Equine Selection

Question 1

Equine Selection

Answer 1

Least studied Livestock (If they can be considered livestock)
Characteristics:
Recreational use
Long Gi
Long gestation
Age fo puberty
Offspring/year
Lack of accurate records

Question 2

Problems Determining h2

Answer 2

Variation
[Tremendous environmental variation]
Data Bias - not all contemporaries allowed same opportunities [limited information available and limited # of individuals]

Question 3

Traits of Economic Importance

Answer 3

1) Fertility [h2=0.05]
2) Performance [h2 varies]
[We assume high h2 for traits]
Trotters and Pacers (T = dom/ P = rec) [h2 = 0.1-0.25]

Question 4

Fertility

Answer 4

h2 = 0.05 (very low)
Average live foal crop = 50-70%
Lower performance compared to other livestock species
Changes in environment more successful

Question 5

Performance

Answer 5

Anatomical and physiological basis
Obvious some degree of h2 based on skeletal structure

Question 6

Cattle work

Answer 6

Ranch work - work livestock over terrain
Roping - close contact with animals, must have high agility
Cutting - highly athletic, response to calf movement after separation from herd

Question 7

Cow sense

Answer 7

Horse appears to have great interest in cattle
Difficult to research h2 of cow sense
Cutting - hight degree of training required

Question 8

Barrel Racing

Answer 8

Speed and agility needed

Question 9

Jumping ability

Answer 9

Various studies
Free jumping
With rider
Winners over course
Style

Question 10

History of Selection

Answer 10

1) Development of distinct breeds and types of horses
2) Manufactured “registered” breeds

Question 11

Manufactured “registered” breeds

Answer 11

Color breeds aren’t purebreds
Ex: Palominos don’t breed true

Question 12

Linebreeding

Answer 12

Very common
Concentrate genes from one individual (But less intense than inbreeding)

Question 13

Positive assortative mating

Answer 13

Breed best to the best
Sire performance is major selection criteria

Question 13

CID

Answer 13

Combined immodeficiency
Autosomal recessive
Defective gene - DNA dependent protein kinase catalytic subunits
[Sometime severe (SCID)]

Question 14

Inbreeding

Answer 14

Used little

Question 15

Crossbreeding

Answer 15

Used somewhat
Used for breed development [Warmbloods, trotters]

Question 16

Bleeders

Answer 16

Exercise Induced Pulmonary Hemorrhage
Bursting of blood vessels in lungs
Increase pulmonary pressure
Adversely affects performance
Negative public perception
Autosomal recessively inherited

Question 17

OCD or DOD

Answer 17

Osteochondritis dissecans or Developmental orthopedic disease
Skeletal disorder due to a disturbance of endochondrial ossification (delayed harding of the bone)
Autosomal recessive

Question 18

Wobblers Syndrome

Answer 18

CVM - Cervical Vertebral Malformation
Found in Thoroughbreds and Quarter horses
Malformation of cervical vertebrae 5, 6, and 7
Varying degrees of spinal cord compression
Autosomal recessive

Question 19

HYPP

Answer 19

Defect on voltage-gated sodium channels of muscle cells
High K in blood
Dominant disorder with incomplete penetrance

Question 20

HC/HERDA

Answer 20

Hyperelastosis cutis
Hereditary equine regional dermal asthenia
Lack of adhesion of out skin with dermis
Collagen defect (Collagen serves as glue to hold skin together)
Trauma to skin
Autosomal recessive

Question 20

Lethal White Foal Syndrome

Answer 20

Overo x Overo = white foal
Autosomal recessive
Aganglionosis - large intestine lacks nerve cells and therefore cannot function
Mutation of Endothelia receptor and type B (EDNRB) gene
Results in early death

Question 21

GBED

Answer 21

Glycogen branching enzyme deficiency
Foals can’t efficiently store and metabolize glucose
Lower than normal glycogen
Weak - die by 8 week old
Autosomal recessive