Comparison of grain sources for swine diets and their effect on meat and fat quality traits

A study was conducted to evaluate the effect of dietary grain sources on various compositional and quality characteristics of pork from pigs reared in a commercial environment. Pigs were fed 1 of 5 dietary treatments containing the following single or blended grain sources throughout most of the grow-finish period: 1) yellow corn, 2) white corn, 3) 1/3 yellow corn and 2/3 white corn, 4) 2/3 yellow corn and 1/3 white corn, and 5) barley. Pigs were from 2 sire genetic types, Duroc and Hampshire x Duroc, mated to PIC 1055 females. A total of 1,040 pigs were included in the study in a 2 x 2 x 5 factorial arrangement with 2 genetic types, 2 sexes (barrows and gilts), and 5 dietary treatments. Eight pigs were randomly selected from each pen of 26 (n = 320) for meat and fat quality evaluation. Pigs were 27.6 kg at the beginning of the experiment and were fed to 130.2 kg. All animals were held overnight at a commercial abattoir before slaughter. One whole, skin-on, boneless loin was collected from each carcass and held at -1 degrees C in a cryovac-sealed bag at the Iowa State University Meat Laboratory. At 25 to 27 d postslaughter, loins were evaluated for meat and fat quality. Dietary treatment had no effect (P > 0.05) on 24-h pH, sensory tenderness, sensory chewiness, Instron tenderness, loin purge, or cook loss. At 25 to 27 d postslaughter, pigs fed diet 4 had a greater (P < 0.05) loin pH than pigs fed diet 1, and diets 2, 3, and 5 were not different from all treatment means. Pigs fed diet 4 had a greater (P < 0.05) Japanese color score than pigs fed diets 2, 3, and 5, and diet 1 was not different from all treatment means. Pigs fed diet 3 had a greater percentage of intramuscular fat than pigs fed diets 1 and 2, although diets 1, 4, and 5 and diets 1, 2, and 5 were not different (P > 0.05). No differences among dietary treatments were found for fat color values on a subjective basis. Pigs fed diet 5 had a more desirable objective fat color than pigs fed all white corn, and diets 1, 3, and 4 were not different (P > 0.05). Pigs fed diet 5 had greater levels of SFA and MUFA, and lower levels of unsaturated fatty acids and PUFA, in the subcutaneous fat than pigs fed all other diets. These results indicate that the energy sources evaluated in this study had little effect on eating quality of pork that was held for 25 to 27 d postslaughter.