Reproduction

Efficiency of reproduction is the single most important trait to consider in the production of meat and fiber.

More money is made and lost due to either the ability to or failure to reproduce.

It includes an understanding of hormones, anatomy and physiology and management.

Puberty- sexual maturity Ovulation- release of ovum (egg) from

ovary Copulation- the act of mating Fertilization- union of male and female

sex cells Conception- becoming pregnant

Estrous Cycle- the interval between two estrus periods

Estrus- the time of receptivity to mating during the estrous cycle; also termed as “heat”

Gestation- pregnancy Parturition- the act of giving birth

The ovaries-2 in number-produce ova and hormones.

Infundibulum-captures the ova after ovulation Oviducts or fallopian tubes-site of fertilization Uterine horns-leads from oviduct to body of

uterus, site of implantation in many-litter species Uterine body-site of implantation in non-litter

species Cervix-guards the uterus Vagina-copulation, parturition Vulva-external genetalia

Scrotum- container for the testes, functions in temperature regulation

Testes(2)-produce sperm and hormones Epididymus-store, transport, mature, conc. Vas deferens-ejaculation Ampulla-widening of tract Seminal vesicles-50% of bulk of semen Prostate-nutrition Cowpers-flushes tract Penis- copulatory organ

Produced in: Hypothalamus-Releasing hormones Anterior Pituitary-Tropic hormones Gonads-Gonadal hormones Uterus-Prostaglandin F2 alpha Placenta-Steroids & gonadotropins Stored in Posterior Pituitary-oxytocin

Part of lower brain that regulates many functions of the body including thirst, hunger, reproduction etc.

Produces releasing hormones for the release of tropic hormones from the anterior pituitary

Anterior pituitary-Small gland in skull that produces 7 tropic hormones.

Gonads-testes and ovaries produce reproductive hormones involved in estrus, ovulation, pregnancy and parturition.

Uterus-produces prostaglandin F2 alpha which is lutylase.

Placenta-produces progesterone, estrogen and species specific gonadotropins (PMSG & HCG).

Beginning with puberty (age at first estrus or ejaculation) Gonadotropin Releasing Hormone (GnRH) from the hypothalamus is secreted from the hypothalamus through a closed blood supply directly into the anterior pituitary where it stimulates the release of Follicle Stimulating Hormone (FSH).

FSH stimulates the follicle to begin the formation of the phases of follicular development. The interior lining of the follicle produces estrogens under FSH influence.

As estrogens rise in the blood stream, the reproductive tract is prepared for pregnancy and the female’s behavior changes (estrus).

When the follicle matures, estrogen is at its peak of secretion which acts on the anterior pituitary to inhibit FSH release and allows GnRH to cause the release of a surge of luteinizing hormone (LH).

This surge of LH causes a softening of the follicle which leads to ovulation.

LH continues to act on the ovulation site (corpus hemorrhagicum) to change it into a corpus luteum which produces a steroid hormone progesterone.

Progesterone has the opposite effects of estrogens in that estrus is suppressed and the uterus is maintained in a pregnant state.

If fertilization occurs, LH maintains the corpus luteum and progesterone is secreted, maintaining pregnancy for the allotted times.

Pregnancy lengths: cattle-283 days, sheep and goats 150 days, swine-114 days and horses-330 days.

If fertilization fails, the uterus senses the absence of an embryo and releases a pseudohormone, prostaglandin F2 alpha on day 14 of the cycle.

PGF2 alpha acts on the CL to destroy it thus dropping progesterone in the blood which releases the inhibition of GnRH and the cycle begins again on day 18 with estrus occurring on day 21.

Fertilization occurs in the oviduct and the fertilized egg reaches the uterine horn in 4 days.

Over the next 45 days, the embryo develops an attachment to the wall of the uterus by implanting its placenta which serves the fetus by transferring oxygen/CO2, nutrients and waste products from the maternal blood to the fetal blood streams.

When the fetus is fully developed its adrenal gland secretes adrenal corticosteroids which stimulates PGF2 alpha to be released by the uterus.

This destroys the CL and allows estrogens from the placenta to begin mild contractions. These contractions cause a reflex release of oxytocin from the posterior pituitary which stimulates increasingly stronger contractions.

As the fetus is delivered, (front legs first with head resting on hooves), contractions continue until the placenta is loosened from its attachment to the uterine wall. Once the placenta is delivered, parturition is complete.

The mammary gland has developed over the last 1/3 of gestation under the influence of progesterone, estrogen and luteotropic hormone (LTH) from the anterior pituitary.

Oxytocin then causes muscle contractions in the udder to cause milk letdown and lactation.

Female born twin to a male Female generally has incomplete

reproductive tract; over 90% are infertile

Fetal membranes anatomose (connect); compounds from the male fetus inhibit normal development of female