Digestibility of standard and low-input diets in chicken commercial hybrids, local breeds, and crossbreds

Sustainability in alternative poultry meat production chains implies the use of local chicken breeds and low-input diets based on raw materials with low environmental impact. The present study evaluated the diet digestibility of a fast-growing commercial hybrid (Ross 308), two local breeds (Bionda Piemontese, BP; Robusta Maculata, RM) and their crosses with a moderate-growth strain (Sasso, SA). A total of 228 male chickens were housed in 20 collective pens (9-13 animals/pen) according to a bi-factorial design with 5 genotypes (Ross 308, n = 49; BP, n = 38; RM, n = 46; BP×SA, n = 48; RM×SA, n = 47) and 2 grower diets differing for apparent metabolizable energy (AME) and crude protein (CP) content (Standard diet, ST: AME 14.2 MJ/kg; CP 18.7% vs. Low-input diet, LI: AME 13.0 MJ/kg; CP 16.7%). In the LI diet, soybean meal from GMO imported soybean was replaced with soybean meal from local GMO-free soybean and faba bean (Vicia faba L. minor) meal. From hatching to 19 d of age, all birds received the same starter diet (AME 14.4 MJ/kg; CP 24.0%); the experimental grower diets were administered from 20 d of age until slaughtering (47 d for Ross 308 and 105 d for other genotypes). From 34 to 40 d of age samples of faces were collected from each pen, dried, and analysed for dry matter (DM), CP, ether extract (EE), gross energy (GE) and acid-insoluble ash (AIA) content. AIA was used as a marker to determine the apparent digestibility coefficient (ADC) of the dietary DM, CP, EE, and GE. The ADC of DM was equal to 0.70 on average, without significant differences among genotypes as it was for the ADC of CP, EE, and GE. The use of LI diet decreased the ADC of DM (P<0.01), CP (P<0.001), and GE (P<0.01). No significant interaction was detected between genotype and diet effects. In conclusion, the use of a low-input diet reduced the apparent digestibility of protein and energy in growing chickens, regardless of the genotype. However, a wider evaluation of the animal response in terms of growth performance, welfare, slaughter yield, and meat quality traits is required to establish the chicken genotype that better fit with the rearing conditions of alternative production systems. Acknowledgements: The present research was funded by PRIN project (Prot. 2017S229WC; year 2017).