Influence of oilseeds in combination with vitamin E supplementation in the diet on backfat quality of pigs

To study combination effects of oilseeds and vitamin E supplements in the diet on backfat quality, two feeding experiments with a total of 60 growing-finishing pigs were designed. Experiment 1 (24 pigs) included a control group with a cereal/soybean-meal diet and two experimental groups with 100 g kg(-1) rapeseed or 200 g kg(-1) full-fat soybeans, resulting in an increase of ether extract from 28 to 74 or 69 g kg(-1) respectively. Three weeks before slaughter, four animals of each group were fed additionally with 1 g alpha-tocopherol acetate per animal per day, In experiment 2, four groups of nine pigs each received a cereal/soybean meal diet, and 0, 1, 2 and 3 weeks before slaughtering, the animals were given 1 g alpha-tocopherol acetate per day. Tocopherol concentration in blood, liver, muscle and backfat was determined by applying the HPLC technique. In addition, the fatty acid pattern of the backfat was analyzed using capillary gas chromatography and the oxidative stability of the fat was determined using the Rancimat test. In experiment 1, oilseed influenced the fatty acid pattern of the backfat, The percentage of linolic and linolenic acid increased significantly and a tendency towards lower proportions of saturated fatty acids was detected. However, the full-fat soybean diet decreased the percentage of oleic acid significantly. Vitamin E supplements three weeks before slaughter increased vitamin E concentration of backfat from 12.3 to 31.1 mg kg(-1). The response to dietary alpha-tocopherol intake in the various organs was found to be in the sequence liver > subcutaneous fat > serum > muscle. Oxidative induction time of backfat varied between 2.9 and 13.7 h depending on the fatty acid pattern and the vitamin E concentration. The shortest induction times were observed when oilseed without vitamin E supplements were fed. The longest times were observed after feeding the soybean/cereal diet with vitamin E supplements. In experiment 2, vitamin E concentration of backfat was much lower (ranging between 7.0 and 12.8 mg kg(-1)) than in experiment 1. Vitamin E administration over three weeks doubled vitamin E concentration in backfat and also induction time. Results demonstrate the antioxidative effects of vitamin E and its meat quality improving properties.