Artificial insemination in cattle
Artificial insemination (AI) is a popular method of breeding cattle in the UK and in this article we look at the benefits to farmers of using this method to increase herd numbers.
If a bull is being mated naturally with a female he will generally deposit a larger quantity of semen than is actually needed to ensure success, and he is only able to service a finite number of females in any one season. Mating is both stressful and tiring for the bull so he must also be rested. However, with AI, semen can be harvested from the bull and then diluted to produce many hundreds of doses from just one ejaculate. This semen can be also be stored for long periods of time meaning that a particular bull’s semen may be used long after his natural productive use has passed. Semen is also easy to transport so can be sent to many locations around the country.
The cost of keeping a bull in prime condition can be substantial. He will consume a large amount of food and very often will need housing and special handling equipment, reflecting his size and power. In addition, as the bull is generally much larger than the female, mating naturally can result in injury to either animal, which again, leads to increased costs in potential veterinary treatments. So, whilst there is a significant cost to the AI process, many farmers consider it to be the cheaper and easier route for breeding.
Better genetic selection
As we have mentioned above, AI allows one bull to produce many more offspring than with natural mating, which means that only the best bulls may be selected for semen collection. The number of progeny just one bull can produce is also very useful in evaluating the genetic value of that male, where the offspring are used in a genetic test programme. Lastly, if a farmer has a larger selection of bull semen to choose from, the gene pool of the herd can be expanded, which has the potential to negate any effects of inbreeding which may have occurred within that herd.
The transmission of diseases between the male and female animals is a possibility during natural mating, but disease transfer is much less likely with AI. There are some pathogens that can be transmitted but screening processes should reduce this possibility. Quality checks on AI samples should also help to avoid infertility problems which may not be apparent during natural mating.
The downsides of AI
Male animals are able to detect instinctively when a female is ready for mating, thus ensuring a good success rate, provided both animals are actually fertile. A farmer has to make the decision when a female is ready when using AI and this can lead to poor detection and in turn, a lower success rate.
A bull being able to produce many more progeny sounds good but is only advantageous if he is of the requisite quality to ensure a selective advantage. If the bull is of lesser quality then there will be a decrease in the genetic merit of its offspring. The logical conclusion, therefore, is that the decrease in variation must be balanced with benefits of a more intense selection.