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The evaluation of raspberry pomace as a feedstuff for growing pigs McDougall, N. Ruth


Raspberry pomace, consisting of seeds, pulp and added rice hulls, is the residue from the pressing of raspberries for juice and concentrate production. Through the determination of chemical composition by laboratory analyses and the measurement of feeding value in animal trials, the pomace was evaluated as a feedstuff for growing pigs. Pomace contains 11.1% crude fat, 10.0% crude protein, 59.5% total dietary fibre, 7.4% soluble carbohydrates, and a gross energy level of 5220 kcal*kg⁻¹. The acid detergent residue of the pomace contains 11.7% lignin, 6.0% cutin, 2.2% acid detergent ash and 26.0% cellulose (by difference). The digestibility of dry matter, fat, protein and energy was determined. Pomace dried at 60 C, whole and ground (1mm) was fed to growing male pigs (30-35 kg) in a replicated 4X4 Latin Square design with treatments basal (B) , B plus 40% unground pomace, B plus 40% ground pomace and B plus 40% barley. Grinding of pomace significantly improved the digestibility of all parameters measured, however, the barley-soybean meal basal ration was consistently better digested than either of the pomace treatments. The digestibility of whole and ground pomace was respectively: dry matter 10.7% and 20.8% (S.E.M. 1.30), fat 24.1% and 79.7% (S.E.M. 3.47), protein 10.6% and 14.7% (S.E.M. 4.83) and energy 7.9% and 28.4% (S.E.M. 1.80). Protein quality of ground (1mm) and freeze-dried pomace was evaluated with rats in metabolism cages to produce the following values: true protein digestibility 36.0% (S.E.M. 0.66), biological value 91.0% (S.E.M. 3.46), and net protein utilization 32.7% (S.E.M. 1.15). In rat growth trials, where pomace replaced barley incrementally, growth rate was not affected at replacement levels up to 40%, although feed efficiency declined consistently as the level of pomace in the diet increased. It is suggested that raspberry pomace could replace up to 20% of an energy feedstuff in a ration for growing swine without significantly reducing growth rate or feed efficiency.

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