Browsing by Author "Howes, C. E."
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- Behavior patterns of chickens from hatching to 10 weeks of ageDawson, John Stanley (Virginia Tech, 1962-06-05)see document
- Correlated response and sexual dimorphism in bidirectional selection experimentsCarte, Ira Franklin (Virginia Tech, 1968-02-05)This dissertation involved two experiments, (1) the study of realized heritabilities of correlated traits, and (2) the study of the inheritance of sexual dimorphism or body weight. The first experiment included data from four generations of double two-way selection for body weight and breast angle at eight weeks of age. Breast angle was considered a correlated trait in the weight subpopulation and body weight a correlated trait in the angle subpopulation. There was a significant divergence between lines for both selected traits. The response to direct selection for breast angle was asymmetrical with the response in the narrow direction being greater then that in the broad direction. The response of body weight to two-way selection was symmetrical through the F₄ generation. Divergence of body weight between the lines selected for breast angle was significant in the F₁, F₃, and F₄ generations. Divergence of breast angle between the lines selected for body weight was significant in the F₂ and subsequent generations. Heritabilities of the unselected traits were obtained by the cumulative difference between lines divided by the expected secondary selection differential and by the regression of the cumulative difference between lines on expected secondary selection differential. The correlated realized heritability of breast angle was greater in the weight lines than was the correlated realized heritability for body weight in the angle lines. Examination of the components of the correlated realized heritability showed that they were the ratio of the genetic to phenotypic covariances of the two traits. The second experiment involved the investigation of sex dimorphism for body weight at eight weeks of age. The heritability estimate for sex dimorphism of this trait was .02, and the genetic correlation of it in males and females was .98. The genetic variability (.02) in sex dimorphism was evidenced by a greater response in males to selection for eight-week body weight than in females. The biological reason for this was additive sex-linkage.
- An evaluation of broiler diets: a progress reportWisman, E. L.; Holmes, C. E.; Howes, C. E. (Virginia Agricultural Experiment Station, 1958-12)6 different diets were tested to grow broilers. Broilers on diets patterned after present day rations performed better than those on a diet formulated 10 years prior. Soybean oil meal was a superior source of protein as compared to peanut oil meal or poultry blood meal
- Feeder and water allowances for broiler crossesSiegel, Paul B.; Siegel, H. S.; Kramer, C. Y.; Howes, C. E. (Virginia Agricultural Experiment Station)Broilers provided with 1.5 linear inches of feeder space to 3 weeks of age and 3 linear inches thereafter had the largest body weight at 9 weeks of age. Both sexes responded similarly to feeder and/or water space.
- Genetics of initial imprinting responses: selection, and heterosisGraves, Hannon Benjamin (Virginia Tech, 1968-05-15)Domestic chicks were tested for initial response, approach, and stay-near tendencies during one 5-minute test exposure to a distant audio-visual 1mprinting apparatus. Significant interline differences demonstrated genetic variation. A bidirectional selection program was initiated with time to respond as the selected trait. Approach and stay-near tendencies were measured as associated traits. Results through the F4 generation disclosed that in the fast response line the realized heritability of the selected trait was .32 and the correlated realized heritabilities for time to approach and for time spent near the apparatus were .36 and .32, respect1vely. In the slow response line selection was ineffective, and heritabilities for the three traits were zero. Genetic and phenotypic relationships among the traits were high in the fast response line, but genetic relationships in the slow response line could not be determined because of the zero heritabilities. The asymmetrical response to selection could not be explained by the usual causes, and it is hypothesized that responsiveness is a threshold trait. Comparisons of 290 purebred chicks with 379 crossbred chicks for response, approach, and stay-near tendencies provided evidence of heterosis. This demonstration of non-additive effects implies fitness roles for these traits and supports the idea that they indicate imprinting tendencies. Time of day tested, sex, hatch, mating type, developmental age, and 24-hr body we1ght were considered independent variables influencing the behavior traits. Multiple regressions showed that the initiation of responsiveness is not predictable. However, once a chick responded, its behavior was highly predictable; this supports the hypothesis from the selection experiment that responsiveness is a threshold trait. Sensory modalities involved in satiating the behavior traits were differentiated by comparisons of non-handled chicks with those exposed to visual, tactile, and visual - plus-tacti1e stimuli just prior to testing. Visual stimulation alone increased responses and approaches, whereas tactile stimulation alone had no effect on these behaviors. Tactile-plus-visual stimulation just prior to testing inhibited response and approach tendencies. Eva1uation of the effects of prior socialization and handling indicated that isolation enhanced approach responses, and that prior handling had the opposite effect. An age and/or memory factor was introduced when chicks were handled in the light at times other than just prior to testing. Handling at 5 and 9 hours had no effect on the approach response, whereas handling at 13, 17. or 23 hours post-hatching decreased such responses. Results were explained on a drive satiation hypothesis.
- Influence of feeder type and form of feed on the performance of broiler crossesBeane, W. L.; Siegel, Paul B.; Howes, C. E. (Virginia Agricultural Experiment Station, 1960-12)Both rate of growth and feed conversion were affected by a form of feed with crumbles giving better results than mash. A sex x form of feed was present for body weight with greater response to the crumbles obtained from the males than from females
- The influence of two light management systems on the growth and production of commercial layersSiegel, H. S.; Beane, W. L.; Howes, C. E. (Virginia Agricultural Experiment Station, 1961-09)The experiment described here was conducted to determine the effect of 2 increasing light schemes on various growth and production characteristics of 2 commercial egg laying strains