Rectal Palpation

1. Proestrus    

    Proestrus is the period before the animal experiences estrus, which is the period when the de Graff follicles are in the body due to the influence of FSH and produce increasing amounts of estradiol. The reproductive system makes preparations for releasing the ovum from the ovary. Follicles or follicles (depending on the species) undergo rapid growth for 2 or 3 days, then enlarge due to increased follicular fluid containing estrogenic hormones.

    Estrogen absorbed by blood vessels from the follicle will stimulate the reproductive tract to undergo changes. Cells and ciliated layers in the fallopian tubes increase in growth, the uterine mucosa is vascularized, the vaginal epithelium is thickened and vascularized, and the cervix is ​​gradually relaxed. There is abundant secretion of thick, mucoid mucus from the goblet cells of the cervix, anterior vagina, and uterine glands. In cattle and horses there is a change from sticky, dry mucus to thick, milky mucus, and at the end of proestrus it changes again to clear, transparent, hanging mucus on the vulva. The corpus luteum of the previous period undergoes rapid vacuolization, degeneration, and shrinkage.

2. Estrus

    Estrus is a period marked by sexual desire and acceptance of males by female animals. During the estrus period, generally the female will seek out and accept the male for copulation. The de Graff follicles mature and enlarge, the estradiol produced by the de Graff follicles will cause changes in the maximum reproductive tract. During or immediately after this period ovulation occurs due to a decrease in FSH and an increase in LH in the blood.

    During this period, the fallopian tubes undergo changes, namely tightening, contracting, mature epithelium, active cilia, and increased fluid secretion. The fimbriated end of the oviduct is attached to the de Graff follicle to capture the mature ovum. The uterus will be erect, tense, and in some species will experience edema. The blood supply increases, the mucosa grows rapidly and mucus is secreted. The cervix is ​​loosened, slightly edematous, and fluid secretion is increased. The vaginal mucosa is very thickened, the secretions increase, the cornified epithelium sheds. The vulva is slack and edematous in all species, particularly in pigs. In cows there is a clear and transparent discharge like a rope hanging from the vulva. At the end of estrus there is an increase in leukocytes migrating into the uterine lumen

Bull

3. Metestrus / Postestrus

    Metestrus is the period immediately after estrus, characterized by rapid growth of the corpus luteum derived from granulosa cells that have ruptured under the influence of LH. Metestrus is largely under the influence of the hormone progesterone produced by the corpus luteum. The presence of progesterone will inhibit FSH secretion so that follicle maturation does not occur and estrus does not occur.

    During this period, the uterus prepares to receive and feed the embryo. In early postestrus, the epithelium of the uterine caruncle is very hyperemic and capillary hemorrhages occur which cause bleeding. Mucus secretion decreases and is followed by rapid growth of the endometrial glands. In the middle to the end of metestrus, the uterus softens somewhat because the muscles relax. If pregnancy does not occur, the uterus and other reproductive tracts will regress to a less active state.

4. Diestrus

    Diestrus is the last and longest phase in the estrus cycle of mammals. The corpus luteum matures and the influence of progesterone becomes dominant. The endometrium thickens, the uterine glands enlarge, and the uterine muscles show increased development. This change is shown to supply nutrients for the embryo when pregnancy occurs. This condition will continue throughout the gestation period and the corpus luteum will be maintained until the end of the gestation period.
The cervix closes tightly to prevent foreign bodies from entering the uterine lumen, the vaginal mucosa becomes pale, and the mucus begins to become cloudy and sticky. If pregnancy does not occur, the endometrium and its glands atrophy or regress to their original size. The follicles begin to develop and eventually return to the proestrus phase.
    In some species that are not included in the polyestrus or seasonal polyestrus groups, after the diestrus period, anestrus will follow. Normal anestrus will be followed by proestrus. Physiologically, anestrus is characterized by quiet, non-functioning ovaries and genital tracts. Physiological anestrus can be observed in countries that have 4 seasons, namely spring and summer in sheep and during winter in horses. During anestrus, the uterus is small and loose, the vaginal mucosa is pale, the mucus is sparse and sticky, and the cervix is ​​tightly closed with pale mucosa. Follicular activity may occur and an ovum may develop but no follicular maturation and ovulation occur.