A novel low-protein diet feeding strategy with reduced amylose/amylopectin ratio: effects on growth performance, gut health, and behaviour in nursery pigs

• Low crude protein (CP) diet (≤15%) may impair early post weaning growth • Low-CP diet (≤15%) increases faecal dry matter post-weaning. • Lower amylose/amylopectin ratio diet sustain feed:gain in late phase of low-CP diet. • Lower amylose/amylopectin ratio boosts beneficial faecal bacteria. Reduction in dietary crude protein (CP) levels is recognized to limit piglet growth. Synchronising blood amino acids and glucose peaks can improve the performance of piglets fed low-CP diets. This study aimed to evaluate the effects of a feeding plan with a low-CP diet and a reduced amylose to amylopectin (AM/AP) ratio, in the second phase, on performance, faecal microbiota and metabolites, and behaviour of nursery pigs. A total of 540 nursery pigs (28 ± 2 d) were fed either a medium-CP (CTR:16.6%, 180 pigs) or low-CP (LCP: 14.9%, 360 pigs) diet during phase 1 (d0 to 21), and then assigned to one of three phase 2 diets (d 21 to 63): medium-CP (CTR: 17.2%;180 pigs), low-CP with normal AM/AP ratio (LP: 15%; 0.17, 180 pigs), or low-CP with reduced AM/AP ratio (LPLA:15%; 0.08, 180 pigs). On d43 and 63, LP and LPLA pigs showed lower body weight than CTR pigs ( P < 0.0001). No differences in feed to gain (F:G) were observed between CTR and LPLA from d43 to 63. The LPLA and LP diets had lower faecal alanine and proline concentrations than CTR at d48 ( P < 0.05). The beta diversity of faecal microbiota was affected by the diet at d43 and d63 ( P < 0.01); at d63, the LPLA diet was characterised by a higher abundance of Lactobacillus ( P < 0.05) and Limosilactobacillus ( P < 0.05). During the late phase of post-weaning, reducing the AM/AP ratio may help improve feed efficiency in pigs fed low-CP diets.