Leucosis in the uterus of a cow

Keywords: bovine, COD, cystic, BLV, leucosis, uterus, bovine

Image size: 1200 x 807px

Bovine leucosis is caused by the bovine leukemia virus (BLV). Many cows are carriers and asymptomatic. In this case, as shown by the arrows, there are multiple foci of leucosis in the uterus of the cow. This cow also had a cystic CL,in the right ovary; a normal structure in many cycling cows (not to be confused with a luteinized cyst).

Luteinized follicles. COD in a cow.

Keywords: COD, cystic, ovarian, ovary, luteinization, disease, cow, production, bovine

Several follicles in one ovary show various degrees of luteinization after chronic low-grade LH stimulation. The presence of numerous follicles indicate that there was no deficiency of FSH in this cow. As is usually the case for cows with cystic ovarian disease (COD) this cow would probably not have shown estrus for a prolonged period of time.

It was once believed that these cows would not ovulate while cystic structures such as these persisted in their ovaries. However it has since been shown that estrous cycles may resume with ovulations adjacent to these cystic structures.

COD in dairy cows is usually associated with high levels of milk production; in beef cows is associated with the use of steroid containing growth promoters.

Cystic follicle in a cow

Keywords:  anestrus, COD, cyst, cystic, follicle, bovine, management, cow, estrous, cycle

Reproductive tract from a cow with cystic ovarian disease (COD); a syndrome associated with high milk production and negative energy balance in high producing dairy cows. COD is usually associated with persistence of large, un-ovulated follicles in the absence of standing estrus, probably because of luteinization (with progesterone production) of the cystic structures due to low pulsatile releases of LH. Nevertheless, this illustration shows that ovulation occasionally occurs in the presence of a cystic follicle. Note the corpus luteum in the left ovary, in the same ovary as the cyst.

In these cases, the cyst may then regress and may even be replaced by other cysts until ovulation becomes predictable and cyclicty returns to normal.

This illustration also suggests that luteinization of cystic follicles may be so limited that they not produce enough progesterone to suppress LH and block ovulation.

The terminology of COD can be confusing, with cystic follicle occasionally being referred to as luteal cysts. In the author's opinion this term should not be used because it can be confused with a structure called a cystic corpus luteum; a non-pathological entity. Instead, when a cyst becomes luteinized it should be called a luteinized cyst rather than a luteal cyst.