Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Animal Science

Major Professor

Kelly R. Robbins

Committee Members

J.P. Hitchcock, R.R. Shrode, M.O. Smith, S.D. Mundy


Six experiments were conducted utilizing broiler breeder females in both windowed and windowless houses to assess or determine: 1) the effect on sexual maturity and subsequent egg production produced by light intensity changes during photostimulation; 2) "black-out" versus natural daylength rearing programs; 3) effect on productivity of broiler breeder pullets caused by rearing and stimulating photoperiods; 4) effect on egg production resulting from light intensity changes and feed allowance during lay; 5) optimum age and body weight at sexual maturity in broiler breeders; and 6) daily ME requirement of the broiler breeder hen.

Traits measured included growth rate, average age and body weight at first egg, peak % hen-day production and age at peak production, rate of decline in % hen-day production, average number of eggs per hen, feed consumed through first egg or per dozen eggs, egg quality and mortality rate.

The results obtained indicated that light intensity changes during photostimulation or peak egg production did not affect any of the measured traits. However, birds maintained under high light intensity from hatching (HH) produced more eggs and achieved a significantly higher peak % egg production than birds housed under low light intensity. Rearing photoperiod on the other hand, significantly affect the age at sexual maturity and subsequent performance of the birds. Optimum age (172 d) or body weight (3.4 kg) at sexual maturity were determined from either feeding management or combination of light and feeding management.

Hens provided with 540 vs. 435 kcal ME/d commenced laying 14 days earlier with a significant improvement in growth and egg production rates. Neither livability nor egg quality was affected by treatment; however, feed efficiency was significantly depressed by the high energy level.

The results indicated also that birds responded significantly better to a higher amount of daily feed intake. Daily dietary energy of 425 kcal ME/bird with 0.0565 g/kcal ME protein:energy ratio was found to support performance adequately through 35 weeks of age but not thereafter, as shown by other diets of either similar protein:energy ratio but higher energy level (500 kcal ME) or lower protein:energy ratios (0.048-0.0533 g/kcal ME) but higher energy levels (450-500 kcal ME).

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