Estimation of jejunal and ileal digestibility of complete diets for broiler chickens using an in vitro method

Abstract

The development of in vitro techniques allows for rapid and cost-effective feed evaluation, but validation through in vivo trials is essential. In this study, we compared in vitro digestibility data of broiler chicken diets with apparent jejunal and ileal digestibility. A randomised block design experimental trial was conducted with 180 Ross female broilers housed in metabolic cages and fed six diets based on one maize variety or two sorghum varieties, either dry or reconstituted (5 birds/cage, 6 cages/diet). At 29 days of age, digesta was collected from the jejunum and ileum to determine apparent dry matter and organic matter digestibility (ADMD, ADOMD). In parallel, in vitro DM and OM digestibility (IVDMD, IVOMD) were assessed by incubating the diets in a DaisyII-ANKOM system at 39°C with pepsin-HCl solution (30 min), followed by pancreatin solution at various incubation times (15–1440 min). For the different diets, IVDMD was comparable to ADMD between 40–240 min in the jejunum and 90–360 min in the ileum; IVOMD was similar to ADOMD between 40–90 min in the jejunum and 90–360 min in the ileum (p>0.05), with shorter incubation times observed for reconstituted grains. Specifically, for dry maize grain, 240 min of incubation closely approximated jejunal ADMD (63.4% vs 59.5%, SEM=1.94), whilst 480 min was required for ileal ADMD (72.5% vs 76.1%, SEM=2.23). For dry sorghum, 90 min of incubation (sorghum-1: 57.4%; sorghum-2: 54.5%) achieved values comparable to jejunal ADMD (sorghum-1: 56.9%; sorghum-2: 57.4%; SEM=2.57 and 2.12, respectively). In the ileum, 360 min were needed (sorghum-1: 74.1%; sorghum-2: 73.3%) to match ADMD (sorghum-1: 74.4%; sorghum-2: 77.1%; SEM=2.57 and 2.12, respectively). These findings highlight the necessity of adjusting in vitro protocols based on diet digestibility and the specific absorption site being evaluated.