Equine Science Microteach Chapters

The nucleus contains one chromosome from each parent

True

What chromosomes do males have?

XY

What chromosomes do females have

XX

How many chromosomes do horses have

64

How many chromosome pairs do horses have

32

How many chromosomes do mules have

63

Why are mules sterile?

horse (64 chromosomes) + donkey (62 chromosomes) = mule (63 chromosomes)
32 from horse, 31 from donkey, extra chromosome with no homologue
-homologous pairs from each parent are incompatible, genes don't match
-gametes require pairing of homologous chromosomes
-lack of homologues blocks spermatogesis making them sterile

What is symbolized by the underlying pink skin that can occur with in a coat color

Tobiano spotting

How many coat color classifications are there

7 genes

W gene

No pigment

G gene

Whitening with age

E gene

Presence of black hair

A gene

Distribution of black hair

C gene

Pigment dilution

D gene

Dun pigment dilution and pattern

TO gene

Tobiano spotting

Horse Improvement Programs

Basic principle is to identify superior animals within each breed.
Designed to raise quality of horses, identify superior horses, and establish markets.
Made by selection based on phenotype or on estimates of breeding values derived from phenotype.
Three evaluators assess yearlings and two year olds on a 1-20 basis in each of five categories:
1. Front limbs 2. Hind limbs 3. Head, neck, body, and balance 4. Athletic movement 5. Type.
Objectives include the evaluation of athletic ability, temperament, and trainability of young horses.

What are the 4 bases of DNA?

Adenine, Thymine, Guanine, Cytosine

A young horse with what allele will be any color but gray will whiten with age

G gene

Karyotype

A picture of all the chromosomes in a cell arranged in pairs

Nucleotide

Composed of one sugar one phosphate and one nitrogen base

Genome

the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes

qualitative traits

Environment has little effect on gene expression

Economically important traits are controlled by single or few gene pairs

False

Inferior genotypes rank higher phenotypically than superior genotypes

True

A bay horse can be expressed by genes AE ww gg

True

Defects in DNA can result in

-failure to form essential proteins
-formation of abnormal proteins
- death or disease

Gene

basic unit of heredity

What color gene causes pigment dilution

C gene

Black point patterns are caused by what gene

E gene

What dominant allele lacks pigment in skin at birth

W gene

If unwound and tied together a horses dna would stretch how many feet?

5 feet long

Each time a cell divided into a daughter cell it's full ______ is duplicated

Genome

The different forms of a gene are called

alleles

What are generally grouped into 2 categories, qualitative and quantitative

Traits

If both of the alleles are identical they are said to be what about that gene

Homozygous

False

Photoperiod is when a mare is receptive to photographers

True

Dystocia means difficult birth (T/F)

False

The practice of artificial insemination is accepted by all breed registries. (T/F)

True

Winking is a sign of estrous in mares. (T/F)

True

Waxed teats are a sign of impending birth.

False

Artificial insemination is 100 percent successful

List parts of the mare's reproductive tract

uterus, ovary, cervix, vulva, follicle, fallopian tubes, vagina, oviducts, clitoris

List parts of the stallion's reproductive organs

testes, scrotum, bulburethral gland, glans penis, seminal vesical, vas deferens, retractor penis muscle, prostate gland

What are the four signs of estrous (heat)?

1. cervix relaxes and is soft rose pink
2. vagina is red and vascular
3. secretions are clear and slimy in diestrus
4. the cervix protrudes into the vagina pale pink and tightly restricted

Name four factors that influence sperm output and production

1. season
2. testicular size
3. age
4. frequency

How soon after parturition (birth) can a mare be bred?

6-12 days

What hormones stimulate milk production?

Prolactin

What is the role of the hormone progesterone in the mare?

Prepares uterus, maintains pregnancy and prepares mammary glands for lactation and provides feedback control.

What is the advantages and disadvantages pasture breeding?

advantages:
reduces labor
convenient "catches" shy breeding mares
high settling percentage
disadvantages:
reduces number of mare a stallion can serve
obscures breeding dates
risk to stallion

What are the advantages and disadvantages of hand mating?

advantages:
controlled
more sanitary
highly supervised
more mares bred

Discuss the meaning of polyestrous in the mare

cycles multiple times per year but not all year around

Define abortion

premature termination of a pregnancy before 300 days of gestation

Define stillborn

foal dies after 300 days of gestation

Causes a mare to come into heat

What does estrogen do?

When does the luteal phase occur and what does it produce?

After ovulation. it produces the corpus luteum and its production of progesterone

What happens when there is no conception?

Prostaglandins are released destroy the corpus luteum , reduces progesterone and allows another cycle.

What happens when conception occurs?

No prostaglandins are released and corpus luteum remains dominant.

Describe stage 1 parturition

uterus begins to contract
foal moves into position to be birthed
cervix relaxes
restlessness, tail switching, sweating, pacing
Mare may urinate and defecate frequently
tail may be carried high
heart and respiratory rate increase
body temperature decreases
can last a few minutes to 24 hours

Describe stage 2 parturition

usually 30 minutes, no longer
intense contractions
amniotic membrane envelopes the fetus
Placenta should not be visible
Mare usually lies down
feet should emerge within 15 minutes

What is the meaning of condition scoring of the mare?

Reproduction efficiency
ability to reproduce
ideal score of 5
quantifies amount of subcutaneous fat cover

Luteinizing hormone

LH

What do follicles produce?

estrogen

What age does heat begin?

15-24 months

What is the minimum age to breed?

24-36 months

How often does estrus reoccur?

10 to 35 days

What does FSH stand for?

Follicle stimulating hormone

How long does a heat last for?

6-8 days progressively shortens to 3-4 days

How long does gestation last?

335 days

Corpus hemorrhagicum

eggless cavity in the follicle fills up with a blood clot

Define diestrus

no sexual activity

Define anestrus

no cycles

Define estrous

When the mare displays behavioral signs of sexual receptivity to the stallion

How long between cycles

20-22 days

What does gestation depend on?

season
nutrition
sex of the fetus

Define maiden mare

never foaled, never bred

Define barren/open

not bred in previous season or did not conceive in previous season

Define wet mare

foaled during current season and is nursing a foal

What factors relate to reproductive potential?

age, status, previous athletic use, breed, breeding record, health, nutrition

What are the three types of breeding seasons?

defined
transitory
year round

How early can pregnancy be diagnosed?

between days 10-15

When can a heartbeat be detected?

As early as day 22

At what point can sex of a fetus be determined?

Between days 60-70

Define caslick

Suture inserted into the vulva

What pituitary hormone stimulates the udders to produce milk?

prolactin

What is the hormone that relaxes the tail head, croup and the perineal area?

relaxin

True

The umbilical cord should be allowed to break on its own? (T/F)

Once the umbilical cord breaks, the foal's navel should be immediately treated with

an iodine solution to prevent entrance of pathogens through the opening

True

The placenta and the fetal membrane being expelled completes stage 3? (T/F)

What does it mean when the membranes are not passed within 2 hours of birth?

They are retained and the veterinarian should be called.

True

The placenta must be naturally released from the uterus? (T/F)

Define metritis

Inflammation that leads to infection of the uterus when a piece of the placenta is left after birth.

True

Metritis can lead to laminitis or death? (T/F)

Define hippomane

A soft dark brown body of tissue floating among the membranes

Define involution

The uterus returning to its nonpregnant size which happens within 10 days

True

Involution may cause abdominal pain and some colic like symptoms. (T/F)

An odorless discharge in the vulva during involution is called?

Lochia

True

Rupturing of the middle uterine artery is common and can cause internal bleeding after pregnancy? (T/F)

Define foal heat

The first estrus after birth

Define silent heat

No outward sign of estrus