The Feeding Value and Digestibility of Waste Fats with Polymers in Poultry and Pig Feeds

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Abstract
Dutch manufacturers of concentrates regularly make use of fat mixtures containing renderers fat combined with industrial waste fats and exhausted frying fats. In a trial involving 1000 broilers, feeds containing 8,9 or 10% TGF fat (triglyceride fraction fat) were compared with a feed containing 8% renderers fat. In the group fed TGF fat, growth after 7 weeks was 4% behind that of animals receiving the ration with renderers fat. Feed conversion was also significantly lower. The ME of the TGF fat was 5562 kcal/kg. The digestibility coefficient was 62, as compared to 89 for renderers fat. In a second feed trial comparable results were obtained when an industrial waste fat (Code: E 8700) from another source was used. The ME of the renderers fat was 8564 kcal/kg and that of the E 8700 fat was 6278. The digestibility coefficients were 89.8 and 66.6 respectively. In two digestibility trials involving young pigs weighing about 35 kg, a commercial fat mixture with 4% polymerized TGF and an exhausted frying fat with 6.9% polymerized TGF were compared with renderers fat. In the first trial a digestibility coefficient of 88.8 was registered for renderers fat and 86.6 for the fat mixture. In the second trial these figures were 78.3 and 82.1 respectively. No explanation could be found for the low digestibility coefficient of renderers fat in this second trial. No polymeric triglycerides were found in the faeces of the pigs, but there were polymeric fatty acids present. After lipolysis of the triglycerides polymeric fatty acids are practically indigestible for chickens and pigs.