Postpartum corpus luteum in a cow

Keywords: cow, bovine, postpartum, ovary, corpus luteum, CL

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Corpora lutea (CLs) in the ovary of a cow approximately one week after she had given birth to twins. The cow was euthanized because she had injured herself during calving. This image shows that corpora lutea are still present within the ovary for at least a week after calving; this despite the fact that they are not required for the maintenance of pregnancy for the last four months of gestation. These corpora lutea would have been producing little if any progesterone. In fact, cows can be ovariectomized after the first month of gestation and will maintain pregnancy and can calve normally. Therefore, the role of the ovaries (and corpora lutea in this case) during late gestation cattle is uncertain.

Follicle and a corpus luteum; ultrasound

Key words: wave, bovine, CL, corpus luteum, follicle, cow, ultrasound

Image size: 640 x 480px

A large follicle (the anechoic structure) adjacent to a corpus luteum (CL) in the ovary of a cow; as seen during transrectal ultrasonography. Follicles grow and regress in waves during the bovine estrous cycle. There are commonly two or three waves of follicle growth during the diestrous period. When there are three waves, the estrous cycle is longer (21 to 22 days) than when they are two follicle waves (19 to 20 days). Less commonly,  cows may even have four follicle waves. Therefore the discovery of a large follicle during diestrus (as in this case) does not necessarily mean that a cow is approaching estrus.

A follicle and a luteinized cystic follicle

Keywords: CL,corpus, luteum, cystic, bovine, cycle, infertility, cow, ultrasound

Image size: 640 x 480px

A follicle and a luteinized cystic follicle seen by transrectal ultrasonography in a cow.

Together with its appearance, a history of postpartum anestrous allowed a diagnosis of a luteinized cystic follicle (sometimes referred to a luteal cyst) in this cow.  Cystic follicles and the luteinized structures they develop into, are abnormal structures, associated with an absence of estrous cycles in the early to late postpartum period; almost always in dairy cows. In dairy cows, abnormal estrogen secretion and abnormal LH surges are thought to be important in the syndrome. Cystic follicles are also seen in beef heifers, but usually only after the use of steroid growth promoters.

Clarification: Cystic corpora lutea are normal structures, associated with normal estrous cycles.  Most corpora lutea luteinize completely, obliterating the antrum of the ovulated follicle but many are left with small to large cysts in the center.  This author does not use the term “luteal cyst” (an abnormal structure) because it can easily be confused with the term “cystic corpus luteum” (a normal structure). Instead, the term luteinized cyst (a cystic follicle that has become luteinized) should be used.

Leucosis in the uterus of a cow

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

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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).

The corpus luteum and corpus albicans.

Keywords: CL, bovine, cow, palpation, progesterone

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The crown of a corpus luteum (CL) in an ovary of a cow.  The CL is a source of progesterone and several other hormones, including relaxin, müllerian inhibiting hormone, inhibin and even GnRH.

A CL is easily palpable per rectum in most cases and is useful for determining if the cow is having estrous cycles and in some cases, assisting one in staging the estrous cycle. The crown of a corpus luteum is seen in all species except horses where the tunica albuginea does not allow the follicle to ovulate through the surface of the ovary.

After ovulation, blood fills the antrum of the follicle, coagulating and forming a corpus hemorrhagicum. As this blood is phagocytosed, the theca granulosa of the ovarian follicle undergoes both hyperplasia and hypertrophy, folding in towards the center of the antrum.

This image shows the size of a mature CL, the author's thumb depressing the cut surface of that structure in a transected ovary.

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In the example shown below, that folding is clearly visible.

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After luteolysis, the corpus luteum undergoes regression and shrinks, forming a corpus albicans. The term "albicans" is derived from the Latin word for white but in domestic animals, this is practically a misnomer. In fact it is only in a few animals (cetaceans for example) where the corpus albicans remains as a large, substantial structure after luteolysis.  In domestic animals it only becomes a small, white body long after luteolysis is complete and in fact, is often invisible to the naked eye by that time.  Indeed, at the end of the luteal phase in domestic animals, when it is commonly referred to as a corpus alicans, the corpus "albicans" (CA) is a dark yellow-to-bright orange structure as shown here.

A CA is seen below, advanced in its luteolysis and degeneration, evidence by rays of fibrous tissue in the structure. Note that this luteal structure has a cavity in the center; a common finding in luteal tissue in cattle. It is not abnormal and is merely a function of luteinization from the theca granulosa growing but never reaching the center of what was previously a follicle. Instead of being referred to as a cystic CL/CA it is often labeled a "luteal cyst".

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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.