Fish breeding and biotechnology in aquaculture.pptx

Inbreeding; is the mating of individuals that are more closely related to each other than individuals mating at random within a population.
The populations actually used in most aquaculture programs are finite populations because they possess a limited number of members.

1. Sokoine university of agriculture (SUA) Aquaculture production system Fish breeding and biotechnology NAME : MAGOTI ERNEST

2. A is the shared ancestor of B and C . At a given locus, there is a possibility that B and C each inherited a copy of the same gene from A . When this occurs B and C possess genes that are identical by descent from A . If B and C have alleles that are identical by descent, there is a possibility that D inherits two alleles that are identical by descent: one from A through B and the other from A through C. Inbreeding; is the mating of individuals that are more closely related to each other than individuals mating at random within a population. The populations actually used in most aquaculture programs are finite populations because they possess a limited number of members.

3. Types of inbreeding Close inbreeding; involves the mating of very close relatives such as between parents and offspring (first-degree relatives) or between full siblings . For example, grandparents and grandchildren , half siblings , uncles/aunts and nephews/nieces . Line inbreeding or linebreeding; involves the mating of animals that are not as closely related but share at least one common ancestor in their pedigree. For example, cousin, grandparents to grand-offspring.

4. Inbreeding is measured by a value called the inbreeding coefficient which is normally represented by the symbol F . Inbreeding coefficient (F) is the probability that two alleles at any locus are identical and descended from a common ancestor. Since the inbreeding coefficient is a probability, it can assume only the values within the range from zero to 1.0 .

5. Causes of inbreeding in aquaculture Enhanced prepotency; is the ability of an individual to produce progeny whose performance closely resembles its own and this will lead to identical genetic makeup as of their parents. Expression of deleterious alleles; The recessive deleterious genes gets expressed in inbreds due to homozygosity that at one point are associated with abnormalities and death of the offspring which otherwise were in low numbers or masked or hidden by the dominant genes in outbreds.

6. Causes of inbreeding in aquaculture cont…. Genetic drift ; this causes a loss in genetic diversity due to loss of alleles, which leads to an increase in homozygosity. If all animals are homozygous, the other allele(s) will be lost from the population then the results from genetic drift leads to a permanent reduction in genetic diversity since alleles are lost indefinitely. Non-random mating ; this can indeed lead to inbreeding, but it is avoidable. Purposefully mating closely related animals, such as brother and sister or father and daughter, increases the likelihood that the offspring will inherit the same allele from both parents.

7. Causes of inbreeding in aquaculture cont.…. Small population size; In a limited population, it is difficult to avoid breeding between the related animals and moreover, the outbred stocks turn into inbred stocks if kept in the limited population size for several generations. This shows that rate of inbreeding depends on the population size.

8. Effects of inbreeding in aquaculture Inbreeding Depression; this refers to the reduced fitness and health of offspring. It can lead to lower survival rates and increased susceptibility to diseases. There are two hypotheses that suggest the genetic basis of inbreeding depression . Partial dominance hypothesis and overdominance hypothesis. Increased Homozygosity; means that individuals are more likely to inherit two identical alleles for a particular gene. This can result in the expression of harmful recessive traits

9. Effects of inbreeding in aquaculture cont… Reduction of genetic diversity; leads failure of organisms to survive over varying environments and adapt over time and leads to the gradual reduction in the overall biological fitness of organisms .

10. Management Strategies for improving inbreeding Genetic Monitoring ; use of DNA Marker Analysis which are used to study the genetic diversity and relatedness of individuals. Selective Breeding Programs ; through Rotational breeding where brood stock is divided into multiple groups and breeding is rotated among the groups.

11. Management Strategies for improving inbreeding cont.…. Cryopreservation; involves freezing and storing sperm, eggs, or embryos for future use. This material can be used to infuse genetic diversity into breeding programs, especially when genetic diversity starts to decline. Population Management; maintaining a sufficiently large breeding population helps ensure genetic diversity. Introduction of New Genetic Material; s tock enhancement programs helps to increase genetic diversity.