Equine Selection Flashcards
Equine Selection
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
Problems Determining h2
Variation
[Tremendous environmental variation]
Data Bias - not all contemporaries allowed same opportunities [limited information available and limited # of individuals]
Traits of Economic Importance
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]
Fertility
h2 = 0.05 (very low)
Average live foal crop = 50-70%
Lower performance compared to other livestock species
Changes in environment more successful
Performance
Anatomical and physiological basis
Obvious some degree of h2 based on skeletal structure
Cattle work
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
Cow sense
Horse appears to have great interest in cattle
Difficult to research h2 of cow sense
Cutting - hight degree of training required
Barrel Racing
Speed and agility needed
Jumping ability
Various studies
Free jumping
With rider
Winners over course
Style
History of Selection
1) Development of distinct breeds and types of horses
2) Manufactured “registered” breeds
Manufactured “registered” breeds
Color breeds aren’t purebreds
Ex: Palominos don’t breed true
Linebreeding
Very common
Concentrate genes from one individual (But less intense than inbreeding)
Positive assortative mating
Breed best to the best
Sire performance is major selection criteria
CID
Combined immodeficiency
Autosomal recessive
Defective gene - DNA dependent protein kinase catalytic subunits
[Sometime severe (SCID)]
Inbreeding
Used little
Crossbreeding
Used somewhat
Used for breed development [Warmbloods, trotters]
Bleeders
Exercise Induced Pulmonary Hemorrhage
Bursting of blood vessels in lungs
Increase pulmonary pressure
Adversely affects performance
Negative public perception
Autosomal recessively inherited
OCD or DOD
Osteochondritis dissecans or Developmental orthopedic disease
Skeletal disorder due to a disturbance of endochondrial ossification (delayed harding of the bone)
Autosomal recessive
Wobblers Syndrome
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
HYPP
Defect on voltage-gated sodium channels of muscle cells
High K in blood
Dominant disorder with incomplete penetrance
HC/HERDA
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
Lethal White Foal Syndrome
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
GBED
Glycogen branching enzyme deficiency
Foals can’t efficiently store and metabolize glucose
Lower than normal glycogen
Weak - die by 8 week old
Autosomal recessive
