The effect of diets containing different levels of structural substances on morphological changes in the intestinal walls and the digestibility of the crude fibrę fractions in geese (Part I I I )

Two experiments were conducted with 270 growing geese fed complete diets differing in the source and content of carbohydrates and structural fractions. The experimental diets contained similar levels of crude fibrę provided by different proportions of one of the following components: corn (50%), dried grass (20%), oats (65%), beet pulp (31%), rye (50%), barley (60%), field bean, pea or rapeseed meal (20% each). The level of the crude fibrę in the experimental diets was twice as high as in the control diet. The digestibilities of the structural fractions in the smali and large intestine were determined with the indicator method. Morphological changes in the walls of intestine were examined in birds slaughtered at 1 and 2 h after feeding. Feeding diets containing large proportions of components rich in cellulose and hemicellulose such as oats, beet pulp and dried grass caused an increase on the thickness of the wali mainly on the muscular part of the smali and large intestine. Longer villi were observed in the large intestine of birds fed the diet which contained beet pulp. Feeding a large proportion of rye containing pentosans resulted in an increase on the thickness of the mucous wali; feeding a diet containing rapeseed meal resulted in a decrease on the thickness of the intestinal wali. Smali differences were found between the extent of digestion of structural substances in the two parts of the intestine. Cellulose was digested, depending on the composition of the diet, by 20 to 40%, A D F by 18 do 38% and hemicellulose by 40 to 57%.


INTRODUCTION
High reąuirement of growing poultry for energy concentration and poor digestion of crude fibrę are the main reasons for the use of feeds with Iow contents of structural substances for this category of birds.Geese are particularly interesting group of animals in this respect.
The source of structural substances has an important effect on the concentration of dry matter and nitrogenous compounds in the digestive tract, the length of the intestine and morphology of the intestinal walls, liver, kidney and pancreas (Brown et al., 1979;Jamrozetal., 1989;Wiliczkiewiczetal., 1987;Wiliczkiewicz et al., 1989).Geese digest structural substances better than other avian species (Drochner et al., 1988;Jamroz and Bieliński, 1975a, b;Nakahiro and Issiki, 1975;Orth, 1985;Pakulska, 1983;Thornburn and Willcox, 1965;Vogt and Stute, 1971).However, there is a scarcity of information on the processes of digestion and fermentation of the carbohydrates and crude fibrę fractions.The published studies were conducted on laying hens and chicken while it seems that due to the type of feeds consumed by geese, analogies with respect to fermentation in the intestine should rather be made with pigs or rabbits (Adrian and Arnal-Peyrot, 1974;Keys et al., 1970;Laplace, 1987;Roth and Kirchgessner, 1985;Stanogias and Pearce, 1985;Żebrowska, 1985).
In order to determine the effect of structural substances on the morphology of the digestive tract and the processes of digestion in geese, a series of studies was carried out in which geese were given complete diets with large proportions of ingredients containing different fractions of carbohydrate and crude fibrę (Jamroz et al., 1989;Wiliczkiewicz et al., 1987Wiliczkiewicz et al., , 1989;;Wiliczkiewicz, 1988).The proportions were chosen so that the amount of crude fibrę in the diets was similar, and that from high fibrę feeds was 100% greater than in the control diet.

MATERIAŁ AND METHODS
Two experiments were conducted with 270 growing White Italian geese.In experiment 1, 2 to 5 week-old geese were assigned to five analogous feed groups and kept in roofed concrete yards.The geese were given complete diets, containing the same amount protein (approximately 17%) but differing in the proportions of corn, dried grass, oats or dry sugar beet pulp (Table 1).The geese were slaughtered after they were 7.5 weeks old.Every four days 4 geese were selected from each group: two were slaughtered one hour after feeding, the remaining two 2 hours after feeding.The intestines were removed immediately after slaughter, the particular segments tied off and their length measured.Samples for histological examination were taken from the middle part of the smali intestine, 20 cm from the remnant of the yolk sac and from the central part of the large intestine.They were fixed in a mixture of formaldehyde, alcohol and acetic acid.Sections were cut from the paraffin błock, placed on slides, the paraffin removed and samples stained with hematoxyline and eozine.The thickness of the layers was measured using an eyepiece micrometer and the mean value was calculated from 20 measurements (Janik and Korniewicz, 1987).
The remaining birds were used for digestibility studies.The digestibilities were determined with the indicator method using Cr 2 0 3 which was included at the level of 0.5% in the diet.They were fed as previously outlined and slaughtered after 11 days following which the contents of the ileum and large intestine were sampled.The digestibility coefficients of the crude fibrę fractions according to Van Soest (1963) were determined in the smali and large intestine.The chromium content in the the diets and excrements was determined by atomie absorption spectrometry (PYE Unicam SP-2300).
Experiment 2 was carried out with 120 geese.Three-weeks-old birds were assigned to 6 groups and fed complete diets (Table 2), which differed primarily on the source of structural substances (Table 1).The diets had equivalent protein contents (approx.17% crude protein) and similar energy values, about 11.0 MJ/kg.The geese were kept on concrete yards and fed twice daily.The amount feed given was chosen so that it was used by the next feeding.Water was given ad libitum.Six days before slaughter, 0.4% Cr 2 0 3 was added to the feed.
After the geese were 8 weeks old, 8 birds from each group were slaughtered 1 or 2 hours after feeding.The procedurę after slaughter was the same as outined in experiment 1.In addition, samples of the pancreas and kidneys were taken in order to determine enzymatic activity.
The results pertaining to changes in wali thickness of the intestinal segments and the degree of digestion of fibrę fractions in the ileum and large intestine are presented below.Ali of the numerical data was analyzed statistically using variance analysis and the multiple rangę test.

Experiment 1
Because of the various types of feeds given, a uniform energy value of the diets was not obtained (Table 1).In agreement with the methodological assumptions, the diets differed in their content of structural substances; the diet with the large amount of oats, followed by the beet pulp diet, had the highest hemicellulose (17%) and cellulose (19.8%) contents.After 5 weeks of the experiment (Table 3) the geese from the following groups grew the most: control and those given the mixture of feeds with a high corn content (3.4-5.1 kg).The smallest gain were found in those given the beet pulp diet (3.1-3.8 kg).Ali of the birds, however, were well developed and healthy.
The thickness of the smali intestine wali of the geese changed depending on the type of feed given and the time elapsing from feeding to slaughter (Table 3).In geese fed diets containing ground oats the intestinal wali was thicker by 12%, containing dried grass and beet pulp, by 9% (P < 0.05) than in the control birds.These changes were not as much the result of changes in the length of the intestinal villi (which changed from 1 to 8%; P < 0.05), but due to the changes in the thickness of the mucous and underlying membranes, which were greater in geese from groups IV and V which were fed diets containing oats and beet pulp.The thickness of the muscular wali is particular increased: it was 23% greater (P<0.05) in birds fed the diet containing beet pulp and 16% in those given ground oats and dried grass.The length of time from feeding to slaughter also affected the thickness of the smali intestine wali, which averaged 1464 /mi after 1 hour and 1362 /mi after 2 hours (P<0.05).The decrease of the villi layer with time after slaughter was highly significant (P<0.01)-from 927 to 747 /mi, while that of the mucous membranę and muscular wali to a lesser degree (P < 0.05).
The components of the crude fibrę fractions had a lesser effect on the thickness of the large intestine (Table 4).Only when beet pulp was fed to the geese (31% content) did the wali of this intestine increase by 14% (P < 0.05), and the length of the villi and thickness of the mucous and underlying membranę by 20-24% (P<0.01) in comparison with respective values in control birds.Other studies have, however, demonstrated the distinct effect of ground barley on increasing the intestinal wali (Jamroz, 1990).The type of feed dominating in the diet had an influence on the digestibility of the crude fibrę fractions in the ileum (Table 5).Celi wali components (NDF and ADF) were digested best from diets containing a high proportion of dried grass, worse from those containing beet pulp (P < 0.05 and P < 0.01).Cellulose was best digested from diets with a 20% content of dried grass (39%) and with a 65% content of ground oats (31%; P<0.05).The digestibility coefficients for hemicellulose did not significantly differ among the groups, but were lower in the birds fed the diet containing beet pulp (P < 0.05).The digestibility coefficients for structural substances in the smali intestine determined 2 hours after feeding were higher by 4-7 units than after the first hour (P<0.05).
The digestibility coefficients of fibrę fractions, calculated on the basis of the large intestine contents, did not differ to significant degree from respective values determined in the ileum.The differences among the groups in the degree of digestion of NDF and ADF fractions eąualled 1-12 units.The digestibility coefficients of cellulose were clearly higher and ranged from 22 to 41%.In this part of the intestine the diet containing beet pulp was also digested more poorly.In spite of rather large differences among groups, they were not proved statistically, which was caused by high individual variability.This fact has also been pointed out by other authors (Jamroz and Bieliński, 1975a, b;Pakulska, 1983).The digestibility of structural substances in the large intestine was 4-6 units higher in the second than in the first hour after feeding (P<0.05).

Experiment 2
The mean weight of the geese at slaughter was 3.1-3.7 kg, body gain was greatest in the geese fed diets containing rapeseed oilmeal and pea (Table 6).The introduction into the diets of large amounts of feeds containing anti-nutritive factors and of various proportion of carbohydrates did not cause large differences in the thickness of the walls of the smali intestine (up to a maximum of 3.8%).Similarly, smali differences were found in villi length, although feeding the diet containing 20% rapeseed oilmeal did cause an 8% increase in their length in comparison with the geese from the control group (P<0.05).
Consumption of a diet containing large amount of rye (50%) caused only a 3.8% thickening of the intestinal wali; on feeding a diet with rapeseed oilmeal the intestinal wali thickness decreased by 10% in comparison with analogous values in control geese.A high rye content in the diet caused a 17% (P < 0.05)increase in the thic kness of the muscular wali of the smali intestine; the effect of the barley was somewhat less marked, in spite of this, the difference between the muscular wali thickness in these birds and the control was 9% (P<0.01).The opposite effect of feeding large amount of barley on the mucous membranę and muscular wali of the smali intestine (that is, a distinct increase in wali thickness) was found in chickens (Jamroz et al., 1990).
The digestibility coefficients of crude fibrę fractions determined on the basis of the compositions of the contents of the ileum were statistically different depending on the type of diet fed (Table 7).The NDF fraction, including cellulose, was best digested from diets containing rapeseed oilmeal or field bean (P < 0.01).The effects of antinutrient factors occurring in rye, field bean, pea and rapeseed oilmeal were not evident in terms of digesting structural substances.Hemicellulose were digested to a significant degree (52-66%).Similar coefficients were obtained by Pakulska (1983).In this experiment too, in which diets composed only of concentrates were provided, the digestibility of structural components 2 hours after feeding geese was greater than after 1 hour (P<0.05 and 0.01).
The increase in the activity of alpha-amylase in the pancreas of the geese fed diets containing field beans and rapeseed meal diet was 23 to 26 % compared to the control diet; a diet containing a large proportion of barley caused a decrease in the activity of this enzyme by 9% (Table 8).A high barley content caused a decrease in the activity of this enzyme in the pancreas by 9%.Feeding a diet containing field bean caused an 18 and 36% increase in the enzymes LAP and GGT in the kidneys, while that of GGT by feeding geese a diet containing pea and rye.In spite of distinct differences between groups, their statisitical significance was not proved.

DISCUSSION
The variety of structural components in the feeds used in experiment 1 clearly modified the thickness of intestinal walls.Giving complete diets containing large proportions of ground oats (65%) and beet pulp (31%), as well as dried grass, that is -hemicellulose, cellulose and pectins, caused an increase in the thickness of the smali and large intestinal walls; in the case of the smali and large intestine this was due mainly to the thickening of the muscular wali (from 16 to 23%).The changes in the large intestine were mainly associated with increases in the length of the villi, which were significant in the geese which were fed beet pulp in the diet (P<0.01).
The thickness of the particular layers of the smali intestinal wali was from 1339 to 1464 /mi, the villi from 726 to 917, the mucous membranę from 247 to 313 and of the muscular wali from 289 to 312 /mi, with the villi constituting 54-62% of the wali thickness.In the large intestine the villi constituted only 39% and muscular layer 45-47% of the wali thickness.
Concentrate, which were used in larger amounts in the diets given to geese in experiment 2, that is barley, rye, field bean, pea and rapeseed oilmeal had a smaller effect on intestinal wali thickness, although some of the differences between the groups were statistically significant.When feeds containing large amount of rye were given, thickening of the mucous membranę was observed, when rapeseed meal was fed a significantly thinner smali intestinal wali was found (P<0.01).In spite of the highest hemicellulose and cellulose content in diets with barley, rye and pea, no essential changes in the morphology of the intestinal wali in comparison with the control group were observed.
Similar changes were found in the thickness of the muscular wali.It may be supposed that when young geese are fed feeds rich in structural carbohydrates, the structure of these substances (eg.pectins in oats and beet pulp) may have a mechanical effect on the intestinal wali (Adrian and Arnal-Peyrot, 1974;  Brown et al., 1979;Drochner et al., 1988;Orth, 1985;Wiliczkiewicz et al., 1987, 1989, Wiliczkiewicz, 1988), while giving feeds containing antinutrient factors (eg. in rye) played a part in the changes in the thickness of the walls, their hypertrophy and softening.
A comparision of the digestibility coefficients of sonie fractions of crude fibrę, determined in the contents of the ileum and large intestine, points to the high degree of digestion of these substances in both parts of the intestine (Table 9).An exception to this is, ADF and cellulose from oats.The role of the large intestine in the digestion of crude fibrę fraction coming from other feeds seems to be less important.In the determination of digestibility coefficients in the ileum, the effect of time elapsing from feeding the birds was significant, with the differences in the value of these coefficients reaching 4 to 7 units, that is, 15-25%.Respective differences in the digestibility coefficients determined in the large intestine amounted only by 1-4 units, which may indicate that time function was here less important.
The interpretation of these facts is not simple and unequivocal, because the degree of digestion of crude fibrę fractions may be the result of the physical and chemical structure of these substances, the degree of water binding by the feeds used and the rate of passage in the intestines.It is also necessary to study the rate and degree to which the digesta passes to the caeca.Their role in the process of digestion in geese has not yet been well understood.The swelling of pectins can lead to dehydration and damage to the villi, which has been found in earlier studies (Jamroz et al., 1989).
The geese best digested the structural substances from diets made up of 65% ground oats, 20% field bean or rapeseed meal in spite of the fact that these diets contained more lignin, cellulose and hemicellulose than diets with beet pulp.Similarly high digestibility was found on feeding a diet containing 20% dried grass, lower when the geese were fed the control diet or one containing 50% corn.This information is also important for breeders.Dry beet pulp, which is given often to young geese, not only decreased gains and the degree of digestibility of fibrę fractions, but also caused the greatest changes in intestinal walls (hypertrophy of the muscular wali) while when oats were given, the mucous membranę, which plays an important role in the absorption of nutrients, thickened.The increase in the thickness of the muscular wali was caused by the large proportion of rye and barley in the diet while the thinning of the mucous membranę -by repeseed meal.Such a specific effect of feeds on the intestine wali may significantly modify the degree of absorption of nutrients, which reąuires further studies.

TABLE 3
Layers thickness of the smali intestine wali in geese (x + s)

TABLE 4
Layers thickness of the large intestine wali in geese (x + S)

TABLE 5
Coefficients of digestibility of fibrę fractions (in %) in ileum and large intestine (x ± s)