Feed processing and structural components affect starch digestion dynamics in broiler chickens

Abstract

1. A 2x2 factorial design was used to test the hypothesis that impaired intestinal starch digestibility is attributable to rapid passage of digesta from the gizzard to the intestine, and that compared to steam pelleting, increasing the availability of starch through extrusion cooking may alleviate the potential negative effect of rapid digesta flow on starch utilisation. 2. Thus, 7-d-old broilers chickens were distributed to 48 cages and given a wheat-based (WB) pelleted diet containing either coarse oat hulls (OH-Pel) or fine cellulose (Cel-Pel) until d 19 to stimulate divergent development of the gizzard. Thereafter, both groups were further subdivided and challenged with a WB diet with cellulose in either pelleted (Cel-Pel) or extruded (Cel-Ext) form on d 20 and 22. Either excreta or intestinal contents were collected at time intervals after feeding and analysed for marker and starch. 3. OH-Pel increased gizzard size and holding capacity. No excessively high starch levels (max 25 g/kg) were detected in the excreta. However, 8 h feed-deprived birds given Cel-Pel and challenged with Cel-Pel exhibited higher starch-excretion and showed large individual variation during the first 135 min of collection.4. Contrary to OH-Pel group, more digesta and starch passed to the jejunum at 1 and 2 h and ileum at 2 and 3 h after feeding for birds given Cel-Pel, resulting in lower jejunal and ileal starch digestibility. 2 5. Increased starch gelatinisation through extrusion processing significantly improved starch digestibility regardless of gizzard function. However, at 1, 2 and 3 h after feeding, more digesta was retained in the foregut of birds given Cel-Ext.6. The current data showed that starch degradation rate is associated with the flow of digesta which is linked to gizzard development and that enzymatic hydrolysis of intact starch granules may be limited with more rapid feed passage through the gut.

Interactions between starch source and gelatinisation degree on performance and small intestinal digestion in broiler chickens

“…Contrary to the findings of Itani and Svihus (2019), there was no difference in starch digestibility between pelleted and extruded wheat diet in the current experiment. Thus, it can be suggested that the presence of other factors may have maximised the digestion of wheat starch in the pelleted diet and masked the effect of increased gelatinisation in the extruded wheat diet.…”

“…As expected, and in agreement with other studies (Itani and Svihus 2019;Zimonja and Svihus 2009), extrusion resulted in a more extensive starch gelatinisation compared to pelleting. Although pelleted diets had a similar amount of gelatinised starch (209 and 207 g/kg in the wheat and FBS diet, respectively), extrusion increased the proportion of gelatinised starch in the FBS (943 g/kg) compared to the wheat diet (715 g/kg).…”

Role of Feed Processing on Gut Health and Function in Pigs and Poultry: Conundrum of Optimal Particle Size and Hydrothermal Regimens

“…Increased ceca weight in broilers fed pelleted feed relative to broilers fed mash-fed was linked to increased flow of undigested starch in the ceca leading to increased fermentation capacity (35). In a more recent study addition of oat hulls in pelleted wheat diet increased gizzard weight and holding capacity (83). Further studies are needed to determine the mechanism behind the stimulation effects of HTP on gut physiology, morphology and immunology.…”

Dietary fibre effects and the interplay with exogenous carbohydrases in poultry nutrition

“…As observed before in experiments with turkeys ( Jackson and Duke, 1995 ), refeeding of birds which have been starved to empty will result in the entire length of the small intestine becoming filled with contents within an hour. Experiments have demonstrated that birds with an underdeveloped gizzard due to lack of structural components in the form of the insoluble fibre oat hulls (compared with a finely ground cellulose control) will allow for a very rapid flow of feed material into the small intestine when starved and then refed ( Sacranie et al., 2017 ; Itani and Svihus, 2019 ). Although the flow is surprisingly fast independent of gizzard function, the amount that bypassed the gizzard was observed to be considerably larger for birds without a well-functioning gizzard.…”

“…However, no such effects have been observed in experiments with isonutritious diets where finely ground and coarsely ground fibre has been compared ( Sacranie et al., 2012 ; Svihus et al., 2013a , Svihus et al., 2013b ; Itani and Svihus, 2019 ). In fact, Sacranie et al.…”