Feeding monogastric livestock in organic agriculture is challenging due to several tradeoffs between animal welfare aspects, resource efficiency, as well as ecological and social sustainability. Organic standards may even increase such conflicts, as is currently the case with upcoming new regulations regarding restrictions of feed sources for organic pigs in Europe. In order to contribute data for balancing reasons to minimize tradeoffs, we compared four different piglet diets, each targeted to reach a high protein quality by either a high proportion of soybean cake (SOY), inclusion of milk powder (MILK), fermentatively produced lysine (LYS) or conventional potato protein (POT). All diets were designed to meet the nutritional requirements of piglets in the best possible way, however they all represented different conflicts with either organic regulations or sustainability goals. In each of five consecutive runs, respectively three litters were assigned to every dietary treatment, resulting in 15 litters per treatment in total. In each litter, seven focus animals were defined. The piglets were studied from birth until 58 days of age. They were weaned at day 46 and sold from the farm at day 58. Piglets were individually weighed at an average age of 3, 21, 43, 50 and 58 days with simultaneous assessment of body condition score (BCS) and prevalence of diarrhea. Feed intake (FI) was recorded litter wise weekly, starting from week three. Feed conversion ratio (FCR) was calculated for the period after weaning. Statistical analysis was executed using linear mixed effect models. Regarding FI, FCR and daily weight gains, no treatment effect was found. Only at day 21, BCS was lower for piglets receiving POT. Prevalence of diarrhea increased after weaning for all treatments. All four tested diets led to similar weight gains and feed conversion in the piglets. Animals fed diet POT recovered better from diarrhea compared to the other treatments. A high soybean cake content or lysine supplementation in the diet was disadvantageous with regard to the occurrence of diarrhea. LYS diet led to signs of threonine deficit, indicating that lysine addition alone may not solve the issue. The addition of milk powder provided no extra benefit. In recognition of the health benefits, the use of 5% potato protein, even if it is sourced from conventional production, must still be considered as a sustainable option for feeding organic piglets. The sustainability implications are discussed in the paper.
