The Estrous Cycle in Does

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Introduction

The estrous cycle is the interval between two estrus dates. The estrous cycle of a female goat lasts for 17 to 24 days. This cycle is characterized by four periods: estrus, metestrus, diestrus, and proestrus.

The estrus or heat phase lasts 12-48 hours; however, the average length is 36 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.

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 luteum (CL) remains active producing progesterone up to 14 to 16 days. In a non-pregnant doe the CL will regress to end diestrus under the action of prostaglandin-PGF2a secreted in the uterus unless the doe is bred and becomes pregnant.

Proestrus or the preparatory phase lasts
2-3 days. It is the phase when several follicles in the ovaries start to grow under the action of follicle stimulating hormones (FSHs). During this time some does may experience vaginal secretions; however, they are not sexually receptive to the male.

During an estrous cycle a large number of follicles grow simultaneously; approximately 300 to 500 new growths. However, 25-50 follicles will develop into a tertiary follicular stage; and from these tertiary follicles only 1 to 2 will reach a dominant follicle state capable of completing maturation and ovulation. The remaining undeveloped follicles undergo degeneration.

Figure 1. Diagram of the Doe's estrous cycle

Signs of a Doe in Heat

A doe in heat can be easily identified by the behavioral and physiological changes that occur, such as:

• Seeking out the buck or staying at the buck pen
• Restlessness
• Frequent urination
• Vocalization
• Mounting or allowing herself to be mounted by other does,
• Swelling, redness, and/or the presence of mucus on the vulva
• Tail wagging
• Presenting a vaginal discharge that can be clear or crystalline at the beginning of estrus, to a cheesy consistency near and after ovulation time.

Figure 2. The corpus luteum (CL) in the ovary produces progesterone to maintain pregnancy.

Estrus Detection

Estrus detection is important because it identifies repeat breeders, facilitates artificial insemination scheduling or hand or pen mating, and it identifies does that are not cycling.

The beginning and duration of heat can be detected by a teaser, the herd sire, or by the producer. A teaser is usually a surgically-altered male that has undergone a vasectomy or an epidectomy. These surgical procedures prevent ejaculation and undesirable pregnancy. A teaser can also be a wethered female that is treated with steroid hormones such as estrogen or androgens. The advantage of utilizing an altered male as a teaser is that he can induce heat when introduced to a group of does.

The teaser must be surgically prepared at least three months prior to the breeding season and must be tested for sterility before being placed in contact with the doe herd. This procedure will avoid undesirable pregnancies. The teaser, like the herd sire, must have good libido; be capable of identifying and mounting a doe in heat; have good feet and articulation; and should be replaced every two years or sooner if libido and mating capacities decrease. However, nothing replaces daily herd observation.

Estrus Detection Aids

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

Hormone Functions

• Melatonin is secreted by the pineal gland and regulates the release of the gonadotropin releasing hormone (GnRH) from the pituitary gland.
• GnRH acts on the cells of the anterior pituitary to promote secretion of FSH and LH.
• FSH acts on the follicles in the ovaries to stimulate growth and development. It also helps to promote spermatogenesis in the seminiferous tubes.
• Luteinizing hormone (LH) promotes final maturation of the follicles and ovulation, the formation of the CL, and it promotes testosterone production in the testicles.
• Estrogens are steroid hormones produced by the follicles. Estrogens promote the physical and behavioral manifestation characteristics of the doe in heat and stimulate the production of cervical and uterine secretions during estrus. Estrogens are responsible for the development of the female's secondary sex characteristics such as the development of the mammary gland and the female appearance.
• Progesterone is a steroid hormone secreted by the CL and helps to promote the secretion of endometrial glands, providing a uterine environment for embryo implantation, nourishment, and maintenance of pregnancy. Progesterone inhibits the anterior pituitary from secreting FSH and LH. It also promotes mammary gland development during pregnancy.
• Oxytocin is secreted by the posterior pituitary. It is released during copula and induces female tract contractions to facilitate ova and spermatozoa motilities in the opposite direction to facilitate fertilization. Oxytocin plays important role in Prostaglandin F2a (PGF2a) synthesis in the uterus. It enhances uterine contraction during parturition process and promotes contraction of cells of the mammary glands to promote milk letdown.
• Prostaglandin F2a is secreted by the glands of the uterus, promoting luteolysis or regression of the CL and uterine contractions.

References

Chemineau, P., Berthelot, X., Daveau, A., Maurice. F, Viguié, C., & Malpaux, B. (1993, October). [Can melatonin be used in out-of-season reproduction in domestic mammals?] Contracepion Fetilité Sexualité, 21(10), 733­738.

Chemineau, P., Guillaume, D., Migaud, M., Thiéry, J. C., Pellicer-Rubio, M. T., & Malpaux, B. (2008, July 9). Seasonality of reproduction in mammals: intimate regulatory mechanisms and practical implications. Reproduction in Domestic Animals, 43 Supplement 2, 40-47.

Gonzalez-Stagnaro, C. (1983). Comportamiento reproductivo de las razas locales de rumiantes en el Tropico Americano. In: Chemineau, P., Gauthier, D., Thimonier, J. (Eds.), Reproduction des Ruminants en Zone Tropicale (pp. 1­80). France: Institut National de la Recherche Agronomique.

Gourdine, J. L., Bidanel, J. P., Noblet, J. & Renaudeau, D. (2006). Effects of season and breed on the feeding behavior of multiparous lactating sows in a tropical humid climate. Journal of Animal Science, 84, 469-480.

Hafez, E. S. E., and Hafex, B. (2000). Reproduction in Farm Animals (7th ed). New Jersey: Blackwell.

Hawken, P. A., Beard, A. P., Esmaili, T., Kadokawa, H., Evans, A. C., Blache, .D, and Martin, G. B. (2007, July). The introduction of rams induces an increase in pulsatile LH secretion in cyclic ewes during the breeding season. Theriogenology, 68(1), 56-66.

Leboeuf, .B, Delgadillo, J. A., Manfredi, E., Piacère, A., Clément, V., Martin, P., et al. (2008, July). Management of goat reproduction and insemination for genetic improvement in France. Reproduction of Domestic Animals, 43 Supplement 2, 379-385.

Martin, G. B., Rodger, J., & Blache, D. (2004). Nutritional and environmental effects on reproduction in small ruminants. Reproduction, Fertility, and Development, 16(4), 491-501.

Morrow, D. A. (1986). Current therapy in theriogenology. Toronto: W. B. Saunders.

Raposo, R. S., Silva, L. D. M., Lobo, R. N. B., Freitas, V. J. F., & Dias, F. E. F. (1999). Perfil citológico vaginal de cabras cíclicas da raça Saanen. Ciência Animal, 9(2), 75-79.

UNP-0111, May 2009, 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