Validation of dual-energy x-ray absorptiometry to measure bone mineral density and identification of quantitative trait loci in chickens
Abstract
The purpose of this research was to validate measurement of bone mineral density (BMD) in chickens using dual-energy X-ray absorptiometry (DEXA) and to use DEXA to identify genetic variation responsible for skeletal integrity. Objectives of chapters II and III were to examine the use of DEXA as a non-invasive tool to monitor skeletal integrity in live chickens and to correlate densitometric scans with other bone strength criteria. Experiments in chapters II and III compared BMD in live birds to excised bones and bone strength criteria in hens fed calcium levels of 1.8, 3.6, and 5.4%. Results showed that DEXA accurately measured BMD in live chickens and was a useful indicator of bone strength. Experiments in chapter IV were conducted to determine if there were detectable changes in BMD while an egg was formed in the oviduct and to monitor the change and degree of variation in skeletal integrity of live birds during the first egg-laying cycle. Results indicated that densitometric scans may be conducted on bones in live birds any time of day, irrespective of stage of egg formation. Age-related increases in BMD were observed, possibly due to the inability of DEXA to distinguish medullary from structural bone. Objectives of chapters V and VI were to identify quantitative trait loci (QTL) associated with BMD, bone strength, egg production, egg quality, and body weight in an F2 resource population generated from a cross between White Leghorn hens and broiler roosters. Overall, 37 significant QTL at the 5% genome-wise level located on chromosomes 2, 4, 10, 24, and 27 were detected. The QTL identified in this study represent regions of the chicken genome important in regulating bone strength and production traits. This study is the first to identify QTL influencing bone characteristics in chickens and contributes to the growing map of QTL influencing egg characteristics and body weight. Further investigation of QTL influencing these traits may help to more clearly define our current understanding of the physiological and genetic mechanisms that integrate and regulate bone metabolism, egg production, and shell quality.
Degree
Ph.D.
Advisors
Moody, Purdue University.
Subject Area
Livestock|Anatomy & physiology|Animals
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