Sheep selection

Question 1

Sheep industry

Answer 1

Small in US
Purebred, Commercial, Dairy

Question 2

Purebred

Answer 2

Seedstock for commercial producers
Show sheep (ex 4-H)

Question 3

Commercial

Answer 3

Lamb/meat - majority of income
Wool - secondary income in Westerns US

Question 4

Dairy

Answer 4

For cheese
Growing industry in Great Lakes region of US

Question 5

Traits of economic importance

Answer 5

[what is selected for]
Meat production
Wool production
Milk

Question 6

Meat Production

Answer 6

[what is selected for]
Number of lambs born/weaned
Growth rate

Question 7

Wool productions

Answer 7

[what is selected for]
Fiber diameter
Fleece weight

Question 8

Milk

Answer 8

[what is selected for]
Pounds/(per) lactation

Question 9

Heritability of Economically Important traits

Answer 9

(usually low h2)
Production:
Ewe fertility
Proliferation
Lamb survival

Growth:
Preweaning gain (birth - 60 d)
Postweaning gain (60-120d)

Carcass:
Carcass weight
Dressing %

Fleece:
Grease fleece weight
Staple length
Fiber diameter

Question 9

Breeds fo Sheep

Answer 9

At lease 425 breeds
47 breeds in US

Question 10

Inbreeding

Answer 10

Some in purebreds, especially breeds with smaller number or imported breeder with limited numbers

Question 11

Crossbreeding

Answer 11

Used extensively in commercial production

Question 12

EPDs

Answer 12

National Sheep Improvement Program - calculates cross flock EPDS for sheep
Generates numbers to support industry
(NOT widely used)

Question 13

Central Ram Tests

Answer 13

Most effective for traits of moderate to high h2 which cam be measured in a young growing ram
(Danger of emphasis on easily measured traits at expense of other traits)

Question 14

Spider Syndrome

Answer 14

Lethal or semi-lethal skeletal abnormalities
Single gene, autosomal recessive disorder
Gene affected - fibroblast growth factor receptor

Question 15

Scrapie

Answer 15

Central Nervous System disease
Some negative impact due to consumer perception (Never transmitted to humans)
Economic cost usually large losses
Many symptoms
NO Treatment

Question 16

Scrapie Diagnosis

Answer 16

Dead: examination of brain and lymph nodes for lesions or abnormal prions
Alive: examination of third eyelid for abnormal prion proteins

Question 17

Scrapie Susceptibility

Answer 17

Variation in prion protein
Codon 136
Condon 154
Codon 171

Question 18

Genes selected for

Answer 18

Booroola
Callipyge

Question 19

Booroola

Answer 19

Increased ovation rate
Mapped to chromosome 6
Higher litter size
Affects traits for lamb survival, lamb growth, and ewe conception

Question 20

Callipyge

Answer 20

Muscle hypertrophy
Mapped ot telomeric region on chromosome 18
High dressing % with extremely tough meat
Polar overdominance (one copy for sire)
Manifests 1 month after birth (doesn’t increase dystocia)
Affected animals have improved feed efficiency and dressing %