Credits: Biovision-Infonet
Planned breeding programs yield the best results when the breeder considers the production and other trait characteristics in individual cows and how they can be passed on to offspring. The breeder must also be able to match these characteristics to what the market demands.
Inbreeding
Inbreeding may be defined as mating of individuals more closely related than the average relationship of the population. The decrease in fitness that results from such inbreeding is known as inbreeding depression.
In small herds inbreeding is a real danger for continued productivity of livestock. Inbreeding can lead to smaller animals, less productive animals, high incidences of deformities and low disease resistance among other undesirable characteristics.
By having a good breeding strategy such inbreeding can not only be totally avoided, but the opposite can be achieved namely higher productivity, better milk and meat yields, healthy animals with good disease resistance just to mention a few of the most common goals for breeding strategies
Farm animals are very sensitive to inbreeding, and usually full-sibling matings should not be done because of a marked decrease in viability and fertility. Breeding within small populations, such as a herd, without introduction of new animals from outside (not related to the herd or flock), leads automatically to a certain amount of inbreeding.
All cows and bulls, even the very best bull, in any breed, have genetic traits that could be desirable or undesirable from a farmers perspective. The problem arises when from in both parents the genetics for the same undesired traits are present Imagine that this trait is present in a particular bull, and that bull is very popular (because he also has some desirable trait, such as superior milk production in daughters). As this bull is bred to many females, half of the resultant offspring would now carry the undesired trait possessed by that bull. If these individuals are mated to one another, then 25% of their offspring would have double the undesired trait (one from each parent), and another 50% would carry the undesired trait in their genetic base. In this extreme form of inbreeding, in just two generations the defect went from being expressed in one out of all the animals to one out of every four animals, with three-quarters of the animals now carrying the defect.
In farm animals, each male may be used to serve a large number of females, and under such conditions the increase of the inbreeding coefficient per generation in a closed breeding unit can be estimated simply by dividing 100 by eight times the number of males used. Thus, when only one homebred sire is used, the decrease in heterozygosity (variability) in each generation is 12.5 percent.
When AI (Artificial Insemination) is used, a small number of sires again are used to serve a large number of females. Nevertheless, the reduction in heterozygosity may be relatively small in such cases, because many young sires are used for progeny testing, and several tested sires enter into service each year. The modern trend in artificial insemination is to use the tested sires for only relatively short periods of time, after which they are replaced with younger sires, which presumably have made even better records. Such rapid turnover in sires serves also to reduce the length of the generation interval in breeding programs. On the other hand, very popular bulls serve worldwide a million cows
Avoid inbreeding, use heterosis instead
When two lines are crossed, then any undesired traits present in one line but not in the other are masked (hidden) and there is typically a boost in the fitness of the offspring. This effect is known as heterosis or hybrid vigor, and is the opposite of inbreeding. This effect even extends to crosses between breeds of cattle, which is why crossbreeding programs are popular (for producing cattle for beef operations, for instance). Essentially, one can get many of the benefits of two breeds of cattle in the first generation of a cross by using unrelated parent stock.
The cheapest way of making sure no inbreeding takes place is to:
- Keep close breeding records of all animals in the herd
- Make sure parents do not breed with offspring and
- Siblings do not breed with each other
- Use AI or natural mating – carefully noting the name of the sire providing semen at each AI service or the bull mating the cow – next to the name of the cow in your diary. So that after some time you will have a record of the family tree of every individual.
- Make sure the same sire semen is not used on his offspring.
- Ask your AI provider to bring different origin semen over time.
Overview of Breeding methodologies
Inheritance of Characteristics
Genes determine the way animals look – the observable trait. Thus the length of ear in sheep is the expression of the genes that regulate ear length. The breeder can only plan according to the trait observed. Repeatability and heritability are two kinds of observation that the breeder can use.
- Repeatability: This refers to the permanence of a type from one observation to the next. It is a measure of the extent to which superiority in any one character is maintained throughout the lifetime. Should sheep in a flock tend to rank in approximately the same order with regard to a certain character, year after year, in spite of environmental changes, the particular character is said to have high repeatability.
- Heritability: This is concerned with the constancy with which the phenotype is passed from parent to offspring. It expresses the proportion of total variance which can be attributed to average effects of the genes. Alternatively, heritability is the degree of inheritance of the trait.
- Selection: Individuals selected for breeding must have desirable characteristics which have good repeatability and heritability and will, therefore, be passed on to offspring. Selection aims to change the gene frequencies in order to improve the animal body types in the following generations.
Selection may be direct or indirect. The direct method selects sheep having the best expression of the trait to be improved. Indirect selection improves a trait by selecting sheep with a related trait. The effectiveness of indirect selection depends upon the correlation between two traits. This is of great importance since animal breeding usually involves more than one trait. An example of indirect selection is given by high growth rate, where selection for this trait is likely to improve early maturity and slaughter weight and also the efficiency of feed conversion.
Breeding strategies
Depending on your goals for breeding animals different breeding techniques can be used. The following is a brief overview of some breeding methodologies. The majority are not practical for most people, but for the dedicated animal breeder combinations can be used depending on the breeding strategy.
- Crisscrossing: A continuous program of crossbreeding in which there is an alternate use of males belonging to two breeds. Using two breeds designated as P1 and P2, a crisscrossing program, beginning with the two-breed cross animal (P1 x P2), would begin by backcrossing to one of the parental breeds [(P1 x P2) x P1]. Females resulting from these matings would be bred to a P2 male, [(P1 x P2) x P1] x P2, and so on.
- Genus cross: Mating of animals belonging to different genera (for example, mating of domestic cattle, Bos taurus or Bos indicus, to the buffalo, Bison).
- Grading: Mating of purebred males of a given breed to non-purebred females and the resultant female offspring in successive generations.
- Inbreeding: Mating of animals more closely related to each other than the average relationship within the breed or population concerned.
- Linebreeding: Generally mild form of inbreeding in which animals mated are related to some supposedly outstanding individual.
- Outbreeding: Mating of animals less closely related to each other than the average relationship within the breed or population concerned.
- Species cross: Mating of animals belonging to different species (for example mating of European breed cattle, Bos taurus, to Brahman cattle, Bos indicus).
- Three-breed rotational cross: A continuous program of crossbreeding in which males of three breeds are used on a rotational basis. Using three breeds designated as P1, P2 and P3, the first generation would involve production of two-breed cross animals, P1 x P2. In the second generation, two-breed cross females would be mated to males of the third breed, (P1 x P2) x P3; three-breed cross females would be mated to males of one of the breeds used to produce the two-breed cross animals, [(P1 x P2) x P3] x P1, and so on.
Descriptions in breeding
- Progeny = Offspring
- Backcross: Progeny resulting from the mating of a two-breed cross animal to one of the parental breed
- Crossbred: Progeny resulting from the mating of outcross animals belonging to different breeds.
- Inbred line: Line of animals produced by mating related animals.
- Incross: Progeny resulting from the mating of animals from different inbred lines within a breed.
- Incrossbred: Progeny resulting from the mating of animals from inbred lines of different breeds.
- Outcross: Progeny resulting from the mating of unrelated animals within a breed.
- Topcross: Progeny resulting from the mating of animals belonging to different families within a breed.
- Topcrossbred: Progeny resulting from the mating of inbred males to non-inbred females of another breed.
- Topincross: Progeny resulting from the mating of inbred males to non-inbred females of the same breed.
- Two-breed cross: Progeny resulting from the mating of males of one breed to females of another breed.
Table comparisons of results of inbreeding/linebreeding and outbreeding
| Trait | Inbreeding/linebreeding | Outbreeding |
| Uniformity | Good | Poor |
| Fertility | Poor (to good with selection) | Good |
| Growth | Poor (to good with selection) | Good |
| Predictability | Good | Poor |
| Longevity | Moderate | Good |
by Marete, 2011
Breeding Strategies and Plans
Distinct objectives are essential to a breeding plan aiming to improve our livestock breeds for better future profitability such as:
1. Higher milk yield
2. Better milk composition (depends on your market)
3. Good udder or body shape
4. Higher beef/meat quality
5. Higher growth rate (also related to good nutrition)
6. Better disease resistance
7. Better fit to available feed and other circumstances
8. Color preference
9. Polled/non polled etc.
Both quantity and quality must go together for efficient production.
Genes determine the way animals look. For example the coat colour in cows is the phenotypic expression of the genes that regulate coat colour. The breeder can only plan according to the trait observed. Other genes determine whether the udder will be small or large, whether the animal has horns, the size of the body etc.
Some examples of simple breeding strategies we can mention:
1. To increase milk production in zebu cattle: This can be achieved by upgrading the Zebu breed with a proven exotic dairy breed (Jersey, Guernsey, Friesian) upto the fourth generation or the larger and more productive Boran or Sahiwal cow depending on disease pressure in your area.
2. To increase disease resistance in exotic dairy breeds: Introduction of animals with better resistance to disease such as Boran or Sahiwal will improve the disease resistance of the dairy breeds. The cross bred offspring may take more after one parent than the other, but there are very good experiences with such crosses.
3. Better performance within a breed: If natural breeding is practiced – exchange the bull if the offspring consistently have undesirable traits.
If AI is practiced – look carefully at the pictures and specifications of sires offered to determine whether the proposed sire will add better body conformation to the animal offspring. Some AI semen providers will supply pictures of offspring, with strengths highlighted.
N/B: The successive offspring from the initial/ subsequent crossing is the one used for successive matings and not the original dam.
Table of some choices of breeding strategy for different producer goals
| Goal | Inbreeding/linebreeding | Outbreeding |
| Uniform offspring crops | Good choice with selection | Good in first cross, then poor |
| Supreme show animals | Poor in most cases | Good if non-uniform goats |
| Rapid growth meat animals | Moderate at best | Good to excellent |
by Marete, 2011
Selection of Individuals:
Individuals selected must possess desirable characteristics which have good repeatability and heritability and will, therefore, be passed on to offspring. Selection aims to change the gene frequencies in order to improve the subsequent generations.
Selection may be direct or indirect. The direct method selects cows having the best expression of the trait to be improved. Indirect selection improves a trait by selecting cows with a related trait. The effectiveness of indirect selection depends upon the correlation between two traits. This is of great importance since animal breeding usually involves more than one trait. An example of indirect selection is given by high growth rate, where selection for this trait is likely to improve early maturity and slaughter weight and also the efficiency of feed conversion.
Selection of Breeding Stock
Selection of breeding animals is based on:
- Pedigree or parentage information
- Performance records (Estimated breeding values and phenotype)
- Cost of semen from proven bulls
- Available bulls in the area
Then mates are assigned accordingly.
Breeding technologies
The following methods are used in breeding:
- Natural mating (proven and healthy bulls where A.I. is not available)
- Artificial insemination (A. I.)
- Multiple ovulation embryo transfer (MOET) (Not approved for Organic certified herds): is the process of taking embryos (fertilized ova) from a super ovulated dam (the donor) and transferring them to a surrogate dam (the recipient). This method was developed in the 1970’s and 80’s, and later modified for small ruminants, to increase the number of offspring from animals with characteristics which humans want to have in the herd. It also have some severe side effects like hormonal disturbances and that it pushes the breeding towards building on a few characteristics without considering a broad spectrum of characteristics which may be lost. It is a method which implies use of hormones in a very artificial way and therefore not relevant in herds which farm to the organic principles.
The Kenya Stud Book
This is a book which contains all the proven animals, their parentage and how one can acquire them. For registered pedigree grade cattle, its best to consult the KSB. When trading in breeding cattle, it is often found that registration with the Kenya stud book, will more than double the price of your animals. Buyers want to know the history of their breeding stock and how to choose the mates without resorting accidentally to inbreeding through AI, and they are willing to pay for this service. The Kenya stud book personnel will also give advice on good breeding strategies suited to your situation. Here is an extract from the Kenya stud book website (need to log in): http://www.klbo.co.ke/
Functions of Kenya Stud Book
- Registering and issuing of certificates for both pedigree and grade livestock.
- Setting the grading-up scheme.
- Setting up the registration rules in liaison with the respective Breed societies.
- Producing annually volumes for registered pedigree and grade livestock.
- Promotion of proper animal identification.
Benefits of Livestock Registration
- Keeping animals with proper Ancestry and identification records
- Adding value to your stock since registered stock fetch better prices.
- By consistently following the up-grading scheme the farmer is assured of owning a proved stock after each successive generation. Hence one can also easily own pedigree stock without necessarily having to spend a fortune buying the same.
- Affords the farmer a chance to contribute in the National Breeding program through the contract mating program which requires that the Bull dam be registered with the KSB.
- There are also many opportunities for the registered stock to participate in competitions such as ASK shows and breeders shows. Prizes are offered in these events and they also offer a perfect opportunity for the farmer to market his/her stock. Most of these events require that the show animals be registered as a condition.
- Registration records are also an important National assets for the management of animal genetic resources and biodiversity conservation.
Functions of the Dairy Recording Service of Kenya
- Recording officially and accurately the quantity (kgs) and quality (Butterfat) of milk produced by each cow in every recorded herd.
- To produce lactation certificates for the registered herds.
- Calculating herd average certificates and life time production for the recorded herds and issuance of the appropriate certificates.
- To avail the production data to the Livestock Recording Centre which is responsible for progeny testing and to the Bull Purchasing Committee for the Contract Mating Program.
- Extension services offered to the Registered and New farmers and sound advise on Livestock management and proper record keeping at the farm level.