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Day-old pullets (Hisex-strain Leghorn) were fed a starter ration ad libitum to 10 weeks of age. Individually weighed at 9 weeks of age they were sorted into 3 weight groups. Treatment 1, from the smallest weight group, was full-fed from 10 to 19 weeks of age. Treatment 3, from the middle third, was full-fed initially then restricted as necessary to maintain the recommended weight. Treatment 4, from the heaviest third, was restricted to attain the recommended weight at 19 weeks of age. Treatments 2 and 5 represented random samples of equal numbers from each weight. Pullets in treatments 2 and 5 were full-fed and restricted-fed, respectively. Differences which existed among the mean weights of treatments 1, 3, and 4 at 9 weeks of age decreased to 15 g at 19 weeks. At 19 weeks of age the pullets in these treatments averaged 80.7% to 84.0 ± 10% of the average weight. At 19 weeks of age, 96 pullets per treatment were further divided into eight replicates and transferred to layer cages. Pullets in treatment 4 (heaviest third, restricted-fed) were significantly older when reaching 10 and 50% production than were pullets in treatments 1, 2, and 3. The mean egg weights of pullets in treatments 4 and 5 were larger (P Differences among treatments in hen-day production, gram of egg per hen day, grams of feed per gram of egg, feed per hen day, Haugh units, shell thickness, and mortality were not significant.

PROGRESS through selection has been partially responsible for the tremendous advances which have come about in the poultry industry during the last fifty years. The process of selection, however, is often conducted on a quantitative basis and problems of linkages, epistasis and other genetic properties may not only limit the rate of progress, but may also result in a reduction of other desirable traits. Genetic experiments which have been designed to study the effects of intense selection for one trait on other traits have been limited. Jones and Lamoreux (1942) studied the effect of intense selection for high and low fecundity in the female on semen characteristics in the males of these lines. Males from the high fecundity line exhibited earlier sexual maturity, larger testes weights, better semen quality and greater fertilizing capacity than the males from the low fecundity line. The authors concluded that the production of eggs and…

CONFIDENCE limits calculated for heritability estimates are crude approximations (Bross, 1950; Jerome, Henderson and King, 1956; and Graybill and Robertson, 1957). Therefore, in this report, repeatability and closeness of heritability estimates to those from a very large sample, are used as indications of methods which may be used to improve the accuracy of smaller samples. Accuracy in estimating heritabilities from small samples may be increased by improving the sample of parents, by choosing the most appropriate mating system and by measuring the performance of sufficient progeny. If the parents are a random sample from each sex of the population, the number of parents is most important for adequate sampling. At the beginning of this subject the junior author, rather arbitrarily, chose 50 sires and 50 dams as a minimum sample from the parental generation. To subdivide additive and non-additive genetic effects, it is necessary to measure sire-dam interaction. This is …

THE degree of heritability of a trait is an indication of the additive genetic variance of that trait. Breeders generally assume that the hereditary variances observed in body weight and width of breast are due to genes with additive effects. Present conventional systems of breeding have been designed to utilize this type of variance. Based upon favorable results that breeders have attained by selecting for body weight at a given age and the magnitude of the heritability estimates calculated for body weight, it is evident that additive genetic variance plays an important part in the inheritance of body weight. Less evidence is available regarding breast angle. In addition to additive genetic variance, hereditary variance may be due to dominance variations and/or epistatic variations. In ordinary breeding practices, epistatic effects are broken up every generation and therefore do not contribute a great deal to permanent changes in a population, while gene …

BODY weight of broilers has been an important trait for a considerable number of years. More recently, breeders of egg production strains have become interested in adult body weight; the trend seems to be toward a small-bodied layer in order to reduce the amount of feed required for body maintenance. Heritability estimates aid the breeder in choosing the most efficient selection method and breeding System. With body weight being an important trait to all breeders, it seems desirable to consolidate all heritability estimates of this trait, as well as to report those that have been calculated at the Oklahoma Agricultural Experiment Station during the past four years. REVIEW OF THE LITERATURE Heritability estimates of body weight, as found in the literature, are summarized by age and method of estimation in Table 1. A simple, arithmetic average of these estimates by ages show that the heritability of body weight at broiler …

THE economic loss resulting from poor hatchability of eggs amounts to several million dollars annually in the United States. A much greater loss results from mortality. In broilers, the loss from mortality includes the cost of raising birds to the age of death plus the potential income that the producer would have received if the birds had lived to market age. The development of new drugs, vaccines, and better feeds have done much to decrease the death loss among domestic birds. Improved management practices, refrigeration and better incubators have improved the percentage hatch of fertile eggs. However, there is still a need to improve these conditions in commercial flocks. There is some evidence that both hatchability and viability are inherited; thus, some improvement can be made by selecting for these two characteristics in breeding programs. Present evidence indicates that the heritabilities of hatchability and viability are low; hence, the rate …

NUMEROUS heritability estimates for egg production and egg quality traits are available in the literature. Most of these reports were calculated from matings of dams within sires and, therefore, include a part of the non-additive variance which may have been present in the population. Relatively few researchers have attempted to partition the additive and non-additive genetic variance for these traits. Jerome, Henderson and King (1956) reported that the magnitude of non-additive genetic variance was larger than the additive genetic variance for survivors’ production over a period of a year. Also, the authors reported that the magnitude of non-additive variance was larger for production for 365 days as compared with shorter production periods up to four months. Fuchs and Krueger (1957) reported that non-additive effects appeared to be important in egg production in single and three-way crosses but of questionable magnitude in pure strains. According to Jerome, King and Henderson (1956),…

BODY weight has been a trait of primary interest to broiler strain breeders for a number of years. In addition, considerable attention has been paid to body conformation as measured by breast plumpness, angle, or some other measuring device. Heritability estimates of broiler body weight are generally considered to be in the range where individual selection is most efficient in improving this trait, but little information is available on the heritability of breast angle. Similarly, little is known about the interrelationship of these two traits. Although many studies have shown that body conformation is heritable (see Jull, 1952, for a review of these studies), only one study to date has reported heritability estimates of this trait. Lerner, Asmundson and Cruden (1947) calculated a heritability estimate for breast width at 12 weeks of age of 0.2. They also found a slight positive genetic correlation between breast width and body weight in …

WHAT economically important characters might be affected by rapidly increasing rate of growth from selection for increased body weight at eight weeks of age? The results may be predicted from the genetic parameters in a randombred population. The validity of these parameters may be checked by measuring the response as well as the correlated responses obtianed from a selection experiment. The first part of this report is concerned with the genetic parameters in the Ohio Randombred White Gold meat-type chickens. The second part reports experiments which measure the increase in eight-week body weight and the correlated egg production characters after growth rate has been increased by selection. 1. GENETIC PARAMETERS IN THE RANDOMBRED WHITE GOLD POPULATION The composition and methods used for maintenance of the Ohio Randombred White Gold chickens were described by Goodman and Jaap (1960b). Genetic parameters have been calculated from progenies of diallel matings as explained by …

ACCURACY in estimating heritabilities may be improved by increasing the number of parents, by choosing the most appropriate mating system, and by increasing the number of progeny. Goodman and Jaap (1960) concluded that, within closed populations, heritability estimates from 50 sets of diallel matings consisting of 200 families with the equivalent of four full sibs per family, were superior to estimates from 30 triallel sets consisting of 270 families with full-sib families of two individuals. The two strains of New Hampshire used in that report had long closed-flock histories and the additive genetic effects on eight-week weight were low compared with reports in the literature. Non-additive genetic effects were very low or non-existent. Also, the parents used in that study had been intensely selected for growth. Weights of the spleen and the bursa of Fabricius in baby chicks from a randombred population were chosen for the tests to be reported …

Data on quality traits were obtained from eggs produced by females of two lines (high and low) representing the 22nd generation of selection for divergent growth. Significant (P

The effects of divergent growth selection for 18 generations on semen characteristics, fertility and hatchability were investigated. Males from the low weight line produced semen with a significantly (P less than or equal to 0.05) higher sperm concentration and a highly significantly (P less than or equal to 0.01) lower methylene blue reduction time than the males from the high line. Differences between lines for semen volume, sperm motility, percent of live sperm, fertility and hatchability were not statistically significant.

THE secondary sex ratio is the proportion of male to female chicks at hatching. The tertiary sex ratio is the proportion of male to female chicks at any stated age after hatching. A difference between these two ratios is expected only if one sex is less viable than the other. Many studies have been conducted to discover the actual sex ratios at various periods of life, and to determine factors which affect them. (See Hutt, 1949, pp. 457–461). As Hutt (1949) points out, sex ratios at various ages have been reported, but complementary figures for those which died in the same populations are not available. In some studies, (cf. Landauer and Landauer, 1931), chicks with lost wingbands, or those which were decomposed before they were found, could not be included. The assumption generally made in such cases is that the sex ratio of these chicks is but a small sample …

THE concept of heritability is well established among geneticists and practical breeders, but the information on the heritability of production traits is still quite fragmentary, especially in turkeys. This paper reports heritability estimates of 25-week body weights in Broad-breasted Bronze and White Holland turkeys. A survey of the literature reveals only a few estimates of the heritability of body weight in turkeys. An estimate of about 0.23 was calculated for 26-week old male turkeys by Kentucky researchers (1950). This estimate was obtained by the intrasire regression method after correction was made for age (date of hatch?). Abplanalp and Kosin (1952), utilizing data from Broad-breasted Bronze and Beltsville Small Whites, calculated estimates by intraclass correlation and offspringdam regression methods at 4, 8, 14 and 26 weeks of age. Their estimates vary considerably because of age, sex and environmental (climatic) factors, but their most reliable restimates were in the medium to high …

The effects of the addition of Zn as ZnO to diets to induce molt were evaluated against a fasted control. Experiment 1 involved 315 Leghorn hens, 15 months old, randomly distributed among five treatments, each replicated seven times with 9 hens per replicate. Hens fasted for 10 days were compared with hens fed diets to which ZnO was added at 10,000, 5,000, or 2,500 ppm for 7, 14, or 21 days. No significant differences were observed among treatments for days to return to 50% production, hen-day and hen-housed production, egg weight, grams egg per hen-day, grams of feed per gram egg, mortality, or Haugh units during the 22-week experimental period. Experiment 2 involved 420 Leghorn hens, 18 months old, randomly distributed among five treatments, each replicated seven times with 12 hens per replicate. Treatments involved fasting for 10 days or feeding diets with 10,000, 5,000, or 2,500 ppm ZnO fed for 7, 14, or 21 days. Hens fasted and hens fed diets with 10,000 ppm ZnO at the start of the experiment ceased production in significantly less time (4.6 to 6 days) than hens fed 5,000 ppm ZnO (14.3 to 14.9 days); however, days to return to 50% production from the start of the experiment did not differ among treatments. Feed consumption and feed cost per hen day during molt were lowest (P less than .05) in the fasted hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent reports indicate that glutathione (GSH) is primarily genetically controlled and may be associated with growth rate (Kunkel et al., 1954; Stutts et al, 1956; Stutts and Kunkel, 1958; Charkey et al., 1965; Best, 1966). Thus, the possibility of using GSH levels as an aid in selection is indicated. It is the purpose of this paper to present the averages for GSH concentration and hematocrits in two-day intervals for chicks from hatching (0 day) to 20 days of age. MATERIALS AND METHODS The chicks used in this study were from a White Leghorn line, a line selected for dressing percentage (evisceration) and a rapid-growth line from a divergent growth-selection experiment. The adult average body weights of the females from these lines were approximately 2.0, 2.7, and 3.6 kilograms for the Leghorn, evisceration and rapid-growth lines, respectively. Blood samples from chicks were taken by cardiac puncture or by decapitation. Micro hematocrit. . .

Phosphatase is a catalyzing enzyme which acts by liberating inorganic phosphate from phosphate esters (Sanger et al., 1966). Common (1936) and Pflanz (1967) indicated that the serum alkaline phosphatase (SAP) level in chick blood exhibited a rapid increase to a maximum at 10 to 12 days after hatching. Published reports on the heritability and correlation of SAP activity with growth are contradictory, indicating that more research is warranted. MATERIALS AND METHOD The chicks used in this study were of a line derived from the Athens-Canadian randombred population. Data were obtained from 288 chicks produced by pedigree matings of 16 sires and 55 dams. Growth data were expressed as 12-day gain in weight, percentage gain to 12 days and 50-day gain in weight. The data collected on serum alkaline phosphatase at 12 days of age were expressed in Sigma units as outlined by Sigma Chemical Co. (1961). Preliminary analyses of the…

THE INFLUENCE of the phenotype for a simply inherited or qualitative trait on a more complex trait such as body weight has been studied to some extent in chickens. Kan et al. (1959) reported that comb type (single or pea) had no significant influence on body weight at six weeks of age; however, when housed at seven months of age, the single-comb birds were heavier than the pea-comb ones. Siegel and Dudley (1963) reported that cockerels with pea combs were significantly heavier than those with single combs at six and nine weeks of age in only one of three experiments. No significant differences were observed in the other two experiments at three, six, or nine weeks of age. Collins et at. (1961) concluded that the weight differences between single and heterozygous pea-comb progeny in favor of the single-comb phenotype were generally greater and more frequently significant in the male than…

Development of strains of broilers to meet the demands of the various segments of the industry is primarily the responsibility of the breeders. The trend toward purchasing broilers on the basis of eviscerated yield (dressing percentage) and grade may be forthcoming, Williams (1956) and Fischer (1957). Thus, information concerning the inheritance of dressing percentage of broilers seems important. MATERIALS AND METHODS Two cases of eggs from the Athens-Canadian randombred population were obtained in 1960 from the U.S.D.A. Southern Regional Poultry Breeding Station at Athens, Georgia. After hatching, the chicks were wingbanded and reared to sexual maturity. Diallel matings of unselected birds were then set up to produce the initial pedigree population. Later generations were also produced from diallel matings; however, the breeders were selected on the basis of the dressing percentage of their full-sibs. An attempt was made to obtain dressing data on a minimum of four progeny from each…

Padgott and Ivey (1959), Wilson et al. (1961) and Howes and Ivey (1961) discussed and evaluated the Japanese quail, Coturnix coturnix japonica, as a pilot animal for research. Jaap (1964) indicated that the Coturnix, due to its tremendous reproductive potential, may take the place of the chicken for research in poultry genetics. Marks and Kinney (1964) reported heritability estimates for various reproductive traits in the quail. In addition, these authors pointed out that if the quail is to be used as a pilot animal for genetic studies, information regarding the similarity of the genetic parameters of quail with those of domestic fowl should be useful. Jones et al. (1964) discussed the problems involved in identification of eggs from different females. The authors reported that the eggs produced by an individual were of similar size, shape, and color. The similarity was sufficiently great that by selecting the females on the basis…

Data from 958 progeny from five generations produced by 70 sires and 180 dams selected for dressing percentage were used to estimate heritability of body weight and dressing percentage and to estimate correlations between the two traits. Heritabilities based on full sibs were 0.58 and 0.29 for body weight and dressing percentage, respectively. Genotypic, phenotypic, and environmental correlations were 0.28, and 0.04, and −0.13, respectively.