Nutrient digestibility and nitrogen balance in different pig breeds fed raw, sprouted, or roasted (Vigna unguiculata) diets

The study examined effects of feeding iso-nutrient (150 g CP, 17.3 MJ ME kg(−1)) raw (RCP), sprouted (SPC), or roasted (RSCP) cowpea diets to Windsnyer (W), Large White (LW) × Landrace (LR), and the 3-way crossbred (W × LW × LR) growing pigs. Diet dry matter (DM) digestibility was estimated using standard, 3-step (gastric, small intestines, colon) in vitro digestion. Dietary in vivo nutrient digestibility and nitrogen balance were evaluated using 3 weaned pigs of each genotype. Pigs were housed in individual metabolic cages. The diets were assigned to pigs in a 3 × 3 change-over factorial experiment within three balanced, 3 × 3 Latin squares. Feeding periods consisted of 7 days adaption + 5 days’ measurement of feed intake, and the total faecal and urine excretions. The SPC diet increased step 3 in vitro DM digestibility compared to RSCP (P < 0.05). Metabolic size-scaled feed consumption was higher on the RCP compared to the RSCP diet (P < 0.05). Cowpea processing reduced apparent DM and ash digestibility (P < 0.05). LW × LR pigs exhibited lower digestibility of ash and acid detergent fiber (ADF) compared to 3-way crossbred pigs (P < 0.05). Significant genotype-diet interactions were observed for nitrogen intake (P < 0.0001), digestible nitrogen (P = 0.043), urinary nitrogen output (P < 0.0001), faecal nitrogen output (P < 0.0001), total nitrogen excretion (P < 0.0001), and nitrogen retention (P < 0.001). The biological value of feed protein was higher for W pigs than 3-way crossbred pigs (P < 0.05). Genotype-diet interactions suggested unique digestive and, or metabolic adaptive traits in the utilization of the differently processed cowpeas, which need further investigation.