Correlated physiological responses in a bidirectional selection experiment for body weight in chickens

The concentration of reduced blood glutathione, feed efficiency, oxygen consumption, and growth were studied in two lines of chickens that had undergone divergent selection for body weight at eight weeks of age. The latter three traits were studied in two light environments, continuous illumination and a ratio of 8 hours light to 16 hours darkness. The dissertation involved two experiments and chickens from the S₁₁, S₁₂, and S₁₃ generations of the high and low weight lines. Blood glutathione, body weight, and percentage packed cell volume were measured in S₁₁ generation males at 1, 4, 7, 10, 13, 16, 19, 28, 56, 112, and 168 days of age. Males from the high weight line were heavier at all ages and had a higher packed cell volume at 28 days of age and thereafter than those from the low weight line. Blood glutathione was consistently greater in the high line than in the low line with the largest differences between lines occurring at the younger ages. The influence of light environments on growth, feed efficiency, and oxygen consumption was studied in two trials utilizing chicks from the S₁₁ and S₁₂ generations. Body weights and feed efficiencies were measured at 14, 28, 42, and 56 days of age and oxygen consumption at 28 and 56 days of age. Chicks from the high weight line were heavier at all ages and they had consistently superior feed efficiencies and lower rates of oxygen consumption than those from the low line. Chicks maintained under continuous illumination were heavier and had superior feed efficiencies than those reared in restricted light. Oxygen consumption of chicks reared in restricted light was greater than that for those under continuous light when the measurements were obtained during the day i.e. the time of their photoperiod. No differences were observed between light environments when determinations were made in the evening, showing a diurnal rhythm between the day and evening measurements. To obtain more information on the metabolism of these lines, oxygen consumption was measured at 28, 42, and 56 days of age on a sample of S₁₃ generation males. The results agreed with those obtained in the S₁₂ generation in that oxygen consumption was lower for males from the high weight line than for those from the low weight line. The primary conclusions from these experiments are that divergent selection for high and low body weight results in correlated responses of blood GSH, feed utilization, and metabolic rates. Further, although different light environments may result in varying responses in feed utilization and metabolic rates, line x light environments interactions were not important for traits other than body weight.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Genetics

Department dc:contributor.department

Genetics

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1970

Author dc:creator

• Owens, Charles Allen

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/77799

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/77799