Ruminant Reproduction- Lecture 13 & 14 Flashcards
Broad ligaments
Mesometrium. Mesosalpinx. Mesovarium.
Tubular components of the female reproductive system
Vagina, cervix, uterus, oviduct.
The estrous cycle
Period of reproductive cyclicity, which only ceases during pregnancy. Estrous cycle consists of two major phases: follicular and luteal.
Phases of the cycle
Estrus/heat –> Metestrus –> Diestrus –> Proestrus –> Estrus/heat
Fig 8.1
image
Luteolysis
In the cow, ewe, and goat: luteolysis is dependent on the presence of the uterus (not in primates). A local effect in ruminants (uterine horn and its ipsilateral ovary). PGF2a enters ovarian artery from utero-ovarian vein via a counter-current exchange mechanism; PGF2a gets to the ovarian artery without entering general circulation.
Prostaglandin
produced by the uterus on day 15-17 travels to the ovary and lyses the CL (if the cow is not pregnant).
Cow repro stats
Age of puberty: 9-11 mon.
Estrous cycle: 21 days.
Ovulation time from estrus onset: 24-30 hrs.
CL life span: 14-17 days.
Source of progesterone: CL until 150-250 days.
Entry of ova into uterus: 5 days.
Sheep and goat anatomy
Miniature cow.
Cannot be palpated via rectum.
Can be palpated vaginally at parturition.
Doe and ewe anatomy
Cervical rings:
Ewe- 4 to 6 rings, tortuous (AI difficult).
Doe- 4 to 6 rings, aligned.
Seasonality
Reproductive activity in caprin and ovine are regulated by seasonal variation. Changes in day length.
Short day breeders
Increased light –> increased firing of retinal nerves –> increased sup. cervical ganglion –> inhibit pineal gland –> decrease melatonin –> decrease GnRH –> decrease FSH and LH –> anestrus.
Ewe repro stats
Age of puberty: 6-9 mon.
Estrous cycle: 17 days.
Ovulation time from onset of estrus: 24-30 hrs.
CL life span: 14 days.
Gestation length: 148 days.
Source of progesterone: CL until 55-60 days.
Doe repro stats
Age of puberty: 6-8 mon. Estrous cycle: 21 days. Ovulation time from onset of estrus: 30-36 hrs. CL life span: 15-17 days. Source of progesterone: CL.
Periods of pregnancy
zygote, embryo (1st division), period of embryo organogenesis (6 weeks).
IFNT/ interferon tau
The pregnancy recognition hormone in sheep and other ruminants. Acts to silence expression of estrogen receptor alpha and, in turn, oxytocin receptor. To prevent luteolytic mechanisms that require oxytocin from CL and pituitary.
Placentation
Epitheliochorial- degree of invasion. Cotyledonary- shape. Villous- interdigitation. Nondeciduous- maternal loss of endometrium. Implantation in cow at 28-33 days.
Placentomes
(Caruncles+ Cotyledons) develop and get larger as pregnancy progresses.
Caruncle- maternal.
Cotyledon- fetal.
Connected by villi.
Placenta regulates exchange of nutrients and waste products from fetus to dam.
Fetal stress. Fig 14-14
image
Stage 1 of parturition
Uterus begins to make small contractions.
Cervix dilates.
Outward signs: isolation, restless, tail raised, uncomfortable.
May not see any signs.
Lasts 2-6 hrs.
Uterine membranes appear
End of stage 1 or beginning of stage 2 of parturition.
1st allantoic fluid: watery brown or yellow fluid. 2nd amniotic fluid: thick, clear-white fluid. Average interval between rupture of 1st and 2nd is 15 min.
Stage 2 of parturition
Active abdominal contractions. Calf enters the birth canal. Cow continues to dilate. Calf is born. Lasts for 15-90 min.
Stage 3 of parturition
Expulsion of the fetal membranes.
Normally done within 2-12 hours.
Retained takes up to 12-24 hours.
