Impact of Feeding Oxidized Oils to Induce Oxidative Stress on the Quality of Pork

Recently, there has been renewed interest in the oxidative status of lipids fed to pigs and poultry. Oxidized lipids and secondary products of oxidation, when part of the diet, can be deposited in animal tissues and lead to compromised oxidative status in those tissues and subsequent meat products. Oxidation of lipids and proteins in meat products negatively affects their quality. Oxidation of lipids occurs during storage, especially in higher fat products like bacon and sausage, and can lead to rancid flavor development. Oxidation of myoglobin during storage and display of fresh meat leads to the formation of metmyoglobin and an overall browning discoloration of meat. Lipid and protein oxidation do not exist in isolation as an increase in one can cause an increase in the other. Despite the importance of oxidative stability in meat products, feeding of oxidized oils to pigs and poultry has resulted in mixed results in terms of product quality. In general, the impact of feeding oxidized oil on meat quality is more pronounced in poultry than in pigs. In a recent study, swine diets were formulated with 10% soybean oil treated to mimic the following oxidizing conditions: feed storage during elevated temperatures (heated at 45°C for 288 h), rendering (heated at 90°C for 72 h), and frying (heated at 180°C for 6 h). A fourth diet was formulated with fresh oil and all diets were fed for 81d. Oil heated to 45°C had the highest thiobarbituric reactive substances value of the four treatments and a similar peroxide value compared with 180°C-heated oil. Average daily gain was depressed in pigs fed 90°C-heated oil compared with 45°C and 180°C oil treatments but was not different from pigs fed fresh oil. Pork loin quality characteristics including pH, color and marbling were similar among all treatments at 24h postmortem. However, during simulated retail display, pork loin chops from pigs fed diets containing the 45°C-heated oil were more red and more intense in color. Unfortunately, those chops also discolored more rapidly during display. Oxidation development during bacon storage was not affected by oil treatment. Therefore, based on these data, while feeding oxidized oils can negatively impact swine growth and performance, it did not appear to have a dramatic impact on product quality.