In Vitro-in Vivo Digestibility and Nitrogen Balance in Indigenous, Exotic and Crossbred Growing Pigs Fed Sprouted or Roasted Cowpea Diets

Abstract The study evaluated effects of processing cowpeas for inclusion in maize-based diets for Windsnyer, Large-White x Landrace, and their 3-way crossbred growing pig genotypes. In-vitro, the raw and roasted cowpea diets, sprouting cowpeas decreased (P<0.05) gastric-ileal non-enzymatic (buffer-only) DM digestibility. Roasting increased (P<0.05) the colon enzymatic digestion relative to sprouting. Total ileal and colon in-vitro diet DM digestibility were not affected (P>0.05) by cowpea processing. In-vivo, Pigs consumed most (P<0.05) feed (g/day/kg BW) in period 1, with significant (P<0.05) genotype X period interaction. Both roasting and sprouting cowpeas reduced (P<0.05) dietary apparent DM digestibility. Pig daily body weight (BW) gain reduced (P0.05) treatment effect on feed conversion efficiency. The 3-way crossbred pigs excreted more (P<0.05) urine N (g/dayBW0.75). Urine N excretion (g/dayBW0.75) peaked (P<0.05) in period 2 (P<0.05), with less (P<0.05) N intake (g/dayBW0.75), faecal N excretion (g/dayBW0.75) and N balance (g/dayBW0.75) than in period 3. Significant diet X genotype interaction in faecal N excretion (g/dayBW0.75) resulted from markedly high (P<0.05) in contrast to low (P0.05) higher urine N excretion. In conclusion, in-vitro, sprouting shifted non-enzymatic digestion to the colon, while roasting increased colon fibrolysis, without effect on overall DM digestibility. In-vivo, the period of feeding, interpreted to reflect pig maturity, the pig genotype and cowpea processing interacted to influence apparent dietary DM digestibility and N utilization, without significant effect on the conversion efficacy of the maize-cowpea diet.