Doctoral Dissertations

Date of Award

12-1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Kelly R. Robbins

Committee Members

B.H. Erickson, J.M. Grizzle, D.S. Sachan

Abstract

Experiments with broiler breeder hens were undertaken to determine the effect of feeding time and environmental temperature on various production parameters, feed consumption, body weight, blood pH and blood concentrations of calcium, estradiol and androstenedione. Two temperature treatments were used: low cyclic temperature (10-25 C or LO); and high cyclic temperature (21-39 C or HI) . Hens were randomly assigned to feeding times of either 0700, 0700 and 1800, or 1800 h. In another experiment, hens were assigned to feeding times of either 0700 or 1800 h.

The results obtained indicated that feeding time and temperature did not markedly affect rate of egg production; however, hens at HI and fed at two times per day produced the fewest eggs. High temperatures caused a significant reduction in egg weight, specific gravity and shell thickness. A numerical improvement occurred in egg specific gravity and shell thickness due to feeding at 1800 h. Significant body weight loss occurred in hens at HI and fed at 0700 h. Time of oviposition, ovulation and the transit time of the egg through the different regions of the oviduct were not significantly changed due to feeding time or temperature despite an increase in number of eggs laid late in the day when feeding time was changed to 1800 h. Different patterns of feed consumption were observed in relation to feeding time, oviposition, and temperature.

High temperatures did not affect blood calcium, plasma total calcium, estradiol, or androstenedione, but increased blood pH in hens fed at 0700 h. Laying hens maintained at LO exhibited a cyclic pattern in blood ionized calcium, and plasma total calcium over the egg cycle, whereas hens at HI exhibited a similar pattern in pH and plasma total calcium but not ionized calcium during this time. Non-laying hens showed no significant changes in blood calcium concentrations throughout the same sampling period.

In conclusion, feeding broiler breeder hens at 1800 h may represent a viable means for improving egg shell quality particularly in hens at high temperatures. The results also indicate that the adverse effects of heat stress on egg shell quality are linked to factors other than a decline in blood ionized calcium.

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