Antinutritional factors in raw and heat-treated cowpea (Vigna unguiculata) and their effects on growth in weanling pigs

A total of 48 weanling piglets were divided into 4 groups and were fed diets containing either 30 % soya bean (T1) or 30 % heat-treated cowpea (T2) or 15 % heat-treated and 15 % raw cowpea (T3) or 30 % raw cowpea (T4) for 34 weeks. From week 18 the T4 group was subdivided into 4 groups which were fed either T1, T2, T3 or T4 until the end of the trial. Average daily gain (ADG) was least in the T4 group (P < 0.01) possibly due to decreased feed consumption (P < 0.01). The level of anti-nutritional factors (ANF) in the diets were measured. The growth depression and poor health observed in the raw cowpea-fed group could possibly be due to impaired digestibility attributable to trypsin inhibitor activity (TIA), as TIA levels were high in the T4 diets. Feed consumption in T4 group was least and this may also have been due to higher tannin levels in the T4 diets. The compensatory growth seen in T4 piglets when fed on T1, T2 or T3 indicates that the antinutritional effects induced by raw cowpeas are reversible.