Characterization of circadian patterns of LH release in stallions in summer and winter

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references.The objective of this study was to characterize the pattern of plasma LH release in a group of normal stallions in the breeding (summer) and non-breeding (winter) season using frequent blood sampling techniques. Stallions were classified as normal based on semen parameters. Blood samples were collected at 15 min intervals for a period of 24 h in both seasons using an indwelling jugular catheter. A double-antibody radioimmunoassay was used to determine plasma LH concentrations. Mean LH concentration ranged from .39 ︢ .034 ng/ml to 4.34 ︢.191 ng/ml in the summer period and from .34 ︢.027 ng/ml to 5.43 ︢.174 ng/ml in the winter period, with all stallions exhibiting a significant (p< .001) difference in mean plasma LH concentration across the two seasons. However, contradictory to prevalent literature, 4 of the nine stallions had higher mean LH concentration in the winter collection period. No obvious reason was stallions for LH means when samples were pooled across seasons. When the data were separated based on day (0600 to 1800) and night (1800 to 0600) periods, all stallions had higher LH concentrations (p < .0001) during the day in both seasons. Age was also a significant (p < .0001) factor in the research model. Data from this research indicate that stallions display a wide variability in plasma LH concentration and may not be as seasonally predictable as previous literature would indicate. Circadian LH concentration in stallions is affected by age, time of day and season