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Reproduction from the inside out

DCRC | Updated: 10/20/2010

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Better understanding of the anatomy and physiology of your cows’ reproductive tract can be used to your advantage to increase conception rates and reproductive efficiency. This article outlines the basics of the reproductive tract and how this knowledge can be used to increase reproductive success.

The Reproductive Tract

Located internally below the rectum, the reproductive tract includes the vulva, vestibule, vagina, cervix, uterus, oviducts and ovaries. The uterus, oviducts and ovaries are attached by a ligament and suspended in the cow’s pelvic region. Suspension of the organs allows them to move freely, which provides space for the growing calf.

Vulva. The only visible external portion of the reproductive tract, with thickened folds of skin; this structure is sensitive to changes in estrogen, the hormone responsible for estrus.

Vestibule. Shared with the urinary system, this part of the reproductive tract has openings for the urinary bladder and suburethral diverticulum located on its floor.

Vagina. Serving as an unrestrictive passageway for the calf at the time of birth, the vagina is also the location of semen deposition during natural service. In addition, an important function of the vagina is a line of defense against the invasion of bacteria into the remainder of the reproductive tract.

Cervix. Located between the vagina and the uterus, the cervix is designed to restrict access to the uterus. Walls of the cervix are very thick and the body of the cervix contains three or four rings called annular folds, easily distinguished by rectal palpation.

Uterus. Consisting of the uterine body and horns, the uterus serves several functions. The walls of the uterus are comprised of three layers—the serosa, myometrium and endometrium. The endometrium is the inner-most layer and aids in the transportation of sperm to the oviduct. The myometrium is the muscle layer, which aids in the expulsion of the calf at the time of birth. Additionally, the uterus provides nourishment and protection to the developing fetus.

Oviduct. At the ovarian end of the oviduct is the infundibulum. The infundibulum is funnel-shaped, catches the egg as it is released from the ovary at ovulation and carries it to the ampulla, the enlarged upper end of the oviduct. After reaching the ampulla, fertilization occurs within 12 hours of ovulation. Following fertilization the newly created ovum is then moved to the uterus over a three- to four-day period.
Ovaries. The ovaries are located toward the end of the oviduct near the tips of the uterine horns. Producing the egg and the hormones involved with regulating the estrous cycle are the main functions of the ovaries.

Management of Reproductive Tract

Understanding the components of the reproductive system is critical to ensuring cows are properly bred. Keys to breeding pen success include:

Good management practices. If unsanitary conditions are present, vaginal health can be at risk of infection. Providing a clean environment can help minimize its effects on the reproductive tract and ensure any challenges related to breeding are due to other causes.
A heat detection tool. Utilize the vulva as a visual indicator of estrus alongside on-farm estrous detection tools, such as visual observation of cows standing to be mounted, tail painting and electronic heat detection aids.
Successful breeding. Knowing the location of the vestibule openings is important during A.I. to prevent insertion of the A.I. rod into the urinary bladder and suburethral diverticulum. If insertion at these sites occurs, the insemination practice will result in failure and possible injury. Furthermore, manipulation of the cervical rings in order to enter the uterine body is necessary for a successful insemination with A.I.
Ovary navigation. At puberty ovulatory follicles develop, and as each follicle enlarges, it appears as a large blister on the surface of the ovary, which is easily detected by rectal palpation. After ovulation, the walls of the follicle collapse, forming what is called a corpus luteum (CL). Development of a follicle is closely associated with the production of estrogen, whereas the CL development leads to progesterone production. Familiarizing yourself with the hormones and their contribution to the reproductive cycle will allow you to better navigate the estrous cycle, ultimately getting cows bred sooner and maintaining pregnancy.
Birthing knowledge. The birth process is broken down into three categories: preparation stage with relaxation of the pelvic ligaments, the delivery of the calf, and delivery of fetal membranes, also referred to as “cleaning.” During the calving phase several hormones including progesterone, estrogen, prolactin, relaxin and corticoids trigger the muscles of the uterus to contract and deliver the calf and membranes through the dilated cervix and vagina. Allowing your cows to calve in a clean environment and treating cows after a difficult calving will help prevent future reproductive problems.
Postcalving knowledge. After calving occurs the uterus should return back to its normal condition following a 30-40 day period. Discharges that take place during this time period are due to repair of the uterine tissues and should be of minimal concern, unless they are watery and fetid during the first 14 days after calving or unless containing puss 21 days postpartum. If watery and fetid during the first 14 days after calving, this indicates local infection, requiring treatment. Monitoring cows frequently postpartum and early treatment of infection will prevent long-term damage to the reproductive tract.

The reproductive organs of the dairy cow have the most direct impact on breeding pen performance. Utilizing your knowledge of each piece of the reproductive tract will allow you to optimize the reproductive performance of your cows.