Meat Quality Assessment of Pork Fed Poultry Fat, Flaxseed Oil, and Supplemented with Vitamin E

Abstract

The objective of this research is to understand carcass and meat quality characteristics of pigs fed a combination of poultry fat, flaxseed oil, and supplemented with vitamin E. It is hypothesized that certain combinations of these ingredients may increase intramuscular fat (IMF) percentage while simultaneously decreasing external fat deposition. Yorkshire pigs (n=96) weighing approximately 50 kg were allocated to pens based on weight and sex, over two trials. Pigs within each trial were born in the same farrowing groups and each pen was allotted two gilts or two barrows. Each pen was randomly assigned to one of 8 dietary treatments in a 4 x 2 factorial arrangement. Corn-soybean meal finisher diets were formulated to contain 0, 2, 4 or 6% lipids and either 11 or 220 IU Vitamin E/kg. For all diets with lipids, 1% flaxseed oil was included and the remaining lipids supplied by poultry fat (0, 1, 3, or 5%). Pigs were harvested (n=8 groups) when an average pen weight of 110 ± 3 kg was achieved. Following harvest, hot carcass weight (HCW) was recorded. At 24 hours post mortem carcasses were evaluated for last rib fat thickness (LRFT), tenth rib fat thickness (TRFT), loin eye area (LEA), muscle score (MS), percent fat free lean (%FFL), color values (L*, a*, b*), ultimate pH of the ham (pHH) and loin (pHL), and National Pork Producers Council (NPPC) color (NPPCCol) and marbling score (NPPCMar). TRFT, LEA, L*, a*, b*, pHH, NPPCCol, and NPPCMar were determined on the loin eye at the 10th/11th rib interface after chilling, prior to carcass fabrication. After carcasses were chilled for 24 h at 4±2°C, 2.54 cm pork chops were fabricated from the left side of the carcass and individually packaged in vacuum-sealed bags and frozen at -20±2°C for further analysis. Bellies were measured for thickness (BT), and both skin-side up (SSU) and skin-side down (SSD) firmness evaluation were made. Chops were analyzed for drip loss (DL), vacuum purge loss (VP), marinade uptake (MU), marinade cook loss (MCL), cook loss (CL), Warner-Bratzler Shear Force (WBS), and thiobarbituric acid reactive substances (TBARS). Proximate analysis was performed for the determination of collagen, fat, moisture, protein, and salt content of loin samples. Sensory evaluation by a trained panel was also performed. Statistical analysis was conducted using Proc GLM procedure in SAS (2002). Carcass was the experimental unit and days on feed (DOF) was used as a covariate. Main effects included trial, sex of pig, lipid level, and vitamin E concentration. All interactions were also included in the model. A 4-way interaction of trial x lipid x sex x vitamin E affected the measurements for SSU (P=0.0430) and CL (P=0.0379). Two 3-way interactions were found in this study. Lipid x vitamin E x sex were different for a* (P=0.0193), pHL (P=0.0007), SSU (P=0.03), belly thickness (P=0.0198), and VP (P=0.0167). A trial x lipid x vitamin E interaction for SSU (P=0.0238), DL (P=0.0471) and CL (P=0.0305) was present. Additionally, a trial x vitamin E interaction was present for TFRT (P=0.03), %FFL (P=0.0350), MS (P=0.0304), SSD (P=0.0042), SSU (P=0.0079), DL (P=0.0490), VP (P=0.0418), and Collagen % (P=0.0225). There was a trial x sex interaction present for LRFT (P=0.0034), VP (P=0.0286), and moisture % (P=0.0390). A lipid x sex interaction was also significant for LRFT (P=0.0031), %FFL (P=0.0164), MS (P=0.0362), and SSU (P=0.0335). A vitamin E x sex interaction was also observed for LRFT (0.0206), SSD (P=0.0003), and SSU (P=0.0018). There was a lipid x vitamin E interaction for TRFT (P=0.0015), %FFL (P=0.0028). Lipid level, vitamin E concentration, and sex had no effect (P>0.05) on HCW, LEA, %FFL, a*, b*, NPPCCol, pHH, pHL, MS, SSD, SSU, belly thickness, DL, VP, MU, MCL, WBS, % fat, % moisture, % collagen, % protein, % salt, and TBARS. Vitamin E concentration had an effect (P<0.05) on LRFT, TRFT, and NPPCMar. Treatments with inclusion of 220 IU vitamin E produced greater values for LRFT (23.19 vs 21.41 mm), TRFT (21.62 vs 19.26 mm), and NPPCMar (1.87 vs 1.41) than 11 IU vitamin E. In addition, differences were seen across trials for HCW (P=0.0204), MS (P=0.0404), pHH (P<0.0001), pHL (P<0.0001), NPPCCol (P=0.0207), and TBARS (P<0.0001). Trial 1 had greater values for HCW (84.76 vs 81.75 kg), MS (2.57 vs 2.35), pHH (5.85 vs 5.53), pHL (5.67 vs 5.45), and TBARS (0.22 vs 0.15); while NPPCCol was greater in trial 2 (3.24 vs 2.84). Lastly, sex had an effect (P<0.05) on L* and CL. Barrows had greater values (P<0.05) for L* (61.50 vs 58.86) and CL percentage as compared to gilts (17.14 vs 14.89%). A feeding program utilizing poultry fat in combination with flaxseed oil and vitamin E at these levels will not negatively affect carcass composition or meat quality. While differences are present in this study, all treatments produced pork products which fall within a normal acceptable range for carcass composition and meat quality analysis, all without compromising belly firmness or sensory attributes. Further analysis of fatty acid composition assessment is needed for determining the additional benefits of flaxseed oil inclusion into swine diets.