A18: Breeding (pure- and cross breeding) methods in sheep and goat production.

Question 1

What are the basic mating systems

Answer 1

Flock/ mass mating
Harem mating
Stud mating / hand mating
Artificial insemination

Question 2

Sex ratio in natural breeding vs AI

Answer 2

-> sex ratio in natural breeding: 1:50 (60-70)
-> in AI from a single ejaculate with fresh diluted semen: 10-15 (20-30).

Question 3

What is Breeding Value Estimate Based On

Answer 3

-> Own/ individual performance: daily gain up to a 120 day of age.
-> Progeny testing of bucks: used to estimate meat production.
-> Conformation: muscling, wool quality, testicle circumference.
-> prolificacy and milk production also considered.

Question 4

Is pedigree important?

Answer 4

less attention is placed on pedigree

Question 5

What are the main breeding goals and selection criteria of sheep?

Answer 5

Depends on breeding objective.
-> LAMB and MUTTON PRODUCTION: (weight gain performance): excellent muscling (muscular hypertrophy in sheep, CLPG) and less fat depositions (lamb production with poor fat deposits, body weight: 40-45 kg, under 6 month of age).
-> PROLIFICACY: higher twinning rate is desired.
-> WOOL PRODUCITON: wool quality is the main selective criterion.
-> MILK PRODUCTION: progeny testing of rams and group selection of best ewes are the most common methods.
-FUR PRODUCTION: only few breed are appropriate (Karakul).

Question 6

What are the Selection Criteria in Dairy & Meat Goats?

Answer 6

-> For MILK production: the primary objective in goat breeding; fertility, form and shape of udder, conformation in dairy goats are important.
-> For MEATproduction: daily gain of kids, muscling, prolificacy of nanny goats (twinning), conformation.
-> For WOOL production: prolificacy and conformation, wool quality in Angora, Cashmere and Mohair goats.

Question 7

What is pure breeding?

Answer 7

when the lineage of a purebred animal is recorded; exclusively to a specific breed.

Question 8

What is inbreeding?

Answer 8

mating of the same breed which are more closely related than the average of the breed

Question 9

What is line breeding?

Answer 9

-> one or more ancestors occur more than once in the pedigree of an animal.
-> the same ancestor occurs in the pedigree of both the sire and the dam.

Question 10

Forms of pure breeding

Answer 10

Inbreeding,
Line breeding,
Improvement,
Preservation.

Question 11

How can genetic improvement be obtained?

Answer 11

genetic improvement can be obtained more efficiently by intense individual selection rather than by forming inbred lines.

Question 12

Give 2 benefits of cross breeding:

Answer 12

1) Heterosis Effect: Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring ( reproduction rate, prolificacy, wool, meat, milk production).

2) Recombination: process by which pieces of DNA are broken and recombined to produce new combinations of alleles. This recombination process creates genetic diversity at the level of genes that reflects differences in the DNA sequences of different organisms.

Question 13

What are reasons for cross-breeding?

Answer 13

-> Grading up: replacement of local breeds by productive ones, mating by purebred, high yielding sires of another breed generation after generation.
-> Breed improvement (gene immigration): preserving valuable breed characters, and only a single crossing to introduce new gene into a breed, also called gene immigration.
-> New breed formations: synthetic breeds, crossbreds.

example: Marino ewes + Leicester rams

-> 2-Breed: (e.g southdown rams x Romney ewes or Suffolk, Texel, Il de France x local native breeds).
-> 3-Breed: (superior sire or terminal sire mated to first-cross ewe of 2 breeds).
-> 4-Breed: (offers twice the opportunity for recombination effects).

Question 14

What is Terminal crossing, breed hybridisation?
Give exmaples

Answer 14

A x B –> AB
A is dam (do not say terminal dam line)
B is ‘terminal’ (paternal) bull
AB is slaughtered so B is terminal bull line.

Combination of breeds to optimise use of meat production.

-> 2-Breed: (e.g southdown rams x Romney ewes or Suffolk, Texel, Il de France x local native breeds).
-> 3-Breed: (superior sire or terminal sire mated to first-cross ewe of 2 breeds).
-> 4-Breed: (offers twice the opportunity for recombination effects).

Question 15

what is rotational crossing?

Answer 15

males of 2 or more breeds used in sequence on crossbred female population, in sheep breeding it’s rarely used, results in loss of breed uniformity.

Question 16

conclusion to crossbreeding?

Answer 16

Conclusion: Differences btw breeds can be quite large (even in the absence of heterosis) a crossing can give substantial gain or breeds can complement each other in different traits.