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Lecture 2

ANSC 101 Lecture Notes - Lecture 2: Passive Immunity, Cloaca, 100 Feet

Animal Science
Course Code
ANSC 101
Kasey Moyes

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Female Reproduction
Estrus Synchronization
Artificial insemination
Approved rugs in US for cattle
Keep animals out of heat and extend estrous cycle (progestins)
o Melengestrol acetate (MGA)
o Controlled Intervaginal Drug Release devices (CIDR)
Bring females into heat and shorten estrous cycle (PGF2alpha)
o Lutalyse
o In-synch
Cause ovulation or start new follicular wave (GnRH)
o Facetrel
o Ovacyst
Estrus synchronization
Timed AI
Observed heat
Two major steps in gestation/pregnancy
o Attachment to the uterus
o Development of an exchange system between dam and fetus (the placenta will
also serve an important endocrine role)
o Accrosomal reaction
o Zona pellucida
Enzymatic digestion
Only 1 sperm
CL continues to function
o Progesterone remains elevated
o No estrus cycles or heat
Embryonic Mortality
25-40% of all pregnancies in farm animals are NOT carried to term
Losses usually occur early in pregnancy
Elimination of unfit genotypes (90% of human conspectuses are genetically abnormal
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Neonatal Losses
Occur between day 3 and 21 of extra-uterine life
Endocrine/hormone role of placenta
Assumes dominant role in progesterone production from the CL in the ewe (50 days) and
the mare (70 days)
The sow (duration) and cow (6-8 months) depend on the CL
Placentome site of nutrient and waste diffusion
Cotyledon fetal tissue
4 placental shapes
o Placentome comprised of cotyledon (fetal)
Process of expelling fetus and placenta from the uterus
3 stages
o Complete cervical dilation and entry of fetus into cervix
o Expulsion of fetus
o Expulsion of placenta
Birth termination of pregnancy
Afterbirth (placenta) extraembryonic membrane shed
Cortisol released from both fetal adrenal cortex and maternal cortisol (HPA axis)
o Initiates parturition
Decreased progesterone
Increased oxytocin, prostaglandin F2alpha, estrogens
Relaxin cervical dilation
Newborns should receive colostrum shortly after birth to acquire passive immunity
(immunoglobulins: IgG, IgM, IgA) which acts as an intermediate level of protection until
the newborn can establish its own antibody production
Dystocia birth difficulty
Factors that contribute
o Birth weight
o Pelvic area of dam
o Nutrient status of dam
o Breed differences
o Age of dam
o Abnormal presentation
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