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Effect of Coccidiosis on Plasma Epinephrine and Norepinephrine Levels in Turkey Poults
Effect of Coccidiosis on Plasma Epinephrine and Norepinephrine Levels in Turkey Poults P. C. AUGUSTINE US. Department of Agriculture, Agricultural Research Service, Livestock and Poultry Science Institute, Beltsville, Maryland 20705 D. M. DENBOW Virginia Polytechnic Institute, Department of Poultry Science, Blacksburg, Virginia 24061 (Received for publication September 24, 1990)
1991 Poultry Science 70:785-789 INTRODUCTION
Earlier studies (Augustine, 1982) showed that heart composition, heart rate, and blood pressure in turkey poults infected with Eimeria adenoeides or Eimeria meleagrimitis differed significantly from those of uninfected poults. The size of the heart was smaller in the infected poults, primarily because of lower lipid content, and there were slight reductions in heart rate and mean blood pressure at 6 days postinoculation (PI). However, the most marked effect was the impaired capacity of the infected poults to maintain normal blood pressure and heart rates when exposed to stress. Injecting the infected poults with epinephrine or immersing their feet in ice water produced a transitory cardiac arrhythmia and an increase in mean blood pressure mat far exceeded those in similarly stressed uninfected poults (Augustine et al., 1982). The adrenal glands function as part of the normal homeostatic mechanism and respond to a variety of types of stress, including infection, by enhanced catecholamine secretion (Bolton, 1971). Catecholamines are known to have
pressor effects in birds (Sturkie, 1976) and, if increased during coccidial infection, may have contributed to the heightened response to stress shown by the infected poults in the earlier study (Augustine et al., 1982). The aim of the present work was to determine whether turkeys infected with E. adenoeides had higher levels of plasma catecholamines than their uninfected counterparts, and whether these levels could be correlated with severity or stage of infection. In the present paper, the term plasma catecholamines specifies plasma epinephrine and norepinephrine. MATERIALS AND METHODS
The strain of E. adenoeides used in the present study was originally isolated by S. A. Edgar, Auburn University, Auburn, AL, purified by single oocyst isolation, and maintained thereafter at the Protozoan Diseases Laboratory, Beltsville, MD. Beltsville medium white turkeys were obtained at 1 day of age and maintained coccidia-free in wire-floored brooding units. They were given turkey starter
785
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
ABSTRACT Plasma epinephrine, norepinephrine, and glucose levels were measured in 3- to 4-wk-old turkey poults that had been infected with the coccidium Eimeria adenoeides. When measured at 6 days postinoculation, the acute stage of the infection, the epinephrine and norepinephrine levels of the infected poults showed a dose-dependent increase over levels in controls, with poults that were most heavily infected having the highest levels. The catecholamines appeared to show a classic stress-elicited response: this response increases with time to high levels during the acute stage of the infection, and then returns to levels approximately the same as those of the controls as the poults recover from the infection. Anorexia, or feed restriction, appeared to be primarily responsible for the increase in norepinephrine. However, epinephrine levels in the infected poults were significantly higher than in their pair-fed, uninfected counterparts, indicating that factors other than reduced feed consumption contributed to the increase. The data indicate that plasma catecholamines are increased during coccidial infection. As pressor compounds, they may contribute to the previously observed changes in blood pressure and heart function in infected poults. (Key words: turkeys, coccidiosis, epinephrine, norepinephrine, anorexia)
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AUGUSTINE AND DENBOW
'Turkey Pre Starter, Southern States Cooperative, Baltimore, MD 21201. 2 Model 870; Dupont Instrument Co., Wilmington, DE 19898. ^ioanalytical Systems, Inc., West Lafayette, IN 47907. "^Model 3390A; Hewlett Packard Co., Palo Alto, CA 94301. 5 Model LC-4; Bioanalytical Systems, Inc., West Lafayette, IN 47907. Procedure 115; Sigma Chemical Co., St Louis, MO 63127.
x 105 oocysts per bird, or were left uninoculated. On Days 3, 6, and 12 PI, groups of 6 to 8 infected and uninfected poults were observed for weight gain and levels of plasma epinephrine, norepinephrine, and glucose. The methods were the same as those used in Experiments 1 and 2. Before catecholamine analysis, 50 ng of 3,4-dihydroxybenzylamine hydrobromide was added to each plasma sample as an internal standard. The plasma catecholamines were then extracted according to the alumina procedure of Anton and Sayre (1962) and resuspended in 200 uL of .1 M HC104. The samples were analyzed using HPLC as described by Myers et al. (1986). Briefly, 100-uL samples were loaded into the HPLC system, which consisted of a Dupont pump,2 a C-18 column,3 a Hewlett Packard integrator,4 and an Amperometric Detector.5 The mobile phase was run at 1.5 mL/min and the detector was set at .8 megaVolts (mV). The mobile phase, which was degassed and filtered through a .22-um filter, contained citric acid (.12 M), NaOH (8.8 mA/)» Na-EDTA (.4 mM), and sodium octyl sulfate (200 mg). The pH was adjusted to 3.1, and 86 mL of acetonitrile and 1.8 mL of triethanolamine were added to bring the volume to 1 L. Plasma glucose levels were determined by the hexokinase method6 using glucose in saturated benzoic acid as a standard. Measurements of catecholamines and glucose are expressed as means ± standard error of the mean; differences among treatment groups were tested by analysis of variance and, where appropriate, by Student's t test. Probabilities equal to or less than .05 were considered to be statistically significant. RESULTS
On day 6 PI, E. adenoeides infection caused increases in levels of plasma catecholamines and glucose that were a function of the severity of the infection (Table 1). The weight gain of turkeys inoculated with 1 X 105 oocysts was decreased by 38% as compared with controls, without significant change in plasma levels of either epinephrine or norepinephrine. However, when the inoculum was doubled (2 x 105 oocysts per bird) and weight gain was decreased by 56%, plasma levels of both epinephrine and norepinephrine were significantly higher than those of the uninoculated controls. Plasma glucose levels were significantly increased in both inoculated groups.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
diet (crude protein = 28%) J and water for ad libitum consumption. For each experiment, turkeys were weighed at 1 to 2 wk of age, assigned to treatment groups by weight, and inoculated orally with E. adenoeides oocysts according to the design of the experiment. Three questions were explored in three separate experiments. In Experiment 1, changes in plasma levels of epinephrine and norepinephrine as a function of parasite dose were examined. Two-wk-old turkeys were assigned to three groups; 20 turkeys were inoculated with 1 X 105 oocysts, 20 were inoculated with 2 x 105 oocysts, and 20 were not inoculated. Feed consumption was measured from Days 1 to 6 PI. On Day 6 PI, weight gain and feed conversion efficiency (FCR; feed consumed + weight gained) of the turkeys were determined. Birds were bled by cardiac puncture on Day 6 PI using syringes treated with lithium heparin. Blood samples were immediately chilled in ice and subjected to centrifugation at 4 C; plasma was recovered and frozen. Aliquots of plasma from each bird were assayed for epinephrine, norepinephrine, and glucose. In Experiment 2, the contribution of anorexia (reduced feed consumption) to changes in catecholamine levels was determined. For this experiment, 10 2-wk-old turkeys were inoculated with 1 x 105 oocysts and 10 were not inoculated. Both inoculated and uninoculated birds were fed daily the same amount of feed as that consumed during the previous 24 h by turkeys inoculated 1 day earlier than the experimental turkeys (i.e., the birds were pair-fed). On Day 6 PI, FCR and weight gains were determined as in Experiment 1; blood plasma was recovered and subjected to catecholamine and glucose assays. In Experiment 3, catecholamine levels were correlated with the stage of infection. Two-wkold turkeys were inoculated with 6 x 104 or 1
787
COCCTDIOSIS IN TURKEY POULTS
TABLE 1. Plasma epinephrine, norepinephrine, and glucose levels (x ± SEM) in turkey poults inoculated with 0, 1 x 10s, or 2 x JO5 oocysts of Eimeria adenoeides and sampled on Day 6 postinoculation
Inoculum (x 10 5 ) 1
BW gain (g) 313 ± 12* 195 ± 17b 137 ± 6 b
0 1 2
Feed conversion (feedrgain) (g:g) 1.47 4.84 5.51
Norepinephrine
Epinephrine
Glucose —
1.31 ± .31 b 1.35 ± .23 b 3.30 ± .69*
1.33 ± .29 b 2.33 ± .59*b 4.93 ± 122'
fmff/100 mLV 265 ± 28 b 337 ± 15* 402 ± 24*
"•Within columns, means with no common superscripts are significantly different (P<05). 'Number of poults sampled = 20 at each inoculum level.
turkeys, norepinephrine levels were significantly higher than those of controls by Day 3 PI, and both epinephrine and norepinephrine levels were increased significantly over control levels during the acute stage of the infection (Day 6 PI). With the recovery of the birds (Day 12 PI), the catecholamines returned to approximately control levels. Plasma glucose levels increased significantly on Day 6 PI and remained slightly but significantly elevated on Day 12 PI. DISCUSSION
In coccidia-infected poults, plasma epinephrine and norepinephrine levels showed a dose-dependent increase over levels in controls, with poults that were most heavily infected having the highest levels. These catecholamines exhibited a classic stress response, which rose with time following infection and then returned to approximately control levels when the birds recovered from the disease. Pair-feeding studies, wherein infected and uninfected birds consumed the same
TABLE 2. Plasma epinephrine, norepinephrine, and glucose levels (x ± SEM) in turkey poults inoculated with 0 or J x oocysts of Eimeria adenoeides and sampled on Day 6 postinoculation1
Inoculum (x 10 5 ) 2
BW gain
Feed conversion (feed:gain)
0 1
(g) 175 ± 21* 138 ± 30 b
(g:g) .91 1.16
Epinephrine
Norepinephrine
Glucose Cmcr/lOO ml 1
b
1.46 ± .56 3.07 ± 1.80*
1.60 ± 1.55* 2.66 ± 1.33*
299 ± 15* 306 ± 27*
*'bWithin columns, means with no common superscripts are significantly different (P<05). 'Both inoculated and uninoculated poults were pair-fed daily the same predetermined amount of feed. Number of poults sampled = 10 at each inoculum level.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
Reduced feed consumption was partially responsible for the changes in the catecholamine and glucose levels associated with the E. adenoeides infection (Table 2). The inoculated and uninoculated turkeys each consumed 160 g of feed; with this amount of feed, the inoculated birds gained 21% less weight than did the uninoculated birds. The plasma epinephrine level of the inoculated birds was significantly increased over that of the uninoculated, pair-fed birds; however, the plasma norepinephrine and glucose levels of pair-fed, infected poults did not differ significantly from those of their pair-fed, uninfected counterparts. At a dose of 6 x 10 4 oocysts per bird, no significant increases in plasma epinephrine, norepinephrine, and glucose levels were detected (data not shown). At a dose of 1 x 105 oocysts, the changes in plasma catecholamine levels in the infected birds appeared to follow a classic stress response (Table 3). The mean levels of epinephrine and norepinephrine in the control birds on Days 3, 6, and 12 PI did not differ significantly. However, in the infected
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AUGUSTINE AND DENBOW
TABLE 3. Plasma epinephrine, norepinephrine, and glucose levels (x ± SEM) in turkey poults inoculated with 0 or 1 x l
Inoculum n1 (x 105)
3
0 1
6
0 1 0 1
12
6 6 8 8 8 8
BW gain
Epinephrine
Norepinephrine
Glucose
(g) 136 144 336 188 720 683
22 .36 .14 .74 .18 .22
1.43 3.28 1.50 6.20 1.76 1.42
231 208 210 264 235 250
(mo-/ino mi ^ ± 5* ± 6* ± 8* ± 21 b ± 41* ± 22*
± ± ± ± ± ±
.10* .29* .06* .41 b .10* .14*
± .20* ± 1.43b ± .23* ± 3.20b ± .60* ± .34*
± ± ± ± ± ±
19* 3* 8* 14b 18* 14b
*,bWithin columns, means with no common superscripts are significantly different (P<05). Number of poults sampled.
present study in 3- to 4-wk-old poults. Improvements in methodology (i.e., HPLC) of the present and earlier studies may explain the discrepancy. It is not known why the epinephrine levels in Experiment 3 were lower than those in the other experiments. However, despite the lower overall concentrations, the levels of the infected poults in Experiment 3 as in Experiments 1 and 2 were higher than those in controls during the acute stage of the infection (Day 6 PI), and returned to control levels at Day 12 PI. The increase in plasma catecholamine levels may explain, at least in part, the relative instability of blood pressure and heart rate reported earlier in poults infected with E. adenoeides. Harvey et al. (1954) documented that injection of from 20 to 1,500 ng/kg of epinephrine or norepinephrine measurably increased blood pressure in chickens. Based upon mean plasma volume of 6 to 6.8% of total body weight (Medway and Kare, 1959), the injection by Harvey et al. (1954) could be expected to increase plasma catecholamine levels of 1 kg chickens by a maximum of .33 to 22 ng/mL. If one surmises that activity of catecholamines in 3- to 4-wk-old turkey poults is similar to activity in chickens, then the increases in plasma norepinephrine (average = 4.2 ng/mL) and epinephrine (average = 1.9 ng/ mL) in the present study would be great enough to increase the blood pressure and heart rate of coccidia-infected turkeys. ACKNOWLEDGMENTS
The authors gratefully acknowledge the excellent technical assistance of L. Carson, J. Smiley, and M. Hickey.
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amount of feed, suggested that the increase in norepinephrine level was primarily associated with decreased feed intake. In contrast, infection-induced factors other than anorexia appeared to be involved with the increase in plasma epinephrine. It is reasonable to assume that handling and restraint of all of the poults during the experimental procedures contributed to the increase in levels of plasma catecholamines. In the present study, it was not determined whether handling alone had a greater effect on the infected poults than on the uninfected controls. Anorexia is generally considered to be one of the major effects of avian coccidiosis and is associated with some of the physiological changes that have been described in infected turkeys (Augustine and Thomas, 1979, 1981). It has been shown in rats (Russek and Racotta, 1980; Russek, 1981; Russek et al., 1987) and in chickens (Howes and Forbes, 1985) that peripheral administration of epinephrine decreases feed intake. It appears possible, therefore, that the anorexia that is associated with coccidiosis may be at least partially due to the increase in plasma epinephrine that occurs during the acute stage of the infection. Sturkie (1976) reported that plasma epinephrine levels in many avian species, including the turkey, were greater than levels of norepinephrine. Their values for epinephrine in 7- to 12-mo-old female turkeys (1.45 ng/ mL) compared favorably with levels reported in the present study (1.31 to 1.46 ng/mL) for mixed sex poults that were 3- to 4-wk old when blood samples were taken. However, the norepinephrine concentrations reported by Sturkie (1976) for the older turkeys (.68 ng/ mL) were lower than those determined in the
COCCIDIOSIS IN TURKEY POULTS REFERENCES
Howes, G. A., and J. M. Forbes, 1985. Portal vein injection of adrenaline: effect on feeding in intact and vagotomised cockerels. Proc. Nutr. Soc. 44: 58A.(Abstr.) Medway, W., and M. R. Kare, 1959. Thiocyanate space in growing domestic fowl. Am. J. Physiol. 196: 873-875. Myers, R. D., H. S. Schwartzwelder, J. M. Peinado, T. F. Lee, J. R. Hepler, D. M. Denbow, and J. M Ferrer, 1986. CCK and other peptides modulate hypothalamic norepinephrine release in the rat: dependence on hunger or satiety. Brain Res. Bull. 17:583-597. Russek, M., 1981. Current status of the hepatostatic theory of food intake control. Appetite 2:137-162. Russek, M., and R. Racotta, 1980. A possible role of adrenaline and glucagon in the control of food intake. Pages 120-137 in: Frontiers of Hormone Research. Vol. 3. T. B. van Wimersma, ed. S. Karger. Basel, Switzerland and New York, NY. Russek, M, C. Vega, J. Barrera, L. M. Soto-Mora, A. Lanzagorta, and R. Racotta, 1987. Anorexia elicited by different catecholamines in rats. Appetite 9: 119-126. Sturkie, P. D., 1976. Heart and circulation: anatomy, hemodynamics, blood pressure, blood flow, and body fluids. Pages 76-101 in: Avian Physiology. P. D. Sturkie, ed. Springer-Verlag, New York, NY.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
Anton, A. H., and D. F. Sayre, 1962. A study of the factors affecting the aluminum oxide-trihydroxyindol procedure for the analysis of catecholamines. J. Pharmacol. Exp. Ther. 138:360-375. Augustine, P. C, W. J. Kuenzel, and O. P. Thomas, 1982. Effect of coccidiosis on heart composition and function in young turkeys. Avian Dis. 26:346-353. Augustine, P. C , and O. P. Thomas, 1979. Eimeria meleagrimitis in young turkeys: effects on weight, blood, and organ parameters. Avian Dis. 23: 854-862. Augustine, P. C , and O. P. Thomas, 1981. Effect of time on response to Eimeria adenoeides and Eimeria meleagrimitis infection in young turkeys. Avian Dis. 25:366-373. Bolton, T. B., 1971. The physiology of the nervous system. Pages 675-705 in: The Physiology and Biochemistry of the Domestic Fowl. D. J. Bell and B. M. Freeman, ed. Academic Press, New York, NY. Harvey, S. C , E. G. Copen, D. W. Eskelson, S. R. Graff, L. D. Poulsen, and D. L. Rasmussen, 1954. Autonomic pharmacology of the chicken with particular reference to adrenergic blockage. J. Pharmacol. Exp. Ther. 112:8-17.
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1991 Poultry Science 70:785-789 INTRODUCTION
Earlier studies (Augustine, 1982) showed that heart composition, heart rate, and blood pressure in turkey poults infected with Eimeria adenoeides or Eimeria meleagrimitis differed significantly from those of uninfected poults. The size of the heart was smaller in the infected poults, primarily because of lower lipid content, and there were slight reductions in heart rate and mean blood pressure at 6 days postinoculation (PI). However, the most marked effect was the impaired capacity of the infected poults to maintain normal blood pressure and heart rates when exposed to stress. Injecting the infected poults with epinephrine or immersing their feet in ice water produced a transitory cardiac arrhythmia and an increase in mean blood pressure mat far exceeded those in similarly stressed uninfected poults (Augustine et al., 1982). The adrenal glands function as part of the normal homeostatic mechanism and respond to a variety of types of stress, including infection, by enhanced catecholamine secretion (Bolton, 1971). Catecholamines are known to have
pressor effects in birds (Sturkie, 1976) and, if increased during coccidial infection, may have contributed to the heightened response to stress shown by the infected poults in the earlier study (Augustine et al., 1982). The aim of the present work was to determine whether turkeys infected with E. adenoeides had higher levels of plasma catecholamines than their uninfected counterparts, and whether these levels could be correlated with severity or stage of infection. In the present paper, the term plasma catecholamines specifies plasma epinephrine and norepinephrine. MATERIALS AND METHODS
The strain of E. adenoeides used in the present study was originally isolated by S. A. Edgar, Auburn University, Auburn, AL, purified by single oocyst isolation, and maintained thereafter at the Protozoan Diseases Laboratory, Beltsville, MD. Beltsville medium white turkeys were obtained at 1 day of age and maintained coccidia-free in wire-floored brooding units. They were given turkey starter
785
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
ABSTRACT Plasma epinephrine, norepinephrine, and glucose levels were measured in 3- to 4-wk-old turkey poults that had been infected with the coccidium Eimeria adenoeides. When measured at 6 days postinoculation, the acute stage of the infection, the epinephrine and norepinephrine levels of the infected poults showed a dose-dependent increase over levels in controls, with poults that were most heavily infected having the highest levels. The catecholamines appeared to show a classic stress-elicited response: this response increases with time to high levels during the acute stage of the infection, and then returns to levels approximately the same as those of the controls as the poults recover from the infection. Anorexia, or feed restriction, appeared to be primarily responsible for the increase in norepinephrine. However, epinephrine levels in the infected poults were significantly higher than in their pair-fed, uninfected counterparts, indicating that factors other than reduced feed consumption contributed to the increase. The data indicate that plasma catecholamines are increased during coccidial infection. As pressor compounds, they may contribute to the previously observed changes in blood pressure and heart function in infected poults. (Key words: turkeys, coccidiosis, epinephrine, norepinephrine, anorexia)
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AUGUSTINE AND DENBOW
'Turkey Pre Starter, Southern States Cooperative, Baltimore, MD 21201. 2 Model 870; Dupont Instrument Co., Wilmington, DE 19898. ^ioanalytical Systems, Inc., West Lafayette, IN 47907. "^Model 3390A; Hewlett Packard Co., Palo Alto, CA 94301. 5 Model LC-4; Bioanalytical Systems, Inc., West Lafayette, IN 47907. Procedure 115; Sigma Chemical Co., St Louis, MO 63127.
x 105 oocysts per bird, or were left uninoculated. On Days 3, 6, and 12 PI, groups of 6 to 8 infected and uninfected poults were observed for weight gain and levels of plasma epinephrine, norepinephrine, and glucose. The methods were the same as those used in Experiments 1 and 2. Before catecholamine analysis, 50 ng of 3,4-dihydroxybenzylamine hydrobromide was added to each plasma sample as an internal standard. The plasma catecholamines were then extracted according to the alumina procedure of Anton and Sayre (1962) and resuspended in 200 uL of .1 M HC104. The samples were analyzed using HPLC as described by Myers et al. (1986). Briefly, 100-uL samples were loaded into the HPLC system, which consisted of a Dupont pump,2 a C-18 column,3 a Hewlett Packard integrator,4 and an Amperometric Detector.5 The mobile phase was run at 1.5 mL/min and the detector was set at .8 megaVolts (mV). The mobile phase, which was degassed and filtered through a .22-um filter, contained citric acid (.12 M), NaOH (8.8 mA/)» Na-EDTA (.4 mM), and sodium octyl sulfate (200 mg). The pH was adjusted to 3.1, and 86 mL of acetonitrile and 1.8 mL of triethanolamine were added to bring the volume to 1 L. Plasma glucose levels were determined by the hexokinase method6 using glucose in saturated benzoic acid as a standard. Measurements of catecholamines and glucose are expressed as means ± standard error of the mean; differences among treatment groups were tested by analysis of variance and, where appropriate, by Student's t test. Probabilities equal to or less than .05 were considered to be statistically significant. RESULTS
On day 6 PI, E. adenoeides infection caused increases in levels of plasma catecholamines and glucose that were a function of the severity of the infection (Table 1). The weight gain of turkeys inoculated with 1 X 105 oocysts was decreased by 38% as compared with controls, without significant change in plasma levels of either epinephrine or norepinephrine. However, when the inoculum was doubled (2 x 105 oocysts per bird) and weight gain was decreased by 56%, plasma levels of both epinephrine and norepinephrine were significantly higher than those of the uninoculated controls. Plasma glucose levels were significantly increased in both inoculated groups.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
diet (crude protein = 28%) J and water for ad libitum consumption. For each experiment, turkeys were weighed at 1 to 2 wk of age, assigned to treatment groups by weight, and inoculated orally with E. adenoeides oocysts according to the design of the experiment. Three questions were explored in three separate experiments. In Experiment 1, changes in plasma levels of epinephrine and norepinephrine as a function of parasite dose were examined. Two-wk-old turkeys were assigned to three groups; 20 turkeys were inoculated with 1 X 105 oocysts, 20 were inoculated with 2 x 105 oocysts, and 20 were not inoculated. Feed consumption was measured from Days 1 to 6 PI. On Day 6 PI, weight gain and feed conversion efficiency (FCR; feed consumed + weight gained) of the turkeys were determined. Birds were bled by cardiac puncture on Day 6 PI using syringes treated with lithium heparin. Blood samples were immediately chilled in ice and subjected to centrifugation at 4 C; plasma was recovered and frozen. Aliquots of plasma from each bird were assayed for epinephrine, norepinephrine, and glucose. In Experiment 2, the contribution of anorexia (reduced feed consumption) to changes in catecholamine levels was determined. For this experiment, 10 2-wk-old turkeys were inoculated with 1 x 105 oocysts and 10 were not inoculated. Both inoculated and uninoculated birds were fed daily the same amount of feed as that consumed during the previous 24 h by turkeys inoculated 1 day earlier than the experimental turkeys (i.e., the birds were pair-fed). On Day 6 PI, FCR and weight gains were determined as in Experiment 1; blood plasma was recovered and subjected to catecholamine and glucose assays. In Experiment 3, catecholamine levels were correlated with the stage of infection. Two-wkold turkeys were inoculated with 6 x 104 or 1
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COCCTDIOSIS IN TURKEY POULTS
TABLE 1. Plasma epinephrine, norepinephrine, and glucose levels (x ± SEM) in turkey poults inoculated with 0, 1 x 10s, or 2 x JO5 oocysts of Eimeria adenoeides and sampled on Day 6 postinoculation
Inoculum (x 10 5 ) 1
BW gain (g) 313 ± 12* 195 ± 17b 137 ± 6 b
0 1 2
Feed conversion (feedrgain) (g:g) 1.47 4.84 5.51
Norepinephrine
Epinephrine
Glucose —
1.31 ± .31 b 1.35 ± .23 b 3.30 ± .69*
1.33 ± .29 b 2.33 ± .59*b 4.93 ± 122'
fmff/100 mLV 265 ± 28 b 337 ± 15* 402 ± 24*
"•Within columns, means with no common superscripts are significantly different (P<05). 'Number of poults sampled = 20 at each inoculum level.
turkeys, norepinephrine levels were significantly higher than those of controls by Day 3 PI, and both epinephrine and norepinephrine levels were increased significantly over control levels during the acute stage of the infection (Day 6 PI). With the recovery of the birds (Day 12 PI), the catecholamines returned to approximately control levels. Plasma glucose levels increased significantly on Day 6 PI and remained slightly but significantly elevated on Day 12 PI. DISCUSSION
In coccidia-infected poults, plasma epinephrine and norepinephrine levels showed a dose-dependent increase over levels in controls, with poults that were most heavily infected having the highest levels. These catecholamines exhibited a classic stress response, which rose with time following infection and then returned to approximately control levels when the birds recovered from the disease. Pair-feeding studies, wherein infected and uninfected birds consumed the same
TABLE 2. Plasma epinephrine, norepinephrine, and glucose levels (x ± SEM) in turkey poults inoculated with 0 or J x oocysts of Eimeria adenoeides and sampled on Day 6 postinoculation1
Inoculum (x 10 5 ) 2
BW gain
Feed conversion (feed:gain)
0 1
(g) 175 ± 21* 138 ± 30 b
(g:g) .91 1.16
Epinephrine
Norepinephrine
Glucose Cmcr/lOO ml 1
b
1.46 ± .56 3.07 ± 1.80*
1.60 ± 1.55* 2.66 ± 1.33*
299 ± 15* 306 ± 27*
*'bWithin columns, means with no common superscripts are significantly different (P<05). 'Both inoculated and uninoculated poults were pair-fed daily the same predetermined amount of feed. Number of poults sampled = 10 at each inoculum level.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on May 24, 2015
Reduced feed consumption was partially responsible for the changes in the catecholamine and glucose levels associated with the E. adenoeides infection (Table 2). The inoculated and uninoculated turkeys each consumed 160 g of feed; with this amount of feed, the inoculated birds gained 21% less weight than did the uninoculated birds. The plasma epinephrine level of the inoculated birds was significantly increased over that of the uninoculated, pair-fed birds; however, the plasma norepinephrine and glucose levels of pair-fed, infected poults did not differ significantly from those of their pair-fed, uninfected counterparts. At a dose of 6 x 10 4 oocysts per bird, no significant increases in plasma epinephrine, norepinephrine, and glucose levels were detected (data not shown). At a dose of 1 x 105 oocysts, the changes in plasma catecholamine levels in the infected birds appeared to follow a classic stress response (Table 3). The mean levels of epinephrine and norepinephrine in the control birds on Days 3, 6, and 12 PI did not differ significantly. However, in the infected
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AUGUSTINE AND DENBOW
TABLE 3. Plasma epinephrine, norepinephrine, and glucose levels (x ± SEM) in turkey poults inoculated with 0 or 1 x l
Inoculum n1 (x 105)
3
0 1
6
0 1 0 1
12
6 6 8 8 8 8
BW gain
Epinephrine
Norepinephrine
Glucose
(g) 136 144 336 188 720 683
22 .36 .14 .74 .18 .22
1.43 3.28 1.50 6.20 1.76 1.42
231 208 210 264 235 250
(mo-/ino mi ^ ± 5* ± 6* ± 8* ± 21 b ± 41* ± 22*
± ± ± ± ± ±
.10* .29* .06* .41 b .10* .14*
± .20* ± 1.43b ± .23* ± 3.20b ± .60* ± .34*
± ± ± ± ± ±
19* 3* 8* 14b 18* 14b
*,bWithin columns, means with no common superscripts are significantly different (P<05). Number of poults sampled.
present study in 3- to 4-wk-old poults. Improvements in methodology (i.e., HPLC) of the present and earlier studies may explain the discrepancy. It is not known why the epinephrine levels in Experiment 3 were lower than those in the other experiments. However, despite the lower overall concentrations, the levels of the infected poults in Experiment 3 as in Experiments 1 and 2 were higher than those in controls during the acute stage of the infection (Day 6 PI), and returned to control levels at Day 12 PI. The increase in plasma catecholamine levels may explain, at least in part, the relative instability of blood pressure and heart rate reported earlier in poults infected with E. adenoeides. Harvey et al. (1954) documented that injection of from 20 to 1,500 ng/kg of epinephrine or norepinephrine measurably increased blood pressure in chickens. Based upon mean plasma volume of 6 to 6.8% of total body weight (Medway and Kare, 1959), the injection by Harvey et al. (1954) could be expected to increase plasma catecholamine levels of 1 kg chickens by a maximum of .33 to 22 ng/mL. If one surmises that activity of catecholamines in 3- to 4-wk-old turkey poults is similar to activity in chickens, then the increases in plasma norepinephrine (average = 4.2 ng/mL) and epinephrine (average = 1.9 ng/ mL) in the present study would be great enough to increase the blood pressure and heart rate of coccidia-infected turkeys. ACKNOWLEDGMENTS
The authors gratefully acknowledge the excellent technical assistance of L. Carson, J. Smiley, and M. Hickey.
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amount of feed, suggested that the increase in norepinephrine level was primarily associated with decreased feed intake. In contrast, infection-induced factors other than anorexia appeared to be involved with the increase in plasma epinephrine. It is reasonable to assume that handling and restraint of all of the poults during the experimental procedures contributed to the increase in levels of plasma catecholamines. In the present study, it was not determined whether handling alone had a greater effect on the infected poults than on the uninfected controls. Anorexia is generally considered to be one of the major effects of avian coccidiosis and is associated with some of the physiological changes that have been described in infected turkeys (Augustine and Thomas, 1979, 1981). It has been shown in rats (Russek and Racotta, 1980; Russek, 1981; Russek et al., 1987) and in chickens (Howes and Forbes, 1985) that peripheral administration of epinephrine decreases feed intake. It appears possible, therefore, that the anorexia that is associated with coccidiosis may be at least partially due to the increase in plasma epinephrine that occurs during the acute stage of the infection. Sturkie (1976) reported that plasma epinephrine levels in many avian species, including the turkey, were greater than levels of norepinephrine. Their values for epinephrine in 7- to 12-mo-old female turkeys (1.45 ng/ mL) compared favorably with levels reported in the present study (1.31 to 1.46 ng/mL) for mixed sex poults that were 3- to 4-wk old when blood samples were taken. However, the norepinephrine concentrations reported by Sturkie (1976) for the older turkeys (.68 ng/ mL) were lower than those determined in the
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