Comparative study of the chemical composition and nutritional value of pumpkin seed cake, soybean meal and casein.

The chemical composition and nutritional value of pumpkin (Cucurbita pepo) seed cake (PSC) were studied and compared with those of casein and soybean meal. Crude protein and ether extract content in dry matter of PSC was 598.0 g/kg and 124.6 g/kg, respectively, and was higher than the percentage of these components (474.2 and 28.3 g/kg, respectively) in soybean meal used in this experiment. The main fatty acids in PSC cake were oleic acid (50.4%) and linoleic acid (29.9%). Protein found in PSC contained considerable quantities of tryptophan (1.54 g/16 g N); by contrast, the content of lysine (3.21 g/16 g N) and isoleucine (3.83 g/16 g N) was low. Small quantities of phenolic compounds (2.61 g/kg), low activity of trypsin inhibitors (1.33 TUI/mg) and small quantities of alpha-galactosides (19.9 g/kg) were found in PSC. Among antinutritive components only the content of inositol phosphates in PSC (40.5 mg/g) was higher than in soybean meal (10.8 mg/g). True digestibility coefficient (TD) of PSC protein was similar (83.1%), but protein efficiency ratio (PER) was lower (1.01) in comparison with soybean meal (83.5% and 1.50, respectively). After supplementation with lysine, TD (85.9%) and PER (1.43) in PSC were comparable with TD and PER to soybean meal. The PSC-soybean meal mix diet (protein ratio 1:1) had a higher PER value than the diet with soybean meal only (1.98 vs. 1.50).