1 Introduction, Hormonal Regulation of Ovarian Activity, Predisposing Factors

Transcript

Dear friends

Greetings to all!

First of all, I would like to introduce myself Dr. K Krishna Kumar Professor and Head, Department of Veterinary Gynaecology and Obstetrics, Madras Veterinary College, Chennai, Tamil Nadu, Veterinary and Animal Sciences University, Tamil Nadu, India. We are going to discuss about Cystic Ovarian Degeneration in cattle. The first lesson comprises of Introduction, Hormonal regulation of Ovarian activity, Predisposing factors, Signs and Symptoms of Cystic Ovarian Degeneration.

Introduction:

Cystic Ovarian Degeneration is a common, clinically recognized cause of infertility in dairy cattle. The incidence has been 6-19%. The huge incidence of Cystic Ovarian Degeneration is recognized as a serious cause of reproductive failure. Cystic Ovarian Degeneration is characterized by one or more large anovulatory follicles greater than 2.5 centimeters in diameter, present in one or both ovaries that persist for at least 10 days in the absence of the corpus luteum with abnormal estrous behavior. Here the diameter of 2.5 centimeters, is meant for large size breeds like HF or Jersey like that, in our Indian breeds or in small breeds like Vechure, that may have 100KG body weight or in case of other indigenous breeds may have 250KG body weight, this 2.5-centimeter diameter is not applicable, hence another definition is required, that is one or more large follicles greater than 17 millimeters, that is 1.7 centimeter in diameter, failed to ovulate and subsequently do not regress and persist for at least 10 days, but maintain growth and steroidogenesis.

What is a Hormonal Regulation of Ovarian Activity? First, we have to know the basics of follicular development, Ovulation, and Endocrinological events that occur in a normal Physiology. First, the GnRH is secreted from the hypothalamus, which will act on the anterior pituitary that in turn release FSH and LH from the anterior pituitary. This FSH is highly essential for the growth of the follicle. This FSH will act on the follicle, so the follicle can get maturity. So, the matured and developing follicle can secrete a sufficient amount of estrogen, that estrogen is having a positive feedback effect on hypothalamus and pituitary, that in turn release of LH, that LH is highly essential for ovulation. This LH will act on the ovarian follicle. Matured follicle ovulation occurs. After ovulation, the corpus luteum formation occurs, this corpus luteum is going to secrete progesterone, this progesterone is highly essential for the negative feedback effect on FSH, then only further development of follicle may not occur, but this negative feedback is not applicable for LH because this LH is highly essential for the corpus luteum maintenance. This is the normal physiological Hormonal Regulation of Ovarian activity in cattle.

What are the Predisposing Factors for Cystic Ovarian Degeneration?

Most prevalent in high-producing dairy cows, especially which occurs 30 to 60 days after calving, mostly up to the first ovulation, 60% of the animals may have cystic ovarian degeneration condition, among this 40% of the animals may get recovery spontaneously, another 20% only may persist. The second one is it is common in closely confined and stabled animals, normally the moment of the animal and exercise is highly essential for the normal reproductive management and maintenance of the animal. Here it is closed confinement and the stabled animals may not have sufficient exercise, that is lack of exercise is a common cause for the Endocrinological disturbance.

The next one is it occurs during winter than summer and fall months. It is clearly indicated that during the winter months, it is closely confined. In the summer months, it is freely movable. Intake of estrogen-containing forages is another cause of Cystic Ovarian Degeneration, because these forages may have a high quantity of estrogen, for example, Alfalfa, Zearalenone, Red Clover like plants.

Then Increased Stress at calving; that is also having negative energy balance.

Metabolic diseases, like calcium deficiency, Ketoses like diseases are predisposing this Cystic Ovarian Degeneration.

Excess negative energy balance.

Hereditary- especially Twinning is highly correlated with the Hereditary.

High protein diet intake.

Uterine infection any postpartum complications like dystocia, RFM, metritis, etc are acting as a predisposing factor for Cystic Ovarian Degeneration.

This picture (showing picture) demonstrates that how heat, stress, and any stress may act as predisposing factors. Here, heat stress, not only heat stress, any stress condition, especially in postpartum condition, animals feed intake will be reduced, and the respiratory rate will be increased, that in turn, negative energy balance occurs. This negative energy balance causes a reduction in GnRH and LH and FSH secretions and increases in CRH and ACTH secretions. This CRH and ACTH secretion may involve in an increase of Glucocorticoid secretion, Catecholamine, and cortisol secretion, which in turn reduction in estradiol secretions, so it will lead to a reduction in follicular dominance, reduction in estrous expression, reduction in Oocyte quality, and finally fertility will be affected.

Another cause is the Subnormal Luteal level of Progesterone which is observed in high-producing dairy cows, especially energy-compromised animals. So, any subnormal luteal levels lead to inadequate formation of LH receptors, in the presence of inadequate formation of LH receptors leads to decreased sensitivity to LH of the growing follicles, so that in turn creation of a persistent dominant follicle and cyst formation occurs. So once the creation of persistent follicle and cyst formation occurs, leads to arrest of the next to follicular waves before dominance and ovulation. Finally, end up in anovulation and anestrous.

So far, we discussed about Introduction, Hormonal Regulation of Ovarian Activity, predisposing factors, Signs and Symptoms, so the remaining parts will be discussed in the next class.

Thank you!