Comparative investigation on the utilization of glycerol, free fatty acids, free fatty acids in combination with glycerol and vegetable oil in fattening of pigs

The utilization of supplemented plant oil or free fatty acids in comparison to free fatty acids and glycerol was investigated in a feeding experiment. The free fatty acids originated from soyabean oil and rape-seed oil (1 : 1). Five groups of six barrows (27 kg average body weight at the beginning) received the experimental diets for 14 weeks. The five dietary treatments were as follows: Control group 1, barley-soya bean meal (basal diet); control group 2, basal diet+10% glycerol; group 3, basal diet +3.2% fatty acids; group 4, basal diet +2.4% fatty acids +0.8% glycerol; group 5, basal diet +3.2% vegetable oil. The metabolizable energy (ME) of diets was increased in groups 3 and 5 by 7.1% and in the group 4 by 5.8% compared with control group 1. Glycerol group 2 showed the highest feed intake. In groups 1-5 the daily live weight gain was 742 g, 787 g, 784 g, 739 g and 716 g, respectively. The feed conversion ratio showed no significant differences between the groups. The back fat thickness was highest in groups 3 and 5, due to the increased ME in these diets. The content of polyenic fatty acids in the back fat was 9.5, 8.0, 15.5, 15.3 and 16.8% in groups 1-5, respectively. The incorporation of polyenic acids was higher when vegetable oil was in the diet in comparison to free fatty acids. The contents of palmitic acid (C16:0) and stearic acid (C18:0) were highest in both control groups without far addition.