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Heat Prostration of Broilers as Influenced by Dietary Energy Source
Heat Prostration of Broilers as Influenced by Dietary Energy Source L . F . K U B E N A 1 , F . N . R E E C E 2 , J. W. D E A X O N 1 AND J. D . M A Y 1
United Slates Department of Agriculture, A.R.S., State College, Mississippi
39762
(Received for publication February 23, 1972)
POULTKY SCIENCE 51: 1744-1747,1972
O
TA et al. (1953) observed t h a t as environmental temperature increases, heat loss from t h e chicken's respiratory t r a c t in the latent form becomes progressively more important. The m a t h ematical model developed b y Bouchillon el al. (1970), predicts t h a t all heat rejected by the chicken must be in the latent form when t h e ambient temperature approaches t h e body temperature of t h e chicken. Reece et al. (1971) observed t h a t the relative humidity was a critical factor on heat prostration when t h e ambient temperature was 40.6° C. These researchers also observed t h a t t h e heavier broilers tended t o be more susceptible t o heat prostration. However, it was found t h a t even t h e heavier broilders could be 1
Animal Science Research Division, Poultry Research Branch, South Central Poultry Research Laboratory, State College, Miss. 2 Agricultural Engineering Research Division, Farm Electrification Research Branch, South Central Poultry Research Laboratory, State College, Miss.
acclimated within 3 days t o withstand the 40.6° C. temperature. Considerable research h a s been done on the effects of high environmental temperatures on poultry, as summarized b y Smith and Oliver (1971). There is not, t o the author's knowledge, a n y d a t a available on the effect of diet on mortality due to heat prostration. The purpose of t h e research reported herein was t o study t h e effect of dietary energy source on mortality due t o heat prostration in 8-week-old male broilers. EXPERIMENTAL
PROCEDURE
Commercial male broiler chickens were reared from 1 day t o 4 weeks of age as a group using standard brooding practices. T h e y received a basal starter diet containing approximately 23.3 percent protein and having a metabolizable energy value of 3285 kilocalories per kilogram. At 4 weeks of age, 60 male broiler chickens were placed in each of four environmental chambers described b y Reece and Deaton
1744
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
ABSTRACT Three trials were conducted to study the effect of dietary energy source on mortality due to heat prostration in 8-week-old male broilers. The two isocaloric diets contained 1.00 or 7.00 percent added animal fat and were fed ad libitum for the 4- to 8-week experimental period. At 8 weeks of age, the dry-bulb temperature was increased from 21.1° C. with a dewpoint temperature of 10.0° C. to 40.6° C. over a 6-hour period, with a dewpoint temperature of 23.9° C. The temperature was held at 40.6° C. for 2 hours, then decreased to 26.7° C. over a 30-minute period. Mortality due to heat prostration was recorded at 30-minute intervals during the stress test. The results obtained indicate that the quantity of energy provided by fat compared to carbohydrate has an effect on mortality during the early stages of heat stress. Higher mortality due to heat prostration occurred in the birds receiving the diet containing the higher level of fat during the first three 30-minute intervals. During subsequent 30-minute intervals, there were no significant differences in mortality due to dietary treatment. The reason for the higher mortality in the birds receiving the diet containing the higher level of fat is not known. When the summer temperature approaches 38° C , mortality due to heat prostration is a problem. Economic losses due to heat prostration are especially large because they usually occur shortly before the broilers are marketable. Field reports indicate that male broilers are more susceptible to heat prostration than the females.
BROILER HEAT
TABLE 1.—Composition of diets
Percent of Diet Ingredient
Treatment 1 Treatment 2
Corn 49.42 Soybean meal, 50% protein 30.00 Fish, peruvian, 65% protein 2.50 Corn gluten meal, 6 1 % protein — Rice bran, sol. ext. 7.00 Alfalfa, 17% protein 1.00 Fat, animal 7.00 Dicalcium phosphate, 22-18.5 1.49 Limestone .95 Salt .25 Zoamix .05 Vitamin-mineral premix* .25 MHA, 9 3 % .09 Lyamine, 50% —
66.90 18.00 2.50 7.83
— —
1.00 1.59 1.03 .25 .05 .25
—
1745
essentially isocaloric (Table 1). These diets and water were provided ad libitum during rearing and stress in the three trials conducted. At 8 weeks of age, the dry-bulb temperature in all chambers was increased from 21.1° C. to 40.6° C. over a 6-hour period, with a dewpoint temperature of 23.9° C. The temperature was held at 40.6° C. for 2 hours, then decreased to 26.7° C. over a 30-minute period. Mortality due to heat prostration was recorded at 30-minute periods during the stress test. Body weights were recorded at the time of mortality, and for the survivors 24 hours after initiation of stress. Continuous light at approximately 10.76 lux was used during rearing and stress. The ventilation rate was approximately 85 liters per minute per chicken. The litter consisted of about 10 centimeters of wood shavings. Statistical examinations of the body weight data by analysis of variance were performed, and examinations of the mortality data by chi-square were made. Significant treatment means were separated using the multiple range test of Duncan (1955). RESULTS AND DISCUSSION
The results of the three trials are shown .60 in Tables 2 and 3. Mortality due to heat 100.00 Total 100.00 prostration did not occur in any of the Calculated Analysis: trials during the initial 30 minutes after Metabolizable Energy, the dry-bulb temperature reached 40.6° C. kcal./kg. 3175 3168 21.68 21.10 Protein, % During the second 30-minute interval, Meth.+Cystine, % .80 .80 higher mortality in all three trials oc1.24 Lysine, % 1.24 Calcium, % .90 .90 curred for the birds receiving the diet Avail. Phosphorus, % .48 .48 containing the higher level of fat. This * Supplied the following amounts per kg. of pre- was statistically significant at the 0.05 mix; Vitamin A palmitate, 2,204,634 U.S.P. units, Vitamin Da 661,390 I.C.U., Vitamin E, 440 I.U., level of probability in Trial 1 and apRiboflavin, 1.76 gms., Niacin, 11.02 gms., D-panto- proached significance in Trials 2 and 3 as thenic acid, 3.53 gms., Folic acid, 55 mgs., Vitamin Bi2,3.5 mgs., Choline chloride, 198.42 gms., Ethoxy- is evidenced by being significant when the quin, 35 gms., Menadione sodium bisulfite, 556 mgs., three trials were combined. Higher morManganese, 5.8%, Zinc, 3.9%, Iodine, .11%, Iron, tality again occurred in the birds receiv1.8%, Copper, .18%, and Cobalt, .018%.
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
(1969), and the dry-bulb temperature maintained at 21.1° C. with a dewpoint temperature of 10.0° C. for the 4- to 8week period. One-half of the birds received a diet which provided a large portion of the energy in the form of carbohydrate (1.00 percent added animal fat) and the other birds received a diet which provided a large portion of the energy in the form of fat (7.00 percent added animal fat). The animal fat was obtained from a local plant which processes both beef and pork. The diets were calculated to be
PROSTRATION
1746
L. F. KTJBENA, F. N., REECE, J. W. DEATON AND J. D. MAY TABLE 2.—Effect
of dietary energy source on heat prostration of 8-week-old male broilers (3 trials—240 birds per trial) Trial 1
Post exposure time2 (minutes)
Trial 3
Total of 3 trials
Treatment 1 2
Treatment 1 2
Treatment 1 2
Treatment 1 2
Mortality No. No.
Mortality No. No.
Mortality No. No.
Mortality No. No.
0a3 8a 19a 22a 14a 9a 72/120a
0a 4a 16a 13a 10a 6a 49/120a
0a Ob 3b 23a 22a 6a 54/120b
Oa 2a 12a 8a 4a 13a 39/120a
Oa 11a 29a 17a 7a 5a 69/120a
Oa 8a 23a 19a 7a 4a 61/120a
Oa Oa 23a 10b 64a 38b 52a 50a 31a 33a 20a 23a 190/360a 154/360b
1 Birds were fed isocaloric diets where birds in treatment 1 received a diet containing 7% added animal fat, and birds in treatment 2 received a diet containing 1% added animal fat. 2 The mortality figures given represent the number of birds that died within each specific time interval after the dry-bulb temperature reached 40.6° C. 3 Within each trial and time period, differing letters denote significance at the .05 level of probability.
ing the diet containing the higher level of fat during the third 30-minute interval. During subsequent 30-minute intervals, there were no significant differences in mortality due to dietary treatment for any of the 3 trials or when the trials were combined. Although total mortality during the 1080-minute period was higher for the birds receiving the diet containing the higher level of fat in all three trials, it was statistically significant only in Trial 1 and when the three trials are combined. From these data, it appears that the quantity of energy provided by fat has an
effect on mortality during the early stages of heat stress. This effect is no longer present after the third 30-minute time interval. The reason for the higher mortality in the birds receiving the diet containing the higher level of fat is not known. Additional research in this area would be of interest and importance. The birds ceased consuming feed when the temperature approached approximately 35° C. and were panting rapidly. Since the birds' energy intake ceased for several hours, energy for the various physiological functions, of necessity, had to be obtained from the body stores. It is
TABLE 3.—Effect of dietary energy source on body weights of 8-week-old male broilers (3 trials—240 birds per trial) Trial 1 Treatment
Average weight, grams Average dead weight, grams Average survivor weight. grams
1
Trial 2
Trial 3
Average of 3 Trials
Treatment
Treatment
Treatment
1726 1750a2
1733 1717ab
1649 1656a
1646 1640a
1675 I703ab
1675 1718a
1686 1709a
1689 1698ab
1690b
1746a
1645a
1649a
1655b
1654b
1661b
1682ab
1 Birds were fed isocaloric diets where birds in treatment 1 received a diet containing 7% added animal fat, and birds in treatment 2 received a diet containing 1% added animal fat. 2 Within each trial and between each of the last 2 categories, differing letters denote significance at the .05 level of probability.
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
0-30 31-60 61-90 91-120 121-150 151-1080 Total
Trial 2 1
1747
BROILER HEAT PROSTRATION REFERENCES
Bouchillon, C. W., F. N. Reece and J. W. Deaton, 1970. Mathematical modeling of thermal homeostasis in a chicken. Trans A.S.A.E. 13: 648-652. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11:1-42. Ota, H., H. L. Garver and W. Ashby, 1953. Heat and moisture production of laying hens. Agri. Eng. 34:163-167. Reece, F. N., and J. W. Deaton, 1969. Environmental control for poultry research. Agri. Eng. 50: 670-671. Reece, F. N., J. W. Deaton and L. F. Kubena, 1971. Effects of high temperature and humidity on heat prostration of broiler chickens. American Society of Agricultural Engineers, Paper No. 71-912. Smith, A. J., and J. Oliver, 1971. Some physiological effects of high environmental temperatures on the laying hen. Poultry Sci. 50: 912-925.
Turkey Leucocytozoon Infection. 2. CRYOBIOLOGIC PRESERVATION OF LEUCOCYTOZOON SMITHI SPOROZOITES 1 JUAN SOLIS Poultry Science Department, Clemson University, Clemson, South Carolina 29631 (Received for publication February 25, 1972)
ABSTRACT Five different cryoprotective agents at various concentrations were evaluated for their effectiveness in preserving the infectivity of Leucocytozoon smithi sporozoites at low temperatures for an indefinite period of time as determined by the degree of parasitemia in inoculated turkey poults. Glycerol at concentrations of 10 and 5 percent, DMSO at 10 percent ethylene and trimethylene glycols at 2.5 percent, and propylene glycol at five percent when dissolved in medium 199 plus 10 percent fetal bovine serum yielded excellent sporozoite survival at a temperature of —196° C. When dissolved in medium 199 supplemented with 10 percent turkey serum, cryoprotection by those chemicals was less effective. In the absence of animal sera, sporozoite survival to freezing was very poor. Regardless of suspending media, all sporozoites frozen by direct immersion in liquid nitrogen lost their infectivity. No differences were observed in the parasite's prepatent period, time of maximum gametocyte density, nor RBC count pattern between turkey poults infected with frozen, stored sporozoites and those infected with fresh unfrozen sporozoites from the same original stock. PODXTKY SCIENCE 51: 1747-1752, 1972
T
URKEY malaria was first observed by Smith (1895) in the peripheral blood of turkeys, and since this original report many species of leucocytozoa have been reported in various wild and domes1
Published with approval of the Director of the S. C. Agricultural Experiment Station as technical publication no. 988.
tic fowl throughout the United States and Canada. From an economic viewpoint, only the infection of ducks and turkeys are of primary importance. Hence the majority of the available literature concerns the disease in these birds. Leucocytozoon smithi is an obligate intracellular protozoan parasite of wild and domestic turkeys. It is frequently found
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
possible that the birds receiving the diet containing the higher level of fat had a larger quantity of readily available energy which caused an increase in body heat production which could not be dissipated at the high environmental temperature and relative humidity. The higher oxygen consumption associated with the oxidation of fat when compared to carbohydrate may possibly be a factor. There was no difference in body weights within each trial due to dietary treatment (Table 3). There was a tendency for the surviving birds to be slightly lighter in weight than the birds that died, which is in agreement with Reece et al. (1971).
United Slates Department of Agriculture, A.R.S., State College, Mississippi
39762
(Received for publication February 23, 1972)
POULTKY SCIENCE 51: 1744-1747,1972
O
TA et al. (1953) observed t h a t as environmental temperature increases, heat loss from t h e chicken's respiratory t r a c t in the latent form becomes progressively more important. The m a t h ematical model developed b y Bouchillon el al. (1970), predicts t h a t all heat rejected by the chicken must be in the latent form when t h e ambient temperature approaches t h e body temperature of t h e chicken. Reece et al. (1971) observed t h a t the relative humidity was a critical factor on heat prostration when t h e ambient temperature was 40.6° C. These researchers also observed t h a t t h e heavier broilers tended t o be more susceptible t o heat prostration. However, it was found t h a t even t h e heavier broilders could be 1
Animal Science Research Division, Poultry Research Branch, South Central Poultry Research Laboratory, State College, Miss. 2 Agricultural Engineering Research Division, Farm Electrification Research Branch, South Central Poultry Research Laboratory, State College, Miss.
acclimated within 3 days t o withstand the 40.6° C. temperature. Considerable research h a s been done on the effects of high environmental temperatures on poultry, as summarized b y Smith and Oliver (1971). There is not, t o the author's knowledge, a n y d a t a available on the effect of diet on mortality due to heat prostration. The purpose of t h e research reported herein was t o study t h e effect of dietary energy source on mortality due t o heat prostration in 8-week-old male broilers. EXPERIMENTAL
PROCEDURE
Commercial male broiler chickens were reared from 1 day t o 4 weeks of age as a group using standard brooding practices. T h e y received a basal starter diet containing approximately 23.3 percent protein and having a metabolizable energy value of 3285 kilocalories per kilogram. At 4 weeks of age, 60 male broiler chickens were placed in each of four environmental chambers described b y Reece and Deaton
1744
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
ABSTRACT Three trials were conducted to study the effect of dietary energy source on mortality due to heat prostration in 8-week-old male broilers. The two isocaloric diets contained 1.00 or 7.00 percent added animal fat and were fed ad libitum for the 4- to 8-week experimental period. At 8 weeks of age, the dry-bulb temperature was increased from 21.1° C. with a dewpoint temperature of 10.0° C. to 40.6° C. over a 6-hour period, with a dewpoint temperature of 23.9° C. The temperature was held at 40.6° C. for 2 hours, then decreased to 26.7° C. over a 30-minute period. Mortality due to heat prostration was recorded at 30-minute intervals during the stress test. The results obtained indicate that the quantity of energy provided by fat compared to carbohydrate has an effect on mortality during the early stages of heat stress. Higher mortality due to heat prostration occurred in the birds receiving the diet containing the higher level of fat during the first three 30-minute intervals. During subsequent 30-minute intervals, there were no significant differences in mortality due to dietary treatment. The reason for the higher mortality in the birds receiving the diet containing the higher level of fat is not known. When the summer temperature approaches 38° C , mortality due to heat prostration is a problem. Economic losses due to heat prostration are especially large because they usually occur shortly before the broilers are marketable. Field reports indicate that male broilers are more susceptible to heat prostration than the females.
BROILER HEAT
TABLE 1.—Composition of diets
Percent of Diet Ingredient
Treatment 1 Treatment 2
Corn 49.42 Soybean meal, 50% protein 30.00 Fish, peruvian, 65% protein 2.50 Corn gluten meal, 6 1 % protein — Rice bran, sol. ext. 7.00 Alfalfa, 17% protein 1.00 Fat, animal 7.00 Dicalcium phosphate, 22-18.5 1.49 Limestone .95 Salt .25 Zoamix .05 Vitamin-mineral premix* .25 MHA, 9 3 % .09 Lyamine, 50% —
66.90 18.00 2.50 7.83
— —
1.00 1.59 1.03 .25 .05 .25
—
1745
essentially isocaloric (Table 1). These diets and water were provided ad libitum during rearing and stress in the three trials conducted. At 8 weeks of age, the dry-bulb temperature in all chambers was increased from 21.1° C. to 40.6° C. over a 6-hour period, with a dewpoint temperature of 23.9° C. The temperature was held at 40.6° C. for 2 hours, then decreased to 26.7° C. over a 30-minute period. Mortality due to heat prostration was recorded at 30-minute periods during the stress test. Body weights were recorded at the time of mortality, and for the survivors 24 hours after initiation of stress. Continuous light at approximately 10.76 lux was used during rearing and stress. The ventilation rate was approximately 85 liters per minute per chicken. The litter consisted of about 10 centimeters of wood shavings. Statistical examinations of the body weight data by analysis of variance were performed, and examinations of the mortality data by chi-square were made. Significant treatment means were separated using the multiple range test of Duncan (1955). RESULTS AND DISCUSSION
The results of the three trials are shown .60 in Tables 2 and 3. Mortality due to heat 100.00 Total 100.00 prostration did not occur in any of the Calculated Analysis: trials during the initial 30 minutes after Metabolizable Energy, the dry-bulb temperature reached 40.6° C. kcal./kg. 3175 3168 21.68 21.10 Protein, % During the second 30-minute interval, Meth.+Cystine, % .80 .80 higher mortality in all three trials oc1.24 Lysine, % 1.24 Calcium, % .90 .90 curred for the birds receiving the diet Avail. Phosphorus, % .48 .48 containing the higher level of fat. This * Supplied the following amounts per kg. of pre- was statistically significant at the 0.05 mix; Vitamin A palmitate, 2,204,634 U.S.P. units, Vitamin Da 661,390 I.C.U., Vitamin E, 440 I.U., level of probability in Trial 1 and apRiboflavin, 1.76 gms., Niacin, 11.02 gms., D-panto- proached significance in Trials 2 and 3 as thenic acid, 3.53 gms., Folic acid, 55 mgs., Vitamin Bi2,3.5 mgs., Choline chloride, 198.42 gms., Ethoxy- is evidenced by being significant when the quin, 35 gms., Menadione sodium bisulfite, 556 mgs., three trials were combined. Higher morManganese, 5.8%, Zinc, 3.9%, Iodine, .11%, Iron, tality again occurred in the birds receiv1.8%, Copper, .18%, and Cobalt, .018%.
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
(1969), and the dry-bulb temperature maintained at 21.1° C. with a dewpoint temperature of 10.0° C. for the 4- to 8week period. One-half of the birds received a diet which provided a large portion of the energy in the form of carbohydrate (1.00 percent added animal fat) and the other birds received a diet which provided a large portion of the energy in the form of fat (7.00 percent added animal fat). The animal fat was obtained from a local plant which processes both beef and pork. The diets were calculated to be
PROSTRATION
1746
L. F. KTJBENA, F. N., REECE, J. W. DEATON AND J. D. MAY TABLE 2.—Effect
of dietary energy source on heat prostration of 8-week-old male broilers (3 trials—240 birds per trial) Trial 1
Post exposure time2 (minutes)
Trial 3
Total of 3 trials
Treatment 1 2
Treatment 1 2
Treatment 1 2
Treatment 1 2
Mortality No. No.
Mortality No. No.
Mortality No. No.
Mortality No. No.
0a3 8a 19a 22a 14a 9a 72/120a
0a 4a 16a 13a 10a 6a 49/120a
0a Ob 3b 23a 22a 6a 54/120b
Oa 2a 12a 8a 4a 13a 39/120a
Oa 11a 29a 17a 7a 5a 69/120a
Oa 8a 23a 19a 7a 4a 61/120a
Oa Oa 23a 10b 64a 38b 52a 50a 31a 33a 20a 23a 190/360a 154/360b
1 Birds were fed isocaloric diets where birds in treatment 1 received a diet containing 7% added animal fat, and birds in treatment 2 received a diet containing 1% added animal fat. 2 The mortality figures given represent the number of birds that died within each specific time interval after the dry-bulb temperature reached 40.6° C. 3 Within each trial and time period, differing letters denote significance at the .05 level of probability.
ing the diet containing the higher level of fat during the third 30-minute interval. During subsequent 30-minute intervals, there were no significant differences in mortality due to dietary treatment for any of the 3 trials or when the trials were combined. Although total mortality during the 1080-minute period was higher for the birds receiving the diet containing the higher level of fat in all three trials, it was statistically significant only in Trial 1 and when the three trials are combined. From these data, it appears that the quantity of energy provided by fat has an
effect on mortality during the early stages of heat stress. This effect is no longer present after the third 30-minute time interval. The reason for the higher mortality in the birds receiving the diet containing the higher level of fat is not known. Additional research in this area would be of interest and importance. The birds ceased consuming feed when the temperature approached approximately 35° C. and were panting rapidly. Since the birds' energy intake ceased for several hours, energy for the various physiological functions, of necessity, had to be obtained from the body stores. It is
TABLE 3.—Effect of dietary energy source on body weights of 8-week-old male broilers (3 trials—240 birds per trial) Trial 1 Treatment
Average weight, grams Average dead weight, grams Average survivor weight. grams
1
Trial 2
Trial 3
Average of 3 Trials
Treatment
Treatment
Treatment
1726 1750a2
1733 1717ab
1649 1656a
1646 1640a
1675 I703ab
1675 1718a
1686 1709a
1689 1698ab
1690b
1746a
1645a
1649a
1655b
1654b
1661b
1682ab
1 Birds were fed isocaloric diets where birds in treatment 1 received a diet containing 7% added animal fat, and birds in treatment 2 received a diet containing 1% added animal fat. 2 Within each trial and between each of the last 2 categories, differing letters denote significance at the .05 level of probability.
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
0-30 31-60 61-90 91-120 121-150 151-1080 Total
Trial 2 1
1747
BROILER HEAT PROSTRATION REFERENCES
Bouchillon, C. W., F. N. Reece and J. W. Deaton, 1970. Mathematical modeling of thermal homeostasis in a chicken. Trans A.S.A.E. 13: 648-652. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11:1-42. Ota, H., H. L. Garver and W. Ashby, 1953. Heat and moisture production of laying hens. Agri. Eng. 34:163-167. Reece, F. N., and J. W. Deaton, 1969. Environmental control for poultry research. Agri. Eng. 50: 670-671. Reece, F. N., J. W. Deaton and L. F. Kubena, 1971. Effects of high temperature and humidity on heat prostration of broiler chickens. American Society of Agricultural Engineers, Paper No. 71-912. Smith, A. J., and J. Oliver, 1971. Some physiological effects of high environmental temperatures on the laying hen. Poultry Sci. 50: 912-925.
Turkey Leucocytozoon Infection. 2. CRYOBIOLOGIC PRESERVATION OF LEUCOCYTOZOON SMITHI SPOROZOITES 1 JUAN SOLIS Poultry Science Department, Clemson University, Clemson, South Carolina 29631 (Received for publication February 25, 1972)
ABSTRACT Five different cryoprotective agents at various concentrations were evaluated for their effectiveness in preserving the infectivity of Leucocytozoon smithi sporozoites at low temperatures for an indefinite period of time as determined by the degree of parasitemia in inoculated turkey poults. Glycerol at concentrations of 10 and 5 percent, DMSO at 10 percent ethylene and trimethylene glycols at 2.5 percent, and propylene glycol at five percent when dissolved in medium 199 plus 10 percent fetal bovine serum yielded excellent sporozoite survival at a temperature of —196° C. When dissolved in medium 199 supplemented with 10 percent turkey serum, cryoprotection by those chemicals was less effective. In the absence of animal sera, sporozoite survival to freezing was very poor. Regardless of suspending media, all sporozoites frozen by direct immersion in liquid nitrogen lost their infectivity. No differences were observed in the parasite's prepatent period, time of maximum gametocyte density, nor RBC count pattern between turkey poults infected with frozen, stored sporozoites and those infected with fresh unfrozen sporozoites from the same original stock. PODXTKY SCIENCE 51: 1747-1752, 1972
T
URKEY malaria was first observed by Smith (1895) in the peripheral blood of turkeys, and since this original report many species of leucocytozoa have been reported in various wild and domes1
Published with approval of the Director of the S. C. Agricultural Experiment Station as technical publication no. 988.
tic fowl throughout the United States and Canada. From an economic viewpoint, only the infection of ducks and turkeys are of primary importance. Hence the majority of the available literature concerns the disease in these birds. Leucocytozoon smithi is an obligate intracellular protozoan parasite of wild and domestic turkeys. It is frequently found
Downloaded from http://ps.oxfordjournals.org/ at Adams State University on April 8, 2015
possible that the birds receiving the diet containing the higher level of fat had a larger quantity of readily available energy which caused an increase in body heat production which could not be dissipated at the high environmental temperature and relative humidity. The higher oxygen consumption associated with the oxidation of fat when compared to carbohydrate may possibly be a factor. There was no difference in body weights within each trial due to dietary treatment (Table 3). There was a tendency for the surviving birds to be slightly lighter in weight than the birds that died, which is in agreement with Reece et al. (1971).