Breeding
Process of mating selected males and females to produce offspring with the desired characteristics.
Reasons:
- To expand the inherited potential of the animal.
- To improve production by introducing new genes.
- To overcome production problems created by the environment.
- To satisfy consumers taste.
- For economic reasons e.g fast growth rate to reach the market early.
Terms Used in Breeding
Inheritance; Genetic transmission of characteristics from parents to offsprings.
The mechanism of inheritance is carried by the sex cells (gametes) and is controlled by genes found in the chromosomes.
Genes are very tiny units of inheritance carrying particular characteristics, such as colour, body shape and amount of milk production. Chromosomes are genetic materials which carry genes.
They exist in pairs paternal and maternal) in the nucleus f the body cells. They are always constant in number.
Dominant and Recessive Characteristics
A dominant gene is one that suppresses the other. It produces a dominant characteristic.
A recessive gene is one that is suppressed by the other. It produces a recessive characteristic.
Hybrid and Hybrid Vigour
A hybrid is an animal which is the product of crossing animals of two different breeds. It has both a dominant and recessive characters. A superior hybrid has 75% dominance and 25% recessive.
Hybrid vigour or heterosis is increased vigour and performance resulting from crossing two superior breeds. When two superior breeds e.g Pedigree friesian and Jersey breeds are mate the resultant offsprings have both the character of high milk yield and high butterfat content. Thus it is said the offsprings have hybrid figure whichis an increased perfomance and figure than both the two parents.
Epistasis
This is the masking of the effect of one gene (reccesive gene) by another gene(dominant) which is non-allelic, that is situated on different locus.
This is aimed at preventing the recesive gene from being expressed.
BREEDING SYSTEMS
They are categorized into two namely; Inbreeding and Outbreeding
1. Inbreeding
Mating of animals which are related i.e have certain alleles of genes in common.
Reasons:
- To increase genetic uniformity in a herd.
- To increase phenotypic uniformity.
- To get proven sires.
- To fix required characteristics when developing a new breed.
- used in animal of higher prepotency (stud Bulls)
It can bring about loss of hybrid vigour.
It may lead to decline in fertility.
It may lead to high rate of pre-natal mortality.
Systems of Inbreeding
Close Breeding: mating between very closely related animals, for example sib-mating and parents sib-mating.
Line Breeding: mating of distantly related animals that had a common ancestor for example cousins, halfbrothers/sisters, grand daughters and grand sires.
2. Outbreeding
Mating of animals which are not related.
Reasons:- To introduce new genes in an existing breeding herd.
- To exploit heterosis resulting from a cross between two breeds.
- To develop a new breed or a grade animal.
Limitations
- Lack of uniformity in animals that result from outbreeding.
- Desirable characteristics may be lost due to variation.
Systems of Outbreeding
i). Cross-breeding
Mating of animals from two different pure breeds to attainhybrid viguor or heterosis such as higher production rate, higher production rate, high growth, disease resistance and heat tolerance.
ii).Out-Crossing
Mating of unrelated animals from the same breed for exxample fresian cow in kenya with Semen of fresian bull from Britain.
iii) Upgrading/Grading up/Backcrossing
Mating where the female of a cow grade stock (locals) is mated with a pure breed sire. The resultant animal is referred to as a high grade.
If the same sire mates with filial generation (F1-6) of its heifers, it will attain a pure breed character. With Artificial insemination (A.I) the systemis used widely to improve the local cattle for better milk production
Mating in Livestock
Mating in Cattle
Heat signs occur every 21 days.
The heat period last for 18-30 hours on average 24 hours.
Cow should be served 12-18 hours after showing the first heat signs.
Heat Signs
Restlessness.
Mounting on others and when mounted on she stands still. Rise in body temperature.
Drop in milk production in lactating cows. Vulva swells and becomes reddish.
Clear or slimy mucus from the vulva.
Bellowing or mooing frequently.
Mating in Pigs
Heat signs in pigs occur after every 21 days. The heat lasts about 72 hours.
Sows or gilts should be served in 18- 36 hours of the heat period.
Signs of Heat
Restlessness.
Frequent urination.
Swelling and reddening of the vulva.
Clear or slimy discharge from the vulva.
Frequent mounting on others.
It responds very well to the 'riding test'.
Mating in Rabbits
Does are ready for mating 6-7 months of age. Heat signs occur every 14 days.
The doe should be taken to the buck and not vice versa.
Signs of Heat
Restlessness.
Frequent urination.
Swollen vulva.
The doe throws herself on the side.
The doe rubs herself against the wall or any other solid object.
The doe tries to contact other rabbits in the next hutch by peeping.
Methods of Service in Livestock
Natural Mating
Advantages:
It is more accurate.
It is less laborious.
Useful when heat signs of females cannot be easily detected.
Disadvantages
Inbreeding is not easily controlled.
Transmission of breeding diseases.
Extra feed for the male is required.
Large males can injure small females.
Wastage of semen.
It is cumbersome and expensive to transport a bull to remote areas.
Artificial insemination
Introduction of semen into the female reproductive tract by artificial means.
Advantages
There is economical use of semen.
It controls transmission of breeding diseases.
Sires that are unable to serve cows due to heavy weight or injury can produce semen to serve cows.
It prevents large bulls from injuring small cows. It reduces the expenses of keeping a male animal.
A small scale farmer who cannot afford to buy a superior bull can have the cows served at a low cost.
Semen can be stored for long. It helps to control inbreeding.
It eliminates the threat of keeping dangerous bulls from the farm.
It makes research work easier.
Disadvantages
Harmful characteristics can be spread quickly by one bull to the offsprings.
It requires skilled labour.
Low chance of conception due to death of semen during storage.
It is laborious:
Embryo Transplant
It is the implantation of an embryo (fertilized ova) from a high quality female (donor) in the uterus of a low grade female (recipient).
Advantages
Faster multiplication of an animal with superior characteristics . It is easier to transport embryos than the whole animal.
Embryos can be stored for a long period awaiting the availability by recipient females.
It stimulates milk production in a female (recipient) that was not ready to produce milk.
Low grade animals can be used in production and rearing of high quality animals. Offsprings of a superior female can spread quickly in an area.
Disadvantages
It is expensive.
It requires skilled personnel.
It requires special equipment for fertilization and storage of embryos.
Signs of Parturition in Livestock
Parturition is the act of giving birth in female animals.
Parturition in Cattle
The gestation period in cattle is 270-285 days averaging 280days.
Signs of Parturition
Restlessness
Enlarged or swollen vulva.
Clear mucus discharge from the vulva.
Slackening of the pelvic muscles.
Full and distended udder.
Thick milky fluid from the teats.
A water bag appears and bursts just before calving.
Parturition in Pigs
The gestation period in pigs is about 4 months or 3 months, 3 weeks and 3 days.
Signs of Parturition
Restlessness.
The vulva turns red and swells.
The udder becomes full with a milky fluid the sow starts to prepare a nest by collecting some beddings at one comer of the pen.
Parturition in Rabbits
The gestation period in rabbits is 28-32 days.
Signs of Parturition
Preparing a nest by plucking off hair from her belly.
Goes off feeding
Restlessness.
The udder distends.