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J APPL POULT RES 2006. 15:266-273
© 2006 Poultry Science Association
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Research Reports

Influence of Dietary Sesame Meal Level on Histological Alterations of the Intestinal Mucosa and Growth Performance of Chickens

K. Yamauchi*,1, M. Samanya{dagger}, K. Seki{ddagger}, N. Ijiri{ddagger} and N. Thongwittaya{dagger}

* Laboratory of Animal Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa-ken, 761-0795 Japan; {dagger} Department of Animal Technology, Faculty of Agricultural Production, Maejo University, Chiang Mai 50290, Thail; and {ddagger} Kadoya Sesame Mills Inc.,6188 Tonosho-cho, Shozu-gun, Kagawa 761-4101 Japan

Correspondence: 1 Corresponding author: yamauchi{at}ag.kagawa-u.ac.jp


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
A feeding experiment was conducted to evaluate the effects of dietary sesame meal (SM) on growth performance and histological intestinal alterations of layer chickens. Thirty-two White Leghorn male chickens were divided into 4 groups of 8 birds. They were fed 0, 10, 20, or 30% dietary SM for 28 d. After the feeding experiment, average villus height, epithelial cell area, and crypt cell mitosis numbers were morphometrically compared with an image analyzer, and the results were analyzed with Duncan’s multiple range test. The morphological changes of epithelial cells on the villus apical surface were observed morphologically using scanning electron microscope. The growth performance data revealed no significant differences in birds fed up to 20% dietary SM, significantly lower values were revealed in the 30% dietary SM group. At 10% dietary SM, growth performance tended to be improved. Most values of the intestinal villus height, epithelial cell area, and crypt cell mitosis numbers were not different among groups for each intestinal segment. Flat epithelial cells were on the intestinal villus apical surface in the group fed 0% dietary SM. Those cells developed into protuberated cells in the group fed 10% dietary SM, and these protuberated cells disappeared gradually with increasing dietary SM levels. Considerations for current growth performance and histological intestinal alterations suggest that the SM would have no detrimental effect on the growth performance with up to 20% dietary SM nor on the intestinal villi with up to 30% dietary SM, but hypertrophy was observed in the epithelial cells of bird fed up to 20% dietary SM. In conclusion, up to 20% SM could be incorporated into diets fed under commercial conditions to male birds of laying strains in the developer period.

Key Words: sesame meal • intestinal epithelial cells • intestinal villi • growth performance


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Many studies have been conducted to evaluate the function of intestinal regulation due to natural substances. Sesame (Sesamum indicum) seed is a traditional health food around the world, and is composed of 45 to 50% lipid, 15 to 20% protein, and 10 to 15% carbohydrate [1]. In Japan, about 155,000 t of sesame seed were imported, and about 38,000 t of sesame meal (SM) were produced in 2004. Because the SM is the residue after pressing the oil from the seed, it is an excellent source of protein (47.1% [2] to 52.9% [3]) and has an amino acid composition similar to that of soybean meal (47.7% CP) [2]. The SM could partially replace soybean meal in the diet as a source of plant protein for chicks [4] and ducklings [5]. Growth performance of broiler chicks fed the diet containing SM at 15% of dietary CP was not different from that of the control chicks fed the soybean meal diet but was depressed by a diet containing SM at 30% of dietary CP [2]. Conversely, sesame seed is not only a good source of edible nutrients, but it is also widely considered to have medicinal value, including antiaging effects [6, 7], antioxidant activity [8, 9], and inhibition of cholesterol absorption from the intestine and synthesis in the liver [10]. Although numerous studies dealing with nutritional and physiological functions of the SM have been published, the histological intestinal alterations induced by the SM have so far not been reported in detail. The present investigation was designed to clarify how morphological alterations of the intestinal villi and epithelial cells are induced by feeding SM diets.

In this study, chickens were fed the dietary SM diets for 28 d to observe the growth performance and the histological alterations of the intestinal villi using light microscopy and epithelial cells using scanning electron microscopy.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Treatments of Birds and Diets
Seventeen-week-old White Leghorn male chickens (Gallus gallus domesticus, Julia strain) were maintained in individual cages in an environmentally adjusted room to natural day light hours with a 13-h photoperiod (0600 to 1900 h) at a mean environmental temperature of 27°C. They were allotted to 4 groups of 8 birds each. The basal diet [11] was replaced with SM [12] (Table 1Go) at 0, 10, 20, or 30% (Table 2Go). Each bird was allowed feed and water ad libitum for 28 d. Feed intake and BW gain were measured every week.


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  		Table 1. Composition of sesame meal used in this experiment
 

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  		Table 2. Feed formulation and nutrient composition of dietary sesame meal diets
 
Tissue Sampling
At the end of the experiment, the remaining feed from each bird was measured and returned to birds. During tissue sampling, birds were fully fed. Four birds per group were randomly decapitated under light anesthesia with diethyl ether. All experiments were carried out according to the humane care guidelines for the care and use of laboratory animals established by Kagawa University. The whole small intestine was removed immediately and put into a mixture of 3% glutaraldehyde and 4% paraformaldehyde fixative solution in 0.1 M cacodylate buffer (pH 7.4). The same fixative solution was also injected into the intestinal lumen. The intestinal sections from the ventriculus to the pancreatic and bile ducts were recognized as the duodenum, the jejunum was from the ducts to Meckel’s diverticulum, and the ileum was from the diverticulum to the ileocecal-colonic junction. The middle of each segment was taken for tissue samples.

Light Microscopic Examination
A 1-cm length of each intestinal segment for light microscopic observation was fixed with Bouin’s solution, prepared for paraplast embedding, cut at a 5-µm cross-section, and stained with hematoxylin-eosin. All villus heights having the lamina propria were measured from villus tip to the base excluding the crypt in one transverse section. An average of these values was expressed as a mean villus height per section. A total of 8 sections were counted from one bird, and an average of these 8 sections was expressed as a mean villus height for each bird. Finally, these 4 mean villus heights from 4 birds were expressed as a mean villus height for one group.

A single epithelial cell area on a 5-µm transverse section was measured at the middle of the villi. First, the epithelial cell layer was randomly selected and measured, and then the number of cell nuclei within this measured epithelial cell layer was counted. Finally, the epithelial cell layer area was divided by the number of cell nuclei to obtain an epithelial cell area. Two cell areas were calculated per transverse section, and an average of these 2 values was expressed as a mean cell area per section. A total of 8 sections were counted from one bird, and an average of these 8 sections was also expressed as a mean cell area for each bird. Finally, these 4 mean cell areas from 4 birds were expressed as a mean cell area for one group.

These values of the villus heights and epithelial cell area were measured using an image analyzer [13].

For crypt cell mitosis numbers, we counted mitotic cells having homogenous, intensely stained basophilic nuclei with hematoxylin as shown in a previous study [14]. All cell mitoses of the crypt observed in one transverse section were measured. A total of cell mitosis numbers was counted from 5 different sections for each bird, and these 5 values were used to calculate a mean of cell mitosis for one bird. Finally, these 4 mean cell mitoses from 4 birds were expressed as a mean of cell mitosis in one group. All light microscopic parameters were measured in each intestinal segment.

Statistical Analysis
The average of villus height, cell area, and crypt cell mitosis number of each bird from each treatment group were analyzed across all treatment groups by 1-way analysis with a Duncan’s multiple range test using Stat View program [15]. Differences at P ≤ 0.05 were considered significant.

Scanning Electron Microscopic Examination
Tissue samples for scanning electron microscope were processed as described as described previously [16, 17]. The duodenal sample was fixed within a mixture of 3% glutaraldehyde and 4% paraformaldehyde in 0.1 M cacodylate buffer (pH 7.4) at room temperature for 2 h and then postfixed with 1% osmium tetroxide for 2 h. After being coated with platinum, epithelial cells on the duodenal villus apical surface were morphologically observed under a scanning electron microscope [18] at 8 kV. Because the exfoliative zone around the central sulcus on the villus apical surface is a final goal of epithelial cell life after birth in the intestinal crypt, we observed the morphological alterations of epithelial cells around the central sulcus.


   RESULTS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Growth Performance
Although feed intake tended to increase with increasing dietary SM level, it was not significantly different among the 0, 10, 20, and 30% dietary SM groups (Table 3Go). Compared with the 0% dietary SM group, BW gain from initial to final BW was not different in the 10 and 20% dietary SM groups but decreased by one-half in the 30% group (P ≤ 0.05), resulting in an increased feed conversion ratio in the 30% SM group (P ≤ 0.05).


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  		Table 3. Feed intake, initial weight, final weight, weight gain and feed conversion ratio in chickens fed dietary sesame meal diets (means ± SD, n = 8)
 
Light Microscopic Parameters
Although the cell mitosis numbers of the jejunum were lower in the 10 and 20% groups than those of the 0% group (P ≤ 0.05), most values of the intestinal villus height, epithelial cell area, and crypt cell mitosis number in each intestinal segment did not show significant differences in the 0, 10, 20, and 30% dietary SM groups (Figure 1Go).


Figure 1
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  		Figure 1. Intestinal villus height, cell area, and cell mitosis number of the duodenum, jejunum, and ileum in chickens fed 0, 10, 20, or 30% sesame meal (SM) diets (means ± SD, n = 4).

 
Epithelial Cells
On the duodenal villus apical surface of the 0% SM group (Figure 2AGo), epithelial cells were composed of flat epithelial cells, and a clear central sulcus (small white arrows) was observed. The flat cells around the central sulcus developed to protuberated cells (black arrows in Figure 2BGo) in the 10% SM group, resulting in a rough surface. In the 20 (Figure 2CGo) and 30% (Figure 2DGo) SM groups, the central sulcus reappeared clearly (small white arrows), and partially exfoliated areas (large white arrows) were observed. The faintly protuberated cells were observed around the central sulcus in the 20% SM group, which had a comparatively rough surface. However, in the 30% SM group, the protuberated cells disappeared and had a smooth surface.


Figure 2
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  		Figure 2. Duodenal villus apical surface in chickens fed 0 (panel A), 10 (panel B), 20 (panel C), or 30% (panel D) sesame meal diets. The villus apical surface shows most hypertrophic morphological change in the 10% group followed by the 20% group. Small white arrows indicate central sulcus; black arrows indicate protuberated cells; large white arrows indicate partially exfoliated area. Scale bar = 37 µm.

 

   DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
In previous papers, broiler chicks fed high protein–low energy diets (20.5% CP and 2.41 Mcal of ME/kg) showed much more improved growth performance in birds than low protein–high energy diets (8.3% CP and 3.74 Mcal of ME/kg) [19, 20]. The birds fed a higher protein diet had wider villi, more epithelial cell mitosis numbers, more protuberated cells [19], and more nutrients absorbed in the intestinal epithelial cells [20] than those fed low protein diets. It was our assumption that, with an increase in protein content (increasing SM levels), growth performance would improve because a high protein diet had previously induced improved growth performance in broilers. However, the present SM groups with higher protein levels than the 0% SM group failed to improve the growth performance of White Leghorn males. Compared with the 0% SM group, the growth performance did not differ in the 10 and the 20% SM groups and decreased in the 30% SM group.

The lack of improved growth performance, even in the high protein diets, might be related to the composition of the SM. Sesamin, a lignan in sesame seed oil, does not affect BW gain or feed intake at the 0.5% dietary diet level [10] in rats. At 14% dietary SM [3] and at 30% dietary CP [2], broiler growth is suppressed. Because SM includes 1.44 to 5.18% phytic acid [21], Hossain and Jauncey [22] suggested that the high phytic acid content of SM is a possible reason for its lower apparent protein digestibility. These reports indicate that lack of improved growth performance, even after feedings of the high protein diets in this study, could be caused by low protein digestibility due to the phytic acid in the SM. However, growth performance did not decrease significantly up to the 20% dietary SM levels. The BW gain and feed conversion ratio tended to be improved at 10% dietary SM. Consideration of these observations and the findings of similar studies in the literature lead to the general conclusion that the SM would have no detrimental effect on the growth performance and could be incorporated at up to 20% in commercial chicken diets fed to males of a laying strain.

The villus height, epithelial cell area, and crypt cell mitosis number are related to the ingested feeds and digestibility of CP [16, 23, 24]. The villus height is reported to vary mainly in regard to the figures representing the epithelial cell numbers [25]. Because villi consist of epithelial cells, the villus height (length) is assumed to change according to the cell area and number. Consequently, villus function could be determined by measuring these parameters under a light microscope. In this study, most parameters measured under a light microscope did not show a difference in each intestinal segment among the 0, 10, 20, and 30% SM groups. It is not clear at present why cell mitosis decreased in the jejunum of the 10 and 20% SM groups. Epithelial cells proliferations were reduced by reduction in energy [26] and nutrient [14] intakes, and fat exerted a strong stimulatory effect for intestinal mucosal regeneration [27]. The high phytic acid content in SM (1.44 to 5.18%) [21] induced low apparent protein digestibility [22]. It may be speculated that the present decreased cell mitosis in the jejunum of the 10 and 20% SM groups may result in part from a complex effect of these findings. Considerations for current light microscopic observations suggest that the intestinal villi did not show abnormality up to the 30% SM level.

Epithelial cells originate by mitosis in the intestinal crypt migrate along the villus surface upward to the villus tip within a few days [28], where they are extruded into the intestinal lumen within 48 h after birth [29]. Thus, epithelial cells may show a dramatic morphological alteration at the exfoliative zone around the central sulcus due to villus function. In the previous studies, although a specific histological alteration did not appear at the light microscopic level, a dramatic morphological change was observed at the epithelial cell level after feeding easily absorptive substances such as a soluble hyperalimentative enteral solution [14] and a semipurified diet [17, 30]. The morphology of the epithelial cells on the villus apical surface was hypertrophied by high protein diets [17, 23]; these cells developed into protuberated cells by nutrient absorption [14]. The high protein–low energy diets induced much more protuberated cells than the low protein–high energy diets [19]. The main aim of the present study was to investigate whether these cell morphological alterations are induced after feeding the dietary SM diets. In this feeding experiment, as the dietary SM level increased, the CP in the diets increased, whereas ME decreased. Therefore, it was our assumption that, with an increase in protein content, protuberated cells would increase because a high protein diet had previously induced increased protuberated cells. However, in this study, although such protuberated cells appeared in the 10% SM groups (19.22% CP and 2.726 Mcal of ME/kg), which was higher protein–lower energy diets than the 0% SM groups (16.00% CP and 2.800 Mcal of ME/kg) but lower protein–higher energy diets than the 20 (22.44% CP and 2.652 Mcal of ME/kg) and 30% (25.66% CP and 2.578 Mcal of ME/kg) SM groups, the protuberated cells disappeared gradually with the increasing SM levels (protein levels). This finding suggests that the dietary SM diet is good for epithelial activity at 19.22% CP in SM (10% SM group). Also, SM has an antiaging effect [6, 7] and antioxidant activity [8, 9]. Therefore, the epithelial cell life of the 10% SM group is thought to be extended more than the conventional cell turnover, and epithelial cells might be staying on the villus apical surface longer than a few days, resulting in greater cell protuberances. This hypothesis correlates well with a tendency of improved BW gain and feed conversion ratio in the 10% SM group. However, as the high phytic acid in the SM [21] induced low protein digestibility [22], an activity of the epithelial cells might be atrophied with the increasing SM levels, resulting in the flat cells in the 30% SM group. This corresponds with the suppressed growth of broilers fed the 14% dietary SM diet [3] and the present tendency of decreased growth performance with the increasing SM levels. The current cellular morphological observations suggest that the SM can hypertrophy the epithelial cells up to the 20% dietary level even with no changes observed under a light microscope.


   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 

  1. Up to 20% dietary SM had no detrimental effect on the growth performance in 17- to 21-wk-old White Leghorn male chickens.
  2. In these chickens, most values of villus height, cell area and cell mitosis were not abnormal when the birds were fed up to 30% dietary SM.
  3. Epithelial cells were hypertrophied in birds fed up to 20% dietary SM.
  4. Consideration for the current histological intestinal alteration and growth performance suggest that up to 20% dietary SM could be incorporated in commercial chicken diets during the developer period of males of a laying strain.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. Lee, S.-C., S.-M. Jeong, S.-Y. Kim, K. C. Nam, and D. U. Ahn. 2005. Effect of far-infrared irradiation on the antioxidant activity of defatted sesame meal extracts. J. Agric. Food Chem. 53:1495–1498.[ISI][Medline]
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  8. Kang, M.-H., Y. Kawi, and M. Naito. 1999. Osawa dietary defatted sesame flour decreases susceptibility to oxidative stress in hypercholesterolemic rabbits. J. Nutr. 129:1885–1890.[Abstract/Free Full Text]
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