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Is the Inheritance of Egg Production an Insoluble Problem?
THe Journal of the
American Association of Instructors and Investigators In Poultry Husbandry Vol. V
N e w Brunswick, N . J., July, 1919
N o . 10
CONTENTS
IS THE INHERITANCE OF EGG PRODUCTION AN INSOLUBLE PROBLEM? Breeding for increased egg production in poultry has been successful in its aim, without however, establishing the laws of its inheritance. It is impossible to devise a set of instructions that could be followed by a poultryman of ordinary intelligence, and which would enable him to proceed step by step in the development of a race of high producers, with the same certainty that a set of instructions could be devised for the production of a race of birds with certain definite morphological characters, such as pea comb, barred plumage color, pigmented skin, silky, frizzled feathers, red earlobes, and grey iris. All that can be done with egg production is to tell a poultryman to use the progeny test, which is good as far as it goes, but does not go far enough. It is perfectly clear that number of eggs alone is not a sufficient basis for procedure. Just as the general appearance of a bird depends upon the character of its parts, e. g., comb, plumage, color etc., so the egg record depends upon its parts or elements. The Inheritance of egg production, therefore becomes the inheritance of Its parts. If we knew the mode of inheritance of each of these parts, we could devise a set of instructions for the poultryman that would be as definite as those for producing a race of birds with a definite set of morphological characters such asr was described. Having reached this conclusion, the next step is to work out the Inheritance of each of the parts that are concerned in the determination of the egg record. The question that concerns us, then, is whether It is possible to achieve this end. Right here, I wish to make it clear that the question of the possibilities of improved egg production thrnueh selection is not under consideration.
Page 73 74 75 77 79 79
That fact is demonstrated. But selection alone is a half blind, slow and more or less unreliable mode of proceedure, compared with the promise of proceedure based on an exact knowledge of the mode of inheritance of the various elements of production. There are, however, very grave and perhaps insurmountable difficulties to be overcome in determining the mode of Inheritance of the elements involved in egg production. It is these difficulties that I propose to discuss, in the hope that ways of overcoming them may come to light. (1) Purity of Stock. It seems unlikely that stock pure for any of the hereditary factors concerned in egg production is in existence. Yet if one is to learn the mode of inheritance of one of these elements, pure stock must be at hand. This difficulty is not insurmountable, but requires much preliminary work. (2) Numbers. The advance In genetics makes it almost certain that the inheritance of the elements of egg production is fundamentally Mendelian in nature. Mendelian inheritance involves ratios. The required number of offspring from a pair will depend upon the number of genetic factors involved. If broodiness, for example, Involved only a simple Mendelian ratio, ten or twelve female offspring would be sufficient, but if it involves more complex ratios, as is certain, then 30 or 40 female offspring per pair become necessary. The difficulty in obtaining large numbers involves a strain on physical facilities. (3) The character, I. e., eg* production, is expressed in one sex only. Here is a difficulty, not Insurmountable, of two-fold nature. In the first place it cuts the number of individuals available for study in two. Second, the genetic composition cf the m*>1e can be Trno^n onlv tnrrui'frh his hrfie
Application made forentrg as second class matter at New Brunswick, N. J., P. 0. 73
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 27, 2015
Is the Inheritance of Egg Production an Insoluble Problem? Problems in Culling Corn Belt Hens Daily Variation in Flock Production Relation of Fall Moult of Leghorn Pullets to Month of Hatch Inheritance of Brodiness in Rhode Island Reds The Guelph Convention—Program and Notices
Unless the investigator can show that disease can be neglected, all supposed solutions of the problem must receive the closest scrutiny. It seems clear that disease cannot be neglected in studies of the fall pause, the winter pause, the rate of production, other pauses, probahlv also the cessation of production in the fall and the time of
maturity. In studies of the Inheritance of broodiness compared with non-broodiness, disease can be ignored but the question of the inheritance of degrees of broodiness is so bound up with egg production factors that it also requires a disease-free environment for its solution. H. D. Goodale, Mass. Agr. College.
PROBLEMS IS CULLING CORN BELT HENS. The purpose of this paper Is to present a few of the problems encountered in the first Poultry Culling Campaign conducted by the Purdue University Poultry Department in 1918. The statements herein made are based mostly on observation and opinion rather than definite data and should be valued only as such. The ideas presented are from the point of view of an Extension worker who deals with farm flocks of various general purpose and mixed breeds, of uncertain ages and time of hatching, kept under a wide range of conditions in a corn belt state, instead of commercial flocks of Leghorns on which most of the experimental work has been conducted and upon which, perhaps too often, poultry propaganda has been based. The time of the campaign this year Is to be limited to August and September, provided it is possible for the available field men to cover the territory, otherwise the work will be carried into October. The latter part of August proved the best time for culling the farm flock in Indiana. It is the easiest time to tell the cull hen. Extension men who gave culling demonstrations in October and November found it very difficult to differentiate closely between the extremely poor hen and the medium layer, since both show similar characteristics at that time. Judging by the experiences of the past year, it appears that the primary feathers, as well as hoH feathers, grow more rapidly as the time of molt becomes later. Furthermore, the medium producer soon regains full color in the shanks after she starts her resting period so that the skin color of the poor and medium hen will be practically the same in October or November. Farmers, unacquainted with culling methods, have great difficulty In learning to separate culls and medium producers when the work is given in October and November, while in late August and early September, they can readily learn to pick out the cull hens. Since the cull hen can readily be told In August there appears very little excuse to feed her longer. Data collected from Demonstration Farm flocks in Indiana show that each farm hen will consume about four pounds of feed per month in addition to material picked up 74
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 27, 2015
as one would test him for color, a very large number of daughters are required. (4) Management. Here rather serious difficulties are encounted, not so much in devising a scheme on paper as in executing that scheme. The labor question is perhaps the most important, because it is almost impossible to get two men who will do tne work exactly alike and there are so many points all along the line, where these differences leave their imprint. It could be solved, of course, by getting men of the right temperament at the start and paying them enough to keep them. But it is a hard matter to convince the powers that be, that such proceedure is as necessary as a delicate balance, or other instrument, is necessary in a chemical laboratory. (5) The four preceeding difficulties can be solved by appropriate means, but the question of disease is far more serious. Clearly recognized disease is bad enough, but at least it is recognized as disease and the record treated accordingly. But the effects of disease are more far reaching in several other respects. The question of resistance to disease is involved. Disease resistance does not always mean vigor, for a very vigorous bird may lack resistance to one disease but possess it for another, while a weak bird may possess resistance to both. Of course, it is important to have disease resistant strains, but their possession would not solve the matter unless they were so pure that non-resistant birds never appear. The question of disease resistance is a problem by itself. The insurmountable part of the matter rests upon the fact that disease may be present, in sufficient amount to interfere with production, but otherwise not recognizable. How then can genetic interruptions in production, which certainly exist, be separated from nongenetic causes? Possibly, if a sufficient number of expert poultry physicians were available to examine each bird daily, we might be able to accomplish the separation. Otherwise, I see no hope, unless some means can be found for excluding disease. I have great hope in a suitable quarantine, but thus far the necessary facilities have been lacking to try out this measure. Without exclusion of disease, at least its exclusio so that it becomes a neglible factor, I believe that all attempts to work out the inheritance of the following factors for egg production will be in vain.
American Association of Instructors and Investigators In Poultry Husbandry Vol. V
N e w Brunswick, N . J., July, 1919
N o . 10
CONTENTS
IS THE INHERITANCE OF EGG PRODUCTION AN INSOLUBLE PROBLEM? Breeding for increased egg production in poultry has been successful in its aim, without however, establishing the laws of its inheritance. It is impossible to devise a set of instructions that could be followed by a poultryman of ordinary intelligence, and which would enable him to proceed step by step in the development of a race of high producers, with the same certainty that a set of instructions could be devised for the production of a race of birds with certain definite morphological characters, such as pea comb, barred plumage color, pigmented skin, silky, frizzled feathers, red earlobes, and grey iris. All that can be done with egg production is to tell a poultryman to use the progeny test, which is good as far as it goes, but does not go far enough. It is perfectly clear that number of eggs alone is not a sufficient basis for procedure. Just as the general appearance of a bird depends upon the character of its parts, e. g., comb, plumage, color etc., so the egg record depends upon its parts or elements. The Inheritance of egg production, therefore becomes the inheritance of Its parts. If we knew the mode of inheritance of each of these parts, we could devise a set of instructions for the poultryman that would be as definite as those for producing a race of birds with a definite set of morphological characters such asr was described. Having reached this conclusion, the next step is to work out the Inheritance of each of the parts that are concerned in the determination of the egg record. The question that concerns us, then, is whether It is possible to achieve this end. Right here, I wish to make it clear that the question of the possibilities of improved egg production thrnueh selection is not under consideration.
Page 73 74 75 77 79 79
That fact is demonstrated. But selection alone is a half blind, slow and more or less unreliable mode of proceedure, compared with the promise of proceedure based on an exact knowledge of the mode of inheritance of the various elements of production. There are, however, very grave and perhaps insurmountable difficulties to be overcome in determining the mode of Inheritance of the elements involved in egg production. It is these difficulties that I propose to discuss, in the hope that ways of overcoming them may come to light. (1) Purity of Stock. It seems unlikely that stock pure for any of the hereditary factors concerned in egg production is in existence. Yet if one is to learn the mode of inheritance of one of these elements, pure stock must be at hand. This difficulty is not insurmountable, but requires much preliminary work. (2) Numbers. The advance In genetics makes it almost certain that the inheritance of the elements of egg production is fundamentally Mendelian in nature. Mendelian inheritance involves ratios. The required number of offspring from a pair will depend upon the number of genetic factors involved. If broodiness, for example, Involved only a simple Mendelian ratio, ten or twelve female offspring would be sufficient, but if it involves more complex ratios, as is certain, then 30 or 40 female offspring per pair become necessary. The difficulty in obtaining large numbers involves a strain on physical facilities. (3) The character, I. e., eg* production, is expressed in one sex only. Here is a difficulty, not Insurmountable, of two-fold nature. In the first place it cuts the number of individuals available for study in two. Second, the genetic composition cf the m*>1e can be Trno^n onlv tnrrui'frh his hrfie
Application made forentrg as second class matter at New Brunswick, N. J., P. 0. 73
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 27, 2015
Is the Inheritance of Egg Production an Insoluble Problem? Problems in Culling Corn Belt Hens Daily Variation in Flock Production Relation of Fall Moult of Leghorn Pullets to Month of Hatch Inheritance of Brodiness in Rhode Island Reds The Guelph Convention—Program and Notices
Unless the investigator can show that disease can be neglected, all supposed solutions of the problem must receive the closest scrutiny. It seems clear that disease cannot be neglected in studies of the fall pause, the winter pause, the rate of production, other pauses, probahlv also the cessation of production in the fall and the time of
maturity. In studies of the Inheritance of broodiness compared with non-broodiness, disease can be ignored but the question of the inheritance of degrees of broodiness is so bound up with egg production factors that it also requires a disease-free environment for its solution. H. D. Goodale, Mass. Agr. College.
PROBLEMS IS CULLING CORN BELT HENS. The purpose of this paper Is to present a few of the problems encountered in the first Poultry Culling Campaign conducted by the Purdue University Poultry Department in 1918. The statements herein made are based mostly on observation and opinion rather than definite data and should be valued only as such. The ideas presented are from the point of view of an Extension worker who deals with farm flocks of various general purpose and mixed breeds, of uncertain ages and time of hatching, kept under a wide range of conditions in a corn belt state, instead of commercial flocks of Leghorns on which most of the experimental work has been conducted and upon which, perhaps too often, poultry propaganda has been based. The time of the campaign this year Is to be limited to August and September, provided it is possible for the available field men to cover the territory, otherwise the work will be carried into October. The latter part of August proved the best time for culling the farm flock in Indiana. It is the easiest time to tell the cull hen. Extension men who gave culling demonstrations in October and November found it very difficult to differentiate closely between the extremely poor hen and the medium layer, since both show similar characteristics at that time. Judging by the experiences of the past year, it appears that the primary feathers, as well as hoH feathers, grow more rapidly as the time of molt becomes later. Furthermore, the medium producer soon regains full color in the shanks after she starts her resting period so that the skin color of the poor and medium hen will be practically the same in October or November. Farmers, unacquainted with culling methods, have great difficulty In learning to separate culls and medium producers when the work is given in October and November, while in late August and early September, they can readily learn to pick out the cull hens. Since the cull hen can readily be told In August there appears very little excuse to feed her longer. Data collected from Demonstration Farm flocks in Indiana show that each farm hen will consume about four pounds of feed per month in addition to material picked up 74
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 27, 2015
as one would test him for color, a very large number of daughters are required. (4) Management. Here rather serious difficulties are encounted, not so much in devising a scheme on paper as in executing that scheme. The labor question is perhaps the most important, because it is almost impossible to get two men who will do tne work exactly alike and there are so many points all along the line, where these differences leave their imprint. It could be solved, of course, by getting men of the right temperament at the start and paying them enough to keep them. But it is a hard matter to convince the powers that be, that such proceedure is as necessary as a delicate balance, or other instrument, is necessary in a chemical laboratory. (5) The four preceeding difficulties can be solved by appropriate means, but the question of disease is far more serious. Clearly recognized disease is bad enough, but at least it is recognized as disease and the record treated accordingly. But the effects of disease are more far reaching in several other respects. The question of resistance to disease is involved. Disease resistance does not always mean vigor, for a very vigorous bird may lack resistance to one disease but possess it for another, while a weak bird may possess resistance to both. Of course, it is important to have disease resistant strains, but their possession would not solve the matter unless they were so pure that non-resistant birds never appear. The question of disease resistance is a problem by itself. The insurmountable part of the matter rests upon the fact that disease may be present, in sufficient amount to interfere with production, but otherwise not recognizable. How then can genetic interruptions in production, which certainly exist, be separated from nongenetic causes? Possibly, if a sufficient number of expert poultry physicians were available to examine each bird daily, we might be able to accomplish the separation. Otherwise, I see no hope, unless some means can be found for excluding disease. I have great hope in a suitable quarantine, but thus far the necessary facilities have been lacking to try out this measure. Without exclusion of disease, at least its exclusio so that it becomes a neglible factor, I believe that all attempts to work out the inheritance of the following factors for egg production will be in vain.