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Heart Rate Changes with Age in Chickens
906
N. K. ALLEN AND D. H. BAKER
Jones, J. D., S. J. Petersburg and P. C. Burnett, 1967. The mechanism of the lysine-arginine antagonism in the chick: effect of lysine on digestion, kidney arginase and liver transamidinase. J. Nutr. 93: 103-116. Klain, G. J., H. M. Scott and B. C. Johnson, 1960. The amino acid requirement of the growing chick fed a crystalline amino acid diet. Poultry Sci. 39: 39-44. Smith, R. E., 1968. Effect of arginine upon the tox-
icity of excesses of single amino acids in chicks. J. Nutr. 95:547-553. Snetsinger, D. C , and H. M. Scott, 1961. Efficacy of glycine and arginine in alleviating the stress induced by dietary excesses of single amino acids. Poultry Sci. 40: 1675-1681. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York.
Heart Rate Changes with Age in Chickens
(Received for publication September 20, 1971) ABSTRACT Heart rates were determined in White Leghorn male and female chickens at 2, 4, 8, 12, 16 and 20 weeks of age before and after administration of atropine alone, propranolol alone and propranolol and atropine administered together. These drugs were administered at the minimal level required to block sympathetic and parasympathetic nerve effects on heart rate. The normal resting heart rates are highest at 2 and 4 weeks of age, then decline appreciably at 8 weeks and then continue to decrease more gradually up to 16 to 20 weeks. Up to 8 weeks of age there are no significant sex differences in rate but at all other ages the rates were significantly different with the higher rate occurring in the female. Sympathetic tone is evident at 8 weeks of age and exhibits a gradual decline at 12 and 16 weeks with no appreciable change afterward. The differences in parasympathetic tone are not significantly different between age groups. POULTRY S C I E N C E 5 1 : 906-911,
R
INGER et al. (1957) showed that the • heart rate of the chick increases greatly from 1 day to 1 week of age and increases slightly and reaches a maximum up to 3 to 4 weeks. Thereafter it declines gradually and reaches the adult level at about 17 weeks of age. Between 12 and 17 weeks a significant sex difference in rate is observed with the higher rate in females. That gonad hormones are not mainly responsible for the difference was demonstrated. Tummons and Sturkie (1969) and Sturkie et al. (1970) studied the relative influence of sympathetic and parasympathetic nerves on heart rate of adult male and female chickens by surgical denervation of sympathetic and parasympathetic nerves and by administering
1972
adrenergic and cholinergic blocking agents. Wekstein (1965) who studied the heart rate in the growing rat reported that rate seemed to be controlled principally by the sympathetic nerves, based on studies involving the adrenergic depleting agent, reserpine; atropine, a parasympathetic blocker, had no effect at any of the ages studied (1-21 days of age). The relative influence of sympathetic and parasympathetic control of heart rate changes in chickens occurring during growth and on to maturity have not been studied and is the main object of this study. MATERIALS AND METHODS
Heart rate determinations were made
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PAUL D. STURKIE AND J. CHILLSEYZN Department of Environmental Physiology, Rutgers University, New Brunswick, New Jersey 08903
907
AGE AND HEART RATE
stances, these same birds were kept until the atropine effect had worn off and a new resting heart rate established (R2). In such instances, propranolol was injected and records taken at the same intervals after injection, and the maximum change recorded. Another group (B) received propranolol alone (P) following the resting rate and this was followed by atropine (A) and within 1 to 2 minutes thereafter the maximum effect was recorded (PA). Most of the determinations were made on birds kept at the Farm in the winter and early spring and until early June. So most of these birds were adapted to winter or control (79-76°F.) temperatures. We (Sturkie et al., 1970) had shown that birds adapted to high temperatures (summer) have lower heart rates than those in winter or control conditions. Our 20 week old birds (males only) were done at a different time and year and represent the average of those adapted to winter and control conditions. RESULTS AND DISCUSSIONS
The results are presented in Tables 1, 2 and 3 and also in Figures 1, 2 and 3. It is
TABLE 1.—Changes in', heart rate from resting rate (Ri) after administration 1if atropine (A)
Age
Number tested
Mean R!
c ^ S E
- -
Mean A
S.E.
A-R,
A%
t
2 weeks
8M&F
445
7.0
492
4.8
+47
10.5
5.5
4 weeks
10M&F
430
9.8
467
11.3
+37
8.6
3.0
10 M
370
10.5
414
9.8
+44
11.9
3
10 F
398
10.8
398
10.8
+43
10.8
3.2
10 M
341
6.6
382
7.3
+41
12.4
4.1
10 F
375
6.7
415
7.7
+40
10.6
3.9
10 M
316
7.2
372
8.3
+56
14.5
5.1
10 F
349
8.2
387
8.1
+38
10.9
3.2
M
321
5.8
359
5.0
+38
10.6
3.9
8 weeks
12 weeks
16 weeks
20 weeks
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on male and female chickens at 1 to 2 weeks, 4, 8, 12, 16 and 20 or more weeks of age, before and after administration of appropriate dosages of atropine alone, propranolol alone and propranolol and atropine together, except for ages 2 and 4 weeks. The reaction to both drugs injected together at these ages was drastic and had to be discontinued. The drugs were injected intravenously via wing vein catheter at dosages of 0.3 mg./kg. for atropine sulphate and 0.4 mg./kg. for propranolol. Heart rates were determined by a Beckman Dynagraph with electror cardiogram leads I with needle electrodes inserted at base of wings. The rates were calculated from the cardiotachograph. Resting heart rates were determined after the bird had been restrained in an upright position for at least 10 minutes under quiet and restful conditions. At least 10 males and 10 females comprised each group except in 2 and 4 week old chicks where the numbers were smaller and where both sexes were grouped. Following the taking of the resting rate, atropine was injected and records taken at 1 to 5 minutes after injection and the maximum change recorded. In some in-
908
P. D. STURKIE AND J. CHILLSEYZN TABLE 2.—Changes from resting heart rate (Rt) after administration of propranolol (P) Group Number tested
R2
S.E.
%
P
S.E.
%
R2-P
A%
t
2 weeks
8M&F 10M&F
438 445
9.7 9.5
303 305
11.1 9.5
+ 135 + 140
30.8 31.4
9.2 9.4
4 weeks
10M&F
449
10.9
319
8.6
+ 130
28.9
8.1
Age
A B
10 M 10 F 10 M 10 F
367 387 397 409
10.3 9.4 6.4 8.0
266 275 280 290
5.8 7.0 7.5 10.1
+ + + +
101 112 117 119
27.5 28.4 29.5 29.1
6.8 7.8 11.8 9.2
12 weeks
A B
10 M 10 F 10 M 10 F
330 368 342 375
9.2 9.3 6.6 9.4
243 252 253 271
6.0 9.9 5.9 9.8
+ + + +
87 116 89 104
26.3 31.4 26. 27.7
7.9 8.6 9.0 7.6
16 weeks
A B
10 M 10 F 10 M 10 F
329 352 345 354
10.9 7.4 9.8 13.3
239 254 250 255
6.1 6.2 6.3 9.1
+ + + +
90 90 95 99
27.3 27.8 27.5 27.9
7.2 10.1 8.1 6.1
M
322
5.8
226
8.4
+ 95
30.0
3.6
20 weeks
evident from the tables and Figure 1 that heart rates are highest at 2 and 4 weeks of age and then decline appreciably at 8 weeks, and then continue to decrease more gradually up to 16 to 20 weeks of age. These results are similar to those reported previously by Ringer el ah (1957). Up to 8 weeks of age there were no significant sex differences in heart rate although the rate tended to be higher in the females
at 8 weeks. At the other ages, rate was significantly higher in the females as has been previously demonstrated. The results on heart rates after administration of atropine and propranolol are shown in the tables and best illustrated in Figure 2. There are significant increases in heart rate following atropine administration, and the degree of increase between age
TABLE 3.—Differences in intrinsic rate (PA) and resting rate (R) after administration of atropine (A) or A —PA and propranolol (PA) or P—PA PA
R-PA
A-PA
%
%
8 Weeks 122 29.4 146 35.0
P-PA
%
-26 -10 -27 -29
8.9 3.5 8.7 7.0
3.0 3.0 5.4 6.2
9.09 7.4
2.9 1.6
AM292±6.4 F 285±6.7 BM307±6.8 F 319 + 9.3
+75 +82 ±90 ±90
20.4 21.2 22.6 22.0
6.1 7.9 7.4 8.2
B M 2 7 6 + 5.1 F 291+8.0
+66 +84
19.0 22.4
5.2 7.1
12 Weeks + 106 27.9 + 124 29.9
S S
-23 -20
B
281+5.0 274±8.0
+64 +80
18.5 22.6
4.2 5.1
16 Weeks 91 24.5 113 29.2
s s
-31 -19
12.6 7.5
3.8 1.6
249±7.0
+72
22.4
4.7
20 Weeks -110 30.6
-23
10.1
3.2
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8 weeks
909
AGE AND HEART RATE
AGEOF BIRDS IN WEEKS
FIG. 1. Normal resting heart rates: (A) of chickens males (*) and females (O) at 2, 4, 8, 12, 16 and 20 weeks of age. (B) Intrinsic heart rates resulting fiom administration of propranolol and atropine (PA).
I so.
<
I! I
20.
i1
P-M
I
12
16
ICE OF BIRDS IN WEEKS
FIG. 2. Differences in heart rate actual and percent (8) from PA rate after administration of atropine (A) or A-PA and after propranolol or P-PA.
After administration of both propranolol and atropine which block both sympathetic and parasympathetic activity, heart rates are significantly higher than for those receiving propranolol alone as might be expected. The PA rate (intrinsic rate) is relatively stable, because it is freed from the influence of acetylcholine and catecholamines both neuronal and circulating. Actually heart rates following PA are 25 to 50 beats lower than in birds after sympathetic and parasympathetic denervation because of blockade of circulating catecholamines also in PA administered birds. Since the rate after administration of PA represents a more stable intrinsic rate, then differences in heart rate above and
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groups is not, in most instances, significant. This suggests that the degree of vagal tone or control is rather consistent for all age groups, although there appears to be some difference with respect to sexes, particularly at 16 weeks of age where the vagal tone appears some higher in the male. The results of the effects of propranolol are presented in Tables 1 and 2 and Figure 2. The actual decrease in heart rate from resting rate after administration of propranolol was greatest in 2 and 4 week old chickens, but the degree (percent) of change was not significantly different from the other age groups. At 8 weeks of age the actual change was less, and continued to decrease up to 16 weeks of age. This change reflects changes in sympathetic nervous tone. The greatest change in heart rate after propranolol administration occurs during the 4 to 8 weeks when the greatest change normally occurs. This suggests that sympathetic control is greatest at 4 weeks and then begins to decline gradually.
910
P . D . S T U R K I E AND J. C H I L L S E Y Z N D=« 0=p
4
I
12
It
21
ICE OF HDDS IN WEEKS
FIG. 3. Actual and percent changes (8) in heart rate from resting rate (O) after atropine (A), propranolol (P) and after administration of both (PA).
below this rate reflect relative degrees of sympathetic tone or acceleration (neuronal and circulating) and parasympathetic tone or influence, better than differences in rate after atropine alone or propranolol alone. Thus, A = intrinsic rate and sympathetic rate in absence of parasympathetic tone; Propranolol (P) = intrinsic rate and parasympathetic tone in absence of sympathetic tone. Then A —PA and P —PA reflect more accurately differences attributable to sympathetic and parasympathetic tone respectively. These differences are shown in Figure 3 for age groups 8 to 20 weeks of age. No such d a t a are available on 2 and 4 week old birds because administration of both drugs had drastic effects resulting in high mortality. I n general, the actual differences in A —PA and sympathetic tone are greatest a t 8 weeks of age and tend to show a
REFERENCES Adolph, E. ]"., and J. M. Ferrari, 1968. Adaptation to temperature in heart rates of salamander larvae before cardiac innervation. Am. J. Physiol. 215: 124-126. Ringer, R. K., P. D. Sturkie and H. S. Weiss, 1957. Heart rate of chickens as influenced by age and gonadal hormones. Am. J. Physiol. 191: 145-147.
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1-2
gradual decline at 12 and 16 weeks with no appreciable change afterward. T h e differences in parasympathetic tone as reflected by differences in the P —PA are not significantly different between age groups. T h e decrease in sympathetic tone was modest b u t not nearly as great as the total change or decrease in heart rate with age (Figure 1A). This suggests t h a t some of the decrease resulted from changes independent of nervous influence, or changes in intrinsic rate. Since heart rate after administration of both propranolol and atropine (PA) reflects intrinsic rate freed from nervous control, then changes in the rate after (PA) should reveal changes in intrinsic rate. Unfortunately we have no d a t a on PA rate at 2 and 4 weeks of age, b u t the change from 8 to 16 weeks indicates a modest decrease in intrinsic rate with age. In order to estimate change in intrinsic rate at 2 and 4 weeks and at other ages PA can be estimated as follows: PA = resting rate R - ( A - R + P - R ) . Estimates for most ages approach actual PA values although they tend to be higher. The relationship of these values to age are shown in Figure IB (sexes pooled). I t is apparent t h a t the decrease in intrinsic rate with age tends to parallel the decrease in resting rates. The fact t h a t intrinsic rate varies considerably between species indicates it is determined by non-neurogenic factors such as body temperature, hormones and metabolic state as has been reported by others (Adolph and Ferrari, 1968).
AGE AND HEART RATE Sturkie, P. D., Yu chong Lin and N. Ossorio, 1970. Effects of acclimatization to heat and cold on heart rate in chickens. Am. J. Physiol. 219:34-36. Tummons, J. L., and P. D. Sturkie. 1969. Nervous control of heart rate during excitement in the
911
adult White Leghorn cock. Am. J. Physiol. 216: 1437-1440. Wekstein, D. R., 1965. Heart rate of the preweaning rat and its automatic control. Am. J. Physiol. 208: 1259-1261.
Inheritance of Plumage and Shank Color in Ring-necked Pheasants and Domestic Fowl Hybrids M. K. BHATNAGAR, B. S. REINHART AND F. N. JEROME Departments of Biomedical Sciences and A nimal and Poultry Science, University of Guelph, Guelph, Ontario, Canada (Received for publication September 21, 1971)
POULTRY SCIENCE 51: 911-915, 1972
T T HAS been conclusively established -*• by Punnett (1923) that in domestic fowl the plumage color gene for silver (S) and gold (s), and by Dunn (1925) that the expression of the dermal melanin gene (id) in the shanks are sex-linked traits. In studies conducted on museum specimens of chicken-pheasant hybrids, Serebrovsky (1929) noted that mutations dominant in the fowl were also dominant in the hybrids, and that sex-linked barring was transmitted to the hybrids as in the fowl. Observations on intergeneric hybrids by Danforth and Sandnes (1939), Shaklee and Knox (1954), and Asmundson and Lorenz (1957) for morphological traits confirmed the findings of Serebrovsky, although some of the reports are equivocal. This investigation was undertaken to study the mode of inheritance of certain characters in chicken-pheasant hybrids in addition to those reported by the investigators mentioned above. MATERIALS AND METHODS
Reciprocal matings between Ringnecked pheasants (Pkasianus colchicus)
and Columbian Plymouth Rock chickens (Gallus domesticus) were carried out by the artificial insemination of 12 Columbian Plymouth Rock (C.P.R.) hens with the semen from four Ring-necked pheasant (R.Ph.) males and 14 R.Ph. hens with the semen from four C.P.R. males. Inseminations were carried out two to three times weekly. On account of the small quantity of semen produced by R.Ph. males, it was found necessary to pool and dilute the semen with physiological saline (0.9%) for equal distribution to all C.P.R. hens. All the female and male pheasants, as well as the male chickens were maintained in wire cages. Chicken females were kept in a small floor pen. The eggs were held at 15°C. and set weekly in a forced air incubator. Fertility was checked by candling eggs after seven days of incubation. After hatching the hybrid chicks were brooded in batteries for three weeks and then moved to floor brooding. Observations for phenotypic characteristics were first made at three to four weeks, and then periodically until the hybrids were 12 months old.
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ABSTRACT Reciprocal crosses were made of Columbian Plymouth Rock chickens and Ring-necked pheasants to produce chicken-pheasant Fi hybrids. The mode of inheritance of plumage and shank color in the Fi hybrids was investigated. The data disclosed that in Ringnecked pheasants the genes responsible for gold plumage and for the expression of dermal melanin are sex-linked recessives and the gene responsible for white shanks is autosomal dominant and that all these genes behave similar to those of the fowl.
N. K. ALLEN AND D. H. BAKER
Jones, J. D., S. J. Petersburg and P. C. Burnett, 1967. The mechanism of the lysine-arginine antagonism in the chick: effect of lysine on digestion, kidney arginase and liver transamidinase. J. Nutr. 93: 103-116. Klain, G. J., H. M. Scott and B. C. Johnson, 1960. The amino acid requirement of the growing chick fed a crystalline amino acid diet. Poultry Sci. 39: 39-44. Smith, R. E., 1968. Effect of arginine upon the tox-
icity of excesses of single amino acids in chicks. J. Nutr. 95:547-553. Snetsinger, D. C , and H. M. Scott, 1961. Efficacy of glycine and arginine in alleviating the stress induced by dietary excesses of single amino acids. Poultry Sci. 40: 1675-1681. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York.
Heart Rate Changes with Age in Chickens
(Received for publication September 20, 1971) ABSTRACT Heart rates were determined in White Leghorn male and female chickens at 2, 4, 8, 12, 16 and 20 weeks of age before and after administration of atropine alone, propranolol alone and propranolol and atropine administered together. These drugs were administered at the minimal level required to block sympathetic and parasympathetic nerve effects on heart rate. The normal resting heart rates are highest at 2 and 4 weeks of age, then decline appreciably at 8 weeks and then continue to decrease more gradually up to 16 to 20 weeks. Up to 8 weeks of age there are no significant sex differences in rate but at all other ages the rates were significantly different with the higher rate occurring in the female. Sympathetic tone is evident at 8 weeks of age and exhibits a gradual decline at 12 and 16 weeks with no appreciable change afterward. The differences in parasympathetic tone are not significantly different between age groups. POULTRY S C I E N C E 5 1 : 906-911,
R
INGER et al. (1957) showed that the • heart rate of the chick increases greatly from 1 day to 1 week of age and increases slightly and reaches a maximum up to 3 to 4 weeks. Thereafter it declines gradually and reaches the adult level at about 17 weeks of age. Between 12 and 17 weeks a significant sex difference in rate is observed with the higher rate in females. That gonad hormones are not mainly responsible for the difference was demonstrated. Tummons and Sturkie (1969) and Sturkie et al. (1970) studied the relative influence of sympathetic and parasympathetic nerves on heart rate of adult male and female chickens by surgical denervation of sympathetic and parasympathetic nerves and by administering
1972
adrenergic and cholinergic blocking agents. Wekstein (1965) who studied the heart rate in the growing rat reported that rate seemed to be controlled principally by the sympathetic nerves, based on studies involving the adrenergic depleting agent, reserpine; atropine, a parasympathetic blocker, had no effect at any of the ages studied (1-21 days of age). The relative influence of sympathetic and parasympathetic control of heart rate changes in chickens occurring during growth and on to maturity have not been studied and is the main object of this study. MATERIALS AND METHODS
Heart rate determinations were made
Downloaded from http://ps.oxfordjournals.org/ by guest on April 11, 2015
PAUL D. STURKIE AND J. CHILLSEYZN Department of Environmental Physiology, Rutgers University, New Brunswick, New Jersey 08903
907
AGE AND HEART RATE
stances, these same birds were kept until the atropine effect had worn off and a new resting heart rate established (R2). In such instances, propranolol was injected and records taken at the same intervals after injection, and the maximum change recorded. Another group (B) received propranolol alone (P) following the resting rate and this was followed by atropine (A) and within 1 to 2 minutes thereafter the maximum effect was recorded (PA). Most of the determinations were made on birds kept at the Farm in the winter and early spring and until early June. So most of these birds were adapted to winter or control (79-76°F.) temperatures. We (Sturkie et al., 1970) had shown that birds adapted to high temperatures (summer) have lower heart rates than those in winter or control conditions. Our 20 week old birds (males only) were done at a different time and year and represent the average of those adapted to winter and control conditions. RESULTS AND DISCUSSIONS
The results are presented in Tables 1, 2 and 3 and also in Figures 1, 2 and 3. It is
TABLE 1.—Changes in', heart rate from resting rate (Ri) after administration 1if atropine (A)
Age
Number tested
Mean R!
c ^ S E
- -
Mean A
S.E.
A-R,
A%
t
2 weeks
8M&F
445
7.0
492
4.8
+47
10.5
5.5
4 weeks
10M&F
430
9.8
467
11.3
+37
8.6
3.0
10 M
370
10.5
414
9.8
+44
11.9
3
10 F
398
10.8
398
10.8
+43
10.8
3.2
10 M
341
6.6
382
7.3
+41
12.4
4.1
10 F
375
6.7
415
7.7
+40
10.6
3.9
10 M
316
7.2
372
8.3
+56
14.5
5.1
10 F
349
8.2
387
8.1
+38
10.9
3.2
M
321
5.8
359
5.0
+38
10.6
3.9
8 weeks
12 weeks
16 weeks
20 weeks
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on male and female chickens at 1 to 2 weeks, 4, 8, 12, 16 and 20 or more weeks of age, before and after administration of appropriate dosages of atropine alone, propranolol alone and propranolol and atropine together, except for ages 2 and 4 weeks. The reaction to both drugs injected together at these ages was drastic and had to be discontinued. The drugs were injected intravenously via wing vein catheter at dosages of 0.3 mg./kg. for atropine sulphate and 0.4 mg./kg. for propranolol. Heart rates were determined by a Beckman Dynagraph with electror cardiogram leads I with needle electrodes inserted at base of wings. The rates were calculated from the cardiotachograph. Resting heart rates were determined after the bird had been restrained in an upright position for at least 10 minutes under quiet and restful conditions. At least 10 males and 10 females comprised each group except in 2 and 4 week old chicks where the numbers were smaller and where both sexes were grouped. Following the taking of the resting rate, atropine was injected and records taken at 1 to 5 minutes after injection and the maximum change recorded. In some in-
908
P. D. STURKIE AND J. CHILLSEYZN TABLE 2.—Changes from resting heart rate (Rt) after administration of propranolol (P) Group Number tested
R2
S.E.
%
P
S.E.
%
R2-P
A%
t
2 weeks
8M&F 10M&F
438 445
9.7 9.5
303 305
11.1 9.5
+ 135 + 140
30.8 31.4
9.2 9.4
4 weeks
10M&F
449
10.9
319
8.6
+ 130
28.9
8.1
Age
A B
10 M 10 F 10 M 10 F
367 387 397 409
10.3 9.4 6.4 8.0
266 275 280 290
5.8 7.0 7.5 10.1
+ + + +
101 112 117 119
27.5 28.4 29.5 29.1
6.8 7.8 11.8 9.2
12 weeks
A B
10 M 10 F 10 M 10 F
330 368 342 375
9.2 9.3 6.6 9.4
243 252 253 271
6.0 9.9 5.9 9.8
+ + + +
87 116 89 104
26.3 31.4 26. 27.7
7.9 8.6 9.0 7.6
16 weeks
A B
10 M 10 F 10 M 10 F
329 352 345 354
10.9 7.4 9.8 13.3
239 254 250 255
6.1 6.2 6.3 9.1
+ + + +
90 90 95 99
27.3 27.8 27.5 27.9
7.2 10.1 8.1 6.1
M
322
5.8
226
8.4
+ 95
30.0
3.6
20 weeks
evident from the tables and Figure 1 that heart rates are highest at 2 and 4 weeks of age and then decline appreciably at 8 weeks, and then continue to decrease more gradually up to 16 to 20 weeks of age. These results are similar to those reported previously by Ringer el ah (1957). Up to 8 weeks of age there were no significant sex differences in heart rate although the rate tended to be higher in the females
at 8 weeks. At the other ages, rate was significantly higher in the females as has been previously demonstrated. The results on heart rates after administration of atropine and propranolol are shown in the tables and best illustrated in Figure 2. There are significant increases in heart rate following atropine administration, and the degree of increase between age
TABLE 3.—Differences in intrinsic rate (PA) and resting rate (R) after administration of atropine (A) or A —PA and propranolol (PA) or P—PA PA
R-PA
A-PA
%
%
8 Weeks 122 29.4 146 35.0
P-PA
%
-26 -10 -27 -29
8.9 3.5 8.7 7.0
3.0 3.0 5.4 6.2
9.09 7.4
2.9 1.6
AM292±6.4 F 285±6.7 BM307±6.8 F 319 + 9.3
+75 +82 ±90 ±90
20.4 21.2 22.6 22.0
6.1 7.9 7.4 8.2
B M 2 7 6 + 5.1 F 291+8.0
+66 +84
19.0 22.4
5.2 7.1
12 Weeks + 106 27.9 + 124 29.9
S S
-23 -20
B
281+5.0 274±8.0
+64 +80
18.5 22.6
4.2 5.1
16 Weeks 91 24.5 113 29.2
s s
-31 -19
12.6 7.5
3.8 1.6
249±7.0
+72
22.4
4.7
20 Weeks -110 30.6
-23
10.1
3.2
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8 weeks
909
AGE AND HEART RATE
AGEOF BIRDS IN WEEKS
FIG. 1. Normal resting heart rates: (A) of chickens males (*) and females (O) at 2, 4, 8, 12, 16 and 20 weeks of age. (B) Intrinsic heart rates resulting fiom administration of propranolol and atropine (PA).
I so.
<
I! I
20.
i1
P-M
I
12
16
ICE OF BIRDS IN WEEKS
FIG. 2. Differences in heart rate actual and percent (8) from PA rate after administration of atropine (A) or A-PA and after propranolol or P-PA.
After administration of both propranolol and atropine which block both sympathetic and parasympathetic activity, heart rates are significantly higher than for those receiving propranolol alone as might be expected. The PA rate (intrinsic rate) is relatively stable, because it is freed from the influence of acetylcholine and catecholamines both neuronal and circulating. Actually heart rates following PA are 25 to 50 beats lower than in birds after sympathetic and parasympathetic denervation because of blockade of circulating catecholamines also in PA administered birds. Since the rate after administration of PA represents a more stable intrinsic rate, then differences in heart rate above and
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groups is not, in most instances, significant. This suggests that the degree of vagal tone or control is rather consistent for all age groups, although there appears to be some difference with respect to sexes, particularly at 16 weeks of age where the vagal tone appears some higher in the male. The results of the effects of propranolol are presented in Tables 1 and 2 and Figure 2. The actual decrease in heart rate from resting rate after administration of propranolol was greatest in 2 and 4 week old chickens, but the degree (percent) of change was not significantly different from the other age groups. At 8 weeks of age the actual change was less, and continued to decrease up to 16 weeks of age. This change reflects changes in sympathetic nervous tone. The greatest change in heart rate after propranolol administration occurs during the 4 to 8 weeks when the greatest change normally occurs. This suggests that sympathetic control is greatest at 4 weeks and then begins to decline gradually.
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P . D . S T U R K I E AND J. C H I L L S E Y Z N D=« 0=p
4
I
12
It
21
ICE OF HDDS IN WEEKS
FIG. 3. Actual and percent changes (8) in heart rate from resting rate (O) after atropine (A), propranolol (P) and after administration of both (PA).
below this rate reflect relative degrees of sympathetic tone or acceleration (neuronal and circulating) and parasympathetic tone or influence, better than differences in rate after atropine alone or propranolol alone. Thus, A = intrinsic rate and sympathetic rate in absence of parasympathetic tone; Propranolol (P) = intrinsic rate and parasympathetic tone in absence of sympathetic tone. Then A —PA and P —PA reflect more accurately differences attributable to sympathetic and parasympathetic tone respectively. These differences are shown in Figure 3 for age groups 8 to 20 weeks of age. No such d a t a are available on 2 and 4 week old birds because administration of both drugs had drastic effects resulting in high mortality. I n general, the actual differences in A —PA and sympathetic tone are greatest a t 8 weeks of age and tend to show a
REFERENCES Adolph, E. ]"., and J. M. Ferrari, 1968. Adaptation to temperature in heart rates of salamander larvae before cardiac innervation. Am. J. Physiol. 215: 124-126. Ringer, R. K., P. D. Sturkie and H. S. Weiss, 1957. Heart rate of chickens as influenced by age and gonadal hormones. Am. J. Physiol. 191: 145-147.
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gradual decline at 12 and 16 weeks with no appreciable change afterward. T h e differences in parasympathetic tone as reflected by differences in the P —PA are not significantly different between age groups. T h e decrease in sympathetic tone was modest b u t not nearly as great as the total change or decrease in heart rate with age (Figure 1A). This suggests t h a t some of the decrease resulted from changes independent of nervous influence, or changes in intrinsic rate. Since heart rate after administration of both propranolol and atropine (PA) reflects intrinsic rate freed from nervous control, then changes in the rate after (PA) should reveal changes in intrinsic rate. Unfortunately we have no d a t a on PA rate at 2 and 4 weeks of age, b u t the change from 8 to 16 weeks indicates a modest decrease in intrinsic rate with age. In order to estimate change in intrinsic rate at 2 and 4 weeks and at other ages PA can be estimated as follows: PA = resting rate R - ( A - R + P - R ) . Estimates for most ages approach actual PA values although they tend to be higher. The relationship of these values to age are shown in Figure IB (sexes pooled). I t is apparent t h a t the decrease in intrinsic rate with age tends to parallel the decrease in resting rates. The fact t h a t intrinsic rate varies considerably between species indicates it is determined by non-neurogenic factors such as body temperature, hormones and metabolic state as has been reported by others (Adolph and Ferrari, 1968).
AGE AND HEART RATE Sturkie, P. D., Yu chong Lin and N. Ossorio, 1970. Effects of acclimatization to heat and cold on heart rate in chickens. Am. J. Physiol. 219:34-36. Tummons, J. L., and P. D. Sturkie. 1969. Nervous control of heart rate during excitement in the
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adult White Leghorn cock. Am. J. Physiol. 216: 1437-1440. Wekstein, D. R., 1965. Heart rate of the preweaning rat and its automatic control. Am. J. Physiol. 208: 1259-1261.
Inheritance of Plumage and Shank Color in Ring-necked Pheasants and Domestic Fowl Hybrids M. K. BHATNAGAR, B. S. REINHART AND F. N. JEROME Departments of Biomedical Sciences and A nimal and Poultry Science, University of Guelph, Guelph, Ontario, Canada (Received for publication September 21, 1971)
POULTRY SCIENCE 51: 911-915, 1972
T T HAS been conclusively established -*• by Punnett (1923) that in domestic fowl the plumage color gene for silver (S) and gold (s), and by Dunn (1925) that the expression of the dermal melanin gene (id) in the shanks are sex-linked traits. In studies conducted on museum specimens of chicken-pheasant hybrids, Serebrovsky (1929) noted that mutations dominant in the fowl were also dominant in the hybrids, and that sex-linked barring was transmitted to the hybrids as in the fowl. Observations on intergeneric hybrids by Danforth and Sandnes (1939), Shaklee and Knox (1954), and Asmundson and Lorenz (1957) for morphological traits confirmed the findings of Serebrovsky, although some of the reports are equivocal. This investigation was undertaken to study the mode of inheritance of certain characters in chicken-pheasant hybrids in addition to those reported by the investigators mentioned above. MATERIALS AND METHODS
Reciprocal matings between Ringnecked pheasants (Pkasianus colchicus)
and Columbian Plymouth Rock chickens (Gallus domesticus) were carried out by the artificial insemination of 12 Columbian Plymouth Rock (C.P.R.) hens with the semen from four Ring-necked pheasant (R.Ph.) males and 14 R.Ph. hens with the semen from four C.P.R. males. Inseminations were carried out two to three times weekly. On account of the small quantity of semen produced by R.Ph. males, it was found necessary to pool and dilute the semen with physiological saline (0.9%) for equal distribution to all C.P.R. hens. All the female and male pheasants, as well as the male chickens were maintained in wire cages. Chicken females were kept in a small floor pen. The eggs were held at 15°C. and set weekly in a forced air incubator. Fertility was checked by candling eggs after seven days of incubation. After hatching the hybrid chicks were brooded in batteries for three weeks and then moved to floor brooding. Observations for phenotypic characteristics were first made at three to four weeks, and then periodically until the hybrids were 12 months old.
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ABSTRACT Reciprocal crosses were made of Columbian Plymouth Rock chickens and Ring-necked pheasants to produce chicken-pheasant Fi hybrids. The mode of inheritance of plumage and shank color in the Fi hybrids was investigated. The data disclosed that in Ringnecked pheasants the genes responsible for gold plumage and for the expression of dermal melanin are sex-linked recessives and the gene responsible for white shanks is autosomal dominant and that all these genes behave similar to those of the fowl.