A. SACRANIE1
P.A. IJI1
L.L. MIKKELSEN1
M. CHOCT2
1School of Rural Science and Agriculture, University of New England, Armidale, NSW Australia
2Australian Poultry CRC, University of New England, Armidale, NSW, Australia
Two experiments were conducted to evaluate the occurrence and possible effects of certain dietary ingredients on reverse peristalsis or reflux in broiler chickens. The first experiment was a preliminary study into the occurrence of reflux while the second experiment investigated the passage of a bacterial marker and Cr-EDTA in birds fed diets of varying viscosities. The results suggest that reflux occurs throughout the digestive tract of both fasted and fed chickens. Reflux appears to be part of normal gut motility and a possible adaptive response to an absence of food, indicating that it serves to extend the digestive process. Dietary ingredients are likely to affect reflux, especially ingredients that increase digesta viscosity in the lumen. In addition, microbial populations may be relocated by reverse peristaltic contractions.
Introduction
The phenomenon of reverse peristalsis, or reflux, has been recorded in a limited number of avian species. As with the overall study of motility, there is insufficient evidence to describe the patterns of these movements or even conclusively associate it with chickens. Digestive reflux, if it does occur in chickens, will have implications for nutrient utilisation, choice of feed ingredients and health. The primary aim of the present study was to investigate the occurrence of digestive reflux, its variation with nature of diet and possible link to bird health.
Assessing the occurrence of reflux using Cr-EDTA as an extrinsic marker
The soluble marker, Cr-EDTA was injected into the cloaca of 48 broiler chickens at 3 or 5 weeks of age. Due to the preliminary nature of this trial replicates were not employed in the study. Four birds (2 fed and 2 fasted) were then slaughtered at 1, 2, 3, 4, 5 and 24 hours post-marker administration. Digesta samples were taken from the crop, gizzard, duodenum, jejunum, ileum and caeca to analyse for the Cr content.
After one hour Cr was detected in all sections of the gastrointestinal tract (GIT) except for duodenum in the 3-week old group (Figure 1). In both fasted and fed groups at both ages, the majority of the marker remained in the caeca. In the 3-week old, fasted group high levels of Cr were observed in the gizzard, equivalent to the levels found in the corresponding caecal samples.
In the fasted birds, Cr was absent in the jejunum and ileum, 4 hours after administration in both the 3- and 5-week old birds, as shown in Figure 2. Chromium was present in other regions, except in the crop of fasted birds (both 3- and 5-week old).
Cr levels were higher in the gizzard and duodenum for fasted birds at both ages. Levels in the caeca remained the highest for all birds.
Twenty-four hours after the marker was administered Cr levels remained highest in the caeca for all but the 3-week fasted birds (Figure 3), with levels only slightly less than those observed one hour post-administration (Figure 1). In fed birds, Cr was present at all regions with the exception of 3-week old fed birds where Cr was absent in the duodenum. For fasted birds, in both age groups, some regions of the GIT were devoid of Cr.
The steady rise of Cr levels in the gizzard, and the subsequent peak at 4 hours, is more noticeable in fasted birds, and is likely a reaction to prolonged fasting. The high levels may be an indication of a rhythmic oscillating complex (ROC), which has been observed to occur after 4-6 hours of fasting and characterised by re-stimulating fed state motility (Clench and Mathias, 1992; Jimenez et al., 1994). Peristalsis rather than reverse-peristalsis would be expected for the fed state, which might explain why after the peak at 4 hours post-marker administration, Cr levels declined after 24 hours.
The high levels of Cr in the caeca are not surprising, since the marker was injected at a point just beyond the colonic sphincter. Colonic-caecal reflux is well established and may serve to recover nitrogen from urea. The levels observed especially in the 5-week old birds, suggest initial increasing levels (probably due to Cr entering via the colonic-caecal reflux), then levels decreased (due to reflux towards more proximal areas in the GIT) and finally increased slightly again (material flowing distally under normal peristalsis).
Effect of diet on the reflux and the retrograde movement of a novel antibiotic resistant strain of E.Coli
The 72 birds used in this study were divided into 6 groups of 12 birds. Groups 1, 2, 3 and 4 were fed diets based on maize, wheat, wheat plus an exogenous microbial enzyme or a commercial diet, respectively. Two markers, Cr-EDTA and a bacterial marker, were administered via the cloaca after 4 hours of feed deprivation at 28 days of age. Group 5 were fed a commercial diet and both markers were administered at 28 days of age via the crop while Group 6 were fed a commercial diet and only Cr-EDTA was administered via the cloaca at 28 days old.
The bacterial marker used was a strain of E. coli, chosen due to its resistance to two antibiotics, Nalidixic acid and Rifamycin, making it almost impossible to find in nature. Digesta samples were taken from the gizzard, duodenum, jejunum, ileum and caeca, and analysed for Cr content and plated on selective media to analyse for the bacterial marker.
Chromium was detected in the gizzard of birds from all four-diet groups, with the lowest mean concentration, although not statistically significant, in birds given the maize diet (Table 1). The antibiotic resistant E. coli was present in the gizzard of birds on all four diets but there was no significant difference between the dietary groups.
Analysis of digesta from the duodenum showed that Cr was present in this section of the GIT for birds from all four-diet groups but there was no significant difference between the groups. The microbial marker was also detected in the duodenum of birds from all four-diet groups. Analysis of variance revealed significant differences (p=0.0296) between the maize diet group and both Wheat + enzyme and commercial diet groups, in terms of number of colonies.
The digesta retrieved from the caeca of birds from all four-diet groups contained Cr and the antibiotic resistant E. coli. Analysis of variance did not reveal significant differences between the Cr levels or E.coli counts in birds on the maize and wheat dietary groups.
The results of this experiment confirm the findings of the previous study, with regard to the reverse passage of the soluble marker, Cr-EDTA. As such, it may be concluded that reflux occurs throughout the GIT.
This experiment also substantiates the hypothesis that bacterial communities may be relocated to more proximal sites in the GIT by reverse peristalsis. The antibiotic resistant strain of E. coli used in the experiment, was recovered from the gizzard of birds from all four diets, indicating that the bacterium was able to travel the length of the GIT when introduced through the cloaca. The implications of this finding could be considerable, especially when related to the relocation of pathogenic microbes such as C. perfringens to areas in the upper tract.
It may be assumed that intestinal viscosities of the maize and enzyme-supplemented wheat-based diets were similar while the wheat control diet would generate a more viscous digesta, particularly in the jejunum and ileum. Consequently, one would expect to see significant differences in the levels of the two markers in the small intestine for the maize and wheat diets.
However, this was not the case: significant differences were not observed between the marker levels in the maize and wheat diet. A significant difference was observed in the number of colonies counted from the digesta obtained from the duodenum and this coupled with the strong tendency for different counts in the jejunum (data not shown) between the maize and commercial diet are worth noting. The fact that this difference was observed in adjoining sections where the counts were higher both in the duodenum and jejunum in birds from the maize diet group suggests that this may be a dietary effect. Because viscosity was not measured, it is difficult to explain why significant differences were not observed between maize and wheat-based diets. However, it has been noted that the intestinal viscosity for maize can be higher than for wheat (Maisonnier et al., 2001). The variability in pentosan content of different wheats may be a factor in the results obtained in this study; this, together with digesta viscosity, should be measured in subsequent studies.
Conclusion
These findings suggest that reflux is an adaptive response to a lack of feed, as well as being characteristic of normal gut motility occurring throughout the digestive tract. In addition, microbial populations may be relocated by reverse peristalsis.
References
Maisonnier, S., Gomez, J. and Carre, B. (2001). British Poultry Science, 42 (1): 102-110.
Clench, M.H. and Mathias, J.R. (1992). American Journal of Physiology 25: G498-G504.
Jiménez, M., Martinez, V., Rodriguez-Membrilla, A., Rodriguez-Sinovas, A., Gonalons, E. and Vergara, P. (1994). American Journal of Physiology 29: G585-G595.
From Proceedings of the "19th Australian Poultry Science Symposium",
