Effect of Dietary Xylitol on Growth Performance and Nitrogen Retention in Male Broiler Chicks during Immunological Stimulation

The effect of dietary xylitol on growth performance and nitrogen retention was studied in male broiler chicks during immunological stimulation. In experiment 1, chicks (10 day of age) were fed a corn-soybean diet containing 10% glucose or 10% xylitol with identical metabolizable energy and crude protein for 14 days. In experiment 2, ten-day-old chicks were fed 10% glucose or 6% xylitol diet for 8 days. During the final 6 days of the experimental periods, a half of birds fed each diet were injected intraperitoneally with 0.5 mg/kg body weight of Escherichia coli lipopolysaccharide (LPS, 0127:B8) on days 1, 3 and 5, and with 250 mg/kg body weight of Sephadex-G50 superfine on days 2 and 4 to stimulate immune system in both experiments. Feeding of the xylitol diets partially prevented the reduction in body weight gain or feed efficiency due to LPS and Sephadex injections, but the glucose diet did not in both the experiments. LPS and Sephadex injections decreased nitrogen retention, whereas the diet containing xylitol partly in experiment 1 and almost completely in experiment 2, prevented the reduction due to immunological stimulation. These results indicate that dietary xylitol probably prevents the reduction in nitrogen retention with growth retardation due to LPS and Sephadex injection. The beneficial effect on nitrogen retention is obtained when chicks are given xylitol 2 days before stimulating the immune system. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 1 : 84-88)


INTRODUCTION
One of the goals for controlling immune system by nutrition is to alleviate decreased performances following immune stimulation without changing the immune responses in domestic animals.The recognition of the deleterious effect of the prolonged catabolic state has led efforts to identify the optimal exogenous energy and protein (amino acids) for minimizing protein catabolism.In chicks, several nutrients such as fish oil (Korver and Klasing, 1997;Korver et al., 1997Korver et al., , 1998)), conjugated linoleic acid (Cook et al., 1993;Miler et al., 1994) and an increasing starch content in diet (Benson et al., 1993), are the candidates for achieving this purpose.It has been known that parental administration of xylitol improved nitrogen and glucose utilization during stress conditions in mammals (Almmdal et al., 1993;Ardawi, 1992;Geirgieff et al., 1990;Georgie et al., 1985).Previous studies (Takahashi et al., 1999(Takahashi et al., , 2000) ) showed that feeding a diet containing xylitol was effective in minimizing body weight loss following immune stimulation by LPS and Sephadex injections without affecting some immune responses in chicks, although Drews and Stein (1992) reported that parenteral administration of excess xylitol had adverse effects on nitrogen balance and body weight changes in rats.One of the previous studies showed that a beneficial effect of dietary xylitol on growth was obtained with 6% xylitol given to chicks one day before stimulating the immune system (Takahashi et al., 2000).Spolarics (1999) and Spolarics et al. (1993) showed that pentose phosphate cycle activity is increased in rats on a stressful condition in order to supply NADPH, which is an essential cofactor for reactive oxygen species (ROS)metabolizing enzymes.Thus, ROS detoxifying capacity e.g., activities of glutathione peroxidase, glutathione reductase, catalase, superoxide dismutase, and NADPH oxidase appear to rise in the stressful condition.Xylitol is a five-carbon polyol and an intermediate product in the glucuronic acidxylulose cycle (Rognstad et al., 1982;Touster et al., 1962) and the pentose phosphate pathway (Spolarics et al., 1996).Xylitol exerts a nitrogen-sparing effect without appreciable effects on insulin secretion, and is metabolized primarily in the liver, where it is converted via an insulin-independent pathway to glucose 6-phosphate (De Kalbermatten et al., 1980;Georgie et al., 1985).Thus by providing a part of dietary energy, xylitol may serve as powerful ROSdetoxifying substance and consequently prevent nitrogen loss during immune stimulation.In this experiment, an attempt was made to know whether dietary xylitol improved performance and nitrogen utilization in broiler chicks during immunological stimulation as parental administration of xylitol did in mammals.

MATERIALS AND METHODS
Male broiler chicks (Ross) were housed in a battery with electronic heater as brooder and fed a commercial

Effect of Dietary Xylitol on Growth Performance and Nitrogen Retention in Male Broiler Chicks during Immunological Stimulation
Kazuaki Takahashi*, Takanori Mashiko, Shigeki Saito and Yukio Akiba Laboratory of Animal Nutrition, Graduate School of Agricultural Science, Tohoku University Aoba-Ku, Sendai-Shi 981-8555, Japan

ABSTRACT :
The effect of dietary xylitol on growth performance and nitrogen retention was studied in male broiler chicks during immunological stimulation.In experiment 1, chicks (10 day of age) were fed a corn-soybean diet containing 10% glucose or 10% xylitol with identical metabolizable energy and crude protein for 14 days.In experiment 2, ten-day-old chicks were fed 10% glucose or 6% xylitol diet for 8 days.During the final 6 days of the experimental periods, a half of birds fed each diet were injected intraperitoneally with 0.5 mg/kg body weight of Escherichia coli lipopolysaccharide (LPS, 0127:B8) on days 1, 3 and 5, and with 250 mg/kg body weight of Sephadex-G50 superfine on days 2 and 4 to stimulate immune system in both experiments.Feeding of the xylitol diets partially prevented the reduction in body weight gain or feed efficiency due to LPS and Sephadex injections, but the glucose diet did not in both the experiments.LPS and Sephadex injections decreased nitrogen retention, whereas the diet containing xylitol partly in experiment 1 and almost completely in experiment 2, prevented the reduction due to immunological stimulation.These results indicate that dietary xylitol probably prevents the reduction in nitrogen retention with growth retardation due to LPS and Sephadex injection.The beneficial effect on nitrogen retention is obtained when chicks are given xylitol 2 days before stimulating the immune system.(Asian-Aust.J. Anim.Sci. 2002. Vol 15, No. 1 : 84-88) broiler starter diet until experimental diets were given.Birds were selected from about 50 chicks in experiment 1 and 70 chicks in experiment 2, respectively so that mean body weights were as uniform as possible.They were randomly assigned to 2 chicks in a cage in the temperaturecontrolled room (24°C).Light were provided 24 h a day.Water was freely accessible during the experiments.
In experiment 1, thirty-two male broiler chicks (10 days of age) were divided into 2 groups.They were fed a cornsoybean diet containing 10% glucose or 10% xylitol for 14 days ad libitum.In experiment 2, forty-eight male chicks (10 days of age) were fed on 10% glucose or 6% xylitol diet for 8 days ad libitum.Composition of experimental diets was shown in table 1.
During final 6 days of the experimental diet feeding in experiments 1 and 2, a half of chicks fed each diets was injected intraperitoneally with Escherichia coli lipopolysaccharide (LPS, 0127:B8, 0.5 mg/kg body weight) on days 1, 3 and 5 and with Sephadex-G50 superfine (250 mg/kg body weight) on days 2 and 4 to stimulate immune system.E. coli LPS was dissolved in a sterilized saline (0.9% sodium chloride solution) at a concentration of 500 µg/ml.Sephadex G-50 superfine (Pharmacia, Piscataway, NJ, USA) was dissolved in the saline at concentration of 50 mg/ml.The remaining chicks (control group) were injected with a saline alone.
All excreta were collected and feed intake was recorded for the periods of the immune stimulation.Nitrogen content of feed and excreta was determined by the Kjeldahl method.Most of visceral organs and tissues including liver, kidney, spleen and bursa were removed and weighed at the end of the experiment 2.
Data were analyzed as a two (dietary treatments) by 2 (immune stimulation) factorial arrangements of treatments using the General Linear Model procedure of SAS (SAS Institute, 1982, Cary, NC, USA) with means separation by Duncan's multiple range test (p<0.05).The analysis for feed intake, feed efficiency and nitrogen retention was done based on cage replication.

RESULTS
Table 2 shows growth performance in male broiler chicks fed on 10% xylitol diet during immunological stimulation.Immunological stimulation by repeated injections of LPS and Sephadex significantly reduced feed intake (p<0.001),body weight gain (p<0.001) and feed efficiency (p<0.003).Dietary xylitol partially, but significantly, prevented the reduction in body weight gain (p<0.05) and feed efficiency (p<0.05).
Table 3 shows growth performance, and ratio of visceral weight to body weight in male broiler chicks fed on 6% xylitol diet during immunological stimulation.Immuno-  Figure 1 shows nitrogen retention during 6 daysimmunological stimulation period in chicks fed the 10% xylitol diet for 14 days (experiment 1, figure -1A) and those fed the 6% xylitol diet for 8 days (experiment 2, figure -1B).Immunological stimulation by injections of LPS and Sephadex significantly reduced nitrogen retention in experiment 1 (p<0.05)and experiment 2 (p<0.01),respectively.Feeding xylitol significantly improved nitrogen retention in experiment 2 (p<0.05) and tended to improve that in experiment 1 in the immune stimulatedchicks The improvement of nitrogen retention during immune stimulation appeared to be much pronounced in chicks given xylitol 2 days before the immune stimulation (figure 1 B, experiment 2) than that in chicks given xylitol 8 days before the stimulation (figure 1 A, experiment 1).

DISCUSSION
Stress responses are associated with numerous alterations of intermediary metabolism in animal.A consistent finding is peripheral skeletal muscle protein breakdown resulting in muscle wasting and net negative balance of whole body nitrogen.An introduction of xylitolsupplemented parenteral nutrition resulted in improved nitrogen balance in septic rats.The rate of loss of intracellular glutamine in skeletal muscle was markedly decreased in response to xylitol-supplemented parenteral nutrition in septic rats (Ardawi, 1992).The xylitol-supplemented parental nutrition decreased urinary 3methylhistidine excretions and enhanced nitrogen retention (Fried et al., 1990).These results suggest that xylitol has a significant nitrogen sparing effect in stressed animals and that the effect is, at least in part, due to decrease in muscle protein degradation.The present study showed that xylitol in diet improved nitrogen retention in stressed chick (figure 1).In this experiment, the ratio of visceral tissues weights including all digestive tracts, liver, kidney, spleen and bursa to body weight did not differ among the treatments (p>0.1),suggesting that effect of dietary xylitol on nitrogen sparing action during immunological stimulations could not be ascribed to some specific organs or tissues (table 3).During immunological stimulation, digestive tract and liver weights increased but skeletal muscle weight decreased in mammals and chicks.Therefore, dietary xylitol possibly reduces protein degradation in skeletal muscle in immune stimulated-chicks, although it was not possible to measure protein turnover and the muscle weights in the present experiments.
The previous experiments in chicks (Takahashi et al., 1999(Takahashi et al., , 2000) ) showed that up to 15% of xylitol in diet did not have any adverse effect on growth performance and immune response in normal chicks while the growthstimulating effect of dietary xylitol appeared in stressed chicks.Rats fed a 10% xylitol diet markedly reduced body weight as compared to rats fed a glucose-based diet (Ellwood et al., 1999;Hamalainen and Makinen, 1985).Our results confirmed that dietary xylitol improved body weight gain and feed efficiency during immunological stimulation in chicks (tables 2 and 3), although the effects of xylitol were less potent than those obtained in the previous experiments (Takahashi et al., 1999(Takahashi et al., , 2000)).The previous experiments (Takahashi et al., 1999(Takahashi et al., , 2000) ) showed that a beneficial effect of dietary xylitol on growth was obtained when a 6% xylitol diet was given to chicks one day before stimulating the immune system.The improvement of nitrogen retention during immune stimulation also appeared to be much pronounced in short terms of xylitol feeding (experiment 2) than that in long terms of feeding (experiment 1).Thus, the beneficial effect of dietary xylitol probably occurs when xylitol was given to chicks one or 2 days before stimulating immune system.In conclusion, dietary xylitol probably prevents the reduction in nitrogen retention and growth retardation due to LPS and Sephadex injection, and the beneficial effect on nitrogen retention is obtained when chicks are given xylitol 2 days before stimulating the immune system.Thus, the practical provision of dietary xylitol may be useful for poultry meat production under stressful condition.

Table 1 .
Dietary composition 1Akiba and Matsumoto (1978). 2 ME value of xylitol was estimated as the same value as glucose.

Table 2 .
Effect of 10% xylitol on growth performance during immune stimulation due to repeated injection of lipopolysaccharide (LPS) and Sephadex in male broiler chicks (experiment 1)

Table 3 .
Effect of 6% xylitol on growth performance and ratio of visceral weight to body weight in male broiler chicks during immune stimulation due to repeated injection of lipopolysaccharide (LPS) and Sephadex (experiment 2)