The Estrous Cycle in Does

ALABAMA A&M AND AUBURN UNIVERSITIES

UNP-111

Introduction During an estrous cycle a large number of follicles grow simultaneously; The estrous cycle is the interval between approximately 300 to 500 new growths. two estrus dates. The estrous cycle of a However, 25-50 follicles will develop into female goat lasts for 17 to 24 days. This a tertiary follicular stage; and from these cycle is characterized by four periods: tertiary follicles only 1 to 2 will reach a estrus, metestrus, diestrus, and proestrus. dominant follicle state capable of completing maturation and ovulation. The estrus or heat phase lasts 12-48 The remaining undeveloped follicles hours; however, the average length is 36 undergo degeneration. hours. It is extremely important to identify the onset of heat to better control mating systems and for artificial insemination schemes. Timing is imperative for the success of these mating programs.

Metestrus is the phase that lasts 2-3 days. It begins with the end of the estrus period, corresponding with the period in which the doe is no longer receptive to the buck. Ovulation in does occurs approximately 12 to 36 hours from the end of standing heat. Figure 1. Diagram of the Doe's estrous cycle Diestrus is the phase of the cycle that lasts 15-19 days. This is a long phase where there is no sexual activity. The corpus Signs of a Doe in Heat luteum (CL) remains active producing progesterone up to 14 to 16 days. In a non- A doe in heat can be easily identified by pregnant doe the CL will regress to end the behavioral and physiological changes diestrus under the action of prostaglandin- that occur, such as: PGF2α secreted in the uterus unless the doe is bred and becomes pregnant. • Seeking out the buck or staying at the ARCHIVEbuck pen Proestrus or the preparatory phase lasts • Restlessness 2-3 days. It is the phase when several • Frequent urination follicles in the ovaries start to grow under • Vocalization the action of follicle stimulating hormones • Mounting or allowing herself to be (FSHs). During this time some does may mounted by other does, experience vaginal secretions; however, • Swelling, redness, and/or the presence they are not sexually receptive to the male. of mucus on the vulva

www.aces.edu/urban • Tail wagging doe herd. This procedure will avoid • Presenting a vaginal discharge that can undesirable pregnancies. The teaser, like be clear or crystalline at the beginning of the herd sire, must have good libido; be estrus, to a cheesy consistency near and capable of identifying and mounting a after ovulation time. doe in heat; have good feet and articulation; and should be replaced every two years or sooner if libido and mating capacities decrease. However, Uterus nothing replaces daily herd observation.

Estrus Detection Aids

• A teaser must have a marking harness Ovary around the abdomen to paint and to identify does in heat or estrus. CL • Marking harnesses should be replaced every 17 days on a teaser or breeding buck.

Hormone Functions Figure 2. The corpus luteum (CL) in the ovary • Melatonin is secreted by the pineal produces progesterone to maintain pregnancy. gland and regulates the release of the gonadotropin releasing hormone Estrus Detection (GnRH) from the pituitary gland. • GnRH acts on the cells of the anterior Estrus detection is important because it pituitary to promote secretion of FSH identifies repeat breeders, facilitates and LH. artificial insemination scheduling or hand or • FSH acts on the follicles in the ovaries pen mating, and it identifies does that are to stimulate growth and development. It not cycling. also helps to promote spermatogenesis in the seminiferous tubes. The beginning and duration of heat can be • Luteinizing hormone (LH) promotes final detected by a teaser, the herd sire, or by maturation of the follicles and ovulation, the producer. A teaser is usually a the formation of the CL, and it promotes surgically-altered male that has testosterone production in the testicles. undergone a vasectomy or an epidectomy. • Estrogens are steroid hormones These surgical procedures prevent produced by the follicles. Estrogens ejaculation and undesirable pregnancy. A promote the physical and behavioral teaser can also be a wethered female that manifestation characteristics of the doe is treated with steroid hormones such as in heat and stimulate the production of estrogen or androgens. The advantage of cervical and uterine secretions during ARCHIVEestrus. Estrogens are responsible for utilizing an altered male as a teaser is that he can induce heat when introduced to a the development of the female's group of does. secondary sex characteristics such as the development of the mammary gland The teaser must be surgically prepared at and the female appearance. least three months prior to the breeding • Progesterone is a steroid hormone season and must be tested for sterility secreted by the CL and helps to before being placed in contact with the promote the secretion of endometrial glands, providing a uterine

2 Alabama Cooperative Extension System environment for embryo implantation, fertilization. Oxytocin plays important nourishment, and maintenance of role in Prostaglandin F2α (PGF2α) pregnancy. Progesterone inhibits the synthesis in the uterus. It enhances anterior pituitary from secreting FSH uterine contraction during parturition and LH. It also promotes mammary process and promotes contraction of gland development during pregnancy. cells of the mammary glands to • Oxytocin is secreted by the posterior promote milk letdown. pituitary. It is released during copula • Prostaglandin F2α is secreted by the and induces female tract contractions to glands of the uterus, promoting facilitate ova and spermatozoa motilities luteolysis or regression of the CL and in the opposite direction to facilitate uterine contractions.

Table 1 Hormones that regulate the reproductive process

Producing Organ Hormone

Pineal Gland Melatonin

Hypothalamus Gonadotropin Releasing Hormone (GnRH)

Anterior Pituitary Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH) Prolactin

Posterior Pituitary Oxytocin

Ovary (Follicles) Estrogens

Ovary (Corpus Luteum) Progesterone

Uterus Prostaglandin F2α ARCHIVE

The Estrous Cycle in Does 3 References

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Maria Lenira Leite-Browning, DVM, Extension Animal Scientist, Alabama A&M University and Richard Browning Jr., Ph.D. Associate Professor, Department of Agricultural Sciences, Tennessee State University Special thanks to Pamela Jude, Technical Assistant, Communications Networking Center, for Figure 1

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