S. Panigrahi et al., EFFECTS OF OVEN-DRYING TUBERS OF 2 HIGH-PROTEIN SWEET-POTATO VARIETIES AT DIFFERENT TEMPERATURES ON THEIR FEEDING VALUE IN BROILERS, British Poultry Science, 37(1), 1996, pp. 173-188
1. Unpeeled tubers from 2 high-protein varieties of sweet potato (whit
e-fleshed Bosbok, and orange-fleshed Carmel) were chipped and oven-dri
ed at 40, 60, or 80 degrees C, to examine the effects on nutritive val
ue. The dried ground chips were substituted for maize at 500 g/kg and
the diets fed to day-old, Ross-l broiler chicks for 3 weeks. 2. Compar
ed with Carmel, Bosbok had a lower crude protein content (90 v. 138 g/
kg DM) and trypsin inhibitor activity (TIA) (3 v. 5 mg of trypsin inhi
bited per g flour). Processing did not significantly affect TIA, but t
he lysine and cystine contents were lowered and the starch content rai
sed as the drying temperature increased. However, whereas this was ref
lected in increased reducing sugars in Carmel, there was no trend in B
osbok. 3. The results of in vitro pancreatin digestibility and total d
ietary fibre assays showed variety and processing temperature to be si
gnificant factors influencing the nutritive value of sweet potato tube
rs, with a variety X temperature interaction also being indicated. The
interaction was also observed for weight gain, dry matter intake, wat
er:food intake ratios, excreta water content, presence of bile in excr
eta and liver weights. The best growth was obtained with Bosbok dried
at 60 degrees C, for which liveweights at 21 d were 11% lower than for
the maize controls.