Question

Briefly write about only two:

(a) Out breeding,

(b) Cross breeding,

(c) Controlled breeding.

Answer 1

(a) Out breeding:

1] Outbreeding is a mating of genetically unrelated animals. It involves the mating of individuals whose genetic relationship is less than the average relationship of the population from which they come.

2] Genotypic effects of outbreeding are as follows:

a. increased heterozygosity.

b. Mask expression of deleterious recessive genes.

c. Hybrid vigour or heterosis.

3] The outbreeding should be carried out for following reasons:

a. Addition of hybrid vigour.

b. Breed complementarity.

c. To avoid inbreeding depression.

4] In outbreeding, sometimes the mixing of gene pools is beneficial producing a hybrid offspring that is genetically superior to either of its parents. This is called outbreeding enhancement.

5] Example of outbreeding is: Jersey Hereford cow is mated to Charolais bulls which results in adequate milk production via Jersey cow as well as desirable carcass traits via charolais bull in their progeny.

(b) Cross breeding:

1] Crossbreeding is the result of combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction.

2] The major advantages of crossbreeding is dairy cattlewhich exhibit the strength of all breeds from which they descend with an added advantage of heterosis which is important for fertility and survival.

3] The major disadvantage of crossbreeding is that crossbreeds have the weaknesses of the breeds from which they descend and heterosis in initial crosses declines with any backcrossing to parental breeds.

4] Benefits of crossbreeding depends upon good sire selection within the pure breeds just as pure breeds depend upon within based selection for genetic improvement.

5] Example of crossbreeding is: crossbreeding a male donkey with a female horse will produce a mule.