Fifteen Years of Selection for Viability in White Leghorns*

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F. MOULTRIE, D. F. KING AND G. J. COTTIER

Neumer, J., and L. R. Dugan, 1952. The use of antioxidants in dry dog food. Food Tech. (in press). Pearson, P. B., and F. Panzer, 1949. The effect of fat in the diet of rats on their growth and their excretion of amino acids. J. Nutrition, 38: 257265. Reiser, R., and P. B. Pearson, 1949. The influence

of high levels of fat with suboptimal levels of riboflavin on the growth of chicks. J. Nutrition, 38: 247-256. Siedler, A., and B. S. Schweigert, 1952. The effect of the level of fat in the diet on the performance of dogs. J. Nutrition, 48:81-90. Slover, H., and L. R. Dugan, 1952. Unpublished data.

FRED MOULTRIE, D. F. KING AND G. J. COTTIER Alabama Agricultural Experiment Station, Auburn, Alabama (Received for publication September 29. 1952)

T

HE existence of genetic differences in resistance to specific diseases of chickens has been reported by many investigators. Likewise, selective breeding for general viability has been practiced with a fair degree of success by several workers. The pertinent information concerning work in these fields has been reviewed by Hutt (1949) and Jull (1952) and will not be covered thoroughly in this report. Briefly, however, diseases for which genetic resistance has been reported include avian diphtheria (Frateur, 1924), pullorum (Roberts and Card, 1926, 1935; DeVolt et ah, 1941), fowl typhoid (Lambert and Knox, 1928, 1932 a, 1932 b), leucosis (Asmundson and Biely, 1932; Gildow et ah, 1940; Hutt et ah, 1941; Jeffery et al., 1942; Taylor et ah, 1943; Waters, 1945; Hutt and Cole, 1947, 1948; and others), "blue comb" disease (Cole, 1950) and a respiratory disease tentatively diagnosed as atypical infectious coryza (Lerner et ah, 1950). Reduced mortality during the laying period as a result of selective breeding for general viability has been reported by Taylor and Lerner (1938), Marble (1939), Bearse et ah, * This project was under the supervision of C. D. Gordon from 1935 to 1939 and P. D. Sturkie from 1939 to 1944.

(1939), Sturkie (1943), Bostian and Dearstyne (1944), Bryant (1946) and others. A study to determine the feasibility of decreasing mortality in adult chickens by breeding strains resistant to diseases and disorders was started at the Alabama Agricultural Experiment Station in 1935. The exposure to pathogenic agents at this station is quite severe as is evident in reports by Sturkie (1943), King and Cottier (1948) and King et al. (1952). In the first publication on the breeding project, Sturkie (1943) reported that, as a result of five years' selection, adult mortality in a White Leghorn flock decreased from 89 percent in 1935 to 27 percent in 1940, and death loss from leucosis decreased from approximately two-thirds of all deaths in 1935 and 1936 to less than 14 percent in 1940. Since Sturkie's (1943) report, the results of ten additional years of selection have been completed and are herein reported along with some of the results of the first five years so as to present an over-all picture of the project from the beginning. The resistant strain produced by this project has been known for several years as the "Auburn Strain" and will be referred to as such throughout this report.

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Fifteen Years of Selection for Viability in White Leghorns

SELECTION EOR VIABILITY IN LEGHORNS

EXPERIMENTAL PROCEDURE

than 0.375, and the average coefficients of inbreeding for the several early flocks were considerably below this figure. Close inbreeding has been generally avoided since 1944. From 16 to 24 pedigree breeding pens were utilized annually in the production of from 3,000 to 4,000 chicks. Generally, there was one hatch each week from about the middle of January until the first of April. Natural exposure was provided by brooding chicks within 100 feet of adult stock until 8 weeks of age at which time all pullets and breeding cockerels were placed on a range that was operated on a three-year rotation plan. All pullets were placed in laying houses at approximately 5 months of age. Artificial lighting was used when necessary to provide 14 hours of light per day. Prior to 1944, a pullet's laying year started when she laid her first egg and ended one year later; however, after 1944, the pullet's laying year started at 156 days of age, whether laying or not laying, and ended one year later or at 520 days of age. Egg production figures prior to 1940 were obtained by continuous daily trapnesting; after that date data were computed from trap-nest records for 5 days per week. All chicks, growing pullets and laying hens that died before the end of the first laying year were autopsied. Culling was practiced only with the first three selected generations (1936, 1937, 1938). Cockerels, except those selected for possible breeders, were disposed of at 10 weeks of age, and only females were considered in the mortality records. In both 1946 and 1947, five of the outstanding White Leghorn strains in Alabama were introduced for performance tests with the Auburn Strain bred for resistance to disease. This procedure was repeated in 1948 with four strains from outstanding White Leghorn breeders in the

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Details of procedure during the early years of the study were given by Sturkie (1943) and are repeated here only in part so as to explain changes in management subsequent to his report. The primary objective of the experiment, as outlined in 1935, was the development of strains of fowl resistant to leucosis; however, by 1943 mortality from this disease complex had declined to only a small fraction (10 percent) of the total mortality. Thus, in that year the project was revised with a new objective of breeding for general viability, but with particular emphasis upon selection for resistance to the disease or disorder causing the most deaths. Foundation stock for the resistant strain was obtained from seven of the outstanding White Leghorn entries of the 1934 Alabama Egg Laying Contest. Birds from four additional strains were introduced later; however, breeding has been on a closed-flock basis since 1941. Criteria of selection were viability during the growing and laying periods, egg production, body weight, egg size, fertility, and hatchability. None of the breeders used in 1935 had been progeny tested; therefore, the flock hatched in that year was considered as an unselected population. In 1936, old hens and sibtested pullets, tested 4 to 6 months, were used in the breeding pens. Subsequent generations were produced from progenytested and sib-tested dams, most of which were old hens. About one-fourth of the males used each year after 1936 were progeny-tested cocks; the others were cockerels from proven sires and dams. Considerable inbreeding was practiced prior to 1944; many sib and half-sib ma tings were made during that time; however, very few chicks were produced that had inbreeding coefficients greater

455

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F. MOULTRIE, D. F. KING AND G. J. COTTIER

United States. The stock was obtained in 1946 and 1947 as day-old chicks (200 from each breeder). For the 1948 test, one case of eggs was obtained from each of the four breeders. These chicks for performance tests were housed from 1 day of age until the end of the laying year with birds of the Auburn Strain. Thus, they received the same management and exposure throughout the tests. Mortality. The results of selection for viability during the laying period expressed as percentage of mortality are shown graphically in Figure 1. Culling was practiced in 1936, 1937, and 1938. Since the birds were culled because of their condition, it is likely that most of those removed during those years would have died before completing the laying year; thus, culled birds are considered in this report as mortality.

1935

1940

YEAR

1945

1950

FIG. 1. Adult mortality of White Leghorn strain selected for viability. A few birds culled due to their condition in 1936, 1937 and 1938 are included as mortality.

The mortality of unculled pullets during the 16-year period decreased from 89 percent in 1935 to 14 percent in 1950. The decrease in percentage of mortality was consistent during the first 5 years of the experiment; however, this decrease was followed by 3 years (1941-1943) of increasing mortality. The exact cause of the

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RESULTS

increased mortality during these wartime years has not been determined, but inferior quality of feed and adverse management conditions due to inefficient and irresponsible labor could have been contributing factors. It is also of interest that more inbreeding was practiced during those years than in any other corresponding period of the experiment. Again during the 8-year period from 1943 to 1950, inclusive, there was a consistent decrease in mortality, except for one year, 1948, when mortality increased 4 percent over the preceding year. The increased mortality of the 1948 flock can be explained by a severe outbreak of blue comb disease that killed 6.7 percent of pullets housed and accounted for 30.6 percent of the total mortality of that year. Yearly percentage of adult mortality from 1944 to 1950 inclusive, according to the most important diseases and disorders are presented in Table 1. It should be pointed out that the decreased mortality of the 1949 and 1950 flocks was not due to more careful selection of pullets at the time of housing as might be surmised from the decreased number of pullets housed in these years. Selection of pullets for testing in these 2 years, in so far as possible, was the same as in previous years. In general, most of the diseases and disorders listed were prevalent each year. The one most obvious exception was blue comb disease in 1948, and it is of considerable interest that reproductive disorders, which were usually numerous, were practically absent that year. As the blue comb deaths occurred soon after the pullets were housed and before high mortality is usually encountered, it is possible that the birds susceptible to reproductive disorders were the ones eliminated by the outbreak of blue comb. The importance of leucosis in the flock

457

SELECTION FOR VIABILITY IN LEGHORNS

TABLE 1.—Total adult mortality and percentage of total mortality according to cause, 1944-1950 1944

1945

1946

1947

1948

1949

1950

Total and Av.

No pullets housed No. died

1,322 516

1,154 369

1,154 254

1,499 270

1,159 255

950 156

548 77

7,786 1,897

Percent mortality

39.03

31.98

22.01

18.01

22.00

16.42

14.05

24.36

37.8 13.4 1.9 11.5 5.8 5.1 1.9

26.0 26.0 6.5 6.5 3.9 3.9 10.4

22.3 13.8 10.3 8.1 6.8 6.4 4.7 4.1 3.7 19.8

Year of hatch

Percentage of total mortality by cause 11.2 19.2 14.9 8.7 7.9 9.9 5.0

—

0.2 22.7

12.7 15.4 12.5 10.3 8.7 2.4 6.2

—

2.7 28.5

28.3 14.6 7.1 3.9 9.1 4.7 5.5

38.2 9.2 11.8 10.7 5.5 10.3 3.3

.—•

—

9.4 17.7

during the first 5 years of the study was discussed by Sturkie (1943). A large part of the tremendous decrease in adult mortality during the first few years of the study was due to a decline in the number of deaths resulting from this disease. Death loss from leucosis is still the most serious disease problem within the flock; during the 7-year period (1944-1950) this disease, primarily the visceral form, accounted for 22.3 percent of all adult mortality. A summary of adult mortality due to leucosis since 1935 is presented in Figure 2. Mortality from this disease decreased from about two-thirds of all deaths in 1935 and 1936 to 14 percent in 1940, but calculated as percentage of total mortality there has been no definite trend since the latter date. Death loss from leucosis calculated on a pullet-housed basis decreased from 58.7 percent in 1935 to 3.7 percent in 1950, but with little variation since 1938. The range for the period 1938-1950, inclusive, was from 7.5 percent of pullets housed in 1939 to 3.7 percent in 1950. Egg Production. First-year egg production calculated for survivors and for

2.2 8.7

24.3 1.2 5.5 3.1 2.4 4.3 2.4 30.6 8.2 18.0

— —

—

5.1 16.7

15.4

pullets housed is summarized in Figure 3. Average egg production per survivor decreased slightly during the 16-year study. However, it must be kept in mind that only 11 percent of pullets housed survived to the end of the laying year in 1935 whereas 86 percent survived in 1950. Average production per pullet housed increased from 64 eggs in 1935 to 195 eggs in 1950. This difference of 131 eggs per pullet housed would be even more pronounced had the method of calculating first-year egg production been consistent throughout the study. In Figure 3, the break in the graphs at 1943 indicates a change in the method of calculating first80 - % OF TOTAL

<60

MORTALITY

% OF PULLETS

HOUSED

o s 40 ;Z0-

1935

1940

1945

1950

YEAR

FIG. 2. Adult mortality due to leucosis in White Leghorn strain selected for viability.

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Leucosis Reproductive Nephritis Respiratory Internal hemorrhage Hepatitis Visceral gout Blue comb Cannibalism Miscellaneous

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F. MOULTRIE, D. F. KING AND G. J. COTTIER

year egg production. Through 1943 a pullet's laying year started when she laid her first egg and ended one year later. However, beginning with 1944 the laying year was from 156 to 520 days of age. The former system, therefore, was more favorable for late-maturing pullets. 250

1935

1940

1945

1950

YEAR

FIG. 3. First-year egg production of strain selected for viability. Prior to 1944, the first year ended 365 days after first egg; during other years, the first year was from 156 to 520 days of age.

Performance Tests with Leading Strains. A summary of mortality and egg production of the three performance tests is presented in Table 2. Considering all 3 years of the tests, the Auburn Strain had slightly lower growing mortality than the average

TABLE 2.—Results of performance tests conducted in 1946-1948* Production (average no. eggs per)

Mortality (%) S train f

Growing

1946

1947

1948

1946

1947

1948

65 55 44 56

208 172 177 167 164

197 172 184 188 183

195 160 164 202

146 128 90 114 74

147 148 118 147 137

94 88 108 117

57 27

177 212

185 202

179 191

108 180

140 176

99 144

1948 1946 1947 1948

1946

1947

A B C D E

13 33 37 38 27

5 7 13 20 10

23 40 28 29

40 37 71 47 82

48 29 69 41 49

Average Auburn

29 13

11 11

32 27

56 22

47 18

Pullet housed

Survivor

Adult

* Tests in 1946 and 1947 were to 520 days of age; the 1948 test was to 490 days of age. f Strains in 1946 and 1947 were outstanding Alabama strains; those of 1948 were from well-known Leghorn breeders from different sections of the United States.

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of the introduced strains. Furthermore, in adult mortality, the strain excelled the average of the introduced strains (had lower mortality) in 1946, 1947, and 1948 by 34, 29, and 30 percent, respectively. An analysis of adult mortality of the introduced strains according to specific diseases revealed that over the three-year period leucosis accounted for 21.5 percent of all deaths. As percentage of all mortality this was almost the same figure (22.3) as presented previously in Table 1 for a seven-year average (1944-1950) of mortality from leucosis in the Auburn Strain. But as the mortality was consistently much higher in the introduced strains than in the Auburn Strain it is evident that losses from leucosis, on a pullet-housed basis, were more severe in the introduced strains. In egg production, on a survivor basis, the Auburn Strain excelled the average of the introduced strains in 1946, 1947, and 1948 by 35, 17, and 12 eggs, respectively. Of the 14 strains tested only 2 strains (A and D of 1948) laid more eggs per survivor than the Auburn Strain. On a pullet-housed basis, however, where mortality influenced first-year production, the differences in favor of the Auburn Strain for 1946, 1947, and 1948 were 72,

SELECTION FOR VIABILITY IN LEGHORNS

The performance of Strain D of the 1948 test was particularly interesting. This strain has compiled many excellent records in official egg-laying contests throughout the United States and was the outstanding egg producer of the four strains introduced for the 1948 test. However, as shown in Figure 1, Strain D died at the rate of 39 percent during the growing period and 56 percent in the laying house. Because of its egg-producing ability, Strain D has been maintained as a pure strain since 1948 and has responded to selection for viability. Adult mortality in this strain decreased from 56 percent in 1948 to 32 percent of pullets housed in 1950. However, adult mortality of the strain in 1950 was 18 percent greater than the 14 percent mortality of the Auburn Strain birds hatched and housed with them. These facts concerning Strain D are mentioned merely to point out the apparent severity of exposure at this station. DISCUSSION

I t is evident from the foregoing results that by selective breeding a strain of White Leghorns has been developed that has considerable resistance to disease. It is realized that many advances have been

made in the fields of nutrition and therapeutics during the course of this study, and it is probable that these advances influenced the data presented here. The increased resistance to disease (shown as a decrease in mortality in Figure 1), if influenced by these factors, would be more apparent than real. However, it is believed that improvements in feeding and therapeutic methods have exerted only minor influences on adult mortality since an effort has been made to keep the year-toyear variations in feeding at a minimum. Furthermore, therapeutic methods, particularly with the laying flock, have been used only to a limited extent since most deaths have resulted from diseases and disorders for which therapeutic methods are not available (Table 1). With the exception of the blue comb outbreak of 1948, no epidemics occurred in the laying flocks. The performance tests demonstrated that in the same environment the Auburn Strain had a significantly lower adultmortality than the introduced strains. I t is recognized that the performance of a transferred strain is sometimes considerably below its performance in its native environment (Hutt, 1949), but this is not always true as shown by King, Cole, Hutt and Cottier (1952) by performance tests of resistant strains developed approximately 800 miles apart and exchanged for testing. Their work demonstrated that strains selected for resistance to leucosis at the New York (Cornell) Station were also resistant at the Alabama (Auburn) Station; likewise, the strain developed at Auburn was found to be resistant at both stations. In fact, in that test, the Auburn Strain's performance at Cornell was superior in both livability and egg production to its performance in its native environment. I t should be noted also that each of the

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36, and 45 eggs, respectively, and none of the strains tested equalled the resistant strain. Other comparisons of performance showed that over the 3-year period the Auburn Strain pullets matured 9 days earlier than the introduced strains (184 days as compared to 193 days of age). There was little difference in January egg weights; the average of the Auburn Strain was 56.5 gm. as compared to 56.7 gm. for introduced strains. In adult body weight taken in January, the introduced strains were slightly heavier, averaging 4.33 pounds as compared to 4.24 pounds for the Auburn Strain.

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F. MOULTRIE, D. F. KING AND G. J. COTTIER

Unfortunately neither a susceptible strain nor an unselected population was maintained throughout the course of this study. Such flocks would have added materially to this study in determining severity of exposure, but they would have been expensive to maintain, and with facilities limited, would have reduced the size of the resistant flock, thereby causing a reduction in selection pressure of that strain. As there was neither a susceptible strain nor an unselected population to serve as an experimental control, the question arises, has there occurred a great reduction in exposure that is reflected as an increase in viability? Average adult mortality of over 50 percent for the 14 strains introduced for performance tests

in 1946, 1947, and 1948 would suggest that there has been little reduction in exposure in recent years. Other strains of White Leghorns and several strains of heavy breeds maintained at this station but not considered in this report have experienced similar high mortality and, thus, lend additional support to this belief. SUMMARY

In an environment with severe exposure to pathogenic agents, a strain of white Leghorns selected concurrently for viability and superiority in other productive traits has shown a decrease in adult mortality of unculled pullets from 89 percent in 1935 to 14 percent in 1950. During the same period, mortality due to leucosis decreased from 58.7 to 3.7 percent of pullets housed. Accompanying the increase in liability was an increase in first-year egg production (pullet-housed basis) from 64 eggs per bird in 1935 to 195 eggs per bird in 1950. In 3 years of performance tests utilizing 10 local (Alabama) strains (1946 and 1947) and four outstanding United States strains (1948), the strain selected for viability (Auburn) excelled the average of the introduced strains in livability by 34, 29, and 30 percent, respectively. On a pullet-housed basis, the resistant strain excelled the introduced strains in egg production during the 3 years of the performance tests by 72, 36, and 45 eggs per bird, respectively. REFERENCES Asmundson, V. S., and J. Biely, 1932. Inheritance of resistance to fowl paralysis {Neurolymphomatosis gallinarum). I. Differences in susceptibility. Canadian J. Res. 6: 171-175. Bearse, G. E., C. F. McClary and W. W. Miller, 1939. The results of eight years' selection for disease resistance and susceptibility in White Leghorns. Poultry Sci. 18: 400-401. Bostian, C. H., and R. S. Dearstyne, 1944. The influ-

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10 Alabama strains introduced in 1946 and 1947 traveled a maximum of 200 miles and experienced climatic conditions differing little from those of their native farms; thus, their high adult mortality could hardly be attributed to climate for which they were not adapted. Jull (1952) in discussing the 89 percent adult mortality of the unselected population housed during the first year of this study mentioned that the flock of White Leghorns must have been a notoriously poor flock or perhaps suffered from some kind of epidemic. It should be pointed out that in the opinion of the authors neither of these suppositions is correct. As mentioned previously and shown in Figure 2, approximately two-thirds of all deaths in 1935 were due to leucosis, which, in general, distributed mortality over the entire year. The parents of the 1935 flock had not suffered severe adult mortality during their year in the 1934 Alabama Egg Laying Contest. However, they were •shipped from various parts of the United States as mature pullets and had not been exposed to the environment of the Alabama Agricultural Experiment Station Poultry Farm as growing pullets.

461

NEWS AND NOTES

King, D. F., and G. J. Cottier, 1948. Comparative performance of the Auburn Strain of White Leghorn. Alabama Agr. Exp. Sta. Progress Report Series No. 38:1-4. Lambert, W. V., and C. W. Knox, 1928. The inheritance of resistance to fowl typhoid in chickens. Iowa State College J. Sci. 2: 179-187. Lambert, W. V., and C. W. Knox, 1932a. Natural resistance to disease in the chicken: I. The effect of selective breeding on natural resistance to fowl typhoid. J. Immunol. 23: 229-240. Lambert, W. V., and C. W. Knox, 1932b. Selection for resistance to fowl typhoid in the chicken with reference to its inheritance. Iowa Agr. Exp. Sta. Res. Bull. 153:262-295. Lerner, I. M., L. W. Taylor and J. R. Beach, 1950. Evidence for genetic variation in resistance to a respiratory infection in chickens. Poultry Sci. 29: 862-869. Marble, D. R., 1939. Breeding poultry for viability. Pennsylvania Agr. Exp. Sta. Bull. 377. Roberts, E., and L. E. Card, 1926. The inheritance of resistance to bacillary white diarrhea. Poultry Sci. 6: 18-23. Roberts, E., and L. E. Card, 1935. Inheritance of resistance to bacterial infection in animals: A genetic study of pullorum disease. Illinois Agr. Exp. Sta. Bull. 419. Sturkie, P. D., 1943. Five years of selection for viability in White Leghorn chickens. Poultry Sci. 22: 155-160. Taylor, L. W., I. M. Lerner, K. B. DeOme and J. R. Beach, 1943. Eight years of progeny-test selection for resistance and susceptibility to lymphomatosis. Poultry Sci. 22: 339-347. Waters, N . F., 1945. Breeding for resistance and susceptibility to avian lymphomatosis. Poultry Sci. 24:259-269.

NEWS AND NOTES {Continued from page 414) and Egg Association, United States Record of Performance Association and Utah Poultry and Farmers Cooperative, elected the following officers at the annual meeting held in January in Chicago: President—W. S. Grotewold, Lake Mills, Iowa; First Vice-President—C. Housh, Elkton, Virginia; and Secretary-Treasurer—A. Van Wagenen, 11 West State Street, Trenton, New Jersey. The National Poultry Producers' Federation is located at 15 West 10th St., Kansas City 5, Missouri.

U.S.D.A. NOTES The Secretary of Agriculture, E, T. Benson, has announced the appointment of C. M. Ferguson of Columbus, Ohio, as Director of the Federal Extension Service. The new director was born on a farm at Parkhill, Ontario, Canada and graduated from the Ontario Agricultural College in 1921. From 1922 to 1928, he was Extension Poultry Specialist at Michigan State College. He spent the year 1928 in Bogota, Colom-

{Continued on page 475)

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ence of breeding on the livability of poultry. North Carolina Agr. Exp. Sta. Tech. Bull. 79. Bryant, R. L., 1946. Breeding Leghorn chickens to increase the life span. Virginia Agr. Exp. Sta. Tech. Bull. 99. Cole, R. K., 1950. Differences in familial incidence of mortality from "blue comb" disease. Poultry Sci. 29: 398-404. DeVolt, H. M., G. D. Quigley and T. C. Byerly, 1941. Studies of resistance to pullorum disease in chickens. Poultry Sci. 20: 339-341. Frateur, J. L., 1924. The hereditary resistance of the fowl to the bacillus of diphtheria. Proc. World's Poultry Congr. 2nd. congr., Barcelona: 68-71. Gildow, E. M., J. K. Williams and C. E. Lampman, 1940. The transmission of and resistance to fowl paralysis (Lymphomatosis). Idaho Agr. Exp. Sta. Bull. 235. Hutt, F. B., 1949. Genetics of the Fowl. New York. McGraw-Hill Book Co., Inc. Hutt, F. B., and R. K. Cole, 1947. Genetic control of lymphomatosis in the fowl. Science 106:379-384. Hutt, F. B., and R. K. Cole, 1948. The development of strains genetically resistant to avian lymphomatosis. Proc. World's Poultry Congr. 8th congr., Copenhagen 1: 719-725. Hutt, F. B., R. K. Cole and J. H. Bruckner, 1941. Four generations of fowls bred for resistance to neoplasms. Poultry Sci. 20: 514-526. Jeffrey, F. P., F. R. Beaudette and C. B. Hudson, 1942. The role of breeding in the control of fowl paralysis. New Jersey Agr. Exp. Sta. Bull. 696. Jull, M. A., 1952. Poultry Breeding. 3rd. Ed. New York. John Wiley and Sons, Inc. King, D. F., R. K. Cole, F. B. Hutt and G. J. Cottier, 1952. Tests in different environments of fowls genetically resistant to leucosis. Poultry Sci. 3 1 : 1027-1029.