Question

questions and problems for discussion

1. which hormone is produced by developing follicles on the ovaries?
2. describe the four stages of estrus.
3. list the organs of the female reproductive tract.
4. where in the male reproductive tract is testosterone produced?
5. explain why no more than one sperm can penetrate a single egg.
6. follow the path of a fertilized egg. where does fertilization and implantation occur?
7. which hormone triggers milk let - down?
8. explain the signs of standing heat in cattle.
9. which two species discussed in this chapter can be seasonal breeders?
10. how long is the estrus cycle for swine, cattle, sheep, and horses?
11. how long is the gestation period for swine, cattle, sheep, and horses?
12. at what age do swine, cattle, sheep, and horses experience their first estrus period?
13. why are dairy cows “dried off” two months prior to calving?
14. do older or younger ewes tend to have more incidents of multiple births?
15. a stallion used to detect mares in heat is called a __________.

Explanation:

1. Follicle - stimulating hormone (FSH) stimulates the growth of ovarian follicles which produce estrogen.
2. The four stages of estrus are proestrus (pre - heat, preparation phase), estrus (heat, when receptive to mating), metestrus (post - heat, regression of corpus luteum if no pregnancy) and diestrus (resting phase).
3. Organs of the female reproductive tract include the ovaries, oviducts (fallopian tubes), uterus, cervix and vagina.
4. Testosterone is produced by the Leydig cells in the testes of the male reproductive tract.
5. Once a sperm penetrates the egg, a series of biochemical events (cortical reaction) occur that prevent polyspermy (multiple sperm penetration).
6. Fertilization occurs in the oviduct (fallopian tube) and implantation occurs in the uterus.
7. Oxytocin triggers milk let - down.
8. Signs of standing heat in cattle include restlessness, increased vocalization, mounting behavior and standing to be mounted.
9. Examples of seasonal breeders can vary but sheep and horses are often seasonal breeders.
10. Swine: 18 - 21 days; Cattle: 21 days; Sheep: 17 - 21 days; Horses: 21 days.
11. Swine: about 114 days; Cattle: 283 days; Sheep: 147 days; Horses: 335 - 340 days.
12. Swine: 5 - 8 months; Cattle: 9 - 15 months; Sheep: 6 - 8 months; Horses: 12 - 18 months.
13. Dairy cows are dried off two months prior to calving to allow the udder to rest and prepare for the next lactation cycle.
14. Older ewes tend to have more incidents of multiple births.
15. A stallion used to detect mares in heat is called a teaser stallion.

Answer:

1. Estrogen
2. Proestrus, estrus, metestrus, diestrus
3. Ovaries, oviducts, uterus, cervix, vagina
4. Leydig cells in the testes
5. Cortical reaction prevents polyspermy
6. Fertilization in oviduct, implantation in uterus
7. Oxytocin
8. Restlessness, increased vocalization, mounting and standing to be mounted
9. Sheep, horses
10. Swine: 18 - 21 days; Cattle: 21 days; Sheep: 17 - 21 days; Horses: 21 days
11. Swine: about 114 days; Cattle: 283 days; Sheep: 147 days; Horses: 335 - 340 days
12. Swine: 5 - 8 months; Cattle: 9 - 15 months; Sheep: 6 - 8 months; Horses: 12 - 18 months
13. To allow udder to rest and prepare for next lactation
14. Older ewes
15. Teaser stallion