Artificial Insemination technician injectes a cow with high quality semen, Ethiopia. Credit, Z. Sewunet, ILRI
Artificial insemination (AI) is the process of collecting sperm cells from a male animal and artificially depositing them into the reproductive tract of a female. AI allows the germplasm from species of superior quality to be effectively utilized.
As one of the most widely available genetic technologies in developing countries, with 34 million artificial inseminations were carried out in India alone in 2007, AI contributes in particular to improving cross breeding. Yet, the relative potential of AI has remained generally unexploited and is mainly used for exploratory purposes by research institutions. A few African countries including Nigeria, Ethiopia, Uganda, Ghana, Botswana, Malawi, Senegal, Mali and Sudan have taken the technology to the field, but mostly to upgrade indigenous stock and to enable a limited number of commercial farmers to keep “exotic” dairy cattle breeds.
Using chilled semen in a smallholder farm. Credit, Bayemi.
Although AI technology is available for other domestic livestock species, AI is still most generally associated with dairy cattle. The use of AI in beef cattle has mainly been limited due to the difficulty in detecting those cattle that are in heat within large herds and where individual cows are handled only occasionally. With sheep and goats there is scope for improvement of the technology. The failure to develop a simple, non-surgical insemination procedure has prevented extensive exploitation of the technology in sheep.[1]
AI has played an important role in enhancing animal productivity, especially milk yields, in developing countries that have a well-defined breeding strategy and a sound technical base to absorb and adapt the technology to meet their needs. AI systems are costly to maintain and require intensive logistic and maintenance because of the need for liquid nitrogen to store semen.[2] Therefore, countries can maintain successful AI systems with: 1) an effective technology transfer mechanism; 2) effectively integrated international assistance into their national germplasm improvement programmes; 3) built and maintained infrastructure; 4) complemented with improvements in animal nutrition and veterinary services; and 5) adequate economic incentives to market dairy products. Many developing countries, however, lack one or more of these requirements.[3]
Contribution to Sustainable IntensificationProgress in semen collection, dilution and cryopreservation (a process where cells or whole tissues are preserved by cooling to sub-zero temperatures) now enables a single bull to be used simultaneously in several countries for up to 100,000 inseminations a year. This implies that a very small number of top bulls can be used to serve a large cattle population. Additionally, each bull is able to produce a large number of daughters thus facilitating accurate progeny testing (a test of the value of an individual’s genotype by looking at the progeny produced by different matings) that allows breeders to select the best cows.
The high intensity and accuracy of selection arising from AI can lead to a four-fold increase in the rate of genetic improvement in cattle relative to that from natural mating. Additionally, AI can reduce the transmission of venereal diseases in a population, limit the need for farmers to maintain their own breeding males, facilitate a more accurate recording of pedigree and is a cheaper means of introducing improved stock.[4] The reduced production costs suggest that farmers can increase their incomes contributing to more profitable livelihoods.
Benefits and limitationsThe technology, although apparently simple, requires relatively high levels of skill and experience; for example, success depends on accurate detection of cattle ‘in heat’ (the period of time when ovulation occurs increasing the probability of conception) and timely insemination. Detecting when an animal is ‘in heat’ requires a certain level of awareness among farmers while timely insemination is dependent on good infrastructure and access to reliable transport networks. However, there are also countries which have used the technology more widely. Kenya and Zimbabwe, for example, have more elaborate AI systems which include national insemination services that incorporate progeny testing schemes. South Africa is probably the biggest user of AI technologies and has what is perhaps the best organised progeny testing scheme on the continent.[5]
During natural breeding a male will deposit much more semen than is technically needed to produce a pregnancy. In addition natural breeding is physically stressful for both the male and the female. Both of these factors limit the number of natural matings a male can make. However, collected semen can be diluted and extended to create hundreds of doses from a single ejaculation. Also, semen can be easily transported allowing multiple females in different geographical locations to be inseminated simultaneously, and semen can be stored for long periods of time meaning that males can produce offspring long after their natural reproductive lives end.[6]
Because artificial insemination (AI) allows males to produce more offspring, fewer males are needed. Therefore, one can choose the best males for use as parents, increasing the selection intensity. Furthermore, because males can have more offspring their offspring can be used in a progeny test program to more accurately evaluate the genetic value of the male (and determine if it is in fact one of the best selections). Finally, individual farmers can use AI to increase the genetic pool with which the herd can be mated, potentially decreasing effects of inbreeding.[7]
Male animals often grow to be larger than females and consume relatively larger amounts of feed. Also, male animals are often stronger, more powerful, and potentially more aggressive and thus require special housing and handling equipment. In addition, due to the relatively larger size of adult males than females, natural mating is more likely to result in accidents and injury to either the cow or the bull compared to artificial insemination.[8]
Natural mating allows for the transfer of venereal diseases between males and females. Some pathogens can be transmitted in semen through artificial insemination (AI), but the collection process allows for the screening of disease agents. Collected semen is also routinely checked for quality, which can help avoid problems associated with male infertility.[9]
Artificial Insemination (AI) can be more laborious than natural reproduction. Male animals instinctively detect the females that are in the correct status for conception. With AI, the detection work falls on the responsibility of the farmer. Poor detection results in decreased rates of fertility. Also, increasing the number of offspring per male has selective advantages only if the best males can be accurately determined. Otherwise this process only decreases the genetic variability in a population. Increasing the number of offspring per male always reduces the gene pool. The benefits of more intense selection must be balanced against the negative effects of decreased variation.[10]
