Thereafter undergoing the MAS technology, the selected individuals that are bred are mated and crossed. Farmers use many techniques that have been developed including artificial insemination to improve the outcomes of selective breeding. Artificial insemination is transferring semen from a male into the uterus of a female cow through vivo fertilisation other than through sexual intercourse. Using the semen from a single male, a much larger number of females can be impregnated when compared with traditional breeding. If performed correctly, there is also a much higher chance of fertilisation. A successful artificial insemination programme relies on various techniques to establish when females are close to their ovulation period.
In Vitro Fertilisation (IVF) is a technique used in artificial insemination in which sperm and egg cells are harvested and combined within a glass dish. Thus fertilisation occurs outside of the animals body. This service has been operating for 10 years and offers the best method of producing multiple offspring from superior female cattle. Procedures are constantly updated, combining the latest technologies used in dairy cows IVF and freezing methods. Next the process of embryo screening and selection occurs. The resulting embryos are analysed for any defects, such as genetic markers associated with certain diseases. Embryo Transfer is a technique in which embryos such as those produced by IVF are transferred into the uterus (womb) of an unrelated female cow called a surrogate cow. The surrogate is genetically unrelated to the embryo developing inside her. This technique is used to enable females with reproductive issues to produce offspring. This makes it possible for a single female to produce a large number of offspring.
Since farmers have begun selectively breeding dairy cows, the genetic biodiversity has decreased as dairy cows are being selected for certain qualities and those qualities only. Selective breeding usually reduces genetic biodiversity as only a select few individuals are used to produce very large numbers of offspring. Future generations of selectively bred organisms will all share very similar gene and some alleles may actually be lost from the gene pool. This could make some diseases more dangerous due to loss of alleles that may have aided disease resistance meaning more organisms would be affected by the disorder. Some alleles will be lost, making it more difficult to produce new varieties and breeds in the future. Therefore leading to a reduction in the size of the gene pool. This could effect the survival of the population. The precise implications are specific to each dairy cow and depend on the gene being added or removed, the organism being modified and it’s environment. Thus, low and genetic biodiversity and an interbreeding small population can result in inbreeding depression natality and offspring viability.
Another biological implication is the health and survival of the individual. The outcome may not be completely successful because of linked genes. Linked genes are those that are found on the same chromosome and tend to be transmitted together. Future generations of selectively bred organisms will all share very similar genes. This could make some diseases more dangerous and susceptible, thus most of the organisms would be affected. Therefore there is an increased risk of genetic disease caused by recessive genes in homozygous recessive individuals. A farmer may select a dairy cow that is the desirable size with the fattiest milk, but with that trait may also come a negative trait such as susceptibility to disease or infertility. The negative consequences of using and reproducing the NZ dairy cow would probably outweigh the positive features. Similarity within species also means that if the dairy cow comes into contact with a disease, there is a high chance of the whole species being wiped out. There is an increased risk of genetic disease caused by recessive alleles, as there is more chance of offspring from closely related parents inheriting two copies of a recessive alleles and hence expressing is in the phenotype. Some genes will be lost, making it more difficult to produce new varieties in the future.
Transgenesis is a completely different method farmers use to produce dairy cows with desirable traits. Transgenesis is the process of a gene from one species is transferred into the genome of another species, using a combination of biotechnological techniques. Therefore making proteins that species cannot normally build. Transgenic cows are genetically modified cows. They have an extra gene or genes inserted into their DNA. The extra gene may come from the same species or from a different species.