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The Proposed Breeding Program of the Regional Poultry Research Laboratory
T h e Proposed Breeding Program of the Regional Poultry Research Laboratory NELSON
F.
WATERS
Senior Geneticist AND JAMES H. BYWATERS Associate Geneticist V. S. Regional Poultry Research Laboratory, East Lansing, Michigan (Presented at annual meeting June, 1940; received for publication August 8, 1940)
T
Fisher (1937) offers two criticisms of scientific research that are quite commonly found, namely, faulty interpretations and faulty design. The present authors believe the latter to be the more serious. Wellmeant interpretations are of little value when based on a poorly designed experiment or unconsciously biased data. A carefully designed experiment permits the
investigator to plan each detail of his research, submit the results to a more complete analysis, and secure a more sound interpretation of the data. Perhaps it would be Utopian to hope that every last detail of an experiment would be complete. Nevertheless, there is general agreement that experiments should be so designed as to yield the most information for the time and money expended. While the first consideration of the genetic program of the laboratory is the formation of resistant and sueceptible families, considerable emphasis must be placed on fertility, hatchability, and egg production lest the desired stock become extinct through the lack of some phase of fecundity. Wright (1939) states, "The breeder must, for example, take into account not merely production, but economy of production in his conception of the character to be improved. Moreover he must at least hold his own with respect to general vigor and fertility, while attempting to improve other characters, if success after years of effort is not to be followed shortly by dwindling numbers and ultimate extinction of the improved strain." Consequently, in addition to data on the pathology of the fowl paralysis complex, data on fertility, hatchability, viability (both embryonic and postembryonic), rate of growth, age at first egg, and egg weight are being taken.
[221]
A survey of breeding stock in the United
Downloaded from http://ps.oxfordjournals.org/ at GWU on April 29, 2015
HE U. S. Regional Poultry Research Laboratory has as one of its objectives a genetic approach to the problem of improving viability in poultry. It was the unanimous opinion of all concerned with the establishment of this laboratory that fowl paralysis and a certain more or less closely related group of diseases constituted the most important problem confronting the poultry industry and that all energy should be directed toward its control. A genetic approach to this problem calls for the formation of families inherently resistant or susceptible to fowl paralysis and possessing, to a marked degree, characters of general economic value. While susceptible families would be of little economic importance their genetic value would be great, for without such lines the mode of inheritance of resistance and the influence of the environment would be difficult to determine. In addition, susceptible non-carrier stocks are necessary for pathologic studies, including epizootiology, immunization, and non-genetic control methods.
222
NELSON F. WATERS AND JAMES H. BYWATERS
The remaining nine strains, represented by about 1,000 males and females of breeding age, probably represented a sample of the best (and perhaps some of the poorest) germplasm available in the White Leghorn fowl. In other words, the laboratory probably had available most of the desired and many undesired genes of the domestic fowl. The frequency of these genes, however, was unknown. In a breeding experiment with a closed flock no inherited trait, barring mutations, can be incorporated into the strain or family unless the genes exist in the original foundation stock. This emphasizes the importance of starting with suitable material. It is hoped that careful selection will permit the retention of many desirable genes and the elimination of most deleterious
factors, thereby resulting in the ultimate improvement of the entire flock. It was decided to close the entire flock to all outside breeding and to attempt a breeding program which would segregate, as quickly as possible, those birds having the most desirable characters and those having the fewest. The success of the breeding program is dependent upon the choice of breeding animals and the way in which they are mated. The method of selection and the system of mating employed are, in turn, dependent upon the investigator's knowledge of the genetic nature of the character studied and the efficiency of the testing program. Very little is known concerning the genetic and environmental nature of resistance and susceptibility to fowl paralysis. Further, since every effort is made to prevent the potential breeders from being exposed to fowl paralysis, selection on the basis of individual phenotype is impossible at the laboratory. Facilities for the 1940 breeding season permitted only 18 mating pens accommodating 18 males and 218 females. On the basis of the incomplete reaction of the inoculated and contact control birds up to the time when matings were made, each family was tentatively classed as resistant or susceptible to fowl paralysis. It was obvious that it would not be possible to rear enough offspring from each of the 218 females to provide adequate data for a progeny test. It seemed more desirable to know much about a few birds rather than a little about many. Accordingly, as the hatching season progressed, hens were eliminated from the matings until only 70 remained. Elimination was on the basis of (1) death of hen, (2) non-productivity, (3) unmistakable signs of ill health, and (4) small number of progeny due to either low production, low fertility, or low hatchability. Arbitrarily a minimum of 25 daughters
Downloaded from http://ps.oxfordjournals.org/ at GWU on April 29, 2015
States indicated that it was possible to obtain from widely separated geographic regions many strains of Single Comb White Leghorns, about which much regarding their viability and production was known. Therefore, the White Leghorn was selected as the most suitable material for initiating research on fowl paralysis. In the spring of 1939 1,000 hatching eggs were introduced from each of 10 different White Leghorn flocks. Upon hatching, the chicks were divided into two groups. One group, used as a control, was confined in strictly quarantined houses on the west or control side of the plant. The other group was subdivided into an inoculated group and a non-inoculated contact control group quarantined in similar houses on the east or infected side of the plant. All of the chicks, except those from one flock which were subsequently discarded, were of known ancestry. This fact permitted a distribution of chicks from the same dam to both control and inoculated groups. The inoculated birds were to provide an estimate of the resistance or susceptibility of their unexposed sibs.
PROPOSED REGIONAL POULTRY RESEARCH LABORATORY BREEDING PROGRAM
ing to the exclusion of all others. Careful selection accompanied by inter- and intrastrain crosses, together with linebreeding, mild inbreeding, and occasionally intense inbreeding will offer considerable diversity of mating systems. The progress of each system can thus be measured and the results should indicate which systems hold the most promise. Finally, since the geneticist must rely on the reaction of birds to inoculation in making his selection, the identification and development of strains of poultry which are resistant or susceptible to the fowl paralysis complex will depend upon the success of the pathologist in developing accurate methods of diagnosing the less obvious phases of this disease complex. Van Es (1932) has aptly said, "There is reason for the belief that problems associated with disease are eternal . ... this, however, by no means signifies that the struggle against disease is a hopeless one." REFERENCES
Fisher, R. A., 1937. The design of experiments. Oliver and Boyd, Edinburgh, 260 pp. Lush, J. L., 1937. Animal breeding plans. Collegiate Press, Ames, Iowa, 350 pp. Van Es, L., 1932. The principles of animal hygiene and preventive veterinary medicine. John Wiley and Sons, New York, 746 pp. Wright, Sewall, 1939. Genetic principles governing the rate of progress of livestock breeding. Proc. Amer. Soc. Ani. Prod. pp. 18-26.
Downloaded from http://ps.oxfordjournals.org/ at GWU on April 29, 2015
from each of these 70 hens have been divided into 15(10 inoculated, 5 contact controls) for the inoculated side and 10 for the uninoculated side. All the males on the inoculated side will be discarded, but six males from each hen will be saved as potential breeders on the uninoculated or control side. None of the parents will be discarded (unavoidable mortality excepted) from the experiment until a complete progeny test has been made. Only birds from the non-inoculated control side of the plant will be used for breeding purposes. One of the main objectives of the breeding program is most quickly to segregate birds resistant or susceptible to fowl paralysis, sacrificing valuable economic characters as little as possible. Lush (1937) states that, "Inbreeding is the most powerful tool the breeder has for establishing uniform families or strains which are distinct from each other." Inbreeding many different pairs of birds from a few chosen ancestors leads to diversity between families, but still permits crossing out to related individuals if homozygosity is progressing at too rapid a rate as manifested by an excess of undesirable traits. Every effort will be made to retain and test for resistance and susceptibility foundation birds of each of the nine strains available at the laboratory. It would be somewhat of a risk to follow, at the start of the experiment, any one system of mat-
223
F.
WATERS
Senior Geneticist AND JAMES H. BYWATERS Associate Geneticist V. S. Regional Poultry Research Laboratory, East Lansing, Michigan (Presented at annual meeting June, 1940; received for publication August 8, 1940)
T
Fisher (1937) offers two criticisms of scientific research that are quite commonly found, namely, faulty interpretations and faulty design. The present authors believe the latter to be the more serious. Wellmeant interpretations are of little value when based on a poorly designed experiment or unconsciously biased data. A carefully designed experiment permits the
investigator to plan each detail of his research, submit the results to a more complete analysis, and secure a more sound interpretation of the data. Perhaps it would be Utopian to hope that every last detail of an experiment would be complete. Nevertheless, there is general agreement that experiments should be so designed as to yield the most information for the time and money expended. While the first consideration of the genetic program of the laboratory is the formation of resistant and sueceptible families, considerable emphasis must be placed on fertility, hatchability, and egg production lest the desired stock become extinct through the lack of some phase of fecundity. Wright (1939) states, "The breeder must, for example, take into account not merely production, but economy of production in his conception of the character to be improved. Moreover he must at least hold his own with respect to general vigor and fertility, while attempting to improve other characters, if success after years of effort is not to be followed shortly by dwindling numbers and ultimate extinction of the improved strain." Consequently, in addition to data on the pathology of the fowl paralysis complex, data on fertility, hatchability, viability (both embryonic and postembryonic), rate of growth, age at first egg, and egg weight are being taken.
[221]
A survey of breeding stock in the United
Downloaded from http://ps.oxfordjournals.org/ at GWU on April 29, 2015
HE U. S. Regional Poultry Research Laboratory has as one of its objectives a genetic approach to the problem of improving viability in poultry. It was the unanimous opinion of all concerned with the establishment of this laboratory that fowl paralysis and a certain more or less closely related group of diseases constituted the most important problem confronting the poultry industry and that all energy should be directed toward its control. A genetic approach to this problem calls for the formation of families inherently resistant or susceptible to fowl paralysis and possessing, to a marked degree, characters of general economic value. While susceptible families would be of little economic importance their genetic value would be great, for without such lines the mode of inheritance of resistance and the influence of the environment would be difficult to determine. In addition, susceptible non-carrier stocks are necessary for pathologic studies, including epizootiology, immunization, and non-genetic control methods.
222
NELSON F. WATERS AND JAMES H. BYWATERS
The remaining nine strains, represented by about 1,000 males and females of breeding age, probably represented a sample of the best (and perhaps some of the poorest) germplasm available in the White Leghorn fowl. In other words, the laboratory probably had available most of the desired and many undesired genes of the domestic fowl. The frequency of these genes, however, was unknown. In a breeding experiment with a closed flock no inherited trait, barring mutations, can be incorporated into the strain or family unless the genes exist in the original foundation stock. This emphasizes the importance of starting with suitable material. It is hoped that careful selection will permit the retention of many desirable genes and the elimination of most deleterious
factors, thereby resulting in the ultimate improvement of the entire flock. It was decided to close the entire flock to all outside breeding and to attempt a breeding program which would segregate, as quickly as possible, those birds having the most desirable characters and those having the fewest. The success of the breeding program is dependent upon the choice of breeding animals and the way in which they are mated. The method of selection and the system of mating employed are, in turn, dependent upon the investigator's knowledge of the genetic nature of the character studied and the efficiency of the testing program. Very little is known concerning the genetic and environmental nature of resistance and susceptibility to fowl paralysis. Further, since every effort is made to prevent the potential breeders from being exposed to fowl paralysis, selection on the basis of individual phenotype is impossible at the laboratory. Facilities for the 1940 breeding season permitted only 18 mating pens accommodating 18 males and 218 females. On the basis of the incomplete reaction of the inoculated and contact control birds up to the time when matings were made, each family was tentatively classed as resistant or susceptible to fowl paralysis. It was obvious that it would not be possible to rear enough offspring from each of the 218 females to provide adequate data for a progeny test. It seemed more desirable to know much about a few birds rather than a little about many. Accordingly, as the hatching season progressed, hens were eliminated from the matings until only 70 remained. Elimination was on the basis of (1) death of hen, (2) non-productivity, (3) unmistakable signs of ill health, and (4) small number of progeny due to either low production, low fertility, or low hatchability. Arbitrarily a minimum of 25 daughters
Downloaded from http://ps.oxfordjournals.org/ at GWU on April 29, 2015
States indicated that it was possible to obtain from widely separated geographic regions many strains of Single Comb White Leghorns, about which much regarding their viability and production was known. Therefore, the White Leghorn was selected as the most suitable material for initiating research on fowl paralysis. In the spring of 1939 1,000 hatching eggs were introduced from each of 10 different White Leghorn flocks. Upon hatching, the chicks were divided into two groups. One group, used as a control, was confined in strictly quarantined houses on the west or control side of the plant. The other group was subdivided into an inoculated group and a non-inoculated contact control group quarantined in similar houses on the east or infected side of the plant. All of the chicks, except those from one flock which were subsequently discarded, were of known ancestry. This fact permitted a distribution of chicks from the same dam to both control and inoculated groups. The inoculated birds were to provide an estimate of the resistance or susceptibility of their unexposed sibs.
PROPOSED REGIONAL POULTRY RESEARCH LABORATORY BREEDING PROGRAM
ing to the exclusion of all others. Careful selection accompanied by inter- and intrastrain crosses, together with linebreeding, mild inbreeding, and occasionally intense inbreeding will offer considerable diversity of mating systems. The progress of each system can thus be measured and the results should indicate which systems hold the most promise. Finally, since the geneticist must rely on the reaction of birds to inoculation in making his selection, the identification and development of strains of poultry which are resistant or susceptible to the fowl paralysis complex will depend upon the success of the pathologist in developing accurate methods of diagnosing the less obvious phases of this disease complex. Van Es (1932) has aptly said, "There is reason for the belief that problems associated with disease are eternal . ... this, however, by no means signifies that the struggle against disease is a hopeless one." REFERENCES
Fisher, R. A., 1937. The design of experiments. Oliver and Boyd, Edinburgh, 260 pp. Lush, J. L., 1937. Animal breeding plans. Collegiate Press, Ames, Iowa, 350 pp. Van Es, L., 1932. The principles of animal hygiene and preventive veterinary medicine. John Wiley and Sons, New York, 746 pp. Wright, Sewall, 1939. Genetic principles governing the rate of progress of livestock breeding. Proc. Amer. Soc. Ani. Prod. pp. 18-26.
Downloaded from http://ps.oxfordjournals.org/ at GWU on April 29, 2015
from each of these 70 hens have been divided into 15(10 inoculated, 5 contact controls) for the inoculated side and 10 for the uninoculated side. All the males on the inoculated side will be discarded, but six males from each hen will be saved as potential breeders on the uninoculated or control side. None of the parents will be discarded (unavoidable mortality excepted) from the experiment until a complete progeny test has been made. Only birds from the non-inoculated control side of the plant will be used for breeding purposes. One of the main objectives of the breeding program is most quickly to segregate birds resistant or susceptible to fowl paralysis, sacrificing valuable economic characters as little as possible. Lush (1937) states that, "Inbreeding is the most powerful tool the breeder has for establishing uniform families or strains which are distinct from each other." Inbreeding many different pairs of birds from a few chosen ancestors leads to diversity between families, but still permits crossing out to related individuals if homozygosity is progressing at too rapid a rate as manifested by an excess of undesirable traits. Every effort will be made to retain and test for resistance and susceptibility foundation birds of each of the nine strains available at the laboratory. It would be somewhat of a risk to follow, at the start of the experiment, any one system of mat-
223