Abstract
A study was conducted to determine the effects of supplementing of soybean oil into diet and its timing during the growing-finishing period upon the physicochemical characteristics of fat tissues and intramuscular fat in longissimus muscle of pigs.
Ten 4-months old piglets were allotted into three groups of different feeding conditions for 6 weeks. Group I was composed of 4 pigs fed a basal diet as the control. Three pigs each in Groups II and III were given the basal diet with 5% soybean oil during the initial 4 weeks and the terminal 4 weeks, respectively, in the experiment, while the basal diet was fed to them for the balance two weeks. The lipids extracted from the inner and outer layers of back fat, leaf fat and intramuscular fat in longissimus muscle were analyzed by physicochemical methods. The results were as follows. The supplementing of soybean oil into diet increased the contents of linoleic and linolenic acids in lipids but reduced those of oleic acid invariably which were collected from various positions of the bodies of pigs studied. The diet containing soybean oil tended to lower the melting point and the hardness by Texturometer and to raise the iodine number and refractive index of fat in fat tissues of the pigs. From the viewpoint of the level of linoleic acid, the fat in fat tissues appeared to be influenced more appreciably by the oil supplementing than the intramuscular fat. From the viewpoint of changes in the melting point and the contents of saturated fatty acids, the influences of the oil supplementing seemed to be more appreciable in leaf fat than in the inner and the outer layers of back fat. The mean levels of linoleic and linolenic acids and the iodine number in all the fat samples collected from various positions of the pigs' bodies tended to be higher in the Group III than in the Group II. However, the level of stearic acid in fat in the Group III seemed to be slightly higher than that in the Group II, while the contents of saturated fatty acids and the hardness by Texturometer of both groups were almost equal to each other.
Consequently, it was realized that the difference in the timing of oil supplementing by about 2 weeks caused hardly any differences in the firmness of porcine fat, but caused somewhat appreciable influences upon the physicochemical characteristics of the fat.
