It is unclear what causes the inconsistent negative effects of high protein diets in nursery pigs, but it could be due to protein source or indigestible protein (IDP) content. A literature search and meta-analysis was done that included ninety-four studies reporting growth performance [average daily gain (ADG), average daily feed intake (ADFI), gain:feed (GF), initial and final body weight (BW)] and duodenal histomorphometrics [villus height (VH), crypt depth(CD), and villus height:crypt depth ratio (VCR)] variables of pigs fed different protein content (CP) and sources in the diet. Diets were recalculated to generate the IDP content from each study. Studies were grouped by similarity in performance in two clusters [C1= mid-late nursery phase (9-18 kg) and C2= immediate post-weaning phase (6-9 kg)]. Quadratic response plateau (QRP) models were fitted to assess the interrelationships between ADG, ADFI, GF, VH, CD, and VCR with the dietary CP or calculated IDP content within cluster. The results suggest that dietary IDP may be a better indicator of potential negative dietary effects than total protein, particularly in the immediate post-weaning phase. Dietary IDP is affected more by the inclusion of plant-based ingredients than animal-based ingredients, most likely as a result of lower digestibility of protein in plant-based ingredients.
Developing an Indigestible Protein Index to Investigate the Effects of Dietary Protein in Pigs (link to the full article)
