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The Influence of Maternal Effects on the Response of Fast and Slow Growing Chickens to a Marek’s Disease Virus1
N A AND CL REQUIREMENTS
ments of poultry. 6th revised ed. Nat. Acad. Sci., Washington, D.C. Nesheim, M. C , R. M. Leach, T. R. Zeigler and J. A. Serafin, 1964. Interrelationships between dietary levels of sodium, chlorine and potassium. J. Nutr. 84: 361-366. Nott, H., 1968. Studies with sodium, calcium, phosphorus and selenium in broiler feeds. Proc. Maryland Nutr. Conf. p. 30-34. Nott, H., and G. F. Combs, 1966. Sodium requirement of the chick. Poultry Sci. 48: 660-665. Savage, J. E., 1972. Amino acid and mineral interrelationships. Poultry Sci. 51: 35-43. Stutz, M. W., J. E. Savage and B. L. O'Dell, 1971. Relation of dietary cations to arginine-lysine antagonism and free amino acid patterns in chicks. J. Nutr. 101: 377-384.
The Influence of Maternal Effects on the Response of Fast and Slow Growing Chickens to a Marek's Disease Virus1 PETER F.-S. HAN 2 AND J. ROBERT SMYTH, J R . Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01002 (Received for publication August 18, 1972) ABSTRACT Reciprocal cross Fi progeny from the Massachusetts High (MH) and Low (ML) Growth lines differed markedly in their response to inoculation at one day of age with the J M Marek's disease (MD) virus. When the M H line was used as the female parent, the Fi progeny were both significantly heavier and more susceptible to MD at 8 weeks of age. A similar relationship between growth and MD susceptibility exists for the parent lines. Since growth rate is known to influence response to MD, the reciprocal crosses were compared at similar and reversed 8-week body weights by controlling feed intake for the heavier Fi group. At similar body weights the cross progeny of the MH dams were still more susceptible to MD infection. Therefore, the maternal effect associated with response to MD exposure is largely independent of the influence of body growth rate. The degree of dominance for susceptibility was also found to differ for the two groups of reciprocal cross progeny. POULTRY SCIENCE 52: 909-915,
T T IS now well established that a •*• chicken's response to exposure to Marek's disease viruses is greatly influenced by genetic factors (Cole, 1964, 1968; Payne and Biggs, 1964; Han el al., 1969; Stone el al., 1970; Zeitlin el al., 1972; Crittenden et al., 1972). The mode 1 Contribution of the Massachusetts Experiment Station, Amherst, Massachusetts 01002. 2 Present address: Department of Biology, Clark College, 240 Chestnut Street, S.W., Atlanta, Georgia 30314.
1973
of inheritance of resistance or susceptibility, however, has not been established at the present time. As pointed out by Zeitlin el al. (1972), the degree of dominance for response to Marek's disease (MD) can vary with the particular stocks crossed. Crittenden et al. (1972) have also shown that dominance can differ with the method of exposure to the viral agent. Reciprocal cross differences have also been demonstrated to occur, although they are not always apparent (Han et al.,
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
Cohen, I., S. Hurwitz and A. Bar, 1972. Acid-base balance and sodium-to-chloride ratio in diets of laying hens. J. Nutr. 102: 1-8. Hurwitz, S., and A. Bar, 1968. Regulation of pH in the intestine of the laying fowl. Poultry Sci. 47: 1029-1030. McWard, G. W., and H. M. Scott, 1960. The potassium and sodium requirement of the young chick fed a purified diet. Poultry Sci. 39: 1274. Miller, D., and J. H. Soares, Jr., 1972. Effect of mineral mixture composition on chick growth and intestinal pH's. Poultry Sci. 51: 182-189. Melliere, A. L., and R. M. Forbes, 1966. Effect of altering the dietary cation-anion ratio on food consumption and growth of young chicks. J. Nutr. 90: 310-314. National Research Council, 1971. Nutrient require-
909
910
P. F.-S. HAN AND J. R. SMYTH, J R .
MATERIALS AND METHODS
The JM strain of Marek's disease (MD) virus isolated by Sevoian el al. (1962) was used as the inoculum throughout this study. It was obtained as a frozen sample from the Cornell JM-pool. The standard dilution of the virus as received from the Cornell sample was 2X10 - 2 , with phosphate buffered saline containing 1000 units of penicillin and 10 mg. of streptomycin per ml. The experimental birds used in this study were the Massachusetts High (MH) and Low Growth (ML) lines. These two lines of White Plymouth Rocks originated from a single base population after being subjected for ten generations to intense two-way selection for high and low 8week body weight. This was followed by six generations of relaxed selection. The
birds used in this trial were from the sixteenth generation. These lines have been described in more detail by Han and Smyth (1972a). The experimental chickens were inoculated at one day of age by intra-abdominal injection of 0.25 ml. of the inoculum. Any clinical manifestations or mortality were recorded daily and all dead birds were examined for gross leukotic lesions by necropsy. The limited amount of mortality occurring without the appearance of gross leukotic lesions was not attributed to MD. At 8 weeks of age all survivors were sacrificed, sexed and examined for the presence of gross lesions. This included an examination of the visceral organs and the dorsal root ganglia (DRG) in the cervicothoracic region. The occurrence of one or more positive lesions was considered as evidence of suceptibility. Such a bird was included in the summaries under the "total lesions" category. Two experiments were conducted in the present study. In Experiment 1 a total of 600 chicks representing the MH and ML lines and their reciprocal Fi crossbred progeny were inoculated with JM virus. The main purposes of this experiment were to compare both the relative susceptibility of the two lines differing in growth rate and their reciprocal cross offspring. The two reciprocal crossbreds are designated as the L X H (ML maleXMH female) and H X L (MH maleXML female) groups. A subsequent hatch containing a similar number of progeny from these four matings served as an uninoculated control group, and were reared separately from the inoculated group. After the completion of Experiment 1, it was observed that the cross progeny of the MH dams were both heavier and more susceptible to MD than were those of the ML dams. Since the recent studies by Han and Smyth (1972a, b) have demon-
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
1969; Zeitlin el al, 1972; Crittenden et al., 1972). These appear to result from some maternal effect rather than sex-linked inheritance. The association of an identical maternal effect with two successive generations of a Brown Leghorn line (Han el al., 1969; Zeitlin et al., 1972) suggests that the causative maternal factor is itself genetically influenced. Two earlier reports by Han and Smyth (1972a, b) have shown that differences in growth rate, either genetic or induced by controlled feed intake, influence, the development of MD. In the present study the existence of maternal effects for both growth rate and resistance to MD was found for reciprocal cross progeny from two lines differing markedly in growth rate after long-term directional selection from a single base population. A study was then conducted to determine the relative contribution of the reciprocal growth rate difference to the observed maternal effect on the response to MD exposure.
911
MATERNAL EFFECTS AND MAREK'S DISEASE
The data were analyzed using the tech-
nique of least-squares analysis of variance for unequal subclass numbers by the method of fitting constants as described by Harvey (1960). Harvey's least-squares and maximum likelihood general purpose program as modified for a CDC-3600' computer by Woodman and Dickinson (1966) was used to solve the least-squares equations. EXPERIMENTAL RESULTS
Experiment 1. The response of the MH and ML lines and their Fi reciprocal crossbred progeny during an 8-week period following inoculation at one day of age with JM virus is shown in Table 1. The results of the analysis of variance are presented in Table 2. In agreement with a previous report (Han and Smyth, 1972a), the MH was significantly more susceptible to Marek's disease (MD) than the ML line. Statistically, the line difference was significant at the 0.005 probability level for all categories of comparison except for the incidence of gonadal lesions (P<0.01).
TABLE 1.—Response of the Massachusetts high {MH) and low {ML) grcnvth lines and their reciprocal Fi cross progeny to JM leukosis virus Percent incidence Matings
MHXMH
MLXMH
MHXML
MLXML 1 i
1
Sex
No.
Positive lesions
Mortality DRG
Gonads
Liver
Total 2
8 week body wt. g-
M F Total
70 72 142
11.4 36.1 23.9
42.8 54.2 48.6
15.7 31.9 23.9
11.4 13.9 12.7
44.3 58.3 51.4
1031
M F Total
67 70 137
19.4 42.8 31.4
43.3 57.1 50.4
17.9 40.0 29.2
10.4 15.7 13.1
49.3 64.3 57.9
715
M F Total
60 69 129
5.0 14.5 10.1
35.0 39.1 37.2
11.7 28.9 20.9
3.3 7.2 5.4
36.7 46.4 41.9
633
M F Total
58 56 114
1.7 7.1 4.4
15.5 17.8 16.7
6.9 14.3 10.5
3.4 1.8 2.6
17.2 21.4 19.3
249
Male parent listed first. Total includeg all birds with one or more positive lesions.
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strated a marked association between growth rate and Marek's disease development, the greater susceptibility of the L X H group over its reciprocal counterpart (HXL) could be all or in part related to its greater growth rate. In Experiment 2 an attempt was made to reduce the difference in growth rate between the two reciprocal cross progeny groups by restriction of total feed intake. To accomplish this, cross progeny from the MH females were restricted to two levels of the ad libitum intake, 90 and 80 percent. A total of 55 progency from the H X L mating and 165 progeny of the reciprocal cross (LXH) were challenged with the JM virus. The latter group was divided into three subgroups of 55 and each assigned to one of the three feed level treatments. A total of 340 birds representing the two reciprocal crossbreds were used as the uninoculated controls. These were maintained at an isolated location and weighted at 3, 6, and 8 weeks of age.
912
P. F.-S. HAN AND J. R. SMYTH, J R . TABLE 2.—Results of analysis of variance for Table 1 Mean Squares d.f.
Source
DRG
Gonads
Liver
Total
3.215f 2.364J 3.029| 0.519*
0.810 6.403t 1.145* 1.377f
3.212J 1.108f 0.493 0.714*
0.080 0.637J 0.402* 0.030
1.493* 6.463t 1.540f 2.473|
0.586* 0.332 0.006 0.131
0.127 0.157 0.015 0.223
0.123 0.038 0.201 0.160
0.026 0.003 0.056 0.079
0.154 0.047 0.034 0.226
t P < 0.005. JP<0.01. * P<0.05.
The two reciprocal cross groups showed a marked difference in their response to MD exposure (Table 1). When the MH line was used as the female parent, the cross progeny (LXH) showed a higher MD incidence. Statistically, the maternal effect was found to be significant for the incidence of mortality (P<0.005), "total lesions" (P<0.01) and positive lesions of DRG and liver (P<0.05). A maternal effect was also found for growth rate. The 8-week body weights obtained from the uninoculated control group showed that when the MH line was as the female parent (LXH), the crossbred progeny weighted on the average 82 grams more than their reciprocal counterparts (HXL). This difference was statistically significant at the 0.005 probability level. TABLE 3.-—Mean
Matings 1
1
There were statistically significant differences between the pureline and the cross progeny in respect to the incidence of mortality and gonadal lesion (P<0.05) as well as for lesions of DRG (P<0.01). A highly significant difference was also found for those having one or more lesions (P<0.005). Although the L X H progeny are slightly more susceptible than the pure MH line, the most pronounced difference was the greatly increased susceptibility of the H X L progeny compared with the pure ML group. There was no clinical sign of MD in the control group for Experiment 1, nor were any leukosis lesions found by necropsy at the end of the 8-week period. Experiment 2. In order to evaluate the importance of the growth weight differ-
body weights ± standard errors for the reciprocal cross progeny from the MH and ML lines at three different ages Mean (gms.) ± standard errors
Sex
No. 3-week
6-week
8-week
MLXMH
M F Total
79 86 165
173.0 + 3.3 169.1+3.2 171.1 + 2.3
492.3 + 9.1 446.6 + 8.7 469.4 + 6.3
827.0 + 14.0 705.0+13.4 766.8 + 9.7
ML XML
M F Total
77 88 165
143.3 + 3.4 134.6 + 3.1 139.9 + 2.3
415.0 + 9.2 383.2 + 8.6 399.1 + 6.3
722.9 + 14.2 638.9±13.2 680.9+ 9.6
Male parent listed first.
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Sex (S) Line within purebreds (L) (M) Maternal effects Purebreds vs. crossbreds (H) 2-Factor interactions SXL SXH SXM Error 514
Mortality
913
MATERNAL EFFECTS AND MAREK'S DISEASE TABLE 4.—Mean body weights of reciprocal cross progeny from the MB and ML lines under several levels of feed restriction Sex
MHXML (100%)
M F
25 22
713.5 619.7
MLXMH (100%)
M F
23 16
801.6 681.4
MLXMH (90%)
M F
25 13
701.6 603.4
MLXMH (80%)
M F
23 16
605.6 520.4
1
Mean 8-week No. body weight (g.)
Male parent listed first.
ences on the response of the reciprocal cross progeny to MD exposure, an experiment was designed to eliminate the size factor by controlling feed intake. The mean body weights and their standard errors for the reciprocal crossbred progeny of the non-restricted control population of the MH and ML lines are presented in Table 3. An analysis of variance shows that the L X H group was significantly heavier (P<0.005) than the H X L group
TABLE 5.—Response of the reciprocal Fi cross progeny from the MB and ML lines to JM virus under different levels of total feed intake Ma tings 1 (Restriction level)
Percent incidence Sex
No.
Positive lesions
Mortality DRG
Gonads
Liver
Total 2
MHXML (100%)
M F Total
26 25 51
3.9 12.0 7.9
23.1 36.0 29.5
11.5 24.0 17.8
0.0 4.0 2.0
26.9 40.0 33.3
MLXMH (100%)
M F Total
27 25 52
14.8 36.0 25.4
37.0 64.0 50.5
18.5 40.0 29.3
3.1 8.0 5.8
46.4 72.0 58.2
MLXMH (90%)
M F Total
28 24 52
10.7 45.8 28.3
25.0 50.0 37.5
21.4 33.3 27.4
7.1 4.1 5.6
35.7 66.7 51.2
MLXMH (80%)
M F Total
26 24 50
11.5 33.5 22.1
19.2 45.8 32.5
19.2 45.8 32.5
3.8 8.3 6.0
34.6 62.5 48.6
1 2
Male parent listed first. Total includes all birds with one or more positive lesions.
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Mating 1 (Restriction level)
at 3, 6, and 8 weeks of age. This confirms the previous observations that a maternal effect does exist in respect to body growth rate in reciprocal crosses between these two growth lines. The effect of the level of feed intake in this experiment was estimated by weighing the survivors of the injected groups. As shown in Table 4, 90% restriction level for the L X H progeny resulted in a mean body weight slightly below that of the progeny of the H X L cross, while the 80% restriction resulted in a substantial weight reduction below the H X L group mean. The response of the reciprocal crossbreds to the JM leukosis virus during the 8-week experimental period is presented in Table 5. Within the L X H progeny groups, the percent MD incidences in general decreased with the increase of restriction level; however, statistically the differences among the three levels of feed restriction are not significant at the 0.05 level. An analysis of variance for the data shown in Table 5 comparing only L X H progeny (100% restriction) with
914
P. F.-S. HAN AND J. R. SMYTH, JR.
In the uninoculated control group no mortality or clinical signs were observed prior to eight weeks of age that could be attributed to MD at the termination of the experiment. Of fifty birds from each of the two reciprocal crossbred groups sacrificed and examined, only one bird from the L X H group was found with a positive lesion, this a slight enlargement of ovary. DISCUSSION
This report describes a striking difference in response to MD exposure for the reciprocal cross progeny of two lines differing markedly in growth rate after ten generations of directional selection from a base population. This difference in
reciprocal cross performance is attributed to some maternal-associated factor rather than sex-linked inheritance. Evidence for involvement of sex-linkage in response to MD infection is not apparent in the present study. Similarly Zeitlin et al. (1972) found no consistent relationship between sex of offspring and response to the virus in reciprocal cross progeny, nor did the analyses of Crittenden et al. (1972) suggest sex-linkage. The actual basis for maternal effect on response to MD has not been determined as yet. The pure parent MH and ML lines also differ significantly in their response to MD with rapid growth rate (MH line) being associated with greater susceptibility and slow growth rate (ML line) showing a higher degree of resistance. As shown in Table 1, a similar relationship between growth rate and response to MD was present in the two groups of reciprocal cross progeny. This raised the question of the role of the reciprocal difference in growth rate on response to the JM virus. The elimination of the growth difference between the reciprocal cross progeny (Experiment 2) did not remove the maternal effect on resistance to MD. Therefore, although the studies of Han and Smyth (1972a, b) have established an important influence of body growth rate on response to MD exposure, the maternal effect associated with response to the disease for the M X L and L X M progeny are influenced by other factors. Although the specific body weight data have not been presented, the presence of a maternal effect for the reciprocal cross progeny from Brown Leghorns and Fayoumi (Han et al., 1969) involve parental stocks that do not differ significantly in growth rate. Maternal effects have been shown to be present in some reciprocal crosses but not in others. This can occur even when the
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H X L progeny (100% restriction) indicates that the cross progeny of the MH female (LXH) is significantly more susceptible than is the latter group (HXL) at the 0.05 probability level for the incidences of mortality and positive lesions of the DRG, and at the 0.01 probability level for those having one or more positive lesions regardless of location (classified as "total"). Analyses of variance for the comparisons of the H X L group (100%) versus the L X H (90%) and L X H (80%) groups show that in both cases cross progeny of the ML female (100%) still have significant lower incidences of mortality at least at the 0.05 level of probability. Although the rest of the comparisons were not statistically significant, the percent incidences (Table 5) suggest that the progeny of the slower growing dams (HXL) had a consistently lower MD incidence for all categories of comparison. These data indicate that there is a maternal effect on MD resistance for the reciprocal cross progeny of the two Massachusetts Growth lines that is independent of the maternal effect for rate of body growth.
MATERNAL EFFECTS AND MAREK'S DISEASE
It has been suggested by Han and Smyth (1972a) that the parent MH and ML lines utilized in this study differ in their response to MD infection through an interaction between general growth promoting factors and potential neoplasia. The data presented in this report on the performance of the reciprocal cross Fx progeny indicate that other factors may be involved in the pureline difference. For example, when the ML line is the female parent, the progeny are approximately intermediate to the parental lines in their level of susceptibility, suggesting incomplete dominance similar to that shown by Zeitlin el al. (1972). On the other hand, when the MH line is the female parent, susceptibility appears to be dominant. In fact, the cross progeny are more susceptible than the pure MH line, thereby demonstrating an example of negative heterosis, previously noted by Hutt and Cole (1952) and Han et al. (1969). In contrast to these results, resistance has more often appeared to be dominant (Stone el al, 1970; Cole, 1971), while Crittenden et al. (1972) concluded that dominance of resistance appears to depend on the
severity of exposure and the relative susceptibility of the lines involved. REFERENCES Cole, R. K., 1964. Strain differences in response to the J M leukosis virus. Poultry Sci. 43: 13081309. Cole, R. K., 1968. Studies on genetic resistance to Marek's disease. Avian Dis. 12: 9-28. Cole, R. K., 1971. The genetic resistance to Marek's disease. Paper presented at Symposium on Oncogenesis and Herpes-type Viruses, Cambridge, England, June, 1971. Abstract: 16. Crittenden, L. B., R. L. Muhm and B. R. Burmester, 1972. Genetic control of susceptibility to the avian leukosis complex. 2. Marek's disease. Poultry Sci. 51: 261-267. Han, P. F.-S., J. R. Smyth, Jr., M. Sevoianand F. N. Dickinson, 1969. Genetic resistance to leukosis caused by the JM virus in the fowl. Poultry Sci. 48: 76-87. Han, P. F.-S., and J. R. Smyth, Jr.,' 1972a. The influence of growth rate on the development of Marek's disease in chickens. Poultry Sci. 51: 975-985. Han, P. F.-S., and J. R. Smyth, Jr., 1972b. The influence of restricted feed intake on the response of chickens to Marek's disease. Poultry Sci. 51: 986-991. Harvey, W. R., 1960. Least-squares analysis of data with unequal subclass numbers. A.R.S. 20-8, U.S.D.A. 1-156. Hutt, F. B., and R. K. Cole, 1952. Heterosis in an interstrain cross of White Leghorns. Poultry Sci. 31:365-374. Payne, L. N., and P. M. Biggs, 1964. Transmission experiments with Marek's disease (fowl paralysis) and lymphoid leukosis. World's Poultry Sci. J. 20:284-297. Sevoian, M., D. M. Chamberlain and F. T. Counter, 1962. Avian lymphomatosis. I. Experimental reproduction of the neural and visceral forms. Vet. Med. 57: 500-501. Stone, H. A., E. A. Holly, B. R. Burmester and T. H. Coleman, 1970. Genetic control of Marek's disease. Poultry Sci. 49: 1441-1442. Woodman, J., and F. N. Dickinson, 1966. Harvey least-squares and maximum likelihood general purpose program. UM00011, Research Computing Center, University of Massachusetts. Zeitlin, G., J. R. Smyth, Jr. and M. Sevoian, 1972. Genetic response of the fowl to exposure to Marek's disease. Poultry Sci. 51: 602-608.
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parent stocks are reared simultaneously in brooding pens separated only by wire partitions, as has been the case in the Massachusetts studies of Han et al. (1969), Zeitlin et al. (1972), Han and Smyth (1972a) and the present study. Any natural exposure to MD should have been similar for the stocks used. If maternal effects are mediated through maternal antibodies, then there must be line specific, genetic differences associated with antibody production and/or transmission through the egg. This in turn appears to interact with the level and route of exposure to MD virus as suggested by the observations of Crittenden et al. (1972).
915
ments of poultry. 6th revised ed. Nat. Acad. Sci., Washington, D.C. Nesheim, M. C , R. M. Leach, T. R. Zeigler and J. A. Serafin, 1964. Interrelationships between dietary levels of sodium, chlorine and potassium. J. Nutr. 84: 361-366. Nott, H., 1968. Studies with sodium, calcium, phosphorus and selenium in broiler feeds. Proc. Maryland Nutr. Conf. p. 30-34. Nott, H., and G. F. Combs, 1966. Sodium requirement of the chick. Poultry Sci. 48: 660-665. Savage, J. E., 1972. Amino acid and mineral interrelationships. Poultry Sci. 51: 35-43. Stutz, M. W., J. E. Savage and B. L. O'Dell, 1971. Relation of dietary cations to arginine-lysine antagonism and free amino acid patterns in chicks. J. Nutr. 101: 377-384.
The Influence of Maternal Effects on the Response of Fast and Slow Growing Chickens to a Marek's Disease Virus1 PETER F.-S. HAN 2 AND J. ROBERT SMYTH, J R . Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01002 (Received for publication August 18, 1972) ABSTRACT Reciprocal cross Fi progeny from the Massachusetts High (MH) and Low (ML) Growth lines differed markedly in their response to inoculation at one day of age with the J M Marek's disease (MD) virus. When the M H line was used as the female parent, the Fi progeny were both significantly heavier and more susceptible to MD at 8 weeks of age. A similar relationship between growth and MD susceptibility exists for the parent lines. Since growth rate is known to influence response to MD, the reciprocal crosses were compared at similar and reversed 8-week body weights by controlling feed intake for the heavier Fi group. At similar body weights the cross progeny of the MH dams were still more susceptible to MD infection. Therefore, the maternal effect associated with response to MD exposure is largely independent of the influence of body growth rate. The degree of dominance for susceptibility was also found to differ for the two groups of reciprocal cross progeny. POULTRY SCIENCE 52: 909-915,
T T IS now well established that a •*• chicken's response to exposure to Marek's disease viruses is greatly influenced by genetic factors (Cole, 1964, 1968; Payne and Biggs, 1964; Han el al., 1969; Stone el al., 1970; Zeitlin el al., 1972; Crittenden et al., 1972). The mode 1 Contribution of the Massachusetts Experiment Station, Amherst, Massachusetts 01002. 2 Present address: Department of Biology, Clark College, 240 Chestnut Street, S.W., Atlanta, Georgia 30314.
1973
of inheritance of resistance or susceptibility, however, has not been established at the present time. As pointed out by Zeitlin el al. (1972), the degree of dominance for response to Marek's disease (MD) can vary with the particular stocks crossed. Crittenden et al. (1972) have also shown that dominance can differ with the method of exposure to the viral agent. Reciprocal cross differences have also been demonstrated to occur, although they are not always apparent (Han et al.,
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
Cohen, I., S. Hurwitz and A. Bar, 1972. Acid-base balance and sodium-to-chloride ratio in diets of laying hens. J. Nutr. 102: 1-8. Hurwitz, S., and A. Bar, 1968. Regulation of pH in the intestine of the laying fowl. Poultry Sci. 47: 1029-1030. McWard, G. W., and H. M. Scott, 1960. The potassium and sodium requirement of the young chick fed a purified diet. Poultry Sci. 39: 1274. Miller, D., and J. H. Soares, Jr., 1972. Effect of mineral mixture composition on chick growth and intestinal pH's. Poultry Sci. 51: 182-189. Melliere, A. L., and R. M. Forbes, 1966. Effect of altering the dietary cation-anion ratio on food consumption and growth of young chicks. J. Nutr. 90: 310-314. National Research Council, 1971. Nutrient require-
909
910
P. F.-S. HAN AND J. R. SMYTH, J R .
MATERIALS AND METHODS
The JM strain of Marek's disease (MD) virus isolated by Sevoian el al. (1962) was used as the inoculum throughout this study. It was obtained as a frozen sample from the Cornell JM-pool. The standard dilution of the virus as received from the Cornell sample was 2X10 - 2 , with phosphate buffered saline containing 1000 units of penicillin and 10 mg. of streptomycin per ml. The experimental birds used in this study were the Massachusetts High (MH) and Low Growth (ML) lines. These two lines of White Plymouth Rocks originated from a single base population after being subjected for ten generations to intense two-way selection for high and low 8week body weight. This was followed by six generations of relaxed selection. The
birds used in this trial were from the sixteenth generation. These lines have been described in more detail by Han and Smyth (1972a). The experimental chickens were inoculated at one day of age by intra-abdominal injection of 0.25 ml. of the inoculum. Any clinical manifestations or mortality were recorded daily and all dead birds were examined for gross leukotic lesions by necropsy. The limited amount of mortality occurring without the appearance of gross leukotic lesions was not attributed to MD. At 8 weeks of age all survivors were sacrificed, sexed and examined for the presence of gross lesions. This included an examination of the visceral organs and the dorsal root ganglia (DRG) in the cervicothoracic region. The occurrence of one or more positive lesions was considered as evidence of suceptibility. Such a bird was included in the summaries under the "total lesions" category. Two experiments were conducted in the present study. In Experiment 1 a total of 600 chicks representing the MH and ML lines and their reciprocal Fi crossbred progeny were inoculated with JM virus. The main purposes of this experiment were to compare both the relative susceptibility of the two lines differing in growth rate and their reciprocal cross offspring. The two reciprocal crossbreds are designated as the L X H (ML maleXMH female) and H X L (MH maleXML female) groups. A subsequent hatch containing a similar number of progeny from these four matings served as an uninoculated control group, and were reared separately from the inoculated group. After the completion of Experiment 1, it was observed that the cross progeny of the MH dams were both heavier and more susceptible to MD than were those of the ML dams. Since the recent studies by Han and Smyth (1972a, b) have demon-
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
1969; Zeitlin el al, 1972; Crittenden et al., 1972). These appear to result from some maternal effect rather than sex-linked inheritance. The association of an identical maternal effect with two successive generations of a Brown Leghorn line (Han el al., 1969; Zeitlin et al., 1972) suggests that the causative maternal factor is itself genetically influenced. Two earlier reports by Han and Smyth (1972a, b) have shown that differences in growth rate, either genetic or induced by controlled feed intake, influence, the development of MD. In the present study the existence of maternal effects for both growth rate and resistance to MD was found for reciprocal cross progeny from two lines differing markedly in growth rate after long-term directional selection from a single base population. A study was then conducted to determine the relative contribution of the reciprocal growth rate difference to the observed maternal effect on the response to MD exposure.
911
MATERNAL EFFECTS AND MAREK'S DISEASE
The data were analyzed using the tech-
nique of least-squares analysis of variance for unequal subclass numbers by the method of fitting constants as described by Harvey (1960). Harvey's least-squares and maximum likelihood general purpose program as modified for a CDC-3600' computer by Woodman and Dickinson (1966) was used to solve the least-squares equations. EXPERIMENTAL RESULTS
Experiment 1. The response of the MH and ML lines and their Fi reciprocal crossbred progeny during an 8-week period following inoculation at one day of age with JM virus is shown in Table 1. The results of the analysis of variance are presented in Table 2. In agreement with a previous report (Han and Smyth, 1972a), the MH was significantly more susceptible to Marek's disease (MD) than the ML line. Statistically, the line difference was significant at the 0.005 probability level for all categories of comparison except for the incidence of gonadal lesions (P<0.01).
TABLE 1.—Response of the Massachusetts high {MH) and low {ML) grcnvth lines and their reciprocal Fi cross progeny to JM leukosis virus Percent incidence Matings
MHXMH
MLXMH
MHXML
MLXML 1 i
1
Sex
No.
Positive lesions
Mortality DRG
Gonads
Liver
Total 2
8 week body wt. g-
M F Total
70 72 142
11.4 36.1 23.9
42.8 54.2 48.6
15.7 31.9 23.9
11.4 13.9 12.7
44.3 58.3 51.4
1031
M F Total
67 70 137
19.4 42.8 31.4
43.3 57.1 50.4
17.9 40.0 29.2
10.4 15.7 13.1
49.3 64.3 57.9
715
M F Total
60 69 129
5.0 14.5 10.1
35.0 39.1 37.2
11.7 28.9 20.9
3.3 7.2 5.4
36.7 46.4 41.9
633
M F Total
58 56 114
1.7 7.1 4.4
15.5 17.8 16.7
6.9 14.3 10.5
3.4 1.8 2.6
17.2 21.4 19.3
249
Male parent listed first. Total includeg all birds with one or more positive lesions.
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strated a marked association between growth rate and Marek's disease development, the greater susceptibility of the L X H group over its reciprocal counterpart (HXL) could be all or in part related to its greater growth rate. In Experiment 2 an attempt was made to reduce the difference in growth rate between the two reciprocal cross progeny groups by restriction of total feed intake. To accomplish this, cross progeny from the MH females were restricted to two levels of the ad libitum intake, 90 and 80 percent. A total of 55 progency from the H X L mating and 165 progeny of the reciprocal cross (LXH) were challenged with the JM virus. The latter group was divided into three subgroups of 55 and each assigned to one of the three feed level treatments. A total of 340 birds representing the two reciprocal crossbreds were used as the uninoculated controls. These were maintained at an isolated location and weighted at 3, 6, and 8 weeks of age.
912
P. F.-S. HAN AND J. R. SMYTH, J R . TABLE 2.—Results of analysis of variance for Table 1 Mean Squares d.f.
Source
DRG
Gonads
Liver
Total
3.215f 2.364J 3.029| 0.519*
0.810 6.403t 1.145* 1.377f
3.212J 1.108f 0.493 0.714*
0.080 0.637J 0.402* 0.030
1.493* 6.463t 1.540f 2.473|
0.586* 0.332 0.006 0.131
0.127 0.157 0.015 0.223
0.123 0.038 0.201 0.160
0.026 0.003 0.056 0.079
0.154 0.047 0.034 0.226
t P < 0.005. JP<0.01. * P<0.05.
The two reciprocal cross groups showed a marked difference in their response to MD exposure (Table 1). When the MH line was used as the female parent, the cross progeny (LXH) showed a higher MD incidence. Statistically, the maternal effect was found to be significant for the incidence of mortality (P<0.005), "total lesions" (P<0.01) and positive lesions of DRG and liver (P<0.05). A maternal effect was also found for growth rate. The 8-week body weights obtained from the uninoculated control group showed that when the MH line was as the female parent (LXH), the crossbred progeny weighted on the average 82 grams more than their reciprocal counterparts (HXL). This difference was statistically significant at the 0.005 probability level. TABLE 3.-—Mean
Matings 1
1
There were statistically significant differences between the pureline and the cross progeny in respect to the incidence of mortality and gonadal lesion (P<0.05) as well as for lesions of DRG (P<0.01). A highly significant difference was also found for those having one or more lesions (P<0.005). Although the L X H progeny are slightly more susceptible than the pure MH line, the most pronounced difference was the greatly increased susceptibility of the H X L progeny compared with the pure ML group. There was no clinical sign of MD in the control group for Experiment 1, nor were any leukosis lesions found by necropsy at the end of the 8-week period. Experiment 2. In order to evaluate the importance of the growth weight differ-
body weights ± standard errors for the reciprocal cross progeny from the MH and ML lines at three different ages Mean (gms.) ± standard errors
Sex
No. 3-week
6-week
8-week
MLXMH
M F Total
79 86 165
173.0 + 3.3 169.1+3.2 171.1 + 2.3
492.3 + 9.1 446.6 + 8.7 469.4 + 6.3
827.0 + 14.0 705.0+13.4 766.8 + 9.7
ML XML
M F Total
77 88 165
143.3 + 3.4 134.6 + 3.1 139.9 + 2.3
415.0 + 9.2 383.2 + 8.6 399.1 + 6.3
722.9 + 14.2 638.9±13.2 680.9+ 9.6
Male parent listed first.
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Sex (S) Line within purebreds (L) (M) Maternal effects Purebreds vs. crossbreds (H) 2-Factor interactions SXL SXH SXM Error 514
Mortality
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MATERNAL EFFECTS AND MAREK'S DISEASE TABLE 4.—Mean body weights of reciprocal cross progeny from the MB and ML lines under several levels of feed restriction Sex
MHXML (100%)
M F
25 22
713.5 619.7
MLXMH (100%)
M F
23 16
801.6 681.4
MLXMH (90%)
M F
25 13
701.6 603.4
MLXMH (80%)
M F
23 16
605.6 520.4
1
Mean 8-week No. body weight (g.)
Male parent listed first.
ences on the response of the reciprocal cross progeny to MD exposure, an experiment was designed to eliminate the size factor by controlling feed intake. The mean body weights and their standard errors for the reciprocal crossbred progeny of the non-restricted control population of the MH and ML lines are presented in Table 3. An analysis of variance shows that the L X H group was significantly heavier (P<0.005) than the H X L group
TABLE 5.—Response of the reciprocal Fi cross progeny from the MB and ML lines to JM virus under different levels of total feed intake Ma tings 1 (Restriction level)
Percent incidence Sex
No.
Positive lesions
Mortality DRG
Gonads
Liver
Total 2
MHXML (100%)
M F Total
26 25 51
3.9 12.0 7.9
23.1 36.0 29.5
11.5 24.0 17.8
0.0 4.0 2.0
26.9 40.0 33.3
MLXMH (100%)
M F Total
27 25 52
14.8 36.0 25.4
37.0 64.0 50.5
18.5 40.0 29.3
3.1 8.0 5.8
46.4 72.0 58.2
MLXMH (90%)
M F Total
28 24 52
10.7 45.8 28.3
25.0 50.0 37.5
21.4 33.3 27.4
7.1 4.1 5.6
35.7 66.7 51.2
MLXMH (80%)
M F Total
26 24 50
11.5 33.5 22.1
19.2 45.8 32.5
19.2 45.8 32.5
3.8 8.3 6.0
34.6 62.5 48.6
1 2
Male parent listed first. Total includes all birds with one or more positive lesions.
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Mating 1 (Restriction level)
at 3, 6, and 8 weeks of age. This confirms the previous observations that a maternal effect does exist in respect to body growth rate in reciprocal crosses between these two growth lines. The effect of the level of feed intake in this experiment was estimated by weighing the survivors of the injected groups. As shown in Table 4, 90% restriction level for the L X H progeny resulted in a mean body weight slightly below that of the progeny of the H X L cross, while the 80% restriction resulted in a substantial weight reduction below the H X L group mean. The response of the reciprocal crossbreds to the JM leukosis virus during the 8-week experimental period is presented in Table 5. Within the L X H progeny groups, the percent MD incidences in general decreased with the increase of restriction level; however, statistically the differences among the three levels of feed restriction are not significant at the 0.05 level. An analysis of variance for the data shown in Table 5 comparing only L X H progeny (100% restriction) with
914
P. F.-S. HAN AND J. R. SMYTH, JR.
In the uninoculated control group no mortality or clinical signs were observed prior to eight weeks of age that could be attributed to MD at the termination of the experiment. Of fifty birds from each of the two reciprocal crossbred groups sacrificed and examined, only one bird from the L X H group was found with a positive lesion, this a slight enlargement of ovary. DISCUSSION
This report describes a striking difference in response to MD exposure for the reciprocal cross progeny of two lines differing markedly in growth rate after ten generations of directional selection from a base population. This difference in
reciprocal cross performance is attributed to some maternal-associated factor rather than sex-linked inheritance. Evidence for involvement of sex-linkage in response to MD infection is not apparent in the present study. Similarly Zeitlin et al. (1972) found no consistent relationship between sex of offspring and response to the virus in reciprocal cross progeny, nor did the analyses of Crittenden et al. (1972) suggest sex-linkage. The actual basis for maternal effect on response to MD has not been determined as yet. The pure parent MH and ML lines also differ significantly in their response to MD with rapid growth rate (MH line) being associated with greater susceptibility and slow growth rate (ML line) showing a higher degree of resistance. As shown in Table 1, a similar relationship between growth rate and response to MD was present in the two groups of reciprocal cross progeny. This raised the question of the role of the reciprocal difference in growth rate on response to the JM virus. The elimination of the growth difference between the reciprocal cross progeny (Experiment 2) did not remove the maternal effect on resistance to MD. Therefore, although the studies of Han and Smyth (1972a, b) have established an important influence of body growth rate on response to MD exposure, the maternal effect associated with response to the disease for the M X L and L X M progeny are influenced by other factors. Although the specific body weight data have not been presented, the presence of a maternal effect for the reciprocal cross progeny from Brown Leghorns and Fayoumi (Han et al., 1969) involve parental stocks that do not differ significantly in growth rate. Maternal effects have been shown to be present in some reciprocal crosses but not in others. This can occur even when the
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H X L progeny (100% restriction) indicates that the cross progeny of the MH female (LXH) is significantly more susceptible than is the latter group (HXL) at the 0.05 probability level for the incidences of mortality and positive lesions of the DRG, and at the 0.01 probability level for those having one or more positive lesions regardless of location (classified as "total"). Analyses of variance for the comparisons of the H X L group (100%) versus the L X H (90%) and L X H (80%) groups show that in both cases cross progeny of the ML female (100%) still have significant lower incidences of mortality at least at the 0.05 level of probability. Although the rest of the comparisons were not statistically significant, the percent incidences (Table 5) suggest that the progeny of the slower growing dams (HXL) had a consistently lower MD incidence for all categories of comparison. These data indicate that there is a maternal effect on MD resistance for the reciprocal cross progeny of the two Massachusetts Growth lines that is independent of the maternal effect for rate of body growth.
MATERNAL EFFECTS AND MAREK'S DISEASE
It has been suggested by Han and Smyth (1972a) that the parent MH and ML lines utilized in this study differ in their response to MD infection through an interaction between general growth promoting factors and potential neoplasia. The data presented in this report on the performance of the reciprocal cross Fx progeny indicate that other factors may be involved in the pureline difference. For example, when the ML line is the female parent, the progeny are approximately intermediate to the parental lines in their level of susceptibility, suggesting incomplete dominance similar to that shown by Zeitlin el al. (1972). On the other hand, when the MH line is the female parent, susceptibility appears to be dominant. In fact, the cross progeny are more susceptible than the pure MH line, thereby demonstrating an example of negative heterosis, previously noted by Hutt and Cole (1952) and Han et al. (1969). In contrast to these results, resistance has more often appeared to be dominant (Stone el al, 1970; Cole, 1971), while Crittenden et al. (1972) concluded that dominance of resistance appears to depend on the
severity of exposure and the relative susceptibility of the lines involved. REFERENCES Cole, R. K., 1964. Strain differences in response to the J M leukosis virus. Poultry Sci. 43: 13081309. Cole, R. K., 1968. Studies on genetic resistance to Marek's disease. Avian Dis. 12: 9-28. Cole, R. K., 1971. The genetic resistance to Marek's disease. Paper presented at Symposium on Oncogenesis and Herpes-type Viruses, Cambridge, England, June, 1971. Abstract: 16. Crittenden, L. B., R. L. Muhm and B. R. Burmester, 1972. Genetic control of susceptibility to the avian leukosis complex. 2. Marek's disease. Poultry Sci. 51: 261-267. Han, P. F.-S., J. R. Smyth, Jr., M. Sevoianand F. N. Dickinson, 1969. Genetic resistance to leukosis caused by the JM virus in the fowl. Poultry Sci. 48: 76-87. Han, P. F.-S., and J. R. Smyth, Jr.,' 1972a. The influence of growth rate on the development of Marek's disease in chickens. Poultry Sci. 51: 975-985. Han, P. F.-S., and J. R. Smyth, Jr., 1972b. The influence of restricted feed intake on the response of chickens to Marek's disease. Poultry Sci. 51: 986-991. Harvey, W. R., 1960. Least-squares analysis of data with unequal subclass numbers. A.R.S. 20-8, U.S.D.A. 1-156. Hutt, F. B., and R. K. Cole, 1952. Heterosis in an interstrain cross of White Leghorns. Poultry Sci. 31:365-374. Payne, L. N., and P. M. Biggs, 1964. Transmission experiments with Marek's disease (fowl paralysis) and lymphoid leukosis. World's Poultry Sci. J. 20:284-297. Sevoian, M., D. M. Chamberlain and F. T. Counter, 1962. Avian lymphomatosis. I. Experimental reproduction of the neural and visceral forms. Vet. Med. 57: 500-501. Stone, H. A., E. A. Holly, B. R. Burmester and T. H. Coleman, 1970. Genetic control of Marek's disease. Poultry Sci. 49: 1441-1442. Woodman, J., and F. N. Dickinson, 1966. Harvey least-squares and maximum likelihood general purpose program. UM00011, Research Computing Center, University of Massachusetts. Zeitlin, G., J. R. Smyth, Jr. and M. Sevoian, 1972. Genetic response of the fowl to exposure to Marek's disease. Poultry Sci. 51: 602-608.
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parent stocks are reared simultaneously in brooding pens separated only by wire partitions, as has been the case in the Massachusetts studies of Han et al. (1969), Zeitlin et al. (1972), Han and Smyth (1972a) and the present study. Any natural exposure to MD should have been similar for the stocks used. If maternal effects are mediated through maternal antibodies, then there must be line specific, genetic differences associated with antibody production and/or transmission through the egg. This in turn appears to interact with the level and route of exposure to MD virus as suggested by the observations of Crittenden et al. (1972).
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