AS-456
animal sciences dairy
PURDUE UNIVERSITY COOPERATIVE EXTENSION SERVICE, WEST LAFAYETTE, INDIANA 47907
Reproduction of Dairy Cattle: Postpartum Disorders
M.E. Lech and R.D. Allrich, Department of Animal Sciences L.A. Horstman and C.J. Callahan, Department of Veterinary Clinical Sciences
The postpartum period of the cow presents the dairy producer with many management challenges. Postpartum dairy cows may have one or more reproductive disorders that delay or prevent the start of rebreeding. Delays in rebreeding, beyond approximately 60 to 80 days after calving, greatly reduce reproductive efficiency of the herd and thus greatly increase costs of production.
This publication discusses, in alphabetical order, the common postpartum disorders of dairy cattle.
Cystic Ovarian Disease
Ovarian cysts are follicular structures at least
*	1 inch in diameter, present 10 or more days on
*	the ovary when there is no functional corpus luteum present. The incidence of ovarian cysts ranges from 5 to 20% in most herds, with just over one third of the cysts reported to occur within a few weeks after calving. The cows with cysts show a much earlier follicular development, delayed follicular rupture, and a longer interval to first ovulation. Cystic ovaries are usually associated with a lack of observable estrus (anestrus); however, erratic estrus and nymphomania may also be seen. Ovarian cysts can be classified as either follicular cysts or luteal cysts.
Cause
Several factors influence cystic ovaries in cattle. Milk production has been implicated as a cause of ovarian cysts, because there is a greater occurrence in high milk producers. It must be emphasized, however, that it is still unclear whether the increased milk production leads to ovarian cysts, or whether the imbalanced hor-
monal environment produced by the cysts leads to the increased milk production.
Age and parity are also factors influencing ovarian cysts. There is a much greater occurrence of ovarian cysts in mature cattle (39% incidence) than in first calf heifers (11% incidence).
Breed of cattle (genetic influence) has been shown to affect the occurrence of cystic ovaries. It has long been reported that cyst formation is a heritable trait. Beef cattle rarely are affected with ovarian cysts, and in a Swedish study, through sire selection and a controlled breeding program, the national incidence of ovarian cysts in dairy cattle was decreased from 10 to 3% over a 20-year period.
Seasonal stresses may also play a role in the occurrence of ovarian cysts. Studies report that fall-freshened cattle have an approximately 5% greater chance of producing ovarian cysts than do their spring-freshened herdmates.
Treatment
Treatments have changed over time. Manual rupture during rectal palpation has been used with only limited success. It also may, in rare cases, cause excessive bleeding from the site of rupture and scar tissue formation around the ovary.
The most successful treatment of follicular cysts is the use of hormones that cause ovulation. Human chorionic gonadotropin (hCG) and, more recently, gonadotropin releasing hormone (GnRH) have been administered with up to an 80% response to the treatment and up to a 60% conception rate at the resulting ovulation. Luteal
This publication was made possible in part by the Indiana State Dairy Association.