The increasing demand for proteins is driving the search for alternative food sources. From this point of view, the valorization of co-products, such as meat co-products that are little valorized in human nutrition, is a promising way, in line with the principle of the circular economy. The present study focused on two protein ingredients of bovine origin, co-products of the fat rendering process, Greasy Greaves Recovered Proteins (GGRP) and Water Recovered Proteins (WRP), previously shown to display valuable but different functional properties. The aim of the present study was to evaluate the nutritional quality of these proteins and the relationship between the structure of these two meals and the postprandial plasma amino acid (AA) kinetics. The structure adopted by these two meals during the gastric digestion was investigated using an in vitro semi-dynamic model (INFOGEST). Gastric digesta were collected at 0, 40, 80 and 120 min; their microstructure was analyzed by confocal microscopy, particle size distribution by laser diffraction, and their viscosity was measured by oscillation test. The nutritional quality and postprandial AA kinetics were determined in vivo on ten growing pigs, cannulated at the ileal level and catheterized in the jugular vein, and receiving over a 2.5-day period one of the two experimental meals according to a cross-over design. Ileal digesta and blood samples were collected during the 9 postprandial hours and AA contents were analyzed by ion-exchange chromatography. Data were statistically analyzed using linear models. WRP and GGRP presented a similar and moderate true ileal protein digestibility (81-84%, p>0.05), however due to their different amino acid profile, the DIAAS was much lower for WRP than GGRP with a value of 18 vs. 74% with Trp being the first limiting AA for both protein sources. The plasma AA concentration reached its maximal value between 3 h and 5 h postprandial for WRP and GGRP, thus qualifying both protein ingredients as slowly digested sources. GGRP tended to have a slower appearance rate of plasma AA. This could be explained by the higher viscosity of this meal (25 to 35 times higher) than that of WRP meal (p < 0.05). Nevertheless, the viscosity of both meals sharply decreased during digestion by an equivalent factor (around 34), from 1.3 to 0.04 Pa.s at 10 s-1 for WRP, and from 35 to 1 Pa.s for GGRP. In addition, the GGRP digesta contained a higher proportion of very large particles than the WRP ones. The higher viscosity and larger particle size for GGRP digesta than for WRP ones could explain the trend for the slower rates of digestion and absorption of GGRP. Overall, the GGRP bovine co-product appears as an interesting dietary protein source for human, while WRP presents mainly valuable functional properties but low nutritional ones.