The overall objective was to determine the effect of an induced molt on the skeletal integrity of White Leghorns. The objectives of chapter II were to assess the integrity of bones of White Leghorns during an induced molt and a second cycle of egg laying, and to determine the correlation of in vivo measurements of skeletal integrity using dual-energy-X-ray absorptiometry (DEXA) with more traditional bone mechanical tests and the incidence of broken bones in carcasses of processed spent hens. Results showed that an induced molt was detrimental to skeletal integrity and incidence of breakage was negatively correlated with densitometric readings of excised bones. Experiments of chapter III determined the effect of an induced molt using non-withdrawal of food (non-fasted molt) on the bone mineralization of White Leghorn hens. Results demonstrated that a nonfeed removal molt diet was less deleterious to bone mineralization during molt as compared to a fasted molting program.; The objectives of chapter IV were 2-fold: (1) to monitor the carryover effect of pre- and postmolt diets containing high omega-3 polyunsaturated fatty acids (PUFA) on the skeletal integrity of White Leghorns before, during, and after a fasted or non-fasted mo and (2) to determine the influence of diets containing high omega-3 PUFA and molting programs on plasma insulin-like growth factor-I (IGF-I) concentrations and the expression of hepatic IGF-I mRNA expression. Results showed that dietary omega-3 PUFA in the pre- and postmolt diets had little effect on the decline of skeletal integrity during molt and that circulating IGF-I concentrations were profoundly affected by molt. This research is the first to examine the effects of induced molt on bone mineralization using DEXA. In addition, this is the first description regarding circulating IGF-I and its mRNA IGF-I gene expression in the liver of hens during molt and the beginning of the second cycle of egg laying.
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