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Variations in Development of Muscles in Chickens1
Variations in Development of Muscles in Chickens1 DOROTHY B. HALVORSON AND MARION JACOBSON Department of Home Economics, Washington Agricultural Research Center, Pullman, Washington 99163 (Received for publication August 8, 1969)
D
URING the progress of a recent study of meat yields from fryers, a variable development of certain muscles was observed (Jacobson et al., 1968). Variation in size of principal muscles with growth is of interest since it will affect the meatiness of the portions usually served separately in meals. Such anatomical changes have fundamental interest as well. In this study the dimensions and weights were taken for 6 muscles dissected from cooked chickens of the Leghorn breed and the Hubbard-White Mountain (hereafter H-WM) cross at 5, 7, and 9 weeks of age. Previous studies of the myology of birds by avian anatomists have been made through dissections of raw carcasses. These have served to describe species differences within the genera. In the present study the nomenclature adopted is that used by investigators of avian anatomy. The principal source used for muscle identification is Hudson et al. (1959)} These identifications of muscles in the thigh portion vary from those made by Evans (1961) and also by Bradley and Grahame (1951). Differences include recognition that the surface muscle of the thigh is the iliotibialis thus locating M. biceps femoris in the second layer. Also, previous publications have named as M. semimembranosus what is more accurately M. semitendinosus. It can be noted further 1 Scientific Paper No. 3331, Department of Home Economics, Washington Agricultural Research Center, College of Agriculture, Pullman, Project 1515. 2 Appreciation is expressed to Dr. G. E. Hudson for invaluable assistance in identification of muscles.
that M. semimembranosus is in the fourth layer of muscles but, in the chicken, a small portion of this muscle extends so as to be visible before dissection. EXPERIMENTAL PROCEDURE Production. Chickens were hatched and grown under controlled conditions by the Animal Sciences Department at Washington State University.3 Ration, management, slaughter, preparation, and freezing were as described for the crossbred broilers previously studied for content of flavor constituents (Chow and Jacobson, 1968). A fast-growing cross (H-WM) and the Leghorn breed were selected for study because these might show differences in muscle development related to meatiness of cut. The age span from 5 through 9 weeks represents a period of rapid anatomical change and encompasses those chickens sold as broilers or fryers; so this age span was chosen for investigation. Preparation. Frozen chickens which had been stored less than a month at — 29°C. ( — 20°F.) were thawed under refrigeration at 2°C. (34°F.) for 24 hrs., then at room temperature until completely defrosted but cold. Carcasses were washed under cool running water, drained, and weighed; then each was placed individually in a kettle containing 250-500 ml. of cold water, covered, and rapidly heated to simmering temperature (approx. 85°C). The chickens were steamed until the muscles of the thigh began to separate. The time required ranged from 45 to 65 3
Production and processing of chickens were supervised by Dr. J. V. Spencer. The Animal Sciences Department cooperates in the project.
132
CHICKEN MUSCLE DEVELOPMENT
minutes. Cooked carcasses were drained, cooled to room temperature, and weighed, after which they were wrapped loosely in aluminum foil and refrigerated overnight. The above techniques facilitated dissection of individual muscles. Dissection. Skin was first removed from the refrigerated cooked bird, after which the wings were removed and not further used. T h e two pelvic limbs were separated by cutting the attached muscles free from the ilium and severing the hip joint while dividing muscles a t their tendon attachment. T h e leg4 was separated from the thigh in a similar way. From the thigh the ileshy posterior region of the M. iliotibialis and the entire M. semitendinosus were released a t the edges with a scalpel, then eased from adjacent structures by gentle linger pressure. The iliotibialis is a triangular-shaped flat muscle which comprises most of the lateral surface of the thigh (Fig. 1). It is closely attached to the M. sartorius anteriorly and to the M. semitendinosus posteriorly. In the genus Gallus, which includes the domestic fowl, the posterior region of M. iliotibialis is flesh)'. The semitendinosus is a fleshy band forming the posterior limitof the thigh musculature and is well developed in the chicken. The M. peronaeus longus is located in the anterior and anterolateral area of the leg. The pars externa of the gastrocnemius occupies the posterolateral portion of the leg. T h e two muscles of the breast (Fig. 2) were both studied. T h e pectoralis is the large muscle which completely overlays this area and the supracoracoideus lies beneath the pectoralis. Measurements. Weights of each dissected muscle from the left and right sides were obtained to the nearest 0.1 gram. After " The commonly used term "leg" is designated "shank" by avian anatomists.
133
FIG. 1. Muscle nomenclature and location in the hind limb of the chicken. (Drawing from specimens made by Washington State University artist, E. J. Poulsen.)
weights had been taken, the length and width of each muscle were measured by the use of a vernier caliper graduated in millimeters. Statistical A nalysis. Analysis of variance of the individual measurements from each chicken were made. Calculated values of t were determined for the data in Campar-
is supracoracoideus
FIG. 2. Muscles in breast of the chicken. M. pectoralis dissected to expose M. supracoracoideus. (Drawn by E. J. Poulsen)
134
D. B. HALVORSON AND M. JACOBSON
TABLE 1.—Averages1 of weights (gm.) and maximum length and width measurements (mm.) for selected muscles dissected from cooked chickens at 5, 7, and 9 weeks of age for the Leghorn breed \ge of bird
1
Muscle M. pectoralis M. supracoracoideus M. iliotibialis (posterior region) M. semitendinosus M. gastrocnemius (pars externa) M. peronaeus longus
Weight Length
9 weeks
7 weeks
5 weeks Width
Weight Length
Width
Weight Length
Width
mm. 47 18
gm. 25.1 8.2
mm. 118 104
mm. 53 20
74 72
25 16
4.0 3.0
80 80
30 20
48 54
15 16
2.4 1.8
58 61
16 18
gm. 7.5 2.5
mm. 82 74
mm. 36 16
gm. 16.2 5.0
mm. 103 93
1.2 0.9
59 57
21 15
2.4 1.9
0.7 0.4
42 44
16 15
1.3 0.9
1 Each average represents muscles from left and right sides of 8 chickens for 5-week Leghorns but 10 chickens at 7 and 9 weeks.
ing means for muscle weights at 5 and 7 weeks and at 7 and 9 weeks of age. RESULTS AND DISCUSSION
Weight. Average values for cooked weights of the six muscles dissected are given in Tables 1 and 2. The mean weights in the Leghorn breed for 5, 7 and 9 weeks of age were significantly different (P < .01) from each other for each of the muscles. For the H-WM cross the differences in mean weights were also significant (P<.01) for these ages except for the semitendinosus muscle in which the changes reached the significant (P<.05) level.
Changes in weight are shown graphically in Fig. 3. As indicated by the figure, the pectoralis of the H-WM chickens showed most rapid increases in weight; average gain was 16.7 gm. between 5 and 7 weeks and 20 gm. from 7 to 9 weeks. For this same muscle, Leghorns showed weight changes of 8.7 gm. between 5 and 7 weeks and 8.9 gm. from 7 to 9 weeks. The supracoracoideus also increased in weight rapidly in the H-WM cross and more slowly in the Leghorns. Weight changes in the other four muscles, though mathematically significant, contribute only minor additions of cooked meat from the carcass as the chicken ages.
TABLE 2.—Averages1 of weights (gm.) and maximum length and width measurements (mm.) for selected muscles dissected from cooked chickens 5, 7, and 9 weeks of age for Hubbard-White Mountain cross Age of bird 5 weeks Muscle M. pectoralis M. supracoracoideus M. iliotibialis (posterior region) M. semitendinosus M. gastrocnemius (pars externa) M. peronaeus longus 1
Weight Length
7 weeks Width
9 weeks
Weight Length
Width
gm. 37.3 11.6
mm. 130 114
mm. 55 20
gm. 57.3 19.8
mm. 150 131
mm. 65 24
Weight Length
Width
gm. 20.6 6.6
mm. 104 93
mm. 46 17
3.0 2.8
81 71
24 17
5.7 4.8
92 86
30 19
9.1 7.0
105 93
40 24
2.0 1.6
47 57
18 19
2.9 2.4
50 65
20 21
4.7 3.8
59 74
22 24
Each average represents muscles from left and right sides of 10 chickens.
135
CHICKEN MUSCLE DEVELOPMENT
Length. Measurements of length of the six muscles are recorded in Tables 1 and 2 and compared graphically in Fig. 4. As with weight measurements, the breast muscles showed the greatest change in length with increase in age. For the pectoralis the increase was 26 mm. from 5 to 7 weeks and 20 mm. from 7 to 9 weeks in the H-WM. In Leghorns the same muscle lengthened 21 mm. from 5 to 7 weeks and 15 mm. from 7 to 9 weeks. The supracoracoideus and iliotibialis followed a similar growth pattern in both types of chickens. The semitendinosus grew slowly between 7 and 9 weeks. Changes in the length of the leg muscles were small. Width. The width of the pectoralis and iliotibialis increased at a greater rate than the other four muscles (Tables 1 and 2, Fig. 5). Between 5 and 7 weeks the pectoralis of the H-WM became 9 mm. wider and from 7 to 9 weeks increased 10 mm.
M. pectora lis • • M. supra coracoideus • M. iliolibiolis A (posterior
M. iliotibialis * (posterior reg M. semitendinosus
Weeks of Age Leghorn breed
Weeks of Age Hubbard-White Mountain cross
FIG. 4. Average measurements in length of six muscles with increase in age for the Leghorn Breed and the Hubbard-White Mountain cross.
M. pectoralis • • M. supracoracoideus • — M. iliotibialis A A
A region)
M. semitendinosus
(posterior region)
M. gastrocnemius
M. semitendinosus
(pars externa) M. peronaeus longus
M. pectoralis • * M. supracorccoideus (
M. gastrocnemius (pars externa)
—
M. peronaeus longus —
Weeks Hubbard-White
of
Age
Mountain
cross
FIG. 3. Average gains in weight of six muscles with increase in age for the Leghorn breed and the Hubbard-White Mountain cross.
Weeks of Age Leghorn breed
Weeks of Age Hubbard-White Mountain
cross
FIG. 5. Average measurements in width of six muscles with increase in age for the Leghorn breed and the Hubbard-White Mountain cross.
136
D. B. HALVORSON AND M. JACOBSON
Leghorns widened 11 mm. from 5 to 7 in meatiness during growth periods from weeks but only 6 mm. in the second age 5 to 7 and from 7 to 9 weeks in either type span. The posterior region of the iliotibi- of chicken. alis increased 6 mm. and 10 mm. during REFERENCES these age intervals in the H-WM, and in Leghorns 4 and 5 mm. Bradley, 0 . C , and T. Grahame, 1951. The Structure of the Fowl, p. 27. J. B. Lippincott Co., The pattern of growth of these two New York. types of chickens becomes evident from the measurements of weight and dimen- Chow, I. S., and M. Jacobson, 1968. Inosine monophosphate, inosine, and hypoxanthine in meat sions of the muscles. The meatiness of the from broilers 5, 7, and 9 weeks of age. Poultry rapidly-growing crossbred H-WM chickSci. 47: 604-608. ens derives mainly from increases in Evans, H. E., 1961. A Guide to the Study and Disweight, length and width of M. pectoralis section of a Chicken, New York State Veterinary College, Cornell University. Ithaca, New York. and increases in weight and length but not width of M. SUpracoracoideus. Both Hudson, G. E., P. J. LanziUotti and G. D. Edwards 1959. Muscles of the pelvic limb in galliform thigh muscles measured (M. iliotibialis birds. The American Midland Naturalist, 61(1): and M.semilendinosus) increased in length, 1-67. and the iliotibailis also increased in width, Jacobson, M., J. V. Spencer and D. B. Halvorson, but weight changes were small Leg mus1969. Yields from meat-type chickens at five cles studied contributed little to changes ages. J. Am. Dietet. Assoc. 54: 308-312.
Hemic Studies in Normal and Bluecomb Diseased Turkeys 1 P. N. SCHULTZ, D. E. NELSON, H. E. DZIUK, G. E. DUKE AND C. T. LARSEN Departments of Veterinary Physiology and Pharmacology and Veterinary Microbiology and Public Health, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55101 (Received for publication August 8, 1969)
ALTHOUGH many studies have been •*• *- done to determine the etiology and pathogenesis of bluecomb in turkeys, the disease is still incompletely understood. Since predictable hemic changes accompany certain diseases, the present study was done to provide information on changes in leucocyte counts and plasma protein concentration during bluecomb in turkeys. The etiologic agents have not been identified, although the infectious nature of bluecomb in turkeys, in Minnesota, 1
This study was made possible with support from the Minnesota Agricultural Experiment Station (Project 2644).
was first described by Pomeroy and Sieburth (1953). Vibrio spp. (Truscott el al., 1960; Truscott and Morin, 1964; Truscott, 1968) and viral agents (Deshmukh el al, 1969; Fujisaki el al, 1969; Wooley and Gratzek, 1969) have been suspected. Antibiotics are thought to be partially effective in reducing mortality and in improving recovery in some flocks which have had bluecomb (Sieburth and Pomeroy, 1956). The lack of success in identifying etiologic agents has hindered the development of a suitable vaccine or therapeutic regimen. There is evidence that turkeys which have recovered are immune for life.
D
URING the progress of a recent study of meat yields from fryers, a variable development of certain muscles was observed (Jacobson et al., 1968). Variation in size of principal muscles with growth is of interest since it will affect the meatiness of the portions usually served separately in meals. Such anatomical changes have fundamental interest as well. In this study the dimensions and weights were taken for 6 muscles dissected from cooked chickens of the Leghorn breed and the Hubbard-White Mountain (hereafter H-WM) cross at 5, 7, and 9 weeks of age. Previous studies of the myology of birds by avian anatomists have been made through dissections of raw carcasses. These have served to describe species differences within the genera. In the present study the nomenclature adopted is that used by investigators of avian anatomy. The principal source used for muscle identification is Hudson et al. (1959)} These identifications of muscles in the thigh portion vary from those made by Evans (1961) and also by Bradley and Grahame (1951). Differences include recognition that the surface muscle of the thigh is the iliotibialis thus locating M. biceps femoris in the second layer. Also, previous publications have named as M. semimembranosus what is more accurately M. semitendinosus. It can be noted further 1 Scientific Paper No. 3331, Department of Home Economics, Washington Agricultural Research Center, College of Agriculture, Pullman, Project 1515. 2 Appreciation is expressed to Dr. G. E. Hudson for invaluable assistance in identification of muscles.
that M. semimembranosus is in the fourth layer of muscles but, in the chicken, a small portion of this muscle extends so as to be visible before dissection. EXPERIMENTAL PROCEDURE Production. Chickens were hatched and grown under controlled conditions by the Animal Sciences Department at Washington State University.3 Ration, management, slaughter, preparation, and freezing were as described for the crossbred broilers previously studied for content of flavor constituents (Chow and Jacobson, 1968). A fast-growing cross (H-WM) and the Leghorn breed were selected for study because these might show differences in muscle development related to meatiness of cut. The age span from 5 through 9 weeks represents a period of rapid anatomical change and encompasses those chickens sold as broilers or fryers; so this age span was chosen for investigation. Preparation. Frozen chickens which had been stored less than a month at — 29°C. ( — 20°F.) were thawed under refrigeration at 2°C. (34°F.) for 24 hrs., then at room temperature until completely defrosted but cold. Carcasses were washed under cool running water, drained, and weighed; then each was placed individually in a kettle containing 250-500 ml. of cold water, covered, and rapidly heated to simmering temperature (approx. 85°C). The chickens were steamed until the muscles of the thigh began to separate. The time required ranged from 45 to 65 3
Production and processing of chickens were supervised by Dr. J. V. Spencer. The Animal Sciences Department cooperates in the project.
132
CHICKEN MUSCLE DEVELOPMENT
minutes. Cooked carcasses were drained, cooled to room temperature, and weighed, after which they were wrapped loosely in aluminum foil and refrigerated overnight. The above techniques facilitated dissection of individual muscles. Dissection. Skin was first removed from the refrigerated cooked bird, after which the wings were removed and not further used. T h e two pelvic limbs were separated by cutting the attached muscles free from the ilium and severing the hip joint while dividing muscles a t their tendon attachment. T h e leg4 was separated from the thigh in a similar way. From the thigh the ileshy posterior region of the M. iliotibialis and the entire M. semitendinosus were released a t the edges with a scalpel, then eased from adjacent structures by gentle linger pressure. The iliotibialis is a triangular-shaped flat muscle which comprises most of the lateral surface of the thigh (Fig. 1). It is closely attached to the M. sartorius anteriorly and to the M. semitendinosus posteriorly. In the genus Gallus, which includes the domestic fowl, the posterior region of M. iliotibialis is flesh)'. The semitendinosus is a fleshy band forming the posterior limitof the thigh musculature and is well developed in the chicken. The M. peronaeus longus is located in the anterior and anterolateral area of the leg. The pars externa of the gastrocnemius occupies the posterolateral portion of the leg. T h e two muscles of the breast (Fig. 2) were both studied. T h e pectoralis is the large muscle which completely overlays this area and the supracoracoideus lies beneath the pectoralis. Measurements. Weights of each dissected muscle from the left and right sides were obtained to the nearest 0.1 gram. After " The commonly used term "leg" is designated "shank" by avian anatomists.
133
FIG. 1. Muscle nomenclature and location in the hind limb of the chicken. (Drawing from specimens made by Washington State University artist, E. J. Poulsen.)
weights had been taken, the length and width of each muscle were measured by the use of a vernier caliper graduated in millimeters. Statistical A nalysis. Analysis of variance of the individual measurements from each chicken were made. Calculated values of t were determined for the data in Campar-
is supracoracoideus
FIG. 2. Muscles in breast of the chicken. M. pectoralis dissected to expose M. supracoracoideus. (Drawn by E. J. Poulsen)
134
D. B. HALVORSON AND M. JACOBSON
TABLE 1.—Averages1 of weights (gm.) and maximum length and width measurements (mm.) for selected muscles dissected from cooked chickens at 5, 7, and 9 weeks of age for the Leghorn breed \ge of bird
1
Muscle M. pectoralis M. supracoracoideus M. iliotibialis (posterior region) M. semitendinosus M. gastrocnemius (pars externa) M. peronaeus longus
Weight Length
9 weeks
7 weeks
5 weeks Width
Weight Length
Width
Weight Length
Width
mm. 47 18
gm. 25.1 8.2
mm. 118 104
mm. 53 20
74 72
25 16
4.0 3.0
80 80
30 20
48 54
15 16
2.4 1.8
58 61
16 18
gm. 7.5 2.5
mm. 82 74
mm. 36 16
gm. 16.2 5.0
mm. 103 93
1.2 0.9
59 57
21 15
2.4 1.9
0.7 0.4
42 44
16 15
1.3 0.9
1 Each average represents muscles from left and right sides of 8 chickens for 5-week Leghorns but 10 chickens at 7 and 9 weeks.
ing means for muscle weights at 5 and 7 weeks and at 7 and 9 weeks of age. RESULTS AND DISCUSSION
Weight. Average values for cooked weights of the six muscles dissected are given in Tables 1 and 2. The mean weights in the Leghorn breed for 5, 7 and 9 weeks of age were significantly different (P < .01) from each other for each of the muscles. For the H-WM cross the differences in mean weights were also significant (P<.01) for these ages except for the semitendinosus muscle in which the changes reached the significant (P<.05) level.
Changes in weight are shown graphically in Fig. 3. As indicated by the figure, the pectoralis of the H-WM chickens showed most rapid increases in weight; average gain was 16.7 gm. between 5 and 7 weeks and 20 gm. from 7 to 9 weeks. For this same muscle, Leghorns showed weight changes of 8.7 gm. between 5 and 7 weeks and 8.9 gm. from 7 to 9 weeks. The supracoracoideus also increased in weight rapidly in the H-WM cross and more slowly in the Leghorns. Weight changes in the other four muscles, though mathematically significant, contribute only minor additions of cooked meat from the carcass as the chicken ages.
TABLE 2.—Averages1 of weights (gm.) and maximum length and width measurements (mm.) for selected muscles dissected from cooked chickens 5, 7, and 9 weeks of age for Hubbard-White Mountain cross Age of bird 5 weeks Muscle M. pectoralis M. supracoracoideus M. iliotibialis (posterior region) M. semitendinosus M. gastrocnemius (pars externa) M. peronaeus longus 1
Weight Length
7 weeks Width
9 weeks
Weight Length
Width
gm. 37.3 11.6
mm. 130 114
mm. 55 20
gm. 57.3 19.8
mm. 150 131
mm. 65 24
Weight Length
Width
gm. 20.6 6.6
mm. 104 93
mm. 46 17
3.0 2.8
81 71
24 17
5.7 4.8
92 86
30 19
9.1 7.0
105 93
40 24
2.0 1.6
47 57
18 19
2.9 2.4
50 65
20 21
4.7 3.8
59 74
22 24
Each average represents muscles from left and right sides of 10 chickens.
135
CHICKEN MUSCLE DEVELOPMENT
Length. Measurements of length of the six muscles are recorded in Tables 1 and 2 and compared graphically in Fig. 4. As with weight measurements, the breast muscles showed the greatest change in length with increase in age. For the pectoralis the increase was 26 mm. from 5 to 7 weeks and 20 mm. from 7 to 9 weeks in the H-WM. In Leghorns the same muscle lengthened 21 mm. from 5 to 7 weeks and 15 mm. from 7 to 9 weeks. The supracoracoideus and iliotibialis followed a similar growth pattern in both types of chickens. The semitendinosus grew slowly between 7 and 9 weeks. Changes in the length of the leg muscles were small. Width. The width of the pectoralis and iliotibialis increased at a greater rate than the other four muscles (Tables 1 and 2, Fig. 5). Between 5 and 7 weeks the pectoralis of the H-WM became 9 mm. wider and from 7 to 9 weeks increased 10 mm.
M. pectora lis • • M. supra coracoideus • M. iliolibiolis A (posterior
M. iliotibialis * (posterior reg M. semitendinosus
Weeks of Age Leghorn breed
Weeks of Age Hubbard-White Mountain cross
FIG. 4. Average measurements in length of six muscles with increase in age for the Leghorn Breed and the Hubbard-White Mountain cross.
M. pectoralis • • M. supracoracoideus • — M. iliotibialis A A
A region)
M. semitendinosus
(posterior region)
M. gastrocnemius
M. semitendinosus
(pars externa) M. peronaeus longus
M. pectoralis • * M. supracorccoideus (
M. gastrocnemius (pars externa)
—
M. peronaeus longus —
Weeks Hubbard-White
of
Age
Mountain
cross
FIG. 3. Average gains in weight of six muscles with increase in age for the Leghorn breed and the Hubbard-White Mountain cross.
Weeks of Age Leghorn breed
Weeks of Age Hubbard-White Mountain
cross
FIG. 5. Average measurements in width of six muscles with increase in age for the Leghorn breed and the Hubbard-White Mountain cross.
136
D. B. HALVORSON AND M. JACOBSON
Leghorns widened 11 mm. from 5 to 7 in meatiness during growth periods from weeks but only 6 mm. in the second age 5 to 7 and from 7 to 9 weeks in either type span. The posterior region of the iliotibi- of chicken. alis increased 6 mm. and 10 mm. during REFERENCES these age intervals in the H-WM, and in Leghorns 4 and 5 mm. Bradley, 0 . C , and T. Grahame, 1951. The Structure of the Fowl, p. 27. J. B. Lippincott Co., The pattern of growth of these two New York. types of chickens becomes evident from the measurements of weight and dimen- Chow, I. S., and M. Jacobson, 1968. Inosine monophosphate, inosine, and hypoxanthine in meat sions of the muscles. The meatiness of the from broilers 5, 7, and 9 weeks of age. Poultry rapidly-growing crossbred H-WM chickSci. 47: 604-608. ens derives mainly from increases in Evans, H. E., 1961. A Guide to the Study and Disweight, length and width of M. pectoralis section of a Chicken, New York State Veterinary College, Cornell University. Ithaca, New York. and increases in weight and length but not width of M. SUpracoracoideus. Both Hudson, G. E., P. J. LanziUotti and G. D. Edwards 1959. Muscles of the pelvic limb in galliform thigh muscles measured (M. iliotibialis birds. The American Midland Naturalist, 61(1): and M.semilendinosus) increased in length, 1-67. and the iliotibailis also increased in width, Jacobson, M., J. V. Spencer and D. B. Halvorson, but weight changes were small Leg mus1969. Yields from meat-type chickens at five cles studied contributed little to changes ages. J. Am. Dietet. Assoc. 54: 308-312.
Hemic Studies in Normal and Bluecomb Diseased Turkeys 1 P. N. SCHULTZ, D. E. NELSON, H. E. DZIUK, G. E. DUKE AND C. T. LARSEN Departments of Veterinary Physiology and Pharmacology and Veterinary Microbiology and Public Health, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55101 (Received for publication August 8, 1969)
ALTHOUGH many studies have been •*• *- done to determine the etiology and pathogenesis of bluecomb in turkeys, the disease is still incompletely understood. Since predictable hemic changes accompany certain diseases, the present study was done to provide information on changes in leucocyte counts and plasma protein concentration during bluecomb in turkeys. The etiologic agents have not been identified, although the infectious nature of bluecomb in turkeys, in Minnesota, 1
This study was made possible with support from the Minnesota Agricultural Experiment Station (Project 2644).
was first described by Pomeroy and Sieburth (1953). Vibrio spp. (Truscott el al., 1960; Truscott and Morin, 1964; Truscott, 1968) and viral agents (Deshmukh el al, 1969; Fujisaki el al, 1969; Wooley and Gratzek, 1969) have been suspected. Antibiotics are thought to be partially effective in reducing mortality and in improving recovery in some flocks which have had bluecomb (Sieburth and Pomeroy, 1956). The lack of success in identifying etiologic agents has hindered the development of a suitable vaccine or therapeutic regimen. There is evidence that turkeys which have recovered are immune for life.