalu- and (TiO2/FA)i is the concentration of the inert marker ated were villus height (VH: from the villus tip to the and the FA in the ileal digesta. crypt junction), crypt depth (CD: from the villus bottom Pen means (24 birds) were used as the experimental to the crypt), and the ratio between VH and CD unit for performance parameters (12 replicates per treat- (VH:CD). The analysis was performed on 10 well- ment). In the case of the digestibility balance and the FA oriented and intact villi and 10 crypts, according to profile of AFP, pen means (3 birds) were used as the methodology described by Schiavone et al. (2018). Mea- experimental unit (6 replicates per treatment). Microbi- sures were taken using ImageJ (1.8.0; NIH; Bethesda, al counts (log transformation for statistical analysis) and MD) via software analysis. histomorphometric analysis were performed on T1 and Jejunal digesta samples were collected in sterile condi- T5, the pen being the experimental unit (6 replicates tions and were stored at 4 C until further analysis. Sam- per treatment). A Shapiro-Wilk test indicated a normal ples were 10-fold serial diluted in Lactated Ringer’s distribution of the data. Data were analyzed by one-way Solution (Sigma-Aldrich Química, Madrid, Spain) to ANOVA using R Statistics (version 3.3.1; R Core Team, Table 2. Total added-fat inclusion in the experimental diets (%, as fed basis). Grower diet (15–28 d) Finisher diet (from 29 d on) Ingredients (%) Starter diet (0–14 d) T1 T2 T3 T4 T5 T1 T2 T3 T4 T5 Total added fats 2.00 3.25 3.25 3.25 3.25 3.25 4.50 4.50 4.50 4.50 4.50 Palm oil 0.00 0.50 0.50 0.50 0.50 0.50 1.00 1.00 1.00 1.00 1.00 Acid oil1 0.00 0.75 0.75 0.75 0.75 0.75 1.50 1.50 1.50 1.50 1.50 Soybean oil 2.00 2.00 1.75 1.50 1.25 1.00 2.00 1.50 1.00 0.50 0.00 Soybean lecithin 0.00 0.00 0.25 0.50 0.75 1.00 0.00 0.50 1.00 1.50 2.00 1 Monounsaturated acid oil (blending 50:50 of olive pomace acid oil and sunflower acid oil). 5656 VIñADO ET AL. Table 3. Chemical analysis of soybean oil (SO) and soybean replacement by SL did not modify any performance lecithin (SL) included in the experimental diets. parameter during the grower and the finisher phases Experimental fats (P . 0.05) nor during the overall period (P . 0.05). Item SO SL Fatty acid composition (%) 1 Ileal FA Digestibility Saturated fatty acids 16.0 23.4 C16:0 10.6 20.4 The effects of SO replacement by SL on ileal FA di- C18:0 4.24 2.97 gestibility are shown in Table 6. SO partial and total Monounsaturated fatty acids 23.4 18.4 replacement by SL in the finisher diets did not modify C18:1 u-9 21.8 18.4 Polyunsaturated fatty acids 60.6 58.2 the total FA (TFA), SFA, and MUFA digestibility C18:2 u-6 52.9 53.3 (P . 0.05). However, PUFA, linoleic, and linolenic ileal C18:3 u-3 7.67 4.81 absorption were lower in T3, T4, and T5 (SL inclusion of Minor fatty acids 2.85 N.D. UFA:SFA 5.25 3.27 1.00, 1.50, and 2.00%, respectively), in contrast to T1 PUFA:SFA 3.79 2.49 (P , 0.020). Acidity (%)1 Free fatty acids 1.30 14.6 Phospholipids (%)1 Jejunal Histomorphometry and Acetone insoluble N.D. 68.3 Total Phospholipids N.D. 44.0 Microbiological Counts of Digesta Phosphatidylcholine N.D. 13.5 Phosphatidylinositol N.D. 13.7 The effects of including either SO (T1) or SL (T5) at Phosphatidylethanolamine N.D. 9.15 2.00% in finisher diets on jejunal morphology and micro- Phosphatidic acid N.D. 7.02 Lysophosphatidylcholine N.D. 0.58 biological counts of digesta are shown in Table 7. The Gross energy (kcal/kg)1 9,602 7,937 different dietary added fats did not influence any morphological measurement (P . 0.05). Concerning je- Abbreviations: N.D., not determined; PUFA:SFA, polyunsaturated-to- saturated fatty acid ratio; UFA:SFA, unsaturated-to-saturated fatty acid junal microbiological counts, the use of SL instead of ratio. SO increased the Lactobacillus spp. population (P 5 0.049); nevertheless, no differences were observed 1 Percentage expressed of total product. regarding Enterobacteria and E. faecium (P . 0.05). Vienna, Austria), with treatment as the main factor and residual standard error estimated the average deviation FA Composition of AFP of any point from the statistical model. Tukey’s multiple range test was performed to determine whether means The effect of SL inclusion on the FA composition of were significantly different (P  0.05). AFP is presented in Table 8. Animals fed T1 showed a higher PUFA (P 5 0.002), concretely linoleic (P 5 0.003), and linolenic acid (P , 0.001) content RESULTS and tended to show a lower palmitic acid content than did animals fed diets with 1.50 and 2.00% SL supplemen- Chemical Composition of the Experimental tation (T4 and T5, respectively; P 5 0.068). Thus, SL Fats and Diets inclusion, as a replacer for SO, reduced the UFA:SFA (T1: 2.42 vs. T5: 2.25; P 5 0.005) and the PUFA:SFA The chemical composition of SO and SL and the chem- (0.88 vs. 0.75; P 5 0.004) of the AFP. ical composition of experimental diets are given in Tables 3 and 4. SO and SL were mainly composed of PUFA and differed in their respective saturated FA DISCUSSION (SFA) and monounsaturated FA (MUFA) content. Chemical Composition of the Experimental SL, in contrast to SO, presented a higher SFA content (23.4 vs. 16.0%, respectively) and a lower MUFA con- Fats and Diets tent (18.4 vs. 23.5%, respectively), hence a lower Fats and oils represent one of the most important unsaturated-to-saturated fatty acid ratio (UFA:SFA) energy-yielding ingredients for broiler chicken diets, and polyunsaturated-to-saturated fatty acid ratio thus their utilization is crucial for efficient growth. It (PUFA:SFA). Furthermore, SL presented higher acidity is widely recognized that SO, as a native oil, presents and lower gross energy content than did SO (7,937 vs. most of its FA structured as triacylglycerols (.90%; 9,602 kcal/kg). The experimental diets were closely B~aiao and Lara, 2005), whereas the SL used in the cur- similar between treatments regarding protein and ether rent experiment presented most of its FA structured extract content; however, they slightly differed in their into PL (44%; Table 3) and 15% of its FA remained respective FA composition. free and unesterified. The chemical composition of SO and SL was in accordance with existing literature Performance Parameters (Øverland et al., 1993; Soares and Lopez-Bote, 2002; Viñado et al., 2019). Furthermore, the FA profile of The effects of SO substitution by SL on performance the experimental diets was influenced by the FA con- parameters are seen in Table 5. SO partial and total tent of SO, SL, and the rest of the added fats (palm SOYBEAN LECITHIN AS ENERGY SOURCE 5657 Table 4. Analyzed gross energy, macronutrient content, and fatty acid composition for starter, grower, and finisher diets. Grower diet1 (15–28 d) Finisher diet2 (from 29 d on) Starter Item diet (0–14 d) T1 T2 T3 T4 T5 T1 T2 T3 T4 T5 Macronutrient content (%) Dry matter 89.73 90.88 91.26 90.45 90.36 90.35 90.31 89.91 90.15 90.64 90.61 Crude protein 21.62 19.16 19.42 19.26 19.49 19.16 18.45 18.32 18.35 18.26 18.44 Crude Fat 5.53 5.34 5.28 5.15 5.02 5.23 5.68 5.37 5.34 5.38 5.24 Crude Fiber 3.31 4.04 4.12 4.38 4.19 3.90 4.07 3.59 3.68 3.95 3.79 Ash 7.67 6.51 7.21 6.86 6.74 6.78 6.02 6.29 6.33 6.37 6.47 Fatty acid composition (%) Saturated fatty acids 17.6 21.0 21.1 21.6 21.8 22.0 24.3 24.9 25.3 25.8 26.5 C16:0 13.4 16.1 16.3 16.7 16.9 17.1 18.7 19.3 19.7 20.1 20.8 C18:0 3.02 3.63 3.57 3.57 3.66 3.65 4.16 4.16 4.18 4.21 4.27 Monounsaturated fatty acids 22.4 26.0 25.8 25.1 25.2 25.0 27.8 27.3 27.1 26.9 26.8 C18:1 u-9 20.1 23.8 23.4 22.8 22.6 22.4 25.4 24.9 24.7 24.4 24.4 Polyunsaturated fatty acids 60.0 53.0 53.1 53.3 53.0 53.0 47.9 47.8 47.6 47.3 46.7 C18:2 u-6 54.1 47.9 47.9 48.1 47.9 47.9 43.6 43.7 43.5 43.4 42.9 C18:3 u-3 5.96 5.24 5.20 5.14 5.13 5.12 4.29 4.19 4.09 3.98 3.82 Minor fatty acids 3.49 3.48 3.59 3.67 3.93 3.92 3.82 3.78 3.82 3.88 3.91 UFA:SFA 4.68 3.76 3.74 3.63 3.59 3.55 3.12 3.02 2.95 2.88 2.77 PUFA:SFA 3.41 2.52 2.52 2.47 2.43 2.41 1.97 1.92 1.88 1.83 1.76 Gross energy (kcal/kg) 4,183 4,249 4,258 4,235 4,155 4,180 4,231 4,181 4,196 4,192 4,179 Abbreviations: UFA:SFA, unsaturated-to-saturated fatty acid ratio; PUFA: SFA, polyunsaturated-to-saturated fatty acid ratio. 1 T1 5 soybean oil (SO) at 2%; T2 5 SO at 1.75% and soybean lecithin (SL) at 0.25%; T3 5 SO at 1.5% and SL at 0.5%; T4 5 SO at 1.25% and SL at 0.75%; T5 5 SO at 1% and SL at 1%. 2 T1 5 SO at 2%; T2 5 SO at 1.5% and SL at 0.5%; T3 5 SO at 1% and SL at 1%; T4 5 SO at 0.5% and SL at 1.5%; T5 5 SL at 2%. oil and monounsaturated acid oil). The gradual replace- Performance Parameters ment of SO by SL increased dietary SFA concentration (19%; T1 vs. T5 finisher diets) and reduced the The chemical differences observed between SO and SL UFA:SFA and PUFA:SFA ratios (211%; T1 vs. T5 may have influenced growth performance parameters finisher diets). However, in general terms, all the exper- because of the different lipid molecular structures, such imental diets were unsaturated, with PUFA being the as triacylglycerols, PL, and FFA influence on lipid diges- most abundant. tion and absorption (Ravindran et al., 2016; Roll et al., Table 5. Growth performance of broiler chickens according to soybean lecithin inclusion level in the grower and finisher diets. Dietary treatments Item T1 T2 T3 T4 T5 RSE P value 1 Starter period (0–14 D) BW 0 d (g) 42.09 41.98 42.03 42.09 42.10 0.176 0.337 BW 14 d (g) 453 459 454 456 459 13.8 0.792 ADFI (g/d/bird) 40.5 40.4 40.4 39.8 40.4 1.07 0.571 ADG (g/d/bird) 29.4 29.8 29.4 29.6 29.8 0.99 0.812 FCR (g/g) 1.37 1.37 1.36 1.35 1.35 0.030 0.305 Grower period (15–28 d)2 BW 28 d (g) 1,552 1,544 1,531 1,541 1,551 36.74 0.647 ADFI (g/d/bird) 121.6 120.3 120.1 119.5 121.8 2.65 0.182 ADG (g/d/bird) 77.7 77.6 76.9 77.8 78.4 0.07 0.436 FCR (g/g) 1.56 1.57 1.56 1.54 1.56 0.024 0.195 Finisher period (29–39 d)3 BW at 39 d (g) 2,439 2,422 2,443 2,437 2,442 73.52 0.961 ADFI (g/d/bird) 173.1 173.5 174.7 174.5 175.5 6.59 0.909 ADG (g/d/bird) 81.2 78.5 83.3 81.2 80.7 5.27 0.324 FCR (g/g) 2.14 2.21 2.13 2.16 2.18 0.100 0.293 Global period (0–39 d) ADFI (g/d/bird) 106.0 106.8 106.5 106.4 107.7 2.57 0.612 ADG (g/d/bird) 61.22 60.61 61.43 61.20 61.45 1.99 0.842 FCR (g/g) 1.74 1.76 1.74 1.73 1.75 0.03 0.154 Abbreviations: ADFI, average daily feed intake; ADG, average daily gain; BW, body weight; FCR, feed conversion ratio; RSE, residual standard error. 1 All pens consumed the same starter diet. 2 T1 5 soybean oil (SO) at 2%; T2 5 SO at 1.75% and soybean lecithin (SL) at 0.25%; T3 5 SO at 1.50% and SL at 0.50%; T4 5 SO at 1.25% and SL at 0.75%; T5 5 SO at 1.00% and SL at 1.00%. 3 T1 5 SO at 2.00%; T2 5 SO at 1.50% and SL at 0.50%; T3 5 SO at 1.00% and SL at 1.00%; T4 5 SO at 0.50% and SL at 1.50%; T5 5 SL at 2.00%. 5658 VIñADO ET AL. Table 6. Apparent ileal digestibility coefficients of fatty acids according to soybean lecithin inclusion level during the digestibility balance performed from day 40 to day 46 of life. Dietary treatments1 Item T1 T2 T3 T4 T5 Residual standard error2 P value Total fatty acids 0.84 0.81 0.79 0.79 0.80 0.036 0.229 Saturated fatty acids 0.77 0.77 0.78 0.76 0.78 0.046 0.945 C16:0 0.77 0.77 0.78 0.76 0.78 0.046 0.915 C18:0 0.78 0.79 0.80 0.79 0.79 0.045 0.960 Monounsaturated fatty acids 0.85 0.84 0.83 0.81 0.82 0.031 0.331 C18:1 u-9 0.85 0.84 0.83 0.81 0.83 0.031 0.364 Polyunsaturated fatty acids 0.85a 0.82a,b 0.78b 0.78b 0.80b 0.035 0.017 C18:2 u-6 0.85a 0.82a,b 0.78b 0.78b 0.80b 0.035 0.019 C18:3 u-3 0.85a 0.83a,b 0.78c 0.78c 0.79b,c 0.039 0.016 Values within the same row with no common superscripts are significantly different, P  0.05. 1 T1 5 soybean oil (S) at 2.00%; T2 5 S at 1.50% and soybean lecithin (L) at 0.50%; T3 5 S at 1.00% and L at 1.00%; T4 5 S at 0.5% and L at 1.50%; T5 5 L at 2.00%. 2 Residual standard error of 3 chickens per replicate (6/six replicates per treatment). 2018). Nevertheless, the results obtained in the present It is important to highlight that no effects were experiment have indicated that SO replacement by SL, observed on feed intake despite SL containing 17% less in grower and finisher diets, did not modify the perfor- gross energy than SO (9,602 vs. 7,937 kcal/kg; mance parameters in any phase or of the trial overall. Table 3). This finding is in accordance with that of This finding was consistent with data reported by Mandalawi et al. (2015), who observed, in laying hens, Viñado et al. (2019), where SO partial replacement by that pork fat replacement by SL did not modify feed SL (1.00 and 2.00 of 3.00% of total fat addition), in intake, even though the SL used was 16% less energetic grower-finisher broiler diets, did not alter growth perfor- than the pork fat (32.6 vs. 38.9 MJ/kg). This fact might mance or energy and FA utilization. Furthermore, our indicate that the inclusion of SL, instead of SO, results also agreed with those of Azman and Ciftci improved the energy utilization of the experimental diets (2004), who observed that a SO partial replacement by that also contained palm and acid oil as added fats SL (1.50 and 3.00 of 6.00% of total fat addition) did (Table 2). Several researchers have demonstrated that not modify BW or FCR in grower-finisher broiler blending different fats and oils with different chemical chickens. Other researchers have stated that soybean- compositions (FA chain length, saturation degree, and lecithin inclusion, as an alternative to saturated added lipid molecular structures) produces positive interac- fats such as tallow or lard, is acceptable without a nega- tions in terms of energy and FA utilization (Blanch tive impact on the productive performance of broiler et al., 1995; Borsatti et al., 2018; Roll et al., 2018). chickens (Cantor et al., 1997; Cox et al., 2000), laying Despite the lack of bibliography regarding dietary PL hens (Mandalawi et al., 2015), or weaned pigs (Jones digestion and absorption in poultry species, PL are et al., 1992; Reis de Souza et al., 1995; Øverland and recognized as energy-yielding molecules (Wang et al., Sundstøl, 1995). On the contrary, Huang et al. (2007) 2013; Ravindran et al., 2016) and are essential during observed, in grower-finisher broilers, that SO partial the solubilization of lipolysis products into the mixed mi- replacement by SL (0.50 and 1.00 of 2.00% of total fat celles (Krogdahl, 1985; Zaefarian et al., 2019). In addi- addition) improved the ADG and FCR. tion, several researchers have demonstrated that SL inclusion, in replacement of other added fats with a Table 7. Effects of either including soybean oil (T1) or soybean higher energetic density, improves dry matter and N lecithin (T5), as added fats, on jejunum morphology and retention in piglets (Jin et al., 1998) and the organic microbiological plate counts in broiler chickens of 46 d. matter utilization in laying hens (Mandalawi et al., Dietary treatments1 2015). Thus, SL beneficial effects may not be limited Item T1 T5 RSE P value only to lipid digestion and absorption. 2 Morphology measurements Villus height (mm) 1,347 1,254 167.0 0.358 Crypt depth (mm) 210 212 26.2 0.912 Ileal FA Digestibility VH:CD 6.21 6.11 0.235 0.585 Microbiology (log UFC/g)3 The use of SL instead of SO did not modify the ileal Enterococcus faecium 6.47 6.33 0.760 0.761 absorption of TFA, SFA, and MUFA at day 46. It is Enterobacteria 4.17 5.65 1.523 0.143 Lactobacillus spp. 8.31 8.54 0.158 0.049 well established that FA absorption is a process highly influenced by the saturation degree of FA (Ravindran Values within the same row with no common superscripts are signifi- et al., 2016; Rodriguez-Sanchez et al., 2019a), and as cantly different, P  0.05. Abbreviations: RSE, residual standard error; VH:CD, villus height-to- was commented previously, the FA profile of both SL crypt depth ratio. and SO was mostly polyunsaturated. The present results 1 T1 5 soybean oil at 2.00%; T5 5 soybean lecithin at 2.00%. were consistent with data reported by Huang et al. 2 Results are means of 10 measurements of intact villus and crypts per replicate. (2007), who observed that partial and total replacement 3 Pool of three chickens per replicate. of SO by a SL (2.00% of total fat addition) did not alter SOYBEAN LECITHIN AS ENERGY SOURCE 5659 Table 8. Fatty acid profile (%) of the abdominal fat pad at 46 d of age according to soybean lecithin inclusion. Dietary treatments1 Item (%) T1 T2 T3 T4 T5 RSE2 P value Saturated fatty acids 29.71 31.33 31.22 31.30 30.80 1.030 0.064 C16:0 23.02 24.20 23.91 24.40 24.41 0.767 0.068 C18:0 5.80 6.24 6.45 6.05 5.84 0.468 0.120 Monounsaturated fatty acids 44.25 44.38 43.14 45.56 44.66 1.655 0.191 C18:1 u-9 36.31 36.97 36.32 37.85 36.81 1.108 0.145 Polyunsaturated fatty acids 26.66a 25.73a,b 25.65a,b 23.14c 24.22b,c 1.347 0.002 C18:2 u-6 23.79a 23.07a,b 23.06a,b 20.74c 21.77b,c 1.217 0.003 C18:3 u-3 2.27a 2.12b 2.04b 1.90c 1.91c 0.101 ,0.001 UFA:SFA 2.42a 2.19b 2.20b 2.20b 2.25b 0.095 0.005 PUFA:SFA 0.88a 0.83a,b 0.82a,b 0.74b 0.75b 0.059 0.004 Values within the same row with no common superscripts are significantly different, P  0.05. Abbreviations: PUFA:SFA, polyunsaturated-to-saturated fatty acid ratio; RSE, residual standard error; UFA:SFA, unsaturated-to-saturated fatty acid ratio. 1 T1 5 soybean oil (SO) at 2.00%; T2 5 SO at 1.50% and soybean lecithin (SL) at 0.50%; T3 5 SO at 1.00% and SL at 1.00%; T4 5 SO at 0.5% and SL at 1.50%; T5 5 SL at 2.00%. 2 Residual standard error of a pool of 3 chickens per replicate. ether extract utilization in finisher broiler chickens (from within PL, could provide us essential information to 40–42 d of life). Similarly, Viñado et al. (2019) studied elucidate this fact. the effect of replacing SO by SL in grower-finisher broiler chickens (from 36–37 d) on total-tract FA digestibility and confirmed that partial and total replacement of Jejunal Histomorphometry and SO by SL (3% of total added fat inclusion) did not Microbiological Counts of Digesta modify TFA, SFA, or MUFA digestibility. Nevertheless, it is important to remark that SO The morphology of intestinal mucosa and microbial replacement rates equal to or higher than 1.00% by SL population represents 2 important biomarkers for evalu- reduced the ileal absorption of PUFA, linoleic, and lino- ating the gastrointestinal health in poultry species lenic acid. The same effect was also reported previously (Yegani and Korver, 2008; Ducatelle et al., 2018). by Viñado et al. (2019), where PUFA digestibility was Several studies have demonstrated that dietary fat is negatively affected with SO replacement by SL at 2.00 capable of modifying intestinal morphology (Khatun and 3.00% (3.00% of total fat inclusion). The mechanism et al., 2018; Sabino et al., 2018) and microbiota underlying this phenomenon is unclear; however, a (D€anicke et al., 1999; Jozefiak et al., 2014). hypothesis may be proposed. As mentioned before, SL Jejunum is the major site of lipid absorption contained 10 times more FFA than does SO (14.6 vs. (Rodriguez-Sanchez et al., 2019a), thus the enterocytes 1.30%; Table 3). In addition, the hydrolysis of PL and present in the jejunal villus tips play an important role triacylglycerols during dietary lipid digestion presents in dietary fat absorption. An increase of the VH is several differences that have also probably influenced. related to enhancements in nutrient absorption, whereas Triacylglycerols are hydrolyzed in a two-times step by deeper crypts are associated with higher tissue turnover the colipase-lipase complex, generating a sn-2-monoa- rates (Choct, 2009; de Verdal et al., 2010). In the current cylglycerol and 2 FFA, while PL are habitually catalyzed experiment, the replacement of SO by SL did not pro- by phospholipase A2, generating a sn-1-lysophospholipid duce modifications on jejunal morphology, supporting and a single FFA (Cohn et al., 2010; Wang et al., 2013). the performance and digestibility results. Several au- In the case of PL, in general terms, unsaturated FA is thors have demonstrated that the inclusion of lysoleci- concentrated at the sn-2 position, while saturated FA thins, products derived from the hydrolyzation of is normally located at the sn-1 position (Estiasih et al., lecithins and mainly composed of lysophospholipids, 2013). It is well studied that FA absorption is reduced promotes enhancements in the VH and VH:CD ratio of in their free form than if they are esterified as a monoa- broiler chicken jejunum (Boontiam et al., 2017; Chen cylglycerol (Blanch et al., 1995; Roll et al., 2018), and and Jung, 2019). Lysophospholipids are capable of this effect is more pronounced in unsaturated diets altering the lipid bilayer of cell membranes (Arouri and than in saturated diets (Rodriguez-Sanchez et al., Mouritsen, 2013), reduce the production of inflamma- 2019b). Furthermore, FFA tends to form insoluble soaps tory mediators (Hartmann et al., 2009), and modify with divalent cations, such as calcium, reducing its gene expression (Chen and Jung, 2019). Our hypothesis absorption (Small, 1991). Thus, a higher SL content in was based on the fact that dietary PL digestion implies FFA and the hydrolytic activity of phospholipase A2 the release of lysophospholipids into the broiler gut; may cause the lower utilization of PUFA in the animals therefore, SL inclusion might improve jejunal fed diets with SL as added fat instead of SO. Conse- morphology. However, the hypothesis could not be quently, a more detailed chemical characterization of confirmed because of the lack of differences between the lecithin, including the FA position and distribution T1 and T5 treatments (SO at 2.00 vs. SL at 2.00%). 5660 VIñADO ET AL. Concerning microbiota counts, no differences were the replacement of SO by SL (2% of total addition) did observed between treatments regarding Enterobacteria not modify TFA absorption or jejunal morphology in and E. faecium counts, supporting the performance, broiler chickens of 46 d of life, whereas it caused minor the digestibility, and the jejunal morphology results. changes in the FA profile of AFP. On the other hand, Nonetheless, the results obtained also suggest that ani- SO total replacement by SL reduced ileal absorption of mals fed T5 (SL at 2.00%) presented more Lactobacillus PUFA and increased Lactobacillus spp. counts at the spp. counts than did animals fed T1 (SO at 2.00%). It is jejunum; however, these modifications had no influence well known that certain inhabitants of poultry gut, such on chicken performance. as Lactobacillus spp. and E. faecium, are widely used as dietary probiotics by controlling the overgrowth of path- ogenic bacteria with the aim to improve animal growth ACKNOWLEDGMENTS and health (Gaggìa et al., 2010). Nevertheless, Lactoba- All coauthors participated equally in the research and cillus spp. and E. faecium also present bile salt hydrolase the writing of this article. The English of this article was capacity (Cole and Fuller, 1984; Knarreborg et al., 2002; proofread by Chuck Simmons, a native English- Geng and Lin, 2017), an enzyme that catalyzes primary speaking, retired university Instructor of English. bile salts to secondary bile salts, which are less efficient Conflicts of Interest Statement: The authors did not emulsifiers (Geng and Lin, 2017). 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