Exam 1: Crossbreeding systems

Question 1

type of breeding is determined by

Answer 1

size of herd
quality of stock
equipment
finances
goals of herd

Question 2

purebred animal

Answer 2

defined as a member of a breed which possess a common ancestry and distinctive characteristics

either registered or eligible for registration in that breed

Question 3

pure breeding

Answer 3

mating of two purebred animals for the commercial producer

The producer has the responsibility of producing genetically superior animals for the commercial producers

Question 4

Key points/pros of pure breeding

Answer 4

superior to crossbreeding animals in transmitting desired trait

produce genetically superior animals compared to commercial

lineage traces back to the foundation of animals accepted by breed

small # of foundation animals

Question 5

what is impossible to avoid in pure breeding

Answer 5

linebreeding or crossbreeding

Question 6

inbreeding

Answer 6

form of pure breeding in which closely related animals are mated

Question 7

inbreeding is suggested for only _____________

Answer 7

highly qualified operators who are making an effort to stabilize traits ina given set of animals

Question 8

__________________ is needed to reduce the risk of producing undesirable traits in breeding stock when inbreeding is practiced

Answer 8

intensive selection

Question 9

why should we inbreed

Answer 9

increase homozygosis
creates pigs that are uniform in type and genetics

Question 10

precautions of inbreeding

Answer 10

enhances the chances that recessive genes will appear

exercise intensive culling

Question 11

examples of inbreeding combinations

Answer 11

sire * daughter
son * dam
brother * sister

Question 12

linebreeding

Answer 12

form of pure breeding in which the degree of relationship is less intensive that with inbreeding

Question 13

goal of linebreeding

Answer 13

directed towards keeping the offspring related to some highly prized ancestor

Question 14

most commonly used type of breeding

Answer 14

outcrossing

Question 15

outcrossing

Answer 15

Mating of animals of the same breed that have no closer relationship than at least 4-6 generations

Question 16

what type of breeding is practiced by purebred breeders

Answer 16

outcrossing

Question 17

crossbreeding

Answer 17

mating of two animals which are members of different breeds or lines (terminal + maternal OR duroc +landrace)

Question 18

why is crossbreeding practiced by the majority of commercial swine producers

Answer 18

because of the resulting hybrid vigor that makes improved production efficiency possible

Question 19

con of crossbreeding

Answer 19

does not guarantee successful offspring

Question 20

pros and cons of purchasing gilts instead of raising

Answer 20

PRO:
-don’t worry about genetic selection

CON:
- Need capital
-no closed herd
-possible supply and demand problems

Question 21

pros and cons of raising gilts

Answer 21

PRO:
-closed herd
-more control of genetics

CON:
more management required

Question 22

crossbreeding system: terminal program

Answer 22

crossbred gilts (F1) mated to terminal boars

goal: raise and produce market hogs; ALL OFFSPRING SENT TO MARKET

replacement gilts: ALL PURCHASED

Question 23

advantages of terminal program

Answer 23

good hybrid vigor
fast growth
simple
uniform market animals

Question 24

disadvantages of terminal program

Answer 24

purchase all replacement females (cost, source, not closed herd)

Question 25

Crossbreeding system: within-herd grandparent program

Answer 25

a variety of terminal breeding programs in which internally produced gilts make up the bulk (~80%) of the sow herd

Question 26

advantages of within-herd grandparent program

Answer 26

produce own replacement females (~85% of herd)
fairly simple

Question 27

disadvantages of within-herd grandparent program

Answer 27

“maternal” barrows sold as market hogs (fatter, grow slower, less profit)

large sow herd required

Question 28

crossbreeding system: 3-breed rotational program

Answer 28

uses three breeds of purebred boars, rotated in a consistent order

offspring are used for market production and replacement gilts

replacement gilts are kept and bred to the breed of purebred boars used least recently

Question 29

advantages of 3-breed rotational program

Answer 29

closed herd; produce all own replacements

easy to manage

Question 30

disadvantages of 3-breed rotational program

Answer 30

not % of heterosis in offspring

breed composition changes every generation (NOT UNIFORM)

Question 31

crossbreeding system: rotaterminal

Answer 31

combines rotation and terminal breeding programs

top gilts are selected and used in a rotational cross that produced replacement gilts

remaining gilts are mated to terminal boars

Question 32

advantages of rotaterminal system

Answer 32

100% heterosis in market hogs

closed herd; produces all replacement gilts

Question 33

disadvantages of rotaterminal system

Answer 33

maternal barrows sold as market hogs

less than 100% heterosis in replacement gilts