Assessment of crop usage in ad libitum fed birds and short-term phytase efficiency as affected by acid addition.

1. A field assessment was performed to map the extent of crop usage and thus retention time in broiler chickens. In addition, a broiler experiment was carried out to study the short-term effect of acid addition on phytase efficacy in the crop.2. In the field assessment, the crop content of 40 ad libitum fed broiler chickens from 4 different farms were sampled at 10, 20 and 30 d of age. The dry matter (DM) content varied from 0 to 32 g.3. From 11 d of age, 120 individually caged chickens were intermittently fed a high phytate-P diet with either no addition or 500 FYT C. braakii-derived phytase added or both phytase and 1.4% formic acid added. Excreta were collected for assessment of phosphorus (P) retention. At 20 and 21 d of age, starved birds were fed for 1 h, and thereafter crop and gizzard contents were collected every 20 min until 140 min after start of the feeding. At 60 and 140 min, the contents from the jejunum and ileum were collected.4. All diets reduced the concentration of phytate in the crop, however the combination of acid and phytase resulted in a higher degradation (P < 0.05) than the other diets from 20 min after the start of feeding. Simultaneously, the concentration of the smaller inositol phosphate isomers, such as inositol-5-phosphate, increased (P < 0.05). Phytase increased (P < 0.05) P retention, and the combination of acid and phytase increased jejunal P digestibility (P < 0.05) compared to the other diets.5. The results indicated that lower pH in the crop due to acid addition improved phytase efficacy and increased P digestibility in the anterior digestive tract, even with short retention times.

Air-classified faba bean protein fraction as a substitute to soybean meal in pelleted and extruded broiler diets.

1. The hypothesis that air-classified faba bean protein fraction (FBP) can replace soybean meal (SBM) in pelleted or extruded broiler diets without adverse effect on performance or nutrient digestibility was tested.2. At 17 d of age, male broilers were randomly distriibuted among four dietary treatments consisting of either SBM or FBP (main dietary protein source) and pelleting or extrusion as processing methods. Treatments had 10 replicate pens containing five birds each.3. Compared to SBM, birds fed FBP had significantly lower feed intake, less weight gain and had poorer feed conversion.4. Pellet durability was high (above 92%) for all diets. In pelleted diets, FBP was harder than SBM whereas extruded diets had similar hardness. Pelleting increased water stability compared to extrusion. FBP diets were more water stable than the SBM diets.5. Gizzard content weight was 2.2-fold higher (P = 0.002) for birds given FBP compared to those fed SBM. The weight of the jejunum and ileum with contents was 1.4-fold lower for the FBP diets, and this effect was larger (P < 0.05) for the extruded FBP diet.6. Birds fed FBP diets had significantly higher nitrogen digestibility in the lower jejunum and ileum compared to those given SBM diets, while the starch digestibility coefficient was above 0.980 in all treatments.7. The high nutrient digestibility of FBP diets indicates that the poor performance of the FBP group was due to lower feed intake which was not explained by the differences in pellet durability or hardness. The reduced palatability of the FBP and the longer retention of the FBP diets in the upper gut are more likely to have depressed feed intake.

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

1. A 2 × 2 factorial arrangement was used to test the hypothesis that, in pelleted diets, legume starch is digested less rapidly and to a lesser extent than cereal starch, and that increased gelatinisation through extrusion would eliminate the differences between the starch sources. In addition, the trial examined whether a lower ratio of starch to nitrogen disappearance rate (SNDR) could improve feed conversion ratio (FCR).2. At 17 d of age, male broilers were randomly distributed among four dietary treatments, consisting of either wheat or faba bean starch-rich fraction (FBS) as the sole starch source and pelleting or extrusion as processing methods. Each treatment had 10 replicate pens containing five birds each.3. Extrusion resulted in a more extensive starch gelatinisation compared to pelleting, as expected.4. No difference in weight gain at 29 d of age was observed between birds fed starch sources. However, birds fed wheat tended (P = 0.080) to have better FCR than those fed FBS, while the effect of processing methods was insignificant. Thus, there was no interaction between starch source and processing method on FCR.5. In pelleted diets, FBS had lower and slower starch digestibility compared to wheat in all intestinal segments (P < 0.05). The interaction between starch source and processing method in all intestinal segments (P < 0.001) demonstrated that FBS responded more to gelatinisation through extrusion than did wheat. Thus, differences in starch digestibility between the wheat and FBS were eliminated with extrusion.6. Feeding extruded diets significantly increased the upper jejunal expression of GLUT1, GLUT2 and SGLT1 compared to pelleted diets, which suggested that glucose absorption was less likely to be a limiting factor for starch utilisation.7. Pelleting resulted in a lower ratio (P < 0.001) of SNDR compared to extrusion (on average 1.4-fold) but did not improve FCR.

Effect of crop retention time and acidification of the feed on phytase efficacy in broiler chickens.

1. An in vitro test to study the effect of pH reduction on phytic acid degradation over time for four commercial phytases was conducted. Changing the pH level affected phytate degradation over time differently for the various phytases (P < 0.05).2. The phytase with the largest response of pH reduction in the in vitro test and a feed pH level of 4.5 was chosen for the broiler experiment. The effect of intermittent feeding, addition of 500 FYT C. braakii-derived phytase and 1% formic acid were tested in a 2 x 2 x 2 factorial arrangement. Ten pens containing 10 birds each were fed each of the treatment combinations from 15 to 36 d of age. Ad libitum fed birds had two 4-h dark periods with 2-h light in-between, while intermittently fed birds in addition had restricted access to the feed through except for four 1-h and one 2-h feeding bouts.3. In addition to assessing performance, excreta were collected on a pen basis. The tibia and contents from jejunum and ileum were collected from one bird per pen. In addition, crop contents were collected from the intermittently fed birds 80, 160 and 240 min after the start of feeding.4. Phytase improved performance, ileal and jejunal P digestibility, P retention and tibia ash and P concentration (P < 0.001). Intermittent feeding increased jejunal P digestibility and P retention (P < 0.001), but ileal P digestibility increased only in the intermittently fed birds compared to the ad libitum fed birds without phytase addition (P = 0.025). Acidification increased jejunal P digestibility only in the ad libitum fed birds (P = 0.019). There was a considerable inositol hexakisphosphate degradation into lower isomers in the crop after 80 min for diets with phytase (InsP3 and 4:P < 0.001), and acidification further increased this degradation (InsP4:P = 0.007). After 160 min retention time, the effect of phytase and acidification was even higher with more significant (P < 0.05) interactions.5. The current data showed that prolonged retention time in the crop combined with feed acidification increased phytase efficacy by improving the phytate degradation.

Varying starch to fat ratios in pelleted diets: II. Effects on intestinal histomorphometry, Clostridium perfringens and short-chain fatty acids in Eimeria-challenged broiler chickens.

1. The hypothesis behind the study was that a high dietary starch level (HS) would lead to impaired gut health compared to a low-starch diet (LS) in Eimeria-challenged broilers. The effects of two diets with different starch to fat ratios on intestinal histomorphometry, Clostridium perfringens counts and toxin profile, necrotic enteritis prevalence and abundance of short-chain fatty acids (SCFAs) were examined. 2. A total of 1,920 one-day-old Ross 308 broiler chickens were fed one of two isocaloric diets formulated either with high (32:1) or low (2:1) starch to fat ratios from d 10 to 29 of age. Each treatment group had 12 pen replicates containing 80 broilers each. On d 17, the chickens were challenged with Eimeria vaccine strains. Samples were collected on d 16, 21-23 and 29. 3. Whereas villus length increased gradually throughout the study in the HS group, a peak level was reached on d 21-23 in the LS group. On d 29, the HS group had significantly longer villi than the LS group. 4. Caecal SCFA concentrations were higher in the HS group compared to the LS group on d 16. In both groups, the SCFA level peaked on d 21-23, with the most pronounced increase seen in the LS group. 5. The C. perfringens netB:cpa ratio increased from d 16 to 29 in the HS group. C. perfringens counts and necrotic enteritis prevalence were similar between the two groups. 6. Diet affected the dynamics of small intestinal villus length and caecal SCFA abundance. These findings suggest that structural remodelling of the small intestine is an adaptation to different dietary starch levels, and that caecal SCFA abundance is associated with the availability of substrate for the microbiota in the posterior intestinal segments. Chickens adapted to higher levels of dietary starch might be more robust against Eimeria infections due to increased mucosal surface area. Studies with other dietary starch sources are required to clarify the impact of dietary starch levels on intestinal health in Eimeria-challenged broilers.

Varying starch to fat ratios in pelleted diets: I. Effects on nutrient digestibility and production performance in Eimeria-challenged broiler chickens.

1. The hypothesis was that a diet with a high starch to fat ratio (HS) impairs nutrient digestibility and growth performance, as compared to a diet with a low starch to fat ratio (LS) in Eimeria-challenged broilers. From days 10 to 29, 12 replicate pens of birds were given isocaloric and isonitrogenous steam-pelleted diets with either HS or LS, by replacing the wheat starch in one diet by a mixture of rapeseed oil and inert sand in the other. On d 17, a 10-fold dose of live vaccine strains of Eimeria spp. was administered via drinking water. Ileal samples were collected on days 16 and 29. 2. Starch content in the ileum tended to be higher on d 16 and was significantly higher on d 29 in the HS group. 3. The HS diet did not induce exceedingly high levels of starch in the ileum, suggesting there was no starch overload in the gut. Ileal starch digestibility was improved with increasing dietary starch level from 23% to 45%. This demonstrated the capacity of the broiler chicken to digest high levels of starch regardless of Eimeria spp. infection. Ileal energy digestibility was not affected by the treatments. 4. Weight gain did not differ between treatments; however, birds fed the LS diet were less efficient in feed conversion as compared to those fed the HS diet. 5. The use of isolated starch and the unintended higher extent of starch gelatinisation in the HS diet may have contributed to the higher starch digestibility in birds given the HS diet. Thus, the hypothesis that high ratios of starch to fat in pelleted diets may impair starch digestibility and production performance in Eimeria-challenged broiler chickens was not verified. Further work is required to clarify this research question, taking into consideration the physical form of starch source and the potentially confounding role of feed processing on starch availability.

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

1. A 2 × 2 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-broiler 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 containing 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 (maximum 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 the 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. 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.

Intermittent lighting improves resilience of broilers during the peak phase of sub-clinical necrotic enteritis infection.

Necrotic enteritis, either in its clinical or sub-clinical form is known to cause massive economic losses in the broiler chicken industry. Currently, the use of in-feed antibiotics as growth promoters is discouraged. Therefore, mechanisms to control NE through diet include reduction of digesta viscosity, promotion of lower pH in the gastrointestinal tract (GIT) through acidification of feed, production of short-chain fatty acids and overall stimulation of beneficial bacteria growth. Intermittent lighting programs increase feed retention in the crop and reduce pH in the foregut compartments in comparison with standard commercial lighting programs and therefore may be a valuable, yet underexploited, barrier to prevent the invasion of the GIT by pathogens. In this experiment, a 2 × 2 factorial arrangement of treatments was employed in a randomized design to investigate whether intermittent lighting would increase broiler resilience to sub-clinical necrotic enteritis. A total of 390 Cobb 500 same-hatch, mixed sex, day-old chicks were assigned to 30 floor pens to test the effect of 2 factors, namely, lighting schedule (continuous, 18L:6D vs. intermittent, 1L:3D:1L:3D:1L:3D:1L:3D:2L:6D) and a sub-clinical necrotic enteritis challenge (challenge vs. no challenge). Challenged birds had lower feed intake and weight gain and poorer feed conversion ratio (FCR; P < 0.005). Intermittent lighting reduced feed intake (P < 0.05) without compromising final body weight gain. During the peak phase of Clostridium perfringens Type A infection, the negative impact of the disease challenge on feed efficiency was lower for animals under intermittent lighting than for those under a 18L:6D schedule (2-way interaction, P < 0.005). Thus, in flocks that are raised under antibiotic-free production systems, intermittent lighting programs applied at least during the critical period for necrotic enteritis risks, i.e., d 18-24, may be a practical, non-medicated way to increase resilience of broilers to this disease.

Effect of intermittent feeding and oat hulls to improve phytase efficacy and digestive function in broiler chickens.

1. Two trials were carried out to investigate the impact of intermittent feeding and oat hulls as methods to stimulate the anterior digestive tract in broiler chickens. 2. In Trial 1, 7-d-old broilers were placed 4 per cage in 48 cages and fed either ad libitum or intermittently on a diet with 50 g/kg of either oat hulls or cellulose, with or without 1000 FTU phytase, in a 2 × 2 × 2 factorial arrangement. Ad libitum fed birds had two 4-h dark periods with 1-h light in between, while intermittently fed birds in addition had restricted access to feed through four 1 h feeding bouts. 3. In Trial 2, 144 broiler chickens were divided amongst 12 pens which were intermittently fed on the same diets as in Trial 1 in a 2 × 2 factorial arrangement. At 34 d of age, after 16 h feed withdrawal, birds were fed for 1 h, followed by dissection of 4 birds per treatment every hour for 9 h. Contents from different segments of the digestive tract were collected quantitatively to assess dry matter (DM) and starch flow. 4. In Trial 1, phytase improved performance and nutrient availability, while oat hulls and intermittent feeding improved some measures of nutrient availability. Intermittent feeding augmented the effect of phytase on myo-inositol hexakisphosphate (IP6) degradation in the anterior digestive tract. 5. In Trial 2, birds filled up their crop and slowly passed these contents on to lower segments of the digestive tract. Already 1 h after commencement of feeding, the entire length of the small intestine was filled with DM, and no significant changes in DM content were observed before 4-5 h later, when the small intestine gradually became emptied. The tendency for a higher initial load of DM and starch in birds without oat hulls seems to support the hypothesis that one important function of the gizzard is feed-flow regulation. 6. In conclusion, the anterior digestive tract seems to have an important regulative function in broiler chickens when stimulated by intermittent feeding or structural components. More research is needed in order to elucidate the role of the crop and gizzard for phytase function.

Performance and digestive function of broiler chickens given grit in the diet.

1. A series of experiments were carried out to study the effect of grit on broiler performance, gizzard development and fate of grit in the digestive tract. 2. In Experiment 1, performance, gizzard weight and content of grit in the gizzard of broiler chickens given access to granite-type grit was investigated. In Experiment 2, the effect of grit stones on performance and gizzard development was assessed in diets with or without whole wheat. 3. In Experiment 3, the effect of grit in the form of zeolite, granite or marble on gizzard development and digestive tract grinding and passage was studied in diets with or without whole wheat. 4. Grit stones had no effect on performance of broiler chickens, which may be explained by the fact that grit stones did not stimulate gizzard development to the same extent as with other structural materials. 5. The lack of stimulation is at least partly due to the fact that a majority of the grit stones eaten pass through the small intestine without being retained in the gizzard. 6. Grit in the form of marble reduced feed intake and weight gain.

Starch digestion capacity of poultry.

Starch is quantitatively the most important nutrient in poultry diets and will to a large extent be present as intact starch granules due to very limited extent of gelatinization during pelleting. Although native starch is difficult to digest due to a semi-crystalline structure, even fast-growing broiler chickens appears to be able to digest this starch more or less completely during passage through the jejunum. However, reduced starch digestibility has been observed, particularly in pelleted diets containing large quantities of wheat. Although properties of the starch granule such as size and components on the granule surface may affect digestibility, the entrapment of starch granules in cell walls and a protein matrix may be even more important factors impeding starch digestion. In that case, this and the fact that amylase secretion is normally very high in poultry may explain the lack of convincing effects of exogenous α-amylase added to the diet. However, few well-designed experiments assessing mechanisms of starch digestion and the effect of α-amylase supplementation have been carried out, and thus more research is needed in this important area.

Effect of intermittent feeding, structural components and phytase on performance and behaviour of broiler chickens.

1. Two experiments were conducted to study the effect of intermittent feeding on performance and the efficacy of an exogenous phytase, and to assess whether intermittent feeding changed the activity pattern of broiler chickens. 2. Broiler chickens were given, either ad libitum or intermittently, a phosphorus deficient pelleted diet containing either coarsely or finely ground oat hulls and either no enzyme or a phytase added from 10 d of age, in a 2 × 2 × 2 factorial arrangement. Ad libitum feeding consisted of continuous access to feed in a room with 18 h of light and 6 h of complete darkness, whereas birds on intermittent feeding had restricted access to feed from 7 d of age, with 4 1-h feeding bouts/d and one 2-h feeding bout/d from d 14. 3. Performance, characteristics of the anterior digestive tract and phosphorus retention were assessed in experiment 1, while in experiment 2, birds were observed during 4-h periods to quantify different behaviours. 4. Intermittent feeding and phytase improved performance, but intermittent feeding did not improve the efficacy of the enzyme added. Ad libitum fed broiler chickens ate and drank on average twice per hour, and spent close to three-quarters of their time resting. Apart from an increased standing and feed searching activity for intermittently fed birds compared to ad libitum fed birds during the last hour before feed was presented, no differences in activity was detected. 5. It was concluded that broiler chickens quickly adapt to intermittent feeding without reduction in final body weight and with improvements in feed efficiency, but without improving the efficacy of dietary phytase. Only small changes occur in the behaviour of intermittently fed birds compared to ad libitum fed birds.

Reduced spread of Campylobacter jejuni in broiler chickens by stimulating the bird's natural barriers.

AIM: We have tested the effect of feed structure and feeding regime to prevent the spread of the zoonotic pathogen Campylobacter jejuni in broiler chicken flocks. METHODS AND RESULTS: Birds were offered two types of feed, control diet and a diet supplemented with 15% oat/barley hulls for structure. In addition, the birds were either fed ad libitum or intermittent. One bird in each treatment group was infected with a three-strain-mix of Camp. jejuni, and the spread of Camp. jejuni within the group was investigated. Feed structure increased the gizzard weight, delayed the spread of Camp. jejuni within the group and reduced the relative amount of Camp. jejuni in the caecum compared with the control diet. CONCLUSIONS: Our results show that stimulating the bird's natural barriers is a novel and promising intervention strategy to reduce the spread of Camp. jejuni in chicken flocks. SIGNIFICANCE AND IMPACT OF THE STUDY: Preventing Camp. jejuni in broiler chicken flocks is essential to ensure food safety because this bacterium is transferred to chicken carcasses during the slaughter process and readily survive in unprocessed poultry products. We have evaluated a novel approach for stimulation of the bird's natural barriers in the upper digestive tract with promising results.

The effect of insoluble fiber and intermittent feeding on gizzard development, gut motility, and performance of broiler chickens.

Two experiments were conducted to test the following hypothesis: exposing broiler chickens to coarse insoluble fiber in the diet will result in enhanced gizzard function and performance, improved adaptability to an intermittent feeding program, and an increase in the occurrence of reverse peristalsis. In experiment 1, 102 Ross 308 broiler chickens were either intermittently or ad libitum fed a basal diet, the basal diet diluted with 15% coarse hulls (consisting of equal weights of hulls from oats and barley), or the basal diet diluted with 15% of the same hulls finely ground in a 2 × 3 factorial arrangement with 17 individually caged birds per treatment. Birds fed ad libitum had access to feed continuously for 18 h/d, whereas those on intermittent feeding had restricted access to feed from 7 d of age. From 18 d of age, the restrictive-feeding program consisted of four 1-h meals and one 2-h meal per day. In experiment 2, 156 broiler chickens in 12 pen cages with wood shaving-lined floors were exposed to 1 of 4 treatment groups with 3 pens/treatment: intermittent or ad libitum feeding of a basal diet and intermittent or ad libitum feeding of a coarse hull diet, as described above. At 31 and 32 d of age, birds in experiment 1 were inoculated with chromium EDTA via the cloaca. There was no interaction between diet and feeding regimen. The addition of hulls increased gizzard weight and content and lowered (P < 0.001) gizzard pH, but it had no effect on the ability of the birds to handle intermittent feeding. Despite the dilution with coarse hulls, weight gain and the gain:feed ratio were not affected, which could partly be explained by an increased (P < 0.001) starch digestibility. Dietary reflux was confirmed by the presence of chromium in all intestinal tract sections. Broilers exhibited reverse peristaltic contractions of sufficient magnitude to propel the marker from the cloaca to the gizzard.

Nutrient utilization and functionality of the anterior digestive tract caused by intermittent feeding and inclusion of whole wheat in diets for broiler chickens.

Two experiments were carried out to study the effect of intermittent feeding, diet structure, and their interaction on the performance, feeding pattern, and digestive adaptation of broiler chickens. In experiment 1, 40 Cobb broiler chickens were fed, either ad libitum or intermittently, a commercial starter diet diluted with 150 g/kg of ground or whole wheat in a 2 × 2 factorial arrangement. Ad libitum feeding consisted of continuous access to feed in a room with 18 h of light and 6 h of complete darkness, whereas birds on intermittent feeding had restricted access to feed from 7 d of age, with 4 one-hour feeding bouts/d and one 2-h feeding bout/d from d 14. No interaction was found between feed structure and feeding regimen for any of the measurements. Although BW gain was not significantly different among any of the treatments, birds given whole wheat or fed intermittently had significantly better feed efficiency than those given ground wheat and fed ad libitum. Inclusion of whole wheat instead of ground wheat also markedly increased (P < 0.001) the AME(n) value and fecal starch digestibility. In experiment 2, 60 Ross broiler chickens were trained to meal feeding on a wheat-based diet containing a commercial phytase, and 5 birds were killed every 15 min after having access to feed, to collect crop contents. Phytate was gradually degraded in the crop, with a 50% reduction in inositol 6-phosphate after a 100-min retention time. In conclusion, these results indicate that broiler chickens have a remarkable ability to maintain growth rate during intermittent feeding because the crop is used as an intermediate storage organ, and that improvements in feed efficiency may occur, among others through increased efficacy of exogenous enzymes. Even though stimulation of the gizzard through a coarse feed structure improves feed efficiency, it does not appear to affect the ability of the bird to handle intermittent feeding.

Influence of graded levels of brewers dried grains on pellet quality and performance in broiler chickens.

The aim of the current study was to evaluate the effect of a gradual substitution of wheat and soy with brewers dried grains (BDG) on pellet quality, performance, and organ weights in broiler chickens. Five diets were formulated in which 0, 10, 20, 30, or 40% BDG replaced wheat and soy, with a concomitant gradual reduction in the calculated AME level. Each of the 5 experimental diets was fed to 12-d-old broiler chickens (Ross 308) kept in 6 pens, with 12 birds/pen. The birds had ad libitum access to feed and water until termination of the experiment at d 33. Feed intake was not affected by BDG inclusion and compensatory feed intake did not occur, perhaps having been neutralized by a significant (P < 0.001) reduction in the pellet durability index. The pellet durability index was 85% in the control diet (0% BDG) and decreased significantly (P < 0.001) to 68% in the diet with 40% BDG. Increased levels of BDG reduced BW gain significantly (P < 0.001) and led to a significant (P < 0.001) increase in the feed:gain ratio. The feed:gain ratio was significantly (P < 0.05) higher in birds fed 30 and 40% BDG compared with birds fed 0, 10, and 20% BDG. The apparent ileal digestibility values of protein and energy were significantly reduced by BDG inclusion (P < 0.01 and P < 0.001, respectively), whereas starch digestibility increased significantly (P < 0.001). The relative gizzard weight increased significantly (P < 0.001), whereas the relative cecal weights were not affected by BDG inclusion. To conclude, 10 to 20% inclusion of BDG supports acceptable growth and feed utilization, and favors the development of a well-functioning gizzard.

Effects of structure and xylanase treatment of brewers' spent grain on performance and nutrient availability in broiler chickens.

1. A factorial (2 x 3) feeding trial was set up to investigate the effects of coarse or finely ground brewers' spent grain (BSG) and xylanase treatment, either with no xylanase, top-dressed with xylanase or pre-treated with xylanase. 2. The experimental diets shared the same basal formulation and were fed to male broiler chickens (Ross 308) housed in individual cages from 12 to 29 d of age. 3. Xylanase pre-treatment reduced the dietary concentration of arabinoxylan by 15-30%. Pellet durability increased when BSG was ground. 4. Feed utilisation was significantly higher (6%) when the birds were given coarse BSG rather than ground BSG, whereas there was no significant effect of enzyme treatment. Apparent metabolisable energy was unaffected by the dietary treatments. 5. The overall starch digestibility was high (99%), with no dietary differences, whereas ileal protein digestibility was low (57%). Xylanase top-dressing tended to improve ileal protein digestibility but, in general, xylanase treatment had no major effect on overall performance in male broilers given diets with BSG.

Effects of two wheat cultivars on physico-chemical properties of wheat flours and digesta from two broiler chicken lines (D+ and D-) differing in digestion capacity.

1. The current experiment is the second part of a study about the effects of wheat quality on digestibility of pelleted diets for broiler chickens. In the first part, it was shown that a hard cultivar resulted in a negative effect on starch digestibility in two divergent lines of chickens (D+ and D-) selected for digestion capacity. The aim of this second part was to investigate the reasons for this negative effect of a hard cultivar (Baltimor) compared to a soft one (Scipion) in D+ and D- lines. 2. Proventriculus pepsin activity and pancreas proteolytic and amylolytic activities were estimated in 4 pools of birds: 'D+ line (Baltimor fed)', 'D+ line (Scipion fed)', 'D- line (Baltimor fed)' and 'D- line (Scipion fed)'. Results suggested the greatest amount of pepsin units per g BW for D+ birds and the lowest amount of pancreas proteolytic units per g BW for D+ birds fed Scipion wheat. Pancreas showed very similar alpha-amylase activities among treatments. 3. In vitro hydrolyses of wheat gluten proteins with proventriculus extracts from pools of D+ and D- birds did not show any differences between hard and soft cultivars, whatever the origin of pools. 4. Pepsin hydrolysis of fine (300 to 425 microm) and coarse (1180 to 1600 microm) fractions from wheat flours (Baltimor or Scipion) showed that the 30 min proteolysis rate was highest for the fine fraction in both cultivars. No difference was observed with extended hydrolysis time. 5. In vitro digestion simulation of whole wheat flours confirmed the results previously obtained in vivo, with a negative effect of hard cultivar on starch digestion rate and no effect on protein digestion. 6. Laser particle size analyses showed that ileum digesta from birds fed with hard wheat cultivar showed the highest proportion of coarse particles. 7. Microscopic analyses of D+ ileum digesta revealed that the concentration of undigested starch granules in the subaleurone area of wheat bran particles was the highest with hard cultivar. 8. The results suggested that physical entrapment of starch granules in coarse particles was a major explanation for decreased starch digestibility values in chickens fed hard wheat diets.

Hagberg falling number and the nutritional value of wheat in broiler chicken diets.

1. Three experiments were performed to study the effect of Hagberg falling number in wheat on performance, nutrient digestibility and AMEN in broilers. In two experiments, one hard and one soft wheat variety were used to study the interaction between falling number and hardness of wheat with regard to nutritional value. In these experiments, wheat batches with high falling number when harvested under dry conditions were used in broiler diets. 2. Wheat with reduced falling numbers (high, medium and low) was obtained by controlled germination. In the third experiment, wheat with reduced falling numbers were obtained by delayed harvesting times. 3. In each experiment, a total of 4 cereal batches with different falling numbers from each wheat variety were used to produce corresponding experimental diets with wheat as the major ingredient. Each diet was fed to broiler chickens ad libitum from d 1 to d 17 of age. 4. There was no consistent effect of falling number on performance. Low falling number did not improve feed utilisation or AMEN compared to the original wheat, despite a higher AMEN associated with higher starch digestibility. This phenomenon was not observed after reduction of falling number by delayed harvesting. Apparently, natural reduction of falling number resulted in enhanced degradation of arabinoxylans compared to controlled germination.

Causes for improvement in nutritive value of broiler chicken diets with whole wheat instead of ground wheat.

1. Two experiments were conducted with broiler chicks to compare nutritive values of ground and whole wheat diets containing titanium oxide as indigestible marker. 2. In Experiment 1, a wheat and soy isolate based cold-pelleted diet, in which all the wheat was ground in a hammer mill to pass through a 3 mm sieve, was compared with a diet in which about half (375 g/kg) of the ground wheat was taken out of the diet and supplied as whole wheat mixed into the diet after pelleting. 3. In Experiment 2, a diet based on ground wheat and soy isolate which was pelleted after preconditioning (final temperature 81 degrees C) was compared with a diet in which 500 g of the ground wheat was replaced by whole wheat mixed into the diet before pelleting. 4. In Experiment 1, replacement of ground wheat with whole wheat increased apparent metabolisable energy (AME) content and starch digestibility measured at ileal as well as faecal level, while weight gain and feed conversion efficiency (FCE) were not affected. Jejunal chyme showed increased amylase activity and bile salt concentration. 5. In Experiment 2, replacement of ground wheat with whole wheat increased dry matter content as well as bile content of gizzard, and stimulated an increase in gizzard as well as pancreas weight. Jejunal amylase and bile concentrations were not significantly affected and neither were growth, FCE or AME. 6. Results from this experiment indicate that the improved feed value sometimes observed with whole wheat may be associated with modulation of digestive processes resulting in increased pancreas and liver secretions.