Dairy Cow Week 2 Study Questions Flashcards
Female Reproductive Tract
-vagina
-cervix
-uterine body
-oviduct
-ovary
Cervix
barrier between vagina and uterine body
Oviduct
Fallopian tube –> site of fertilization
Parts of the Ovary
follicle + corpus luteum (CL)
Corpus Luteum
-“crown” (top ball pf ovary)
produces the hormone progesterone
Follicle
-base of the CL
–>where the egg is
produces the hormone estradiol
Approximately how many primordial (resting) follicles are present at birth in the heifer?
100,000 eggs
Stages of follicular development
-primordial
-primary
-secondary
-tertiary
-preovulatory
Primordial Follicles
A resting follicle
Primary Follicle
follicle activation
Secondary Follicle
follicle growth
Tertiary Follicle
Follicle growth
-recruitment
-selection
-dominance
Preovulatory Follicle
Ready to be ovulated
Would you expect all primordial follicles to begin development on the same day?
NO
What is follicular atresia?
follicular death, fails to develop, prevents from ovulating
Hormone
a chemical produced by an endocrine gland that travels through blood and exerts an effect on target organ
Endocrine Glands
secrete hormones
Target organs
have specific receptors
–> ex: progesterone – target organ is uterus
GnRH
Source: hypothalamus
Target: pituitary
Function: release LH/FSH
FSH
Source: pituitary
Target: follicle
Function: grow follicles
LH
Source: pituitary
Target: follicle/CL
Function: ovulation
Estradiol
Source: ovarian follicle
Target: hypothalamus, uterus
Function: bring cow into estrus, ovulation
Progesterone
Source: CL
Target: uterus
Function: quiet uterus, histotroph production
PGF 2a
Source: Uterus
Target: CL
Function: regress CL
Define puberty in a heifer
first ovulation
–> about 8 months of age
age of puberty: beef vs dairy heifer
dairy: 8 mo
beef: 1 year
Why do dairy heifers ovulate earlier?
– push feed on dairy heifers
– genetics are different in the heifers
Ovulation definition
process where the follicle releases an egg
Follicular waves: Recruitment
recruit a bunch of follicles
Follicular waves: Selection
Follicles compete for position
Follicular waves: Dominance
dominant follicle, one follicle becomes larger than the others
Ovulation in prepubertal heifers
go through follicular waves but don’t ovulate
–> uterus too small to ovulate
What hormone from the follicle must reach a threshold concentration to cause the LH surge and first
ovulation (puberty)?
estradiol triggers LH surge which triggers ovulation
In addition to the presence of a CL, what overt (external behavior sign) would indicate that a heifer has
reached puberty and is cycling?
mounting
What % of a group of heifers should be in heat (estrus) on one day if the entire group of heifers has
reached puberty and is cycling?
about 5% of heifer in heat on any one day
What are the signs of estrus (or heat) in the cow or heifer?
-Mount other cows
-Restless (walking around more than normal)
-Mucous secretion from vagina
What hormone from the ovary causes estrus and also causes the GnRH release from the hypothalamus
that leads to the LH surge?
estradiol
If the heifer is in heat today, when will she ovulate?
estrus is day 0, ovulation is day 1
What do we mean by a “walk and chalk” system for heat detection and AI?
spray paint on the backs to mark mounting
What is an electronic method of heat detection?
Activity System, increased activity means in heat
What are some reasons that a heifer may not show heat?
-pregnant
-not well grown
-freemartain
What is a freemartin and why are freemartins undesirable?
If you have twins: one male + one female = female is sterile
–> can’t have babies and lactate
Approximately how long is the estrous cycle of the cow or heifer?
21 days
Approximately how long is the estrous cycle of the cow or heifer?
21 days
What is happens to the CL if the animal is pregnant?
CL is maintained
What hormone cause the CL to regress if the animal is not pregnant?
PGF 2a
How do you define puberty in bulls and at what age does it occur?
capacity to get a cow pregnant
–> about 1 year of age
How do you define puberty in bulls and at what age does it occur?
capacity to get a cow pregnant
–> about 1 year of age
How many sperm cells does a bull produce each second?
10,000 sperm cells
Why use frozen semen?
-genetic improvement
-reduce injury from mounting
-greater safety for workers
Approximately how many straws of semen can be produced from a single bull ejaculate?
250 to 500 straws of frozen semen per ejaculate
Approximately how many times a week can you collect a bull?
2 to 3 times
How many daughters did Toy Story have?
500,000 daughters
What is a “bull stud”?
a farm of bulls
What two things can be sampled from a cow or heifer to isolate DNA for genomic testing?
-hair
-blood
What two things can be sampled from a cow or heifer to isolate DNA for genomic testing?
-hair
-blood
What are genetic markers and SNP?
genetic marker: a DNA sequence that can be used to assess phenotypic variability
—> SNP (single nucleotide polymorphism) is a type of genetic marker, which is a variation at a single position in a DNA sequence
How many SNP are used in a typical genomic chip test?
50,000
Genomic Sires
semen from a young bull whose worth is based only on a DNA test
How can you create a genomic sire in 2 years by using a series of advanced embryo technologies and
genomics?
mate a genetically tested cow to a genetically tested sire to create the best combination of genes
Genetic Testing (male vs female)
-female: 88%
-male: 12%
