Effects of Exogenous Estrogen and/or Androgen on Performance, Egg Shell Characteristics and Blood Plasma Changes in Laying Hens

Abstract

THE physiological factors responsible for decline in egg production and egg shell characteristics with age in the chicken are not fully known. Recent research has indicated that certain dietary alterations may prevent a portion of the decline in egg shell quality. Hurwitz and Griminger (1960 Hurwitz and Griminger (1962) reported that maximum calcium (Ca) retention was 1.5 to 1.7 mg. per bird per day in old hens as compared to 2.0 gm. or more with young hens. Based upon work with mice, Draper (1964) suggested that the tendency of aged animals towards a negative Ca balance is not due to a decreased absorption rate from the intestine, but is due to an incomplete replacement of Ca eroded from the skeleton. Gardner and Pfeiffer (1943) reported that estrogen increased the transfer of Ca from gut to blood stream, increased serum Ca and accelerated formation of endosteal bone in pullets. In immature pullets, Common…