Rapeseed and soybean products as protein sources for growing turkeys of different ages

(1) Apparent ileal and total tract protein digestibilities of rapeseed meal and cake and soybean meal and cake were assayed in growing turkeys at 4, 8 and 12 weeks of age. (2) In addition, the effect of killing technique on apparent ileal protein digestibility values obtained by a slaughter method and effect of rapeseed feeding on size of specific organs were studied. (3) Protein digestibility coefficients of rapeseed products were mostly 0.10 to 0.15 units lower than those of soybean products. Ileal digestibility of protein increased slightly or remained unchanged from 4 to 8 weeks and decreased thereafter. No effect of feed processing method (meal vs cake) on ileal digestibility was observed. (4) Killing the birds by carbon dioxide inhalation and bleeding led to slightly lower ileal digestibility values than mechanical stunning and neck dislocation. (5) Total tract digestibility of protein decreased from 4 to 8 weeks of age for soybean meal and rapeseed meal but increased for soybean cake and rapeseed cake. From 8 to 12 weeks of age total tract digestibility of protein decreased for all the products tested. (6) Feed containing rapeseed led to enlargement of thyroid glands and hearts, but did not affect liver size or mortality.