Frequency of luteinizing hormone surges and egg production rate in turkey hens

Whether the interval between preovulatory surges of LH was different betwee n lines of turkey hens with either poor (RBCS line, peak at 55%) or excelle nt rate of egg production (Egg line, peak at 85%) was examined. Laying hens were cannulated and bled hourly for 10 days at peak of production. A const ant light photoschedule was used to avoid diurnal masking of innate circadi an rhythms. The mean interval between LH surges in the RBC3 line was longer than in the Egg line and had a higher coefficient of variation. A few long er LH surge intervals (> 72 h) were found in some RBC3 line hens (2 of 7 he ns), but none were found in Egg line hens (0 of 11 hens). All progesterone (P-4) surges were coupled with LH surges, but not all LH-P-4 surges were co upled with ovipositions (blind LH-P-4 surges). The percentage of blind LH-P -4 surges was not different between lines. The baseline concentration of LH was higher in Egg line than RBCS line hens, but LH surge amplitude, and su rge duration were not different. The baseline and surge amplitude concentra tions of P-4 were not different between lines, nor was the concentration of estradiol-17 beta. The longer interval between LH surges was the major fac tor tested that was associated with the poorer egg production rate in RBC3 line hens in comparison to Egg line hens. A higher incidence of blind LH su rges further contributed to lower egg production in RBC3 line turkey hens.