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. 2022 Mar 9;100(3):skac071. doi: 10.1093/jas/skac071

Effects of feeding high oleic soybean oil to growing-finishing pigs on growth performance and carcass characteristics

Katelyn N Gaffield 1, Dustin D Boler 1, Ryan N Dilger 1, Anna C Dilger 1, Bailey N Harsh 1,✉
PMCID: PMC9030199  PMID: 35262699

Abstract

Feeding growing-finishing pigs supplemental fat is a common practice in the swine industry and can result in improved feed efficiency and reduced feed intake; however, dietary lipids also play a key role in determining pork composition. The objectives of the current study were to evaluate the effects of feeding graded levels of high oleic soybean oil (HOSO) on growth performance and carcass characteristics. A total of 288 pigs raised in two separate blocks (144 pigs each) were assigned to one of four diets containing either 25% dried distiller’s grains with solubles (DDGS), 2% high oleic soybean oil (HOSO2), 4% high oleic soybean oil (HOSO4), or 6% high oleic soybean oil (HOSO6). Pigs were housed 4 per pen and fed for 98 d using a 3-phase feeding system. Pigs were individually weighed and feed intake was recorded throughout the trial to calculate average daily feed intake (ADFI) and gain to feed ratio (G:F). A total of 144 pigs were transported to the University of Illinois Meat Science Laboratory and fabricated into primal and subprimal cuts to calculate carcass cutting yields. Differences in growth performance were observed, with pigs fed the DDGS treatment exhibiting greater (P ≤ 0.01) overall ADFI consuming 0.21, 0.18, and 0.28 kg/d more than HOSO2, HOSO4, and HOSO6 diets, respectively. Pigs fed the HOSO6 diet had greater (P ≤ 0.03) overall G:F than pigs fed DDGS and HOSO2 diets but did not differ (P = 0.12) from pigs fed HOSO4. Furthermore, differences in carcass traits were observed. Hot carcass weight was increased (P ≤ 0.03) in pigs fed the HOSO6 diet compared with pigs fed the DDGS and HOSO2 diets, while pigs fed HOSO4 did not differ (P > 0.05) from either extreme. Additionally, pigs fed HOSO4 and HOSO6 produced fatter (P ≤ 0.01) carcasses with reduced (P ≤ 0.01) standardized fat-free lean. Minimal differences were observed in primal weights expressed as a percentage of chilled side including bone-in Boston butt, trimmed loin, and trimmed ham with primal weights decreasing with increasing inclusion of dietary HOSO. Overall, pigs fed HOSO2 had reduced ADFI with similar backfat thickness and standardized fat-free lean compared with pigs fed the DDGS treatment. However, pigs fed HOSO 4% and 6% not only had improvements in ADFI and G:F but also had increased backfat thickness, which resulted in reductions in standardized fat-free lean and primal weights expressed as a percentage of chilled side weight.

Keywords: carcass characteristics, growth performance, high oleic soybean oil, pork, swine

Lay Summary

Feeding pigs supplemental fat to increase caloric density is a common practice in the swine industry and can result in improved feed efficiency. However, high oleic soybean oil (HOSO), a relatively new feed ingredient, has not been extensively researched in pig diets. HOSO differs from conventional soybean oil in that it contains an increased proportion of oleic acid, a monounsaturated fatty acid. Therefore, our goal was to investigate the use of HOSO in the diets of pigs in the weeks leading up to marketing. A total of 288 pigs were fed one of four diets that differed in their source of fat. One diet contained 25% dried distiller’s grains with solubles (DDGS), while the other three had graded levels of HOSO (2%, 4%, or 6%). Pigs were fed diets for the last 14 wk leading up to slaughter. Pigs fed the highest level of HOSO grew more efficiently and were heavier than those fed the diet containing DDGS. However, pigs fed 6% HOSO were also fatter and yielded a reduced percentage of boneless meat cuts than those fed DDGS.

High oleic soybean oil (HOSO) can be fed as a supplemental dietary fat source to growing-finishing pigs to increase marketing weights. Feeding diets containing 6% HOSO resulted in increased feed efficiency but reduced boneless meat yield compared with an industry-reference diet.

Introduction

Feeding growing-finishing pigs supplemental fat is a common practice in the swine industry and can result in improved feed efficiency and reduced feed intake (Engel et al., 2001; NRC, 2012). However, dietary fats are also a key determinant of pork fat composition (Azain, 2001) and represent one of the most expensive dietary components in supplying energy to the pig (Patience, 2012). Inclusion of unsaturated fats in swine diets, especially polyunsaturated fatty acids (PUFAs) like those present in dried distillers’ grains with solubles (DDGS), alters carcass fat composition, which can reduce fat quality and result in belly and bacon processing issues (Wahlstrom et al., 1971; Ellis and McKeith, 1999; White et al., 2009; Xu et al., 2010). This has led to increased interest in the use of monounsaturated fatty acids (MUFAs) to minimize fat quality problems. Unfortunately, many oils with increased amounts of MUFAs also contain high concentrations of PUFAs (St. John et al., 1987; Miller et al., 1990).

High oleic soybean oil (HOSO) is a potential dietary fat source for swine diets due to its increased oleic acid (C18:1) content. Commodity soybean oil contains approximately 51% linoleic acid and 23% oleic acid (NRC, 2012), while HOSO contains approximately 75% oleic acid and only 7% linoleic acid (United Soybean Board, 2021). This increased oleic acid content sets HOSO apart from not only conventional soybean oil but also many other dietary lipids commonly used in swine diets. For example, DDGS typically contains between 4% and 10% corn oil and has a fatty acid composition of approximately 54% linoleic acid, 26% oleic acid, and 14% palmitic acid (Shurson, 2019). In contrast to these other sources, the majority of HOSO is MUFAs and contains only limited amounts of the PUFA linoleic acid, which is regarded as having the greatest influence on fat quality (Wood, 1984). Additionally, high oleic soybeans are expected to increase in availability as yields are similar and demand from the food service sector is expected to grow (Qualisoy, 2021). As production of HOSO continues to increase, there will be increased opportunities for use within the swine industry. While incorporating HOSO into ruminant diets did not alter growth performance or carcass characteristics (Belon et al., 2021), there are no data available characterizing the use of HOSO in swine diets.

The primary objective of this study was to determine the effect of feeding HOSO to growing-finishing pigs on growth performance, carcass composition, and primal cutting yield. Furthermore, the study aimed to determine the optimal inclusion level of HOSO in growing-finishing diets to maximize growth potential and limit negative effects on carcass performance. Overall, it was hypothesized that feeding HOSO as a dietary substitute for DDGS would not negatively impact growth performance or carcass cutability.

Materials and Methods

All animal care and use procedures were approved by the Institutional Animal Care and Use Committee (Protocol # 18231) at the University of Illinois and followed standard practices described in the Guide for the Care and Use of Agricultural Animals in Research and Teaching (ASAS, 2020).

Dietary treatments

HOSO and DDGS ingredients were analyzed by a commercial laboratory (Barrow-Agee; Memphis, TN). The composition of DDGS and HOSO is available in Supplementary Table S1. Lipid for the DDGS ingredient was extracted using petroleum ether (method Ba 3-38; AOCS, 2017) followed by gravimetric ether extraction (method 920.39; AOAC, 2007). Fat for the HOSO ingredient was analyzed using the gravimetric ether extract method (method 954.02; AOAC, 2007). Total fatty acids were analyzed using a wet extraction method (method G 3-53; AOCS, 2017) for both DDGS and HOSO. Free fatty acids for the DDGS (method Ac 5-41; AOCS, 2017) and HOSO (method Ca 5a-40; AOCS, 2017) were analyzed. The DDGS ingredient was analyzed for moisture and volatile matter using the forced draft oven method (method Ba 2a-38; AOCS, 2017). The HOSO ingredient was analyzed for moisture and volatile matter in addition to insoluble impurities using both the forced draft oven method (method Ba 2a-38; AOCS, 2017) and extraction in kerosene and petroleum ether (method Ca 3a-46; AOCS, 2017). The unsaponifiable matter was determined for both ingredients using the gravimetric method following saponification of the sample using liquid–liquid extraction (method Ca 6a-40; AOCS, 2017). Furthermore, both ingredients were also analyzed for peroxide value using potassium iodide (method Cd 8-53; AOCS, 2017), oil stability index (method Cd 12b-92; AOCS, 2017), and p-Anisidine value (method Cd 18-90; AOCS, 2017).

Four dietary treatments (Table 1) were formulated, including an industry-typical reference diet containing 25% DDGS, plus treatments containing 2% high oleic soybean oil (HOSO2), 4% high oleic soybean oil (HOSO4), or 6% high oleic soybean oil (HOSO6). The reference diet was formulated with 25% DDGS as evidence suggests that feeding below 30% DDGS does not negatively impact growth rate or feed efficiency (Xu et al., 2010). The intent was to permit a general comparison between the HOSO2 diet and DDGS reference at similar oil inclusion, though the DDGS sourced for the study was analyzed to contain 5.6% extractable lipid.

Table 1.

Ingredient and calculated composition of phased treatment diets, as-is basis1

Ingredient, % Phase 1 Phase 2 Phase 3
DDGS HOSO2 HOSO4 HOSO6 Control HOSO2 HOSO4 HOSO6 Control HOSO2 HOSO4 HOSO6
Corn 50.53 72.99 70.99 68.98 54.98 77.45 75.44 73.43 57.53 80.05 78.01 75.98
Soybean meal 22.00 22.00 22.20 22.00 18.00 18.00 18.00 18.00 16.00 16.00 16.00 16.00
DDGS 25.00 0.00 0.00 0.00 25.00 0.00 0.00 0.00 25.00 0.00 0.00 0.00
High oleic soybean oil 0.00 2.00 4.00 6.00 0.00 2.00 4.00 6.00 0.00 2.00 4.00 6.00
Limestone 1.80 0.84 0.84 0.84 0.98 0.75 0.75 0.75 1.00 0.76 0.76 0.75
Dicalcium phosphate 0.64 1.10 1.10 1.10 0.40 0.84 0.84 0.84 0.10 0.50 0.54 0.55
Vitamin premix2 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.05 0.05 0.05 0.05
Trace mineral premix3 0.35 0.35 0.35 0.35 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30
l-Lysine HCl 0.28 0.39 0.39 0.40 0.22 0.33 0.33 0.34 0.00 0.11 0.11 0.12
dl-Methionine 0.00 0.08 0.08 0.08 0.00 0.08 0.08 0.08 0.00 0.08 0.09 0.09
l-Threonine 0.00 0.13 0.13 0.14 0.00 0.13 0.14 0.14 0.00 0.13 0.13 0.14
Antioxidant4 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02
Calculated composition
 ME, kcal/kg 3,107 3,385 3,488 3,592 3,123 3,400 3,504 3,607 3,141 3,421 3,523 3,626
 CP, % 21.09 15.38 15.24 15.09 19.59 13.88 13.74 13.59 18.86 13.16 13.01 12.86
 SID Lys, % 0.99 0.99 0.99 0.99 0.85 0.85 0.85 0.85 0.63 0.63 0.63 0.63
 SID Lys:ME, g/Mcal 3.19 2.92 2.84 2.76 2.72 2.50 2.43 2.36 2.01 1.84 1.79 1.74
 Ca, % 0.65 0.65 0.65 0.65 0.54 0.54 0.54 0.54 0.47 0.47 0.47 0.47
 P, % 0.56 0.55 0.54 0.54 0.49 0.48 0.48 0.47 0.43 0.41 0.42 0.41
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Phases 1, 2, and 3 diets were fed from study day 0 to 35, day 36 to 70, and day 70 to 90, respectively. Abbreviations: CP, crude protein; DDGS, dried distillers’ grains with solubles; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%; ME, metabolizable energy; SID, standardized ileal digestible.

Provided the following per kilogram of diet: vitamin A as retinyl acetate, 11,150 IU; vitamin D3 as cholecalciferol, 2,210 IU; vitamin E as dl-alpha tocopheryl acetate, 66 IU; vitamin K as menadione nicotinamide bisulfate, 1.42 mg; thiamin as thiamine mononitrate, 1.10 mg; riboflavin, 6.59 mg; pyridoxine as pyridoxine hydrochloride, 1.00 mg; vitamin B12, 0.03 mg; d-pantothenic acid as d-calcium pantothenate, 23.6 mg; niacin, 44.1 mg; folic acid, 1.59 mg; and biotin, 0.44 mg.

Provided the following per kilogram of diet: Cu, 20 mg as copper chloride; Fe, 125 mg as iron sulfate; I, 1.26 mg as ethylenediamine dihydriodide; Mn, 60.2 mg as manganese hydroxychloride; Se, 0.30 mg as sodium selenite and selenium yeast; and Zn, 125.1 mg as zinc hydroxychloride.

Santoquin 6, Novus International, Inc., St. Louis, MO, USA.

Multiple batches of feed for each of the three phases were sampled after mixing and then pooled across phases to create a composite sample for further analyses. Additionally, samples of both HOSO and DDGS ingredients were collected. All samples were stored at 0 °C prior to analyses (Table 2). Composite samples of the reference diet and treatments for the three phases were analyzed at the University of Illinois (Urbana, IL). Dry matter determination was conducted following the loss on drying for feeds procedures (method 934.01; AOAC, 2007). Crude protein was determined using the combustion method (TruMac N, Leco Corp., St. Joseph, MO) standardized with ethylenediaminetetraacetic acid (EDTA; method 990.03; AOAC, 2007) and Lys by high-performance liquid chromatography (method 994.12; AOAC, 2007). Ash was determined through dry ashing (method 942.05; AOAC, 2007), and both Ca and P quantities were determined from the remaining residue (method 968.08; AOAC, 2007). Finally, the total lipid was determined after acid hydrolysis (method 922.06; AOAC, 2007), and fatty acid profiles were determined by preparing fatty acid methyl esters (FAME) using the procedure outlined by Lepage and Roy (1986) and analyzed following standardized procedures (AOCS, 2007).

Table 2.

Analyzed composition of dietary treatments, DM basis1

Item Phase 1 Phase 2 Phase 3
DDGS2 HOSO2 HOSO4 HOSO6 DDGS HOSO2 HOSO4 HOSO6 DDGS HOSO2 HOSO4 HOSO6
DM, % 87.84 87.71 88.05 88.20 86.90 86.99 87.16 87.71 87.03 86.84 87.19 87.29
CP, % 25.61 18.49 18.63 17.95 22.23 16.74 16.66 16.08 21.24 16.08 15.59 15.30
Lys, % 1.56 1.35 1.37 1.29 1.16 1.15 1.14 1.10 0.99 0.95 0.95 0.93
Ash, % 5.95 4.86 5.32 5.56 5.39 4.66 4.59 4.42 4.87 4.33 4.09 3.71
Ca, % 0.58 0.53 0.59 0.61 0.56 0.49 0.56 0.53 0.46 0.46 0.55 0.43
P, % 0.62 0.54 0.56 0.46 0.52 0.39 0.46 0.39 0.44 0.39 0.42 0.39
Fat, % 4.97 6.21 8.60 10.72 4.92 6.18 7.78 10.39 5.25 6.40 8.25 10.26
FA3, mg/g
 C8:0, caprylic ND ND ND ND ND ND ND ND ND ND ND ND
 C16:0, palmitic 9.81 7.77 9.10 10.45 10.30 8.63 9.55 10.03 10.20 8.73 9.37 10.93
 C16:1, palmitoleic ND ND ND ND ND ND ND ND ND ND ND ND
 C17:0, margaric ND 0.20 0.40 0.56 ND 0.22 0.37 0.53 ND 0.23 0.38 0.58
 C18:0, stearic 1.59 1.79 2.66 3.39 1.58 1.90 2.62 3.16 1.56 1.88 2.62 3.45
 C18:1, oleic 15.59 27.46 48.22 65.64 17.11 30.81 48.09 61.92 16.55 31.19 48.46 67.77
 C18:2, linoleic 35.58 25.03 25.65 26.89 37.53 27.61 27.05 25.53 36.27 27.73 25.60 27.49
 C18:3, linolenic 3.14 2.96 3.45 4.01 2.98 3.10 3.34 3.73 2.82 2.97 3.19 3.97
 C19:0, nonadecanoic ND ND ND ND ND ND ND ND ND ND ND ND
 C20:0, arachidic 0.25 0.23 0.31 0.38 0.25 0.25 0.32 0.38 0.27 0.25 0.31 0.40
 C20:1, gadoleic 0.22 0.22 0.41 0.54 0.20 0.22 0.40 0.49 0.19 0.24 0.44 0.52
 C22:0, behenic ND ND 0.28 0.35 ND ND 0.27 0.35 ND ND 0.28 0.37
 C24:0, lignoceric 0.20 0.19 0.22 0.26 0.21 0.18 0.23 0.23 0.20 0.19 0.21 0.26
Total SFA4 11.86 10.17 12.97 15.39 12.34 11.17 13.37 14.68 12.23 11.26 13.16 15.99
Total MUFA5 16.50 28.56 50.00 67.95 18.01 31.99 49.84 64.08 17.42 32.39 50.24 70.08
Total PUFA6 38.72 27.99 29.10 30.90 40.51 30.70 30.38 29.26 39.09 30.71 28.78 31.47
UFA:SFA7 4.66 5.56 6.10 6.42 4.74 5.62 6.00 6.36 4.62 5.60 6.00 6.35
PUFA:SFA8 3.26 2.75 2.24 2.01 3.28 2.75 2.27 1.99 3.20 2.73 2.19 1.97
IV ACOS9 125.24 113.36 104.72 101.07 124.56 112.93 105.14 100.95 123.89 112.49 103.97 100.60
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Phases 1, 2, and 3 diets were fed from study day 0 to 35, day 36 to 70, and day 70 to 90, respectively. Abbreviations: CP, crude protein; DDGS, dried distillers’ grains with solubles; DM, dry matter; FA, fatty acids; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%; IV, iodine value; MUFA, monounsaturated fatty acid; ND, not detected; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; UFA, unsaturated fatty acids.

DDGS ingredient used in all three phases was analyzed to contain 5.6% extractable lipid.

FA per gram of diet.

Total SFA = ([C8:0] + [C14:0] + [C15:0] + [C16:0] + [C17:0] + [C18:0] + [C19:0] + [C20:0] + [C21:0] + [C22:0] + [C24:0]); brackets indicate concentration.

Total MUFA = ([C14:1] + [C16:1] + [C18:1trans-9] + [C18:1n-9] + [C18:1n-7] + [C19:1] + [C20:1] + [C21:1]).

Total PUFA = ([C18:2n-6] + [C18:3n-6] + [C18:3n-3] + [C20:2n-6] + [C20:3n-6] + [C20:3n-3] + [C20:4n-6] + [C20:5n-3] + [C22:5n-3] + [C22:6n-3]).

UFA:SFA = (total MUFA + total PUFA)/total SFA.

PUFA:SFA = total PUFA/total SFA.

IV = C16:1 (0.95) + C18:1 (0.86) + C18:2 (1.732) + C18:3 (2.616) + C20:1 (0.785) + C22:1 (0.723) (American Oil Chemists' Society, 2017).

Animal housing and growth performance

A total of 288 pigs were raised in two separate blocks of equal size. For each block, pigs were housed in same-sex pens with 4 pigs per pen (36 pens/block). A total of 9 pens per dietary treatment were represented for each block. The experimental design was a 2 × 4 factorial arrangement of sex and dietary treatments. Pigs were weighed and allocated to treatments by sex and weight to minimize variation among pens at study initiation.

The first block of pigs (PIC 1050, Line 02 × Line 03) had an initial body weight (BW) of 35.7 ± 4.51 kg. These pigs were housed in three separate barns containing fully slated floors. Each pen was 1.60 × 3.96 m (1.58 m2/pig) and contained a double-door, dry-box feeder fastened to the side gate and one nipple drinker. In each barn, there were three replicates of each dietary treatment. For the second block, pigs (PIC 359 sires × PIC Camborough females) had an initial BW of 25.1 ± 4.59 kg. These pigs were housed in a single barn containing all 36 pens with partially slatted flooring. Each pen was 1.83 × 2.59 m (1.18 m2/pig) and contained a single-space, dry-box feeder and a nipple drinker. For both blocks, the temperature in barns was maintained using fan ventilation and controlled heaters using age-appropriate protocols.

Pigs were fed for 98 d using a 3-phase feeding system. A grower diet was fed to the pens from day 0 to 35, an early finisher diet from day 36 to 70, and a late finisher diet from day 71 to 98. Pigs were individually weighed on days 0, 35, 70, and 98 of the trial. Feed consumption was recorded throughout the trial to calculate average daily feed intake (ADFI) and gain to feed ratio (G:F). Day 98 was considered the end of the trial, and overall average daily gain (ADG), ADFI, and G:F were calculated. On day 98, the heaviest pig from each pen was selected resulting in 36 pigs from each block (72 total) being transported to the University of Illinois Meat Science Laboratory (Urbana, IL) for slaughter on day 99. The second heaviest pig was transported on day 100, which included 36 pigs from each block (72 total) and slaughtered on day 101 at the University of Illinois Meat Science Laboratory.

Slaughter and carcass characteristics

Pigs were held in lairage for a minimum of 16 h prior to slaughter at the University of Illinois Meat Science Laboratory (Urbana, IL) and provided ad libitum access to water but not feed. Ending live weight (ELW) was determined by weighing pigs immediately prior to slaughter. Slaughter occurred under the supervision of the Food Safety and Inspection Service of the U.S. Department of Agriculture. Pigs were immobilized using head-to-heart electrical stunning and terminated via exsanguination. Approximately 45 min postmortem, carcasses were weighed to determine hot carcass weight (HCW). Carcass leaf fat was left intact for the collection of HCW. Carcass yield was calculated and expressed as a percentage by dividing HCW by ELW.

Estimates of carcass composition were determined on the left side of each carcass, which were chilled at 4 °C for a minimum of 20 h. The left sides of each carcass were separated between the 10th and 11th rib to expose the longissimus thoracis (LTL). Backfat thickness was measured at the 10th rib, three-quarters of the length of the LTL from the dorsal process of the vertebral column. Loin eye area (LEA) was determined by tracing the surface of the LTL onto acetate paper. The LTL tracings were later measured twice using a digitizer tablet (Wacom, Vancouver, WA) and Adobe Photoshop CS6. The average of the two measurements was considered the final LEA. The standardized fat-free lean percentage was determined by the equation (8.588 + (0.465 × HCW, lb) – (21.896 × fat thickness, in) + (3.005 × loin muscle area, in2))/ HCW, lb) × 100 as described in procedure 1 for ribbed carcasses (Burson and Berg, 2001).

Carcass fabrication

The method outlined by Boler et al. (2011) was followed for carcass fabrication. The left side of each chilled carcass was weighed and then fabricated at 1-d postmortem into a pork leg (North American Meat Processors [NAMP] #401), skin-on whole loin, pork shoulder (NAMP #403), neck bones (NAMP #421), jowl (NAMP #419), skin-on natural fall belly (NAMP #408), and spareribs (NAMP #416) to meet the specifications as described in the North American Meat Institute Meat Buyer’s Guide (NAMI, 2014). Each primal was weighed and recorded before further fabrication. Legs were skinned and trimmed (NAMP #402) and then the hams were further fabricated by the method stated by Boler et al. (2012). The loins were separated into anterior and posterior portions between the 10th and 11th rib and were skinned and trimmed to the specifications of NAMP #410 bone-in loin. Both portions were weighed to determine the weight of the whole skinless bone-in loin. Each portion was then fabricated into a NAMP #414 Canadian back loin, NAMP #415A tenderloin, and NAMP #413D sirloin. The shoulder was skinned and trimmed to meet the specifications of a NAMP #404 skinned pork shoulder. The skinned pork shoulder was further fabricated into a NAMP #406 bone-in Boston butt and NAMP #405 bone-in picnic and weighed individually. A NAMP #406A boneless Boston butt and a NAMP #405A boneless picnic with the triceps brachii (shoulder cushion) attached were fabricated by removing the bones from each piece following the fabrication guidelines. Natural fall bellies and Canadian back loins were collected to further assess fresh belly quality characteristics and fresh chop quality traits. Carcass cutability was expressed as a percentage of chilled side weight. The following equations were used to calculate cutability:

Bone-in lean cutting yield, % = [(trimmed ham (NAMP #402), kg + bone-in trimmed Boston butt (NAMP #406), kg + bone-in picnic (NAMP #405), kg + trimmed loin (NAMP #410), kg)/ chilled left side weight, kg] × 100

Bone-in carcass cutting yield, % = [(bone-in lean cutting yield components + natural fall belly (NAMP #408), kg)/ chilled left side weight, kg] × 100

Boneless carcass cutting yield, % = [(inside ham (NAMP #402F), kg + outside ham (NAMP #402E), kg + knuckle (NAMP #402H), kg) + inner shank, kg + liter butt, kg + Canadian back (NAMP #414), kg +tenderloin (NAMP #415A), kg + sirloin (NAMP #413D), kg) + boneless Boston butt (NAMP #406A), kg + boneless picnic (NAMP #405A), kg + natural fall belly (NAMP #408), kg))/ chilled left side weight] × 100

Statistical analysis

Data were analyzed using the MIXED procedure of SAS (SAS Inst. In., Cary, NC) as a 2 × 4 factorial arrangement of treatments. Pen (N = 72) served as the experimental unit for all variables. Fixed effects were diet, sex, and the interaction between diet and sex. Because sex was unbalanced across barns in block 1, both block and barn nested within block served as the random effects. There were no interactions between block and diet. Effects of diet, sex, and the interaction between diet and sex were considered significant at P < 0.05. The least squares means were separated using a probability of difference (PDIFF) statement in the MIXED procedure of SAS. The normality of residuals was tested using the UNIVARIATE procedure of SAS. Homogeneity of variances was tested using the Levene’s hovtest option in the GLM procedure of SAS.

Results and Discussion

Body weight, average daily gain, average daily feed intake, and feed efficiency

There were no interactions (P ≥ 0.07) between dietary treatment and sex for any performance characteristics throughout the finishing trial (Table 3). BW did not differ among treatments at any phase of the 98-d finishing period. In phase 1, growth performance characteristics did not differ among dietary treatments including ADG (P = 0.42), ADFI (P = 0.71), and G:F (P = 0.22). However, during phase 2, differences in performance emerged. Pigs fed the DDGS treatment had the greatest (P ≤ 0.01) ADFI, while both HOSO2 and HOSO4 had greater (P ≤ 0.03) ADFI compared with HOSO6. Inversely, HOSO6 had the greatest (P ≤ 0.04) G:F, with HOSO4 and HOSO2 intermediate but greater (P ≤ 0.02) than DDGS for G:F. A similar pattern was observed during phase 3, with differences in ADFI and G:F persisting. Pigs fed the DDGS diet had greater ADFI (P ≤ 0.01) compared with pigs fed HOSO diets, while pigs fed HOSO diets did not differ (P > 0.05) from each other. However, G:F was greater (P ≤ 0.01) for pigs fed the HOSO diets compared with all other treatments. Differences in both phase 2 and phase 3 translated into overall differences throughout the finishing trial. Pigs fed DDGS had greater (P ≤ 0.01) overall ADFI than pigs fed HOSO, consuming 0.21, 0.18, and 0.28 kg/d more than HOSO2, HOSO4, and HOSO6 diets, respectively. However, ADFI was not different (P > 0.06) among HOSO-fed pigs. Pigs fed the HOSO6 diet had greater (P ≤ 0.03) overall G:F than pigs fed DDGS and HOSO2 diets but did not differ (P = 0.12) from pigs fed HOSO4.

Table 3.

Main effects of diet and sex on daily gain and feed intake1

Item Dietary treatment SEM Sex SEM P-value
DDGS HOSO2 HOSO4 HOSO6 Barrow Gilt Diet Sex Diet × Sex
Pens2, n 18 18 18 18 36 36
Phase 1 (day 0 to 35)
 BW day 0, kg 30.47 30.27 30.28 30.61 5.36 30.99 29.83 5.35 0.79 <0.001 0.91
 ADG, kg/d 0.91 0.87 0.89 0.92 0.13 0.96 0.84 0.13 0.42 <0.001 0.23
 ADFI, kg/d 1.94 1.90 1.87 1.88 0.35 2.02 1.78 0.35 0.71 <0.001 0.92
 G:F 0.468 0.467 0.480 0.492 0.02 0.478 0.476 0.02 0.22 0.80 0.61
 BW day 35, kg 62.15 60.87 61.38 62.65 9.85 64.39 59.14 9.83 0.39 <0.001 0.42
Phase 2 (day 36 to 70)
 ADG, kg/d 1.10 1.09 1.09 1.09 0.02 1.18 1.00 0.01 0.93 <0.001 0.63
 ADFI, kg/d 3.04a 2.79b 2.81b 2.65c 0.20 3.09 2.56 0.20 <0.001 <0.001 0.07
 G:F 0.364c 0.392b 0.392b 0.413a 0.03 0.387 0.394 0.02 <0.001 0.33 0.34
 BW day 70, kg 100.74 98.94 99.60 100.62 10.14 105.77 94.19 10.11 0.63 <0.001 0.40
Phase 3 (day 71 to 98)
 ADG, kg/d 1.00 0.97 1.00 1.04 0.05 1.07 0.94 0.04 0.35 <0.001 0.44
 ADFI, kg/d 3.44a 3.08b 3.18b 3.07b 0.07 3.47 2.92 0.06 <0.001 <0.001 0.37
 G:F 0.293c 0.320b 0.316bc 0.346a 0.01 0.311 0.326 0.01 <0.01 0.09 0.37
 BW day 98, kg 129.23 126.67 127.91 130.28 9.35 136.14 120.90 9.29 0.33 <0.001 0.37
Overall (day 0 to 98)
 ADG, kg/d 1.02 0.96 1.00 1.00 0.05 1.05 0.94 0.04 0.17 <0.001 0.29
 ADFI, kg/d 2.76a 2.55b 2.58b 2.48b 0.21 2.81 2.37 0.20 <0.001 <0.001 0.37
 G:F 0.371b 0.379b 0.389ab 0.409a 0.02 0.377 0.398 0.01 0.02 0.02 0.86
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Abbreviations: ADFI, average daily feed intake; ADG, average daily gain; BW, body weight; DDGS, dried distillers’ grains with solubles; G:F, gain to feed ratio; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%.

Each pen housed four pigs of the same sex.

Different superscript letters within the same row reflect dietary treatment differences (P ≤ 0.05).

Differences between sexes were observed during all three feeding phases. Barrows were heavier (P < 0.01) than gilts at every time point. During phases 1, 2, and 3, no differences (P ≥ 0.09) in G:F between barrows and gilts were observed; however, barrows had greater (P < 0.01) ADG and ADFI than gilts. Over the entire 98-d feeding trial, barrows had 10.5% greater (P < 0.01) overall ADG and 15.7% greater (P < 0.01) overall ADFI. Despite the lack of difference in individual phases, gilts exhibited greater (P = 0.02) overall G:F compared with barrows.

Feeding diets containing HOSO generally improved G:F as a result of reduced ADFI within individual and overall feeding periods. This phenomenon was expected, given that graded HOSO inclusion increased the metabolizable energy (ME) across the series of treatment diets, and was likely the result of metabolic and physiologic regulatory processes involved in the relationship between dietary ME and voluntary feed intake (De la Llata et al., 2001; Nyachoti et al., 2004; Beaulieu et al., 2009; NRC, 2012; Patience, 2012). Feeding of monounsaturated dietary oils, including those from peanut or canola, has resulted in similar reductions in ADFI and feed efficiency (i.e., feed:gain ratio) when a static Lys:ME ratio was maintained (Myer et al., 1992a, 1992b). The increase in efficiency of approximately 12% reported by Myer et al. (1992a) when feeding peanut- and canola oils is similar in magnitude to the 10% difference in G:F in the present trial when feeding the HOSO6 diet. However, it is important to note that the levels of dietary lipid fed in the previous trials were up to 10%, which is greater than in diets fed in this trial and what is typically fed in the U.S. pork industry. In this way, HOSO appears to elicit improvements in feed efficiency without negatively impacting growth rate when included at low concentrations relative to other oil sources.

Our dietary formulation strategy included the addition of graded HOSO levels without adjustments to the dietary Lys concentration within each feeding phase. This approach inherently produced differences in the calculated standardized ileal digestible (SID) Lys:ME ratio between HOSO-containing diets. Pigs are known to decrease voluntary feed intake in response to increasing dietary ME levels, which translates into a reduction in the absolute daily Lys requirement and increased deposition of body fat (Marçal et al., 2019). In our study, the differences in SID Lys:ME ratio between HOSO2 and HOSO6 diets within each feeding phase were relatively small (0.16, 0.14, and 0.10 in sequential phases) compared with the range of ratios explored previously (Marçal et al., 2019; Smith et al., 1999). Moreover, the concentrations of SID Lys used in our study exceeded current recommendations (NRC, 2012), so it is unlikely that Lys intake would have limited growth, given the additional ME provided by graded HOSO addition. Regardless, because dietary formulation strategy affects both efficiency of growth and carcass composition, our results should be interpreted with the proper context, and investigating the influence of HOSO addition using constant SID Lys:ME ratios is warranted.

Carcass characteristics

There were no interactions (P ≥ 0.73) between dietary treatment and sex for ELW, HCW, and LEA. However, interactions between dietary treatment and sex were observed for carcass yield, 10th rib backfat, and standardized fat-free lean. While there were no differences in carcass yield of gilts among dietary treatments, carcass yield of barrows was greater in HOSO-fed treatments compared with those fed DDGS. The backfat thickness of gilts fed HOSO2 was reduced compared with gilts fed other diets, while in barrows, the backfat thickness was increased by feeding diets containing HOSO compared with diets containing DDGS (Figure 1). Given these changes in backfat thickness, standardized fat-free lean was increased in gilts fed the HOSO2 diet compared with the three other dietary treatments and was increased for barrows fed the DDGS diet compared with HOSO treatments (Figure 2).

Figure 1.

Figure 1.

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Effect of diet and sex on 10th rib backfat depth, cm. Least squares means lacking a common superscript letter differ (P < 0.05). Abbreviations: DDGS, dried distillers’ grains with solubles; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%.

Figure 2.

Figure 2.

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Effect of diet and sex on standardized fat-free lean, %. Standardized fat-free lean was determined by the equation ((8.588 + (0.465 × HCW, lbs.) − (21.896 × fat depth, in) + (3.005 × LEA area, in2))/HCW) × 100 described by Burson and Berg (2001). Least squares means lacking a common superscript letter differ (P < 0.05). Abbreviations: DDGS, dried distillers’ grains with solubles; HCW, hot carcass weight; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%.

ELW was increased (P ≤ 0.01) in pigs fed HOSO6 compared with pigs fed HOSO2, with the two other treatments intermediate but not different (P > 0.05) from either extreme (Table 4). Similarly, HCW was increased (P ≤ 0.03) in pigs fed the HOSO6 diet compared with pigs fed DDGS or HOSO2 diets, while pigs fed HOSO4 were intermediate but not different (P > 0.05) from either extreme. Pigs fed DDGS had a reduced (P ≤ 0.03) carcass yield compared with pigs fed the HOSO diets, while the pigs fed HOSO diets did not differ (P > 0.57) from each other. Despite differences in carcass weights, LEA did not differ (P = 0.21) among dietary treatments. Carcasses from pigs fed HOSO4 and HOSO6 diets had greater backfat thickness (P ≤ 0.01) than pigs fed DDGS and HOSO2. Differences in HCW and backfat thickness translated into carcasses from pigs fed DDGS and HOSO2 having increased (P ≤ 0.01) fat-free lean compared with carcasses from pigs fed HOSO4 and HOSO6. Carcass differences between barrows and gilts were as expected, with barrows having greater ELW (P < 0.01), HCW (P < 0.01), carcass yield (P = 0.01), and backfat thickness (P < 0.01) and gilts having greater standardized fat-free lean (P < 0.01).

Table 4.

Main effects of diet and sex on carcass characteristics1

Item Dietary treatment SEM Sex SEM P-value
DDGS HOSO2 HOSO4 HOSO6 Barrow Gilt Diet Sex Diet × Sex
Pens, n 18 18 18 18 36 36
Ending live weight, kg 133.38ab 129.67b 133.89ab 136.91a 9.07 140.27 126.65 9.01 0.01 <0.001 0.73
HCW, kg 103.67b 102.20b 105.71ab 107.91a 8.54 110.77 98.98 8.49 0.01 <0.001 0.74
Chilled side weight, kg 49.99b 49.19b 50.75ab 52.01a 3.78 53.38 47.58 3.76 0.02 <0.001 0.60
Carcass yield, % 77.72b 78.65a 78.88a 78.80a 1.10 78.88 78.14 1.09 0.02 0.01 0.02
Loin muscle area, cm2 53.46 51.22 50.65 52.12 0.85 51.32 52.40 0.60 0.12 0.21 0.89
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Values based on data collected from heaviest and second heaviest in each pen (142 total pigs); Abbreviations: DDGS, dried distillers’ grains with solubles; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%; HCW, hot carcass weight; LEA, loin eye area.

Different superscript letters within the same row reflect dietary treatment differences (P ≤ 0.05).

The inclusion of HOSO also altered carcass characteristics and, in general, resulted in heavier and fatter carcasses. Carcasses from pigs fed HOSO diets had greater carcass yields than pigs fed DDGS, likely due to lesser visceral weights as a result of reduced dietary fiber (Linneen et al., 2008). Overall, backfat increased approximately 0.3 cm for pigs fed HOSO treatments compared with pigs fed the DDGS reference diet. Previous reports of feeding diets enriched in monounsaturated fat to pigs also demonstrated an increase in backfat thickness (Rhee et al., 1988; Miller et al., 1990; Myer et al., 1992a). For example, pigs fed diets containing 12% high oleic sunflower oil had increased backfat thickness compared with pigs fed a sorghum–soybean meal-based diet (Rhee et al., 1988). However, others did not report differences in backfat when pigs were fed diets with canola oil or peanut oil compared with control diets without added dietary lipids (West and Myer, 1987; Myer et al., 1992b).

Lean yield is often an important consideration for the pork industry (Fredeen and Weiss, 1981; Johnson et al., 2004). As a consequence of increased backfat, calculated standardized fat-free lean was reduced by feeding HOSO at 4% or 6% of the diet. However, 10th rib backfat depth values ranged from 1.84 to 2.26 cm, still representative of industry-acceptable backfat thicknesses (USDA Swine Direct Report, 2021). Increased backfat may also correlate to improvements in belly thickness (Tavarez et al., 2016). With the belly being the most valuable primal cut (Soladoye et al., 2015; USDA Carlot Report, 2021) and processors preferring thicker bellies as they are thought to have higher yields and ultimately greater profitability (Person et al., 2005), increased backfat from feeding HOSO may have belly quality advantages, potentially more than offsetting lean yield disadvantages.

Carcass cutting yields

Absolute and relative (percent of chilled side) weights of select primal and subprimal cuts are displayed in Table 5. The remainder of cut weights are available in Supplementary Tables S2–S4. There were no differences (P ≥ 0.11) among dietary treatments for the absolute weight or percent of chilled side weight for the whole ham. While there were no differences (P = 0.32) between dietary treatment for absolute weight of boneless ham, when expressed as a percentage of chilled side weight, pigs fed DDGS had a greater (P < 0.02) percentage of boneless ham compared with pigs fed HOSO4 and HOSO6. However, HOSO2 did not differ (P ≥ 0.11) from either DDGS, HOSO4, or HOSO6 diets for boneless ham weight. Whole shoulder weight was increased (P ≤ 0.01) for pigs fed HOSO6 compared with pigs fed HOSO2, while pigs fed DDGS and HOSO4 did not differ (P > 0.06) from either extreme. The differences in absolute weights did not translate into differences in percent chilled side weight. Boneless Boston and boneless picnic absolute and relative weights were not different (P ≥ 0.06) among dietary treatments. Absolute weight for the natural fall belly was greater (P ≤ 0.02) for pigs fed HOSO6 compared with pigs fed DDGS and HOSO2, while pigs fed HOSO4 did not differ (P ≥ 0.15) from either extreme. However, differences in absolute weight did not translate into differences (P = 0.43) in natural fall belly as a percent of chilled side weight. There were no differences (P ≥ 0.07) in absolute or proportional weight for the spareribs.

Table 5.

Main effects of diet and sex on characteristics of selected primal and subprimal cut weights and proportions1

Item Dietary treatment SEM Sex SEM P-value
DDGS HOSO2 HOSO4 HOSO6 Barrow Gilt Diet Sex Diet × Sex
Pens, n 18 18 18 18 36 36
Whole Ham, kg 11.90 11.60 11.85 12.15 0.56 12.38 11.36 0.55 0.11 <0.001 0.93
 % chilled side wt 23.85 23.69 23.44 23.45 0.68 23.26 23.95 0.67 0.20 <0.001 0.33
Boneless ham2, kg 6.97 6.74 6.78 6.92 0.37 7.06 6.64 0.37 0.32 <0.001 0.85
 % chilled side wt 13.97a 13.81ab 13.44b 13.35bc 0.31 13.27 14.01 0.30 <0.01 <0.001 0.09
Whole shoulder, kg 13.20ab 12.89b 13.12ab 13.57a 0.98 13.87 12.52 0.98 0.04 <0.001 0.77
 % chilled side wt 26.42 26.23 25.90 26.13 0.15 26.02 26.32 0.10 0.11 0.05 0.51
Boneless Boston butt, kg 3.93 3.84 3.84 4.03 0.28 4.12 3.70 0.27 0.08 <0.001 0.62
 % chilled side wt 7.87 7.82 7.59 7.75 0.08 7.73 7.79 0.05 0.06 0.40 0.79
Boneless picnic, kg 4.07 3.96 4.12 4.12 0.26 4.30 3.84 0.26 0.20 <0.001 0.67
 % chilled side wt 8.16 8.05 8.14 7.94 0.10 8.08 8.06 0.08 0.17 0.85 0.37
Natural fall belly, kg 7.44b 7.37b 7.67ab 8.02a 0.76 8.16 7.09 0.75 0.04 <0.001 0.36
 % chilled side wt 14.87 14.91 15.02 15.38 0.42 15.23 14.86 0.39 0.43 0.13 0.50
Spareribs, kg 1.82 1.79 1.84 1.88 0.09 1.91 1.76 0.09 0.07 <0.001 0.62
 % chilled side wt 3.66 3.66 3.64 3.63 0.11 3.58 3.72 0.10 0.98 0.02 0.33
Whole loin, kg 13.62 13.36 13.81 14.07 1.20 14.56 12.87 1.18 0.20 <0.001 0.65
 % chilled side wt 27.22 27.11 27.17 27.00 0.35 27.22 27.03 0.32 0.82 0.26 0.47
Canadian back, kg 3.92 3.77 3.74 3.84 0.26 3.86 3.78 0.26 0.21 0.23 0.43
 % chilled side wt 7.86a 7.71a 7.40b 7.41b 0.09 7.23 7.96 0.07 < 0.001 <0.001 0.02
Tenderloin, kg 0.51 0.49 0.50 0.51 0.04 0.50 0.50 0.04 0.50 0.69 0.61
 % chilled side wt 1.03 1.00 1.00 0.98 0.02 0.95 1.05 0.01 0.20 <0.001 0.18
Boneless loin3, kg 5.88 5.66 5.68 5.81 0.82 5.83 5.68 0.82 0.29 0.12 0.31
 % chilled side wt 11.74a 11.52ab 11.20bc 11.16c 0.80 10.88 11.93 0.79 <0.01 <0.001 <0.01
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Abbreviations: DDGS, dried distillers’ grains with solubles; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%; NAMP, North American Meat Processors.

Boneless ham = inside ham (NAMP#402F), kg + outside ham (NAMP #402E), kg + knuckle (NAMP #402H), kg + inner shank, kg + lite butt, kg.

Boneless loin = Canadian back loin (NAMP#414), kg + tenderloin (NAMP #415A), kg + sirloin (NAMP #413D), kg.

Different superscript letters within the same row reflect dietary treatment differences (P ≤ 0.05).

There were no differences (P ≥ 0.07) in absolute weight for the spareribs or any of the loin cuts. Despite the lack of differences in absolute weights, there were differences in the percentage of chilled side weight for many of the loin carcass cuts. Trimmed loin percentage was greater (P ≤ 0.01) in pigs fed DDGS compared with pigs fed HOSO4 and HOSO6, while pigs fed HOSO4 did not differ (P ≥ 0.28) from the other treatments (Supplementary Table S4). Canadian back loin percent was greater (P ≤ 0.02) for pigs fed DDGS and HOSO2 compared with pigs fed HOSO4 and HOSO6. Sirloin percentage was greater (P ≤ 0.03) in pigs fed DDGS compared with pigs fed HOSO4 and HOSO6, while pigs fed HOSO4 did not differ (P ≥ 0.09) from other treatments (Supplementary Table S4). Furthermore, pigs fed DDGS and HOSO4 produced greater (P ≤ 0.02) back rib percentage compared with pigs fed HOSO6, while pigs fed HOSO2 did not differ (P ≥ 0.11) from either extreme. Finally, pigs fed DDGS had a greater (P ≤ 0.01) boneless loin percentage than pigs fed HOSO6.

In agreement with Overholt et al. (2016), comparing sexes in the present study, barrows generally had heavier cuts, while gilts had a greater relative weight of cuts. For example, barrows had greater (P ≤ 0.03) absolute weights for the whole ham, boneless ham, whole shoulder, whole loin, Canadian back loin, and boneless loin. However, gilts had increased weights as a percent of chilled side weight for each of those cuts. For the natural fall belly, absolute weight was increased (P < 0.01) in barrows, but as a percent of chilled side weight, there was no difference (P = 0.13) between sexes.

There were no interactions (P ≥ 0.11) for any of the carcass cutability traits between dietary treatment and sex (Table 6). 
Bone-in carcass cutting yield was greater (P ≤ 0.01) for pigs fed DDGS compared with pigs fed HOSO, regardless of inclusion level. Similarly, bone-in lean cutting yield was greater (P ≤ 0.01) for pigs fed DDGS compared with pigs fed HOSO, regardless of inclusion level. However, pigs fed HOSO2 also had greater (P ≤ 0.01) bone-in lean cutting yield compared with pigs fed HOSO6, while HOSO4 did not differ (P ≥ 0.07) from either. Finally, pigs fed DDGS has a greater (P ≤ 0.01) boneless carcass cutting yield percentage compared with pigs fed HOSO4. As expected, gilts had greater (P < 0.01) bone-in carcass cutting yield, bone-in lean cutting yield, and boneless carcass cutting yield than barrows.

Table 6.

Main effects of diet and sex on carcass cutting yields1

Item Dietary treatment SEM Sex SEM P-value
DDGS HOSO2 HOSO4 HOSO6 Barrow Gilt Diet Sex Diet × Sex
Pens, n 18 18 18 18 36 36
Bone-in carcass cutting yield2, % 77.64a 76.70b 75.97b 76.05b 1.10 75.70 77.48 1.09 <0.01 <0.01 0.16
Bone-in lean cutting yield3, % 62.77a 61.79b 60.96bc 60.67c 1.47 60.47 62.62 1.46 <0.01 <0.01 0.11
Boneless carcass cutting yield4, % 54.60a 54.09ab 53.32c 53.56bc 0.85 53.23 54.55 0.83 <0.01 <0.01 0.46
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Abbreviations: DDGS, dried distillers’ grains with solubles; HOSO2, high oleic soybean oil 2%; HOSO4, high oleic soybean oil 4%; HOSO6, high oleic soybean oil 6%.

Bone-in carcass cutting yield = [(trimmed ham, kg + bone-in Boston, kg + bone-in picnic, kg + trimmed loin, kg + natural fall belly, kg)/ left side chilled weight, kg] × 100.

Bone-in lean cutting yield = [(trimmed ham, kg + bone-in Boston butt + bone-in picnic + trimmed loin)/ left side chilled weight] × 100.

Boneless carcass cutting yield = [((inside ham, kg + outside ham, kg + knuckle, kg + inner shank, kg + lite butt, kg) + (Canadian back loin, kg + tenderloin, kg + sirloin, kg) + (boneless Boston, kg + boneless picnic, kg) + (belly, kg))/ left side chilled weight] × 100.

Different superscript letters within the same row reflect dietary treatment differences (P ≤ 0.05).

In general, feeding HOSO resulted in increased weights of cuts. Given that feeding HOSO increased HCW, this result was not surprising. However, a portion of that HCW could also be attributed to increased fat deposition. As much of this fat is trimmed from boneless lean cuts of the carcass, the proportion of carcass weight in boneless cuts was reduced, especially at 4% and 6% HOSO inclusion. Offsetting that disadvantage of feeding HOSO was the increased belly weight of pigs fed diets with 6% HOSO. Typically, diets or management systems that result in heavier, fatter pigs similar to the present study also result in heavier bellies due to the high fat content of this cut (Harsh et al., 2017). Pigs in the present study were slaughtered at an equal age and time on treatment diets. However, in commercial production systems, pigs may be targeted for marketing on a weight basis. Doing so may minimize the differences in fat deposition between conventional diets and those containing HOSO.

Conclusion

Inclusion of HOSO up to 6% in growing-finishing swine diets improved growth performance, including reduced ADFI and increased G:F. However, carcasses from pigs fed HOSO at 4% or 6% of the diet were fatter resulting in reduced fat-free lean. Additionally, bone-in and boneless cutting yields were reduced in pigs fed HOSO compared with those fed DDGS. Therefore, further research evaluating HOSO and other diets while maintaining constant ME could potentially provide insights into differences independent of energy intake. Additionally, further research characterizing the impacts of HOSO on pork quality will help elucidate whether HOSO may be an acceptable dietary feed ingredient within the swine industry.

Supplementary Material

skac071_suppl_Supplementary_Tables
Click here for additional data file. (23.6KB, docx)

Glossary

Abbreviations

ADFI

average daily feed intake

ADG

average daily gain

DDGS

dried distiller’s grains with solubles

EDTA

ethylenediaminetetraacetic acid

ELW

ending live weight

FAME

fatty acid methyl esters

G:F

gain to feed ratio

HCW

hot carcass weight

LEA

loin eye area

LTL

longissimus thoracis

ME

metabolizable energy

MUFA

monounsaturated fatty acid

NAMP

North American Meat Processors

PDIFF

probability of difference

PUFA

polyunsaturated fatty acid

SID

standardized ileal digestible

Acknowledgment

Financial support for this project was provided by the United Soybean Board (award USB 1930-362-0602-B)

Conflict of interest statement

The authors have no conflicts of interest.

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