title: Corpus luteum growth and function in lactating Holstein cows during spring and summer.
abstract: Corpus luteum growth and function were monitored daily for a complete estrous cycle by ultrasonography and peripheral serum progesterone in lactating, cyclic Holstein cows during spring (n = 8) and summer (n = 8). For spring and summer, respectively, daily ambient temperatures (mean +/- SEM) were 21.2 +/- .9 and 31.1 +/- .3 degrees C. In summer compared with spring, early morning rectal temperatures were higher on d 1, 2, and 3, when the corpus luteum was forming, and on d 15 and 19. The length of the luteal phase and the corpus luteum cross-sectional area were similar for the two seasonal groups. Central luteal cavities were observed during spring and summer. Serum progesterone secreted between d 6 and 18 was lower during summer. In addition, progesterone concentrations during the entire luteal phase and the peak magnitude of progesterone tended to be lower during summer. Suppressed luteal function may contribute to low fertility when cows are inseminated during summer.
authors.affiliation: Department of Animal and Dairy Sciences, Mississippi State University 39762.
authors.forename: J L
authors.initials: JL
authors.lastname: Howell
authors.forename: J W
authors.initials: JW
authors.lastname: Fuquay
authors.forename: A E
authors.initials: AE
authors.lastname: Smith
mesh_terms: D000818:Animals; D001831:Body Temperature; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000000981:diagnostic imaging / Q000502:physiology*; D004971:Estrus; D005260:Female; D006813:Humidity; D007774:Lactation / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D012621:Seasons; D013696:Temperature; D014463:Ultrasonography
chemical_list: D011374:Progesterone