Interrelationships between Diet and Elevated Temperatures (Cyclic and Constant) on Concentrations of Progesterone, Estradiol-17β, and Testosterone in Blood Plasma of Laying Hens

In Trial 1, blood was collected from 120 hens after 12 weeks of exposure to an environment of either 21 C constant (21 Co), 31 C constant (31 Co) or 26.7 to 35.6 C cyclic (31 Cy). Relative humidity was 50% in all environments. Subgroups of 20 hens in each environment were fed either a typical corn-soy laying diet or a “High Nutrient Density” diet (HND) which contained an additional 25% of all nutrients except energy which was increased 10%. In Trial 2, one week after Trial 1, blood was collected four times at 2-hr intervals from 35 hens divided among two diets and two environments (21 Co and 31 Cy). Progesterone and estradiol-17β were measured in blood plasma from both trials by radioimmunoassay (RIA) after initial extraction with diethyl ether. Testosterone was measured by RIA in Trial 1 after isolation from progesterone and other steroids by column chromatography. Concentrations of progesterone, estradiol-17β, and testosterone across environments were higher in the hens fed HND. Across diets these steroids were elevated at 31 Co as compared to 21 Co. The 31 Cy environment was intermediate. In Trial 2, environment was a more important variable than diet and it affected primarily hens that ovulated during the day of sampling rather than anovulatory hens. In ovulatory hens, progesterone was about three-fold higher in 31 Cy than in 21 Co and estradiol also was elevated at each of five periods prior to ovulation (from >6.5 hr to <1 hr). Concentrations of progesterone in blood plasma within treatments were correlated significantly with estradiol-17β in Trial 1 (r =.23) and Trial 2 (r = .50) and with testosterone in Trial 1 (r = .24). Testosterone and estradiol-17β also were correlated (r = .57) in Trial 1.