N Balance Studies Emphasize the Superior Protein Quality of Pig Diets at High Inclusion Level of Algae Meal (Spirulina platensis) or Insect Meal (Hermetia illucens) when Adequate Amino Acid Supplementation Is Ensured

SIMPLE SUMMARY: This study aimed to evaluate diets with complete substitution of soybean meal (SBM) by an algae meal from Spirulina platensis (SM) or partly defatted larvae meal from Hermetia illucens (HM) as feed for piglets and growing pigs. Main feed ingredients of the experimental diets were wheat, barley, and SM or HM. The final diets contained 21% (piglets) and 13% (growing pigs) of SM or HM and nitrogen (N) balance studies were applied to measure parameters of apparent N digestibility, complex dietary protein quality, and individual amino acid (AA) efficiency according to the ‘Goettingen approach’. Diets were well accepted by the animals and an extended level of AA supplementation yielded improved dietary protein quality with both of the alternative feed proteins. However, HM based diets provided superior apparent N digestibility. ABSTRACT: Two age-dependent nitrogen (N) balance studies (average body mass 25 and 60 kg) utilized 16 male castrated piglets and 16 barrows to measure N utilization parameters of diets with complete substitution of SBM by alternative protein sources (SM, HM), but different AA fortifications. Lysine supplementation up to 80% of the recommended lysine (Lys) supply in diets HM (A) and SM (A) yielded similar protein quality data (63.6 ± 2.1 and 63.7 ± 3.4). Surprisingly, only in piglet diet HM (AA) did the extended AA supplementation (Lys, methionine (Met), threonine (Thr)) enhance protein quality (72.8 ± 6.7) significantly (p = 0.004). Similar trends were observed in growing pigs. However, when the level of histidine (His) in diet SM (AA) was increased, feed protein quality (71.8 ± 1.3) was significantly (p < 0.001) improved indicating the importance of adequate His supply in diets with a complete substitution of SBM by the algae meal (SM) under study. AA efficiency data extend the possibilities to explain the observed responses on protein quality. When an adequate AA balancing in the diet is guaranteed, from nutritional point of view both of the alternative proteins may replace SBM in pig diets.