Evaluation of nutritional quality for weaner piglets of a new methanotrophic microbial cell-derived protein feed

This study aimed to test the hypothesis that a new methanotrophic microbial cell protein (MCP) product, Uniprotein (R), has a protein value comparable to other high-quality feeds for weaner piglets. Two experiments were conducted. Experiment 1 was a balanced 6 x 6 Latin square design experiment with six ileal cannulated castrated pigs (start weight 30.2 +/- 1.4 kg). They were fed six different diets (one diet did not belong to this study) over six periods, each of one week duration. Four of the diets contained 180 g crude protein (CP)/kg as-fed with either MCP, potato protein (PP), fishmeal (FM), or soy protein concentrate as the sole N-source. The fifth diet was N-free. Experiment 2 was a dose-response trial, where piglets during the first 14 days post-weaning were fed diets including increasing amounts of MCP (0, 30.0, 60.0, or 100.0 g MCP/kg as-fed, equiv-alent to 0, 112, 221 and 359 g microbial-derived CP/kg diet CP) at the expense of FM and PP. Crystaline CP, Lys, Met, Thr, Trp and Val were added to minimize differences across diets, and no medicinal zinc was added to any of the diets. In experiment 1, MCP had the second highest content of essential amino acids (EAA), but the lowest coefficient of standardized ileal di-gestibility for all EAA except Lys (P < 0.001). However, when contents of ileal digestible EAA were expressed relative to contents of ileal digestible Lys, MCP complied with Danish nutrient recommendations for weaner piglets for 7 out of 9 EAA, and with particularly high levels of digestible Met and Trp. Microbial cell protein had a superior profile as compared to FM for digestible EAA relative to digestible Lys. In experiment 2, MCP could constitute up to 221 g CP/kg diet without any addition of medicinal zinc during the first 14 days post-weaning without any negative impacts on daily weight gain or feed efficiency (gain:feed) compared to the control diet (0 MCP). In conclusion, MCP fulfills Danish recommendations for EAA composition for most EAA and can replace other high quality protein sources to constitute up to 22% of diet CP for weaner piglets without compromising piglet performance.