GENETICS AND BREEDING 3025A REPRODUCTION

I.REPRODUCTION IN MALES

A.After sexual maturity of the male, sperm production is continuous under most conditions.

B.Testosterone is the primary male sex hormone responsible for: The growth, development, and secretory activity of the accessory glands. The survival of spermatozoa. The secondary sex characteristics, crest, male voice, and sex drive.

C.“Semen” is the fluid ejaculated by the male for reproductive purposes. It is made up of: Fluid from the many accessory glands. Sperm cells.

D.The amount of spermatozoa and total volume of seminal fluid varies in each species.

E.Spermatozoa may be stored in the epididymis for several days. In the female, sperm will survive for hours. If frozen for artificial insemination, it will last many years.

II.REPRODUCTION IN FEMALES

A.Most farm animals reach sexual maturity in 4-24 months; at this time the follicles begin to develop, then: The female comes in heat (estrus). The follicle containing the maturing ovum bursts. The egg is ovulated and travels down the oviducts to a point at which it can be fertilized by the sperm.

B.The age of puberty varies between species and individuals.

C.Puberty is brought on by hormone secretions, primarily of estrogen.

III.ESTRUS AND THE ESTROUS CYCLE.

A.Estrus in farm animals is the time the female has or is about to ovulate and is “receptive” to the male

B.The first estrous cycle begins at puberty and is the interval between two estrous periods while the animal is not pregnant.

C.There are four different phases of the estrous cycle.

1.Proestrus, the phase just before estrus. The vaginal wall thickens in preparation to receive the fertilized egg. The ovary is about to release the ovum.

2.Estrus is the time for acceptance of the male and normally coincides approximately with ovulation.

3.Matestrus is: The period immediately following estrus. If conception has taken place the uterus prepares for pregnancy. The fertilized egg will settle and attach there.

4.Diestrus occurs between metestrus and proestrus and is the longest period of the cycle.

D.Non-pregnant females normally express both inward and outward signs of heat throughout the year. It includes: Noise and aggressive behavior. Swelling of the external portions of the reproductive tract. Color change of the vaginal wall.

E.Estrous cycles stop after conception.

F.Estrous cycles begin again soon after parturition (birth), in: Sows: 1-5 days post-partum mares: 5-10 Cows: Ewes are seasonal breeders

G.Control of estrus cycles by hormone injections and management schemes.

H.Synchronizing estrus cycles.