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Phenotypic and Genotypic Selection of Breeding Females*
RESEARCH NOTES
sistent differences in amount of feed consumed. It is thus apparent that protein intake is involved in the problem of wet litter in poultry houses. Birds fed high protein diets drink more water which results in greater water elimination. The extra water eliminated is found in the greater volume of droppings produced rather than in a higher water content of the droppings. It is calculated on the basis of the evidence presented here that 1,000 birds would void 25 percent (5 gallons) more water per day if fed a 20 percent protein diet instead of a 15 percent protein diet. REFERENCES
Eley, C. P., and E.Hoffmann, 1949. Feed Particle size as a factor in water consumption and elimination. Poultry Sci. 28: 216-222. White, H. D., 1943. The Georgia home dehydrator. Ann. Report Col. of Agr., University of Ga, 43: 1-12.
PHENOTYPIC AND GENOTYPIC SELECTION OF BREEDING FEMALES* F. A. HAYS University of Massachusetts, A mherst, Mass. (Received for publication March 7, 1949)
The problem of selecting breeding females in breeding for high fecundity becomes increasingly difficult as the production level of the flock increases. Egg production in itself is such a complex interaction of processes that every effort should be made to employ selective breeding to the very best advantage. The heritability of gross egg production on the basis of individual performance is low, somewhere around .045 according to Lerner and Hazel (1947), so that selection * Contribution No. 709 from the Mass. Agricultural Experiment Station.
of breeders on the basis of their egg record could not be very effective in raising the production level of the flock. This observation had previously been made by Hays (1946) in Rhode Island Reds. The actual first year production record of a female might be taken to represent her phenotype but as far as the writer is aware there is no information regarding the range in annual production that may constitute one phenotype. Genotype is based on breeding behavior. Here again there is lack of specific information as to what range in production constitutes a genotype. Abundant experimental evi-
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 28, 2015
droppings produced varies almost directly with the percent of protein in the diet, while the amount of feed consumed and the water content of the droppings are not affected. The direct association of the dietary protein content and the amount of water consumed is probably related to the well known fact that greater amounts of water are required for the metabolism of proteins than for carbohydrates or fats. A possible explanation for the relationship of protein content of the diet to the amount of droppings produced is at hand if we assume that some if not all of the extra weight of the droppings is due to increased elimination of uric acid. Since the fowl is incapable of breaking down uric acid into urea, an appreciable amount of water consumed is thus tied up in the metabolism of the excess protein ingested. This view is supported by the lack of con-
467
468
RESEARCH NOTES
dence indicates that annual egg production is governedjay a series of inherited internal factors so that neither phenotype nor genotype is indicated by gross annual records. Hays (1946) showed in gross data on Rhode Island Reds that dams ranging in production from 180 to 219 eggs gave daughters averaging about 190 eggs; dams ranging in production from 220 to 259
Kind of Dam Pullets Yearlings 2-yr. olds 3-yr. olds
No. of Dams 105 122 30 6
Mean No. of rio„„i,^^, Production Daughters ofDaughters 735 718 144 29
228 229 226 233
gave daughters averaging 214 eggs; dams ranging from 260 to 299 gave daughters averaging 220 eggs; and dams laying from 300 to 330 eggs produced daughters averaging 228 eggs. These data suggest that a genotype of dams may have a range in production of about 40 eggs in the flock studied. On the whole, the evidence indicates that gross egg production is not a reliable guide for selecting breeders in a high-producing flock. NEW DATA AVAILABLE
Data on the Massachusetts Experiment Station flock of Rhode Island Reds bred for high fecundity were examined over seven generations hatched from 1939 to 1946. The records include 263 dams and 1626 daughters. The dams ranged in age from about 12 months to 48 months. As females grow older more information accumulates regarding their laying ability and their breeding ability. Females with no progeny record may be considered as being selected for breeders on their phenotype, while females with a progeny test
RELATION OF AGE OF DAMS TO PRODUCTION OF DAUGHTERS Consideration may be given first to the actual mean egg production of daughters from dams of different ages. In this case a few of the older females were tested females and all females were mated to supposedly superior males. If the basis of selection were truly constructive, there should be an increase in the mean production of daughters parallel to the age of dams. The complete data are set down in table 1 for the seven-year period. Table 1 shows that daughters of pullets, yearlings, and two-year-olds all averaged to lay the same number of eggs. The six three-year-old hens were actually 48 months old and their daughters averaged 4 to 5 eggs more than those of the other dams. This small group of dams represents the most rigid selection, and this type of selection is only feasible in a large flock because of the limited life span in Rhode Island Reds. UNTESTED VERSUS PROGENY-TESTED DAMS
Lerner and Hazel (1947) reported that untested White Leghorn dams gave low production even when mated to tested sires. Daughters from partially tested dams were decidedly superior to those from untested dams. Daughters from completely tested dams were higher producers than daughters from partially tested dams. In our data the untested dams were mostly pullets but there were also a few
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 28, 2015
TABLE 1.—Mean egg production of daughters from dams of different ages in seven generations
were selected both on phenotype and genotype. When breeding females are selected on this double basis there should be an increase in the production level of daughters over that of the daughters of dams not progeny-tested provided the standard for progeny testing was well above the mean of the general population.
RESEARCH NOTES
469
the coefficient of variation about 20 percent. Certainly there is little evidence of homogeneity in a n n u a l egg production which m a y be caused by environmental factors. TABLE 2.—Mean egg production of untested, partially tested and completely tested dams in seven years In general, it appears that the greatest handicap in attempting to increase the Mean ProKind of No. of No. of egg production level of this flock lies in , . _ duction of Dam Dams n the limited size of the population which Daughters D a u g h t e r s prevents the selection of sufficient breeders 228 1279 Untested 198 228 318 59 Partially tested of highest merit to reproduce the flock. 225 61 11 Completely tested Our d a t a show that, when pullet families are selected from about 38 dams each The records in table 2 indicate essen- year, raising the production level of tially the same egg production in daugh- daughters above 230 eggs has n o t been ters of the three types of dams. This fact feasible. We suggest t h a t a minimum of suggests two possibilities: first, the stand- about 100 families of daughters be seards for selected partially tested and com- lected with no fewer than 1000 daughters pletely tested dams may have been too tested each year in order to apply more low; second, the flock m a y be highly rigid selective breeding. Another conhomogeneous with respect to genes af- structive procedure might consist in the fecting egg production. I t is our opinion use of two or three sires used successively t h a t the standards for selecting breeding in each breeding pen to produce each females were too low because of the limited generation. size of the flock which produced a very REFERENCES small number of superior females. Variability in annual egg production of Hays, F. A. 1946. Egg records as a criterion for selecting breeding hens. Poultry Sci. 25: 622-627. daughters is extremely high as pointed Lerner, I. M., and L. N. Hazel. 1947. Population out by H a y s (1946). T h e standard deviagenetics of a poltry flock under artificial selection in production is about + 4 3 eggs and tion. Genetics 32: 325-339 yearlings and two-year-olds t h a t had not been progeny-tested. These are included in Table 2.
C. R. G R A U AND M .
KAMEI
Division of Poultry Husbandry, University of California, Berkeley (Received for publication April 5, 1949)
In the course of studies of the amino acid requirements for egg production, we have observed a number of instances of delayed oviposition in birds fed purified control diets. Normally, an egg remains in 1
This study was aided by a grant from Swift & Company.
the uterus from 19 to 24 hours, according to Warren and Scott (1935a, 1935b), and during the last 13 hours the egg has a hard shell. Scott and Warren (1936) found no evidence for the belief t h a t " t h e clutch was terminated by the holding over until the next morning of the egg which was
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 28, 2015
DELAYED OVIPOSITION OBSERVED IN HENS FED PURIFIED DIETS1
sistent differences in amount of feed consumed. It is thus apparent that protein intake is involved in the problem of wet litter in poultry houses. Birds fed high protein diets drink more water which results in greater water elimination. The extra water eliminated is found in the greater volume of droppings produced rather than in a higher water content of the droppings. It is calculated on the basis of the evidence presented here that 1,000 birds would void 25 percent (5 gallons) more water per day if fed a 20 percent protein diet instead of a 15 percent protein diet. REFERENCES
Eley, C. P., and E.Hoffmann, 1949. Feed Particle size as a factor in water consumption and elimination. Poultry Sci. 28: 216-222. White, H. D., 1943. The Georgia home dehydrator. Ann. Report Col. of Agr., University of Ga, 43: 1-12.
PHENOTYPIC AND GENOTYPIC SELECTION OF BREEDING FEMALES* F. A. HAYS University of Massachusetts, A mherst, Mass. (Received for publication March 7, 1949)
The problem of selecting breeding females in breeding for high fecundity becomes increasingly difficult as the production level of the flock increases. Egg production in itself is such a complex interaction of processes that every effort should be made to employ selective breeding to the very best advantage. The heritability of gross egg production on the basis of individual performance is low, somewhere around .045 according to Lerner and Hazel (1947), so that selection * Contribution No. 709 from the Mass. Agricultural Experiment Station.
of breeders on the basis of their egg record could not be very effective in raising the production level of the flock. This observation had previously been made by Hays (1946) in Rhode Island Reds. The actual first year production record of a female might be taken to represent her phenotype but as far as the writer is aware there is no information regarding the range in annual production that may constitute one phenotype. Genotype is based on breeding behavior. Here again there is lack of specific information as to what range in production constitutes a genotype. Abundant experimental evi-
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 28, 2015
droppings produced varies almost directly with the percent of protein in the diet, while the amount of feed consumed and the water content of the droppings are not affected. The direct association of the dietary protein content and the amount of water consumed is probably related to the well known fact that greater amounts of water are required for the metabolism of proteins than for carbohydrates or fats. A possible explanation for the relationship of protein content of the diet to the amount of droppings produced is at hand if we assume that some if not all of the extra weight of the droppings is due to increased elimination of uric acid. Since the fowl is incapable of breaking down uric acid into urea, an appreciable amount of water consumed is thus tied up in the metabolism of the excess protein ingested. This view is supported by the lack of con-
467
468
RESEARCH NOTES
dence indicates that annual egg production is governedjay a series of inherited internal factors so that neither phenotype nor genotype is indicated by gross annual records. Hays (1946) showed in gross data on Rhode Island Reds that dams ranging in production from 180 to 219 eggs gave daughters averaging about 190 eggs; dams ranging in production from 220 to 259
Kind of Dam Pullets Yearlings 2-yr. olds 3-yr. olds
No. of Dams 105 122 30 6
Mean No. of rio„„i,^^, Production Daughters ofDaughters 735 718 144 29
228 229 226 233
gave daughters averaging 214 eggs; dams ranging from 260 to 299 gave daughters averaging 220 eggs; and dams laying from 300 to 330 eggs produced daughters averaging 228 eggs. These data suggest that a genotype of dams may have a range in production of about 40 eggs in the flock studied. On the whole, the evidence indicates that gross egg production is not a reliable guide for selecting breeders in a high-producing flock. NEW DATA AVAILABLE
Data on the Massachusetts Experiment Station flock of Rhode Island Reds bred for high fecundity were examined over seven generations hatched from 1939 to 1946. The records include 263 dams and 1626 daughters. The dams ranged in age from about 12 months to 48 months. As females grow older more information accumulates regarding their laying ability and their breeding ability. Females with no progeny record may be considered as being selected for breeders on their phenotype, while females with a progeny test
RELATION OF AGE OF DAMS TO PRODUCTION OF DAUGHTERS Consideration may be given first to the actual mean egg production of daughters from dams of different ages. In this case a few of the older females were tested females and all females were mated to supposedly superior males. If the basis of selection were truly constructive, there should be an increase in the mean production of daughters parallel to the age of dams. The complete data are set down in table 1 for the seven-year period. Table 1 shows that daughters of pullets, yearlings, and two-year-olds all averaged to lay the same number of eggs. The six three-year-old hens were actually 48 months old and their daughters averaged 4 to 5 eggs more than those of the other dams. This small group of dams represents the most rigid selection, and this type of selection is only feasible in a large flock because of the limited life span in Rhode Island Reds. UNTESTED VERSUS PROGENY-TESTED DAMS
Lerner and Hazel (1947) reported that untested White Leghorn dams gave low production even when mated to tested sires. Daughters from partially tested dams were decidedly superior to those from untested dams. Daughters from completely tested dams were higher producers than daughters from partially tested dams. In our data the untested dams were mostly pullets but there were also a few
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 28, 2015
TABLE 1.—Mean egg production of daughters from dams of different ages in seven generations
were selected both on phenotype and genotype. When breeding females are selected on this double basis there should be an increase in the production level of daughters over that of the daughters of dams not progeny-tested provided the standard for progeny testing was well above the mean of the general population.
RESEARCH NOTES
469
the coefficient of variation about 20 percent. Certainly there is little evidence of homogeneity in a n n u a l egg production which m a y be caused by environmental factors. TABLE 2.—Mean egg production of untested, partially tested and completely tested dams in seven years In general, it appears that the greatest handicap in attempting to increase the Mean ProKind of No. of No. of egg production level of this flock lies in , . _ duction of Dam Dams n the limited size of the population which Daughters D a u g h t e r s prevents the selection of sufficient breeders 228 1279 Untested 198 228 318 59 Partially tested of highest merit to reproduce the flock. 225 61 11 Completely tested Our d a t a show that, when pullet families are selected from about 38 dams each The records in table 2 indicate essen- year, raising the production level of tially the same egg production in daugh- daughters above 230 eggs has n o t been ters of the three types of dams. This fact feasible. We suggest t h a t a minimum of suggests two possibilities: first, the stand- about 100 families of daughters be seards for selected partially tested and com- lected with no fewer than 1000 daughters pletely tested dams may have been too tested each year in order to apply more low; second, the flock m a y be highly rigid selective breeding. Another conhomogeneous with respect to genes af- structive procedure might consist in the fecting egg production. I t is our opinion use of two or three sires used successively t h a t the standards for selecting breeding in each breeding pen to produce each females were too low because of the limited generation. size of the flock which produced a very REFERENCES small number of superior females. Variability in annual egg production of Hays, F. A. 1946. Egg records as a criterion for selecting breeding hens. Poultry Sci. 25: 622-627. daughters is extremely high as pointed Lerner, I. M., and L. N. Hazel. 1947. Population out by H a y s (1946). T h e standard deviagenetics of a poltry flock under artificial selection in production is about + 4 3 eggs and tion. Genetics 32: 325-339 yearlings and two-year-olds t h a t had not been progeny-tested. These are included in Table 2.
C. R. G R A U AND M .
KAMEI
Division of Poultry Husbandry, University of California, Berkeley (Received for publication April 5, 1949)
In the course of studies of the amino acid requirements for egg production, we have observed a number of instances of delayed oviposition in birds fed purified control diets. Normally, an egg remains in 1
This study was aided by a grant from Swift & Company.
the uterus from 19 to 24 hours, according to Warren and Scott (1935a, 1935b), and during the last 13 hours the egg has a hard shell. Scott and Warren (1936) found no evidence for the belief t h a t " t h e clutch was terminated by the holding over until the next morning of the egg which was
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 28, 2015
DELAYED OVIPOSITION OBSERVED IN HENS FED PURIFIED DIETS1