Exam 1: Crossbreeding systems Flashcards
type of breeding is determined by
size of herd
quality of stock
equipment
finances
goals of herd
purebred animal
defined as a member of a breed which possess a common ancestry and distinctive characteristics
either registered or eligible for registration in that breed
pure breeding
mating of two purebred animals for the commercial producer
The producer has the responsibility of producing genetically superior animals for the commercial producers
Key points/pros of pure breeding
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
what is impossible to avoid in pure breeding
linebreeding or crossbreeding
inbreeding
form of pure breeding in which closely related animals are mated
inbreeding is suggested for only _____________
highly qualified operators who are making an effort to stabilize traits ina given set of animals
__________________ is needed to reduce the risk of producing undesirable traits in breeding stock when inbreeding is practiced
intensive selection
why should we inbreed
increase homozygosis
creates pigs that are uniform in type and genetics
precautions of inbreeding
enhances the chances that recessive genes will appear
exercise intensive culling
examples of inbreeding combinations
sire * daughter
son * dam
brother * sister
linebreeding
form of pure breeding in which the degree of relationship is less intensive that with inbreeding
goal of linebreeding
directed towards keeping the offspring related to some highly prized ancestor
most commonly used type of breeding
outcrossing
outcrossing
Mating of animals of the same breed that have no closer relationship than at least 4-6 generations
what type of breeding is practiced by purebred breeders
outcrossing
crossbreeding
mating of two animals which are members of different breeds or lines (terminal + maternal OR duroc +landrace)
why is crossbreeding practiced by the majority of commercial swine producers
because of the resulting hybrid vigor that makes improved production efficiency possible
con of crossbreeding
does not guarantee successful offspring
pros and cons of purchasing gilts instead of raising
PRO:
-don’t worry about genetic selection
CON:
- Need capital
-no closed herd
-possible supply and demand problems
pros and cons of raising gilts
PRO:
-closed herd
-more control of genetics
CON:
more management required
crossbreeding system: terminal program
crossbred gilts (F1) mated to terminal boars
goal: raise and produce market hogs; ALL OFFSPRING SENT TO MARKET
replacement gilts: ALL PURCHASED
advantages of terminal program
good hybrid vigor
fast growth
simple
uniform market animals
disadvantages of terminal program
purchase all replacement females (cost, source, not closed herd)
Crossbreeding system: within-herd grandparent program
a variety of terminal breeding programs in which internally produced gilts make up the bulk (~80%) of the sow herd
advantages of within-herd grandparent program
produce own replacement females (~85% of herd)
fairly simple
disadvantages of within-herd grandparent program
“maternal” barrows sold as market hogs (fatter, grow slower, less profit)
large sow herd required
crossbreeding system: 3-breed rotational program
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
advantages of 3-breed rotational program
closed herd; produce all own replacements
easy to manage
disadvantages of 3-breed rotational program
not % of heterosis in offspring
breed composition changes every generation (NOT UNIFORM)
crossbreeding system: rotaterminal
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
advantages of rotaterminal system
100% heterosis in market hogs
closed herd; produces all replacement gilts
disadvantages of rotaterminal system
maternal barrows sold as market hogs
less than 100% heterosis in replacement gilts
