Introduction
Bacon is consumed worldwide for its sensory characteristics that are developed during curing and smoking (Saldana et al., 2018). Among pork primal cuts, the belly accounts for approximately 16% of carcass weight (Pulkrabek et al., 2006) and is more valuable than other cuts. Thus, the belly significantly contributes to the total value of the pork carcasses (USDA, 2024). Increasing the market weights of pigs can be exploited as a practical strategy to meet the growing demand for pork products such as belly and bacon (Metz et al., 2024).
Increased levels of unsaturated fatty acids in the swine diet lead to an incidence of soft pork bellies (Cannon et al., 1996). Moreover, soft pork is associated with increased lipid oxidation and inferior belly quality (Person et al., 2005; Trusell et al., 2011). The meat industry considers soft belly fat undesirable because it leads to poor bacon slicing and decreased bacon yields. The Pork Chain Quality Audit reported that around 10% of pork bellies are thin for bacon production and 2% are too soft to be used in bacon manufacturing (Cannon et al., 1996), resulting in a revenue loss of USD 97 million for the U.S. pork industry (Stetzer and McKeith, 2003). Due to reduced processing yields and profitability, the production of thin bellies should be minimized in the pork industry (Person et al., 2005).
Fat from a variety of sources (plant and animal origins) has been used as a nutritional intervention to improve swine growth and production traits (Soladoye et al., 2015). Diets with tallow are associated with increased belly firmness (Wang et al., 2022), whereas diets formulated with corn oil (Guo et al., 2006; Apple et al., 2009) have been shown to decrease belly firmness. In addition to fat sources, vitamins have been employed as dietary ingredients to improve production traits and meat quality in pigs. Vitamin E is an antioxidant that has a beneficial effect on the oxidative stability of pork when used in the swine diet (Monahan et al., 1990; Guo et al., 2006; Boler et al., 2009). Among the 4 isoforms of vitamin E (alpha, beta, gamma, and delta), alpha-tocopherol has the highest biological activity, whereas gamma-tocopherol promotes beneficial health effects in humans (Wagner et al., 2004).
Vitamin E has been effective in improving the oxidative stability of unsaturated lipids in fresh pork (Lanari et al., 1995; Phillips et al., 2001; Bottegal et al., 2025), whereas the effects of vitamin E on bacon quality are less pronounced, possibly due to the antioxidant activity of nitrites (Buckley and Connolly, 1980). Previous studies evaluated the effect of different fat sources (Rentfrow et al., 2003; McClelland et al., 2012) or vitamin E (Coronado et al., 2002) on belly and bacon quality. In contrast, limited investigations examined the effect of fat sources and vitamin E isoforms on belly and bacon quality. Therefore, the aim of the present study was to evaluate the effect of different dietary fat sources and vitamin E isoforms in the swine diet on the quality of belly and bacon from heavy slaughter weight (150 kg) pigs.
Materials and Methods
The protocols for the animal experiments were approved by the Institutional Animal Care and Use Committee of the University of Kentucky. The live animal phase of the experiments was completed in the environmentally controlled rooms at the University of Kentucky’s Swine Research Center. Animal harvest and meat processing were carried out at the USDA-inspected Meat Science Laboratory of the University of Kentucky.
Animals, diet, and experimental design
In experiment 1, a total of 64 individually fed pigs (32 barrows and 32 gilts; approximately 24–30 kg initial body weight) were blocked by body weight and sex, and then randomly assigned to 1 of the 8 dietary treatments in 4 × 2 factorial arrangement. Fat sources in the treatments included cornstarch (CS), tallow (TW), corn oil (CO), and coconut oil (CN). Vitamin E supplementation was at 11 IU/kg and 200 IU/kg in the form of DL (all-rac)-alpha-tocopheryl acetate (ATA)(PROVIMIX D 50 SD, DSM Nutritional Products Inc., NJ, USA). As defined in National Research Council (2012), one IU of vitamin E equals 1 mg of DL-alpha-tocopheryl acetate.
In experiment 2, a total of 72 individually fed pigs (36 barrows and 36 gilts; approximately 24–30 kg initial body weight) were blocked by sire, body weight, and sex, and then were randomly assigned to 1 of the 12 dietary treatments in a 2 × 6 factorial arrangement. Fat sources included TW and CO. Vitamin E treatments included 4 levels of ATA (11, 40, 100, and 200 ppm) and 2 levels of mixed tocopherols, primarily gamma-tocopherol (GT; 40 and 100 ppm). While the 11 ppm represented the dietary requirement of vitamin E for growing-finishing pigs (National Research Council, 2012), the others were elevated levels to elicit biological responses in swine (Wang et al., 2023).
For both experiments, corn-soybean meal-based diets in mash form were used. The pigs were fed in 5 feeding phases, including phase 1 (25 to 50 kg), phase 2 (50 to 75 kg), phase 3 (75 to 100 kg), phase 4 (100 to 125 kg), and phase 5 (125 to 150 kg). All experimental diets were formulated to meet or exceed National Research Council (2012) nutrient requirement estimates for growing-finishing pigs. Basal compositions of the diets are presented in Tables 1 (experiment 1) and 2 (experiment 2). In both experiments, pigs were fed until they reached a slaughter weight of 150 kg. The ATA was supplied in the form of DL (all-rac)-alpha-tocopheryl acetate (ROVIMIX E 50 ADS, DSM Nutritional Products, Inc., NJ, USA) in a dry form. The mixed tocopherols were supplied as Mixed Tocopherols 95 (DSM Nutritional Products, Inc., NJ, USA) in liquid form, containing 0–15% alpha-tocopherol, less than 5% beta-tocopherol, 55–75% gamma-tocopherol, and 20–30% delta-tocopherol.
Basal composition of diets with different fat sources (corn starch, corn oil, tallow, and coconut oil) and alpha-tocopheryl-acetate levels1 from phase 1 to phase 5 (as fed basis).
| Ingredient, % | Phase 1 | Phase 2 | Phase 3 | Phase 4 | Phase 5 | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| CS | Fat | CS | Fat | CS | Fat | CS | Fat | CS | Fat | |
| Corn | 60.08 | 62.85 | 66.48 | 69.55 | 70.55 | 73.81 | 73.64 | 77.04 | 76.75 | 80.30 |
| Soybean meal, 48% CP | 27.24 | 28.50 | 21.03 | 22.00 | 17.21 | 18.00 | 14.34 | 15.00 | 11.47 | 12.00 |
| Fats2 | - | 5.00 | - | 5.00 | - | 5.00 | - | 5.00 | - | 5.00 |
| Corn starch | 9.19 | - | 9.19 | - | 9.19 | - | 9.19 | - | 9.19 | - |
| L-Lysine HCl | 0.21 | 0.22 | 0.23 | 0.24 | 0.20 | 0.21 | 0.16 | 0.17 | 0.12 | 0.13 |
| DL-Methionine | 0.11 | 0.12 | 0.08 | 0.09 | 0.04 | 0.04 | 0.01 | 0.01 | 0.00 | 0.00 |
| L-Threonine | 0.09 | 0.09 | 0.08 | 0.09 | 0.06 | 0.06 | 0.03 | 0.04 | 0.02 | 0.03 |
| Limestone | 1.03 | 1.08 | 0.95 | 0.99 | 0.84 | 0.88 | 0.74 | 0.77 | 0.65 | 0.68 |
| Dicalcium phosphate | 0.88 | 0.92 | 0.79 | 0.82 | 0.75 | 0.78 | 0.72 | 0.75 | 0.62 | 0.65 |
| Salt | 0.48 | 0.50 | 0.48 | 0.50 | 0.48 | 0.50 | 0.48 | 0.50 | 0.48 | 0.50 |
| Vitamin premix3 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 |
| Mineral premix4 | 0.14 | 0.15 | 0.14 | 0.15 | 0.14 | 0.15 | 0.14 | 0.15 | 0.14 | 0.15 |
| Choline5 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 |
| Santoquin6 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 |
| AB-207 | 0.48 | 0.50 | 0.48 | 0.50 | 0.48 | 0.50 | 0.48 | 0.50 | 0.48 | 0.50 |
| Total | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 |
| Calculated nutrient level, % | ||||||||||
| ME, Mcal/kg | 3.32 | 3.47 | 3.33 | 3.49 | 3.34 | 3.50 | 3.35 | 3.50 | 3.36 | 3.51 |
| Crude protein, % | 18.31 | 19.13 | 15.87 | 16.58 | 14.31 | 14.94 | 13.12 | 13.70 | 11.96 | 12.48 |
| SID Lys | 0.99 | 1.04 | 0.86 | 0.90 | 0.74 | 0.78 | 0.64 | 0.67 | 0.54 | 0.56 |
| SID Lys/ME | 2.99 | 2.99 | 2.58 | 2.58 | 2.22 | 2.22 | 1.92 | 1.92 | 1.61 | 1.61 |
| SID Met | 0.37 | 0.38 | 0.30 | 0.32 | 0.25 | 0.26 | 0.20 | 0.21 | 0.18 | 0.19 |
| SID Cys | 0.25 | 0.26 | 0.22 | 0.24 | 0.21 | 0.22 | 0.20 | 0.21 | 0.18 | 0.19 |
| SID M+C | 0.62 | 0.65 | 0.53 | 0.55 | 0.45 | 0.47 | 0.40 | 0.42 | 0.37 | 0.38 |
| SID Thr | 0.64 | 0.67 | 0.56 | 0.58 | 0.48 | 0.50 | 0.42 | 0.44 | 0.37 | 0.39 |
| SID Trp | 0.19 | 0.20 | 0.16 | 0.17 | 0.14 | 0.14 | 0.12 | 0.13 | 0.11 | 0.11 |
| SID Arg | 1.08 | 1.13 | 0.90 | 0.94 | 0.79 | 0.82 | 0.70 | 0.73 | 0.62 | 0.65 |
| SID His | 0.43 | 0.45 | 0.37 | 0.39 | 0.34 | 0.35 | 0.31 | 0.33 | 0.29 | 0.30 |
| SID Ile | 0.66 | 0.69 | 0.55 | 0.58 | 0.49 | 0.51 | 0.44 | 0.46 | 0.39 | 0.41 |
| SID Leu | 1.37 | 1.43 | 1.23 | 1.28 | 1.14 | 1.19 | 1.07 | 1.12 | 1.01 | 1.05 |
| SID Phe | 0.77 | 0.81 | 0.66 | 0.70 | 0.60 | 0.62 | 0.55 | 0.57 | 0.50 | 0.52 |
| SID Tyr | 0.50 | 0.53 | 0.43 | 0.45 | 0.39 | 0.40 | 0.35 | 0.37 | 0.32 | 0.33 |
| SID P+T | 1.28 | 1.34 | 1.10 | 1.15 | 0.98 | 1.03 | 0.90 | 0.94 | 0.81 | 0.85 |
| SID Val | 0.72 | 0.75 | 0.62 | 0.64 | 0.55 | 0.58 | 0.51 | 0.53 | 0.46 | 0.48 |
| Ca | 0.67 | 0.70 | 0.59 | 0.62 | 0.54 | 0.56 | 0.48 | 0.51 | 0.42 | 0.44 |
| STTD P | 0.31 | 0.32 | 0.28 | 0.29 | 0.26 | 0.27 | 0.25 | 0.26 | 0.22 | 0.23 |
| Total P | 0.52 | 0.54 | 0.47 | 0.49 | 0.45 | 0.46 | 0.43 | 0.45 | 0.40 | 0.41 |
Dietary alpha-tocopheryl-acetate at 2 levels (11 ppm and 200 ppm) was applied to each basal diet.
Fat sources included corn oil, tallow, and coconut oil.
Supplied the following per kg of diet: 7,000 IU of vitamin A; 1,500 IU of vitamin D3; 2.0 mg of vitamin K; 0.03 mg of vitamin B12. 7.0 mg of riboflavin; 25.0 mg of pantothenic acid; 20.0 mg of niacin; 1.0 mg of folic acid; 2.5 mg of vitamin B6; 2.0 mg of thiamin; and 0.15 mg of biotin.
Supplied the following per kg of added fat diet: 50 mg of Mn as manganese hydroxychloride; 100 mg of Fe as ferrous sulfate monohydrate; 125 mg of Zn as zinc hydroxychloride; 20 of Cu as tribasic copper chloride; 0.35 mg of I as calcium iodate; and 0.30 mg of Se as sodium selenite.
Provided 150 mg per kg of choline to the final diet.
Santoquin (Monsanto, St. Louis, MO) supplied 130 mg/kg ethoxyquin to the final diet.
Clay product from Prince Agri Products, Inc., Quincy, IL.
Animal harvest and fresh belly measurements
Pigs were humanely slaughtered at approximately 150 kg live weight at the University of Kentucky’s USDA-inspected Meat Laboratory according to standard industry practice. The bellies (Institutional Meat Purchasing Specifications [IMPS] #408; squared at each end) were removed from the carcasses’ sides and processed according to Institutional Meat Purchasing Specifications (IMPS, 2010) and divided into 6 sections. Belly flex was measured to determine belly firmness using objective flex test equipment developed by Rentfrow et al. (2003) and the procedure previously described (Cromwell et al., 2011). Briefly, as the spareribs, related cartilage, and remaining leaf fat were removed, the bellies were squared. Fresh bellies with the skin on were then centered, fat side down, on a 7.5-cm diameter polyvinyl chloride (PVC) pipe mounted perpendicular to a board marked with a 2.54-cm grid matrix.
Lateral and vertical flexes were determined from the degree of belly flex relative to the grid matrix. A vertical belly flex of zero meant the belly was parallel to the floor and completely stiff. A lateral belly flex of 10 cm meant that the belly flexed to a point where there was 10 cm between the end of the squared belly and a vertical line directly below the center of the supporting PVC pipe. A smaller lateral flex and a greater vertical flex indicated a softer and more flexible belly. The belly flex measurements were determined in a room maintained at 7°C. Then, the belly angle was calculated using the equation below.
-
(1)
Belly angle = arctangent (left side lateral distance/left side vertical distance) + arctangent (right side lateral distance/right side vertical distance).
Belly depths were measured in 6 locations from the shoulder to the flank end. Upon completion of the belly flex and depth test, each squared belly was individually tagged with the appropriate identification, vacuum packaged, and frozen at −22°C for later processing.
Bacon processing and yields
Uncooked bellies were thawed at 4°C for 24 h and were transported to a commercial packing plant, where they were skinned and weighed before (green weight) and after injection (pumped weight). The bellies were pumped fat side down using a Townsend multi-needle bacon injection pump (Townsend INC., Des Moines, IA, USA). A commercial brine was injected at 117% of the bellies’ green weight and allowed to drain to 110% of the green weight. Bellies were hung by a bacon comb attached at the flank end and thermally processed according to the plant’s commercial protocol. Following processing, bacon slabs were removed from the smokehouse and then chilled overnight at 3°C. The following morning, individual bacon slabs were weighed to determine smokehouse yield and placed in a tempering cooler (−4°C) to facilitate optimal pressing and slicing.
Full bacon slabs were pressed using a commercial bacon press (Hoegger, Provisur Technologies, Inc., Chicago, IL, USA) and then sliced by a high-speed slicer (IBS 2000 Vision, Marel, Norwich, United Kingdom) at 12 slices per 2.54 cm. The full sliced bacon was placed on slip sheets (complete with all ends and pieces) and placed in boxes. Boxes were sealed, properly labeled, and delivered to the University of Kentucky Meat Laboratory.
Slicing yield was determined by weighing the center portions of the bacon slab after the removal of comb marks and all incomplete slices. Slicing yield was calculated as (slice weight/final weight) × 100. The remaining bacon slab, containing only commercially acceptable slices, was divided into 5 separate sections and labeled as A, B, C, D, and E (Rentfrow et al., 2003; Mandigo, 1998).
Bacon quality
Five slices of bacon, representing one slice from each section, were cooked on a George Foreman Basic Plate Grill (George Foreman, Spectrum Brands, Inc., Madison, WI, USA) to determine slice cooking loss and slice cooking shrink (Rentfrow et al., 2003). Preliminary testing was conducted to verify the degree of doneness (golden brown; not crisp). Each slice was weighed (Carolina Compact Balance, Burlington, NC, USA) before and after cooking to the nearest 0.1g. After cooking, the slices were cooled for 10 min at room temperature on absorbent paper towels. Slice cooking loss was calculated as ((raw weight-cooked weight)/raw weight) ×100. Bacon slice length was measured to the nearest 0.5 cm before and after cooking. Bacon slice cooking shrink was calculated as ((raw length-cooked length)/raw length) ×100.
For the bacon stretch, 7 slices from the same section of the bacon slab were taken and measured to the nearest 0.5 cm. The slices were vacuum packaged for 7 d, then placed on a foam tray and overwrapped with PVC film. The trays were kept at 4°C for an additional 7 d. The slices were then removed from the trays and measured again. The shelf-life stretch was calculated from the difference between day 7 and day 1.
Statistical analysis
Data analysis was performed in SAS (SAS Institute Inc., Cary, NC, USA) by least-squares analysis of variance using the Generalized Linear Model as a randomized complete block design. The individual pig served as the experimental unit. Statistical differences were established at P ≤ 0.05, and tendencies were established at P ≤ 0.10. P values greater than 0.20 were replaced with “-” in Tables 3–8. For the influence of ATA levels and fat sources, P values for the main effects are provided, and the interactions (P ≤ 0.05) between ATA levels and fat sources are indicated in Tables 3–5. For the evaluation of isoforms, only P values for the effects of isoforms and their interactions with main effects (fat sources and levels of isoforms) are provided in Tables 6–8.
Basal composition of diets with different fat sources (corn oil and tallow) and vitamin E isoforms1 from phase 1 to phase 5 (as fed basis).
| Ingredient, % | Phase 1 | Phase 2 | Phase 3 | Phase 4 | Phase 5 |
|---|---|---|---|---|---|
| Corn | 62.85 | 69.55 | 73.81 | 77.04 | 80.17 |
| Soybean meal, 48% CP | 28.50 | 22.00 | 18.00 | 15.00 | 12.00 |
| Fat (corn oil or tallow) | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 |
| L-Lysine HCl | 0.22 | 0.24 | 0.21 | 0.17 | 0.22 |
| DL-Methionine | 0.12 | 0.09 | 0.04 | 0.01 | 0.01 |
| L-Threonine | 0.09 | 0.09 | 0.06 | 0.04 | 0.05 |
| Limestone | 1.08 | 0.99 | 0.88 | 0.77 | 0.68 |
| Dicalcium phosphate | 0.92 | 0.82 | 0.78 | 0.75 | 0.65 |
| Salt | 0.50 | 0.50 | 0.50 | 0.50 | 0.50 |
| Vitamin premix2 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 |
| Mineral premix3 | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 |
| Choline4 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 |
| Santoquin5 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 |
| AB-206 | 0.50 | 0.50 | 0.50 | 0.50 | 0.50 |
| Total | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 |
| Calculated nutrient level, % | |||||
| ME, Mcal/kg | 3.47 | 3.49 | 3.50 | 3.50 | 3.51 |
| Crude protein, % | 19.13 | 16.58 | 14.94 | 13.70 | 12.59 |
| SID Lys | 1.04 | 0.90 | 0.78 | 0.67 | 0.64 |
| SID Lys/ME | 2.99 | 2.58 | 2.22 | 1.92 | 1.82 |
| SID Met | 0.38 | 0.32 | 0.26 | 0.21 | 0.20 |
| SID Cys | 0.26 | 0.24 | 0.22 | 0.21 | 0.19 |
| SID M+C | 0.65 | 0.55 | 0.47 | 0.42 | 0.39 |
| SID Arg | 1.13 | 0.94 | 0.82 | 0.73 | 0.65 |
| SID His | 0.45 | 0.39 | 0.35 | 0.33 | 0.30 |
| SID Ile | 0.69 | 0.58 | 0.51 | 0.46 | 0.41 |
| SID Leu | 1.43 | 1.28 | 1.19 | 1.12 | 1.05 |
| SID Phe | 0.81 | 0.70 | 0.62 | 0.57 | 0.52 |
| SID Tyr | 0.53 | 0.45 | 0.40 | 0.37 | 0.33 |
| SID P+T | 1.34 | 1.15 | 1.03 | 0.94 | 0.85 |
| SID Thr | 0.67 | 0.58 | 0.50 | 0.44 | 0.41 |
| SID Trp | 0.20 | 0.17 | 0.14 | 0.13 | 0.11 |
| SID Val | 0.75 | 0.64 | 0.58 | 0.53 | 0.48 |
| SID Ca | 0.7 | 0.62 | 0.56 | 0.51 | 0.44 |
| Total P | 0.54 | 0.49 | 0.46 | 0.45 | 0.41 |
| STTD P | 0.32 | 0.29 | 0.27 | 0.26 | 0.23 |
Vitamin E supplementation included alpha-tocopheryl-acetate at 4 levels (11, 40, 100, and 200 ppm) and gamma-tocopherol at 2 levels (40 and 100 ppm).
Supplied the following per kg of diet: 7,000 IU of vitamin A; 1,500 IU of vitamin D3; 2.0 mg of vitamin K; 0.03 mg of vitamin B12; 7.0 mg of riboflavin; 25.0 mg of pantothenic acid; 20.0 mg of niacin; 1.0 mg of folic acid; 2.5 mg of vitamin B6; 2.0 mg of thiamin; and 0.15 mg of biotin.
Supplied the following per kg of added fat diet: 50 mg of Mn as manganese hydroxychloride; 100 mg of Fe as ferrous sulfate monohydrate; 125 mg of Zn as zinc hydroxychloride; 20 of Cu as tribasic copper chloride; 0.35 mg of I as calcium iodate; and 0.30 mg of Se as sodium selenite.
Provided 150 mg per kg of choline to the final diet.
Santoquin (Monsanto, St. Louis, MO) supplied 130 mg/kg ethoxyquin to the final diet.
Clay product from Prince Agri Products, Inc., Quincy, IL.
Effect of different fat sources1 and alpha-tocopheryl-acetate levels2 on characteristics of fresh bellies from heavy slaughter weight (150 kg) pigs.
| ATA 11 ppm | ATA 200 ppm | P Value | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fat source | CS | TW | CO | CN | CS | TW | CO | CN | SE | ATA | Fat | ATA × Fat | |
| Belly depth (cm) | 5.49 | 5.44 | 5.16 | 5.94 | 5.21 | 4.88 | 4.93 | 5.79 | 0.17 | 0.03 | <0.01 | - | |
| Belly weight (kg) | 8.46 | 8.55 | 9.77 | 8.65 | 8.85 | 9.05 | 9.16 | 9.01 | 0.30 | - | 0.08 | - | |
| Belly flex (cm) | |||||||||||||
| Left side | Lateral | 21.29 | 21.41 | 13.03 | 32.66 | 19.69 | 20.32 | 11.43 | 32.72 | 1.51 | 0.19 | <0.01 | - |
| Vertical | 25.1 | 24.31 | 29.85 | 13.79 | 25.4 | 23.7 | 32.23 | 16.51 | 1.70 | - | <0.01 | - | |
| Right side | Lateral | 21.29 | 19.96 | 10.31 | 30.84 | 15.88 | 19.05 | 10.16 | 31.12 | 1.76 | 0.13 | <0.01 | - |
| Vertical | 27.31 | 25.76 | 33.17 | 16.69 | 28.91 | 27.51 | 33.81 | 18.11 | 1.88 | - | <0.01 | - | |
| Belly angle | 79.05 | 79.66 | 40.70 | 130.64 | 70.00 | 66.97 | 36.53 | 122.49 | 6.72 | 0.10 | <0.01 | - | |
Fat sources included corn starch (CS), corn oil (CO), tallow (TW), and coconut oil (CN).
Alpha-tocopheryl-acetate (ATA) was applied at 2 levels (11 ppm and 200 ppm).
Effect of different fat sources1 and alpha-tocopheryl-acetate levels2 on processing traits of bellies from heavy slaughter weight (150 kg) pigs.
| Parameters | ATA 11 ppm | ATA 200 ppm | P Value | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CS | TW | CO | CN | CS | TW | CO | CN | SE | ATA | Fat | ATA × Fat | |
| Green weight (kg) | 5.64 | 5.60 | 6.11 | 5.86 | 6.05 | 6.00 | 5.96 | 6.25 | 0.79 | - | - | - |
| Pump weight (kg) | 6.55 | 6.54 | 7.23 | 7.13 | 6.90 | 7.01 | 7.05 | 7.06 | 0.85 | - | - | - |
| Pump percentage (%) | 16.07 | 15.86 | 18.18 | 16.42 | 16.19 | 16.95 | 18.25 | 14.84 | 2.53 | - | 0.18 | - |
| Smoke weight (kg) | 5.93 | 5.92 | 6.54 | 6.45 | 6.24 | 6.34 | 6.38 | 6.39 | 0.77 | - | - | - |
| Chill weight (kg) | 5.24 | 5.15 | 5.77 | 5.47 | 5.80 | 5.97 | 5.58 | 5.73 | 0.77 | - | - | - |
| Final weight (kg) | 5.81 | 5.71 | 6.40 | 6.07 | 6.43 | 6.62 | 6.19 | 6.36 | 0.86 | - | - | - |
| Slice weight (kg) | 5.53 | 5.08 | 5.65 | 5.55 | 5.75 | 5.52 | 5.47 | 5.77 | 0.90 | - | - | - |
| Slicing yield (%) | 94.98 | 95.68 | 93.27 | 91.70 | 89.62 | 89.18 | 88.69 | 91.53 | 5.52 | 0.04 | - | - |
Fat sources included corn starch (CS), corn oil (CO), tallow (TW), and coconut oil (CN).
Alpha-tocopheryl-acetate (ATA) was applied at 2 levels (11 ppm and 200 ppm).
Effect of different fat sources1 and alpha-tocopheryl-acetate levels2 on quality traits of bacon from heavy slaughter weight (150 kg) pigs.
| Parameters | ATA 11 ppm | ATA 200 ppm | P Value | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CS | TW | CO | CN | CS | TW | CO | CN | SE | ATA | Fat | ATA × Fat | |
| Raw weight (kg) | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | 0.00 | - | 0.11 | 0.15 |
| Cooked weight (kg) | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.00 | - | - | - |
| Bacon slice cook loss (%) | 59.96 | 62.51 | 63.97 | 58.73 | 60.86 | 65.67 | 62.96 | 60.40 | 5.69 | - | - | - |
| Raw length (cm) | 23.64 | 23.95 | 25.85 | 24.50 | 24.40 | 24.53 | 25.50 | 24.17 | 1.14 | - | 0.05 | - |
| Cooked length (cm) | 14.28 | 14.04 | 13.44 | 15.03 | 14.53 | 14.07 | 14.28 | 14.73 | 1.21 | - | - | - |
| Bacon slice cooking shrink (%) | 39.60 | 42.18 | 45.80 | 36.67 | 40.53 | 42.74 | 44.21 | 39.98 | 5.53 | - | 0.12 | - |
| Stretch (cm) | 0.47 | 0.48 | 0.90 | 0.81 | 0.43 | 0.36 | 0.90 | 0.28 | 0.55 | - | - | - |
Fat sources included corn starch (CS), corn oil (CO), tallow (TW), and coconut oil (CN).
Alpha-tocopheryl-acetate (ATA) was applied at 2 levels (11 ppm and 200 ppm).
Effect of different fat sources1 and vitamin E isoforms2 on characteristics of fresh bellies from heavy slaughter weight (150 kg) pigs.
| Parameters | Fat Source | Vitamin E Isoforms | P Value | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ATA, ppm | GT, ppm | ATA Level3 | Fat | Isoforms (IF) | ||||||||||
| 11 | 40 | 100 | 200 | 40 | 100 | L | Q | IF | IF × Level | IF × Fat | ||||
| Belly depth (cm) | TW | 5.15 | 5.23 | 5.13 | 4.94 | 5.21 | 5.05 | - | - | 0.04 | - | - | - | |
| CO | 4.63 | 4.95 | 4.81 | 4.83 | 4.85 | 4.42 | ||||||||
| Belly weight (kg) | TW | 9.75 | 9.52 | 9.41 | 9.36 | 8.88 | 9.53 | - | - | - | 0.11 | 0.14 | - | |
| Belly flex (cm) | ||||||||||||||
| Left side | Lateral | TW | 18.03 | 14.29 | 16.09 | 17.15 | 15.49 | 15.75 | - | - | <0.01 | - | - | - |
| CO | 11.68 | 10.48 | 11.01 | 11.26 | 10.16 | 9.14 | ||||||||
| Vertical | TW | 29.53 | 27.94 | 27.73 | 27.94 | 28.36 | 27.18 | - | - | 0.04 | - | - | - | |
| CO | 31.50 | 31.05 | 29.85 | 29.13 | 32.17 | 31.24 | ||||||||
| Right side | Lateral | TW | 16.51 | 13.97 | 13.34 | 15.24 | 15.49 | 13.46 | - | 0.17 | <0.01 | - | - | - |
| CO | 10.41 | 10.41 | 11.01 | 11.18 | 10.37 | 9.40 | ||||||||
| Vertical | TW | 29.85 | 29.46 | 30.23 | 29.72 | 30.48 | 28.15 | - | - | 0.15 | - | - | - | |
| CO | 32.26 | 30.16 | 31.33 | 31.88 | 30.48 | 31.24 | ||||||||
| Belly angle | TW | 52.75 | 44.31 | 47.18 | 48.28 | 50.69 | 44.45 | - | - | <0.01 | - | - | - | |
| CO | 31.65 | 34.26 | 34.94 | 34.08 | 33.48 | 29.52 | ||||||||
Fat sources included corn oil (CO) and tallow (TW).
Vitamin E supplementation included alpha-tocopheryl-acetate (ATA) at 4 levels (11, 40, 100, and 200 ppm) and gamma-tocopherol (GT) at 2 levels (40 and 100 ppm). IF = Isoforms.
Linear (L) and quadratic (Q) responses are based on 4 levels of ATA.
Effect of different fat sources1 and vitamin E isoforms2 on processing traits of bellies from heavy slaughter weight (150 kg) pigs.
| Parameters | Fat Source | Vitamin E Isoforms | P Value | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ATA, ppm | GT, ppm | ATA Level3 | Isoforms (IF) | ||||||||||
| 11 | 40 | 100 | 200 | 40 | 100 | L | Q | Fat | IF | IF × Level | IF × Fat | ||
| Green weight (kg) | TW | 6.09 | 6.31 | 6.28 | 5.82 | 5.77 | 5.82 | 0.15 | - | - | 0.04 | - | - |
| CO | 6.33 | 6.21 | 6.09 | 5.58 | 6.00 | 5.50 | |||||||
| Pump weight (kg) | TW | 7.17 | 7.41 | 7.28 | 6.83 | 6.72 | 6.78 | - | - | - | 0.02 | - | - |
| CO | 7.36 | 7.31 | 7.30 | 6.62 | 7.13 | 6.04 | |||||||
| Pump percentage (%) | TW | 17.59 | 17.51 | 17.46 | 17.17 | 14.38 | 16.21 | 0.15 | - | - | 0.05 | - | - |
| CO | 18.88 | 17.87 | 18.43 | 16.57 | 18.74 | 15.10 | |||||||
| Smoke weight (kg) | TW | 6.67 | 6.90 | 6.77 | 6.35 | 6.25 | 6.30 | - | - | - | 0.02 | - | - |
| CO | 6.84 | 6.80 | 6.79 | 6.16 | 6.63 | 5.62 | |||||||
| Chill weight (kg) | TW | 6.64 | 6.86 | 6.74 | 6.32 | 6.22 | 6.28 | - | - | - | 0.02 | - | - |
| CO | 6.81 | 6.77 | 6.76 | 6.13 | 6.60 | 5.59 | |||||||
| Final weight (kg) | TW | 6.25 | 6.48 | 6.38 | 5.98 | 5.92 | 5.90 | - | - | - | 0.07 | 0.14 | - |
| CO | 6.48 | 5.67 | 6.41 | 5.79 | 6.28 | 5.33 | |||||||
| Slice weight (kg) | TW | 5.95 | 6.14 | 5.98 | 5.45 | 5.53 | 5.31 | 0.08 | - | - | 0.04 | - | - |
| CO | 6.38 | 5.93 | 5.79 | 5.40 | 5.80 | 5.25 | |||||||
| Slicing yield (%) | TW | 95.41 | 94.75 | 93.76 | 94.20 | 93.37 | 94.89 | - | - | - | - | - | - |
| CO | 94.23 | 91.73 | 92.57 | 92.94 | 92.65 | 93.73 | |||||||
Fat sources included corn oil (CO) and tallow (TW).
Vitamin E supplementation included alpha-tocopheryl-acetate (ATA) at 4 levels (11, 40, 100, and 200 ppm) and gamma-tocopherol (GT) at 2 levels (40 and 100 ppm). IF = Isoforms.
Linear (L) and quadratic (Q) responses are based on 4 levels of ATA.
Effect of different fat sources1 and vitamin E isoforms2 on quality traits of bacon from heavy slaughter weight (150 kg) pigs.
| Vitamin E Isoforms | P Value | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ATA, ppm | GT, ppm | ATA Level3 | Isoforms (IF) | ||||||||||
| Parameters | Fat Source | 11 | 40 | 100 | 200 | 40 | 100 | L | Q | Fat | IF | IF × Level | IF × Fat |
| Raw slice weight (kg) | TW | 0.04 | 0.04 | 0.04 | 0.04 | 0.03 | 0.04 | 0.13 | - | - | 0.03 | - | - |
| CO | 0.04 | 0.04 | 0.04 | 0.03 | 0.04 | 0.03 | |||||||
| Cooked slice weight (kg) | TW | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | - | - | 0.10 | 0.01 | - | - |
| CO | 0.02 | 0.02 | 0.01 | 0.02 | 0.02 | 0.01 | |||||||
| Bacon slice cook loss (%) | TW | 54.76 | 49.33 | 50.42 | 50.86 | 51.98 | 49.22 | - | - | - | - | - | - |
| CO | 57.08 | 48.99 | 58.75 | 52.43 | 56.22 | 57.76 | |||||||
| Raw length (cm) | TW | 24.70 | 25.56 | 24.63 | 24.84 | 23.82 | 25.85 | - | - | 0.02 | - | 0.09 | - |
| CO | 26.18 | 26.45 | 26.33 | 25.58 | 25.98 | 25.54 | |||||||
| Cooked length (cm) | TW | 15.48 | 15.38 | 17.07 | 16.24 | 15.57 | 17.72 | - | - | - | - | - | - |
| CO | 15.64 | 16.03 | 14.32 | 16.36 | 16.78 | 14.90 | |||||||
| Bacon slice cooking shrink (%) | TW | 37.47 | 35.58 | 30.87 | 34.89 | 34.73 | 31.32 | - | - | 0.02 | - | - | - |
| CO | 41.89 | 40.06 | 45.78 | 39.29 | 36.00 | 41.80 | |||||||
| Stretch (cm) | TW | 0.09 | 0.16 | 0.27 | 0.24 | 0.06 | 0.19 | - | - | 0.15 | - | - | - |
| CO | 0.71 | 0.50 | 0.52 | 0.11 | 0.74 | 0.19 | |||||||
Fat sources included corn oil (CO) and tallow (TW).
Vitamin E supplementation included alpha-tocopheryl-acetate (ATA) at 4 levels (11, 40, 100, and 200 ppm) and gamma-tocopherol (GT) at 2 levels (40 and 100 ppm). IF = Isoforms.
Linear (L) and quadratic (Q) responses are based on 4 levels of ATA.
Results
Experiment 1
Belly depth and belly flex were affected (P < 0.01) by different fat sources (Table 3). Belly from pigs fed CO diet exhibited the softest belly, with a lower lateral distance (P < 0.01) as well as belly angle (P < 0.01) and a greater vertical distance (P < 0.01), compared with the belly from pigs fed CS, TW, and CN. In contrast, the belly of animals fed CN exhibited the firmest belly, with a greater lateral distance (P < 0.01) as well as belly angle (P < 0.01) and a lower vertical distance (P < 0.01) than the belly from pigs fed other fat sources. Additionally, belly depth was affected by ATA levels (P = 0.03; experiment 1; Table 3). Regardless of the fat source, the increase of ATA levels (from 11 ppm to 200 ppm) decreased (P < 0.05) belly depth.
An effect of ATA levels was observed on slicing yield (P = 0.04); slicing yield decreased with an increase in the level of ATA from 11 to 200 ppm (Table 4). No interactions between ATA levels and fat sources were observed for bacon processing traits (P > 0.05). Additionally, ATA levels and fat source did not (P > 0.05) impact green weight, pump weight, pump percentage, smoke weight, chill weight, final weight, and slice weight (Table 4).
The levels of ATA did not (P > 0.05) influence bacon quality. On the other hand, an effect (P = 0.05) of fat sources was observed on raw length (Table 5). Raw length was greater in bacon from pigs fed CO than those fed CS, TW, and CN. No interactions (P > 0.05) were observed between ATA levels and fat sources on bacon quality (Table 5).
Experiment 2
Belly depth was not affected (P > 0.05) by vitamin E isoforms but was influenced (P < 0.05) by fat sources (Table 6). Pigs fed TW exhibited greater belly depth (P = 0.04) and lateral distance (P < 0.01) than those fed CO. Additionally, a lower vertical distance (P = 0.04) was observed only in bellies from the left sides of pigs fed TW than those from their counterparts in CO diets.
There was an effect of vitamin E isoforms on green weight (P = 0.04), pump weight (P = 0.02), pump percentage (P = 0.05), smoke weight (P = 0.02), chill weight (P = 0.02), and slice weight (P = 0.04) of bellies (Table 7). Bellies from pigs fed 40 and 100 ppm ATA were heavier than those from pigs fed the same concentration of GT. However, there was no difference (P > 0.05) in slicing yield between the 2 isoforms. There were no interactions between vitamin E isoforms and levels (P > 0.05) as well as between the isoforms and fat sources (P > 0.5) for belly processing traits.
The levels of ATA had no effect (P > 0.05) on bacon quality (Table 8). However, there was an effect of fat sources on raw length (P = 0.02), and slice shrink (P = 0.02). The bacon slices from pigs fed TW exhibited lower raw length and slice shrink than the slices from pigs fed CO. An effect of vitamin E isoforms was observed on raw weight (P = 0.03) and cooked weight (P = 0.01). Pigs fed ATA exhibited heavier (raw and cooked weight) bacon than those fed GT. No interactions were observed between vitamin E isoforms and levels (P > 0.05) as well as between the isoforms and fat sources (P > 0.5) on bacon quality.
Discussion
Pigs fed CN exhibited the firmest belly, which is positively correlated with the increased levels of saturated fatty acids in swine diets (Rentfrow et al., 2003; Kellner et al., 2014). Additionally, Wang et al. (2022) reported softer bellies from pigs fed corn oil compared to those fed tallow and coconut oil. Kellner et al. (2014) documented that the pigs fed tallow produced firmer bellies (lower belly firmness score) than those fed corn oil, and this observation agreed with the greater iodine value in corn oil than in beef tallow. McClelland et al. (2012) investigated the effect of corn-soybean meal diets containing various levels of distillers dried grains with solubles (DDGS) on pork quality and reported an increase in vertical flex and a decrease in lateral flex of bellies with an increase in the levels of DDGS, which has a high content of unsaturated fatty acids.
Our results agree with Wang et al. (2022) that evaluated the effect of ATA supplementation (11 and 200 ppm) and fat source (corn starch, tallow, distiller’s corn oil, and coconut oil) on growth performance, carcass characteristics, and meat quality of heavy slaughter weight pigs. These authors documented that the bellies of pigs fed a coconut oil diet had a greater lateral distance and belly angle but lower vertical distance than the bellies of pigs fed a tallow and corn starch diet. On the other hand, bellies obtained from pigs fed the distiller’s corn oil demonstrated lower lateral distance as well as belly angle and a greater vertical distance than their counterparts from pigs fed tallow and corn starch diets. These authors also reported that increasing dietary ATA levels from 11 ppm to 200 ppm decreased belly depth, which agrees with the present results.
Pigs fed ATA yielded heavier bellies and bacon than those fed GT. Vitamin E is stored mostly in the adipose tissue and is involved in stabilizing lipids (Mayes, 2000). Furthermore, the concentrations of vitamin E isoforms vary in muscle and fat (Rey et al., 2006). These authors investigated the accumulation of alpha and gamma tocopherols in skeletal muscles (longissimus dorsi and biceps femoris) and backfat from Iberian pigs and reported a greater accumulation of alpha-tocopherol compared to gamma-tocopherol in all samples, indicating a possible relation between alpha-tocopherol deposition and pig weight gain. This in turn, may explain the lower weight of pigs fed GT than those fed ATA. On the other hand, Guo et al. (2006) reported that vitamin E supplementation did not affect carcass traits; these authors investigated the effects of dietary alpha-tocopherol (40 IU/kg and 200 IU/kg) and fat (normal corn, high oil corn, high oil corn plus added beef tallow) supplementation on pork quality and documented that adding fat or vitamin E had no effect on dressing percentage, back fat, marbling, and firmness.
The increase of ATA (from 11 ppm to 200 ppm) levels resulted in a decrease in belly depth and bacon slicing yield, which is a negative impact on belly/bacon quality. Bacon from thick bellies exhibited increased processing yields throughout the smoking and cooking phases (Person et al., 2005). Similar results were documented by investigations of Wang et al. (2022) that reported a decrease in belly depth with the increase in dietary ATA level from 11 ppm to 200 ppm.
The lowest belly angle and lateral distance observed in CO could be attributed to the high content of unsaturated fatty acids in CO, leading to soft bellies. In partial agreement, Wang et al. (2022) reported that bellies from pigs fed with coconut oil (high in saturated fatty acids) had greater belly angle and lateral distance compared with those from pigs fed with corn starch, tallow, and distiller corn oil.
Conclusions
Dietary fat sources with increased saturated fatty acids (such as TW) could improve the belly firmness and the quality of bacon compared to fat sources high in polyunsaturated fatty acids (such as CO) in heavy slaughter weight pigs. The increase in the levels of ATA (from 11 ppm to 200 ppm) decreased belly depth and slicing yield. Additionally, heavy slaughter-weight pigs fed ATA exhibited heavier bacon compared with pigs fed GT at the corresponding levels. The findings demonstrated the importance of dietary fat sources and vitamin E isoforms on belly and bacon quality. Elevated levels of ATA, as well as saturated fatty acid sources such as TW, could be exploited as a dietary strategy to improve the quality of bacon from heavy slaughter-weight pigs.
Declaration of Competing Interest
The authors declare no conflicts of interest.
Acknowledgments
This work was supported by the National Pork Board, Fats and Proteins Research Foundation, and DSM Nutritional Products.
Author Contribution
Marlee Kelley: data curation, formal analysis, and writing – original draft. Ding Wang: data curation. Ana Paula Salim: writing – original draft, and writing – review & editing. Gregg Rentfrow: conceptualization, funding acquisition, investigation, methodology, resources, supervision, and writing – original draft. Merlin Lindemann: conceptualization, funding acquisition, investigation, methodology, resources, supervision, and writing – review & editing. Surendranath P. Suman: investigation, methodology, supervision, and writing – review & editing.
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