Genetics: New tools for improving animal genetics
Wednesday, May 5, 2010
Cloning, transgenics and genomics all show potential for improving breeding stock and population genetics, as the University of Guelph's Enviropig is demonstrating
by JIM DALRYMPLE
In all livestock species, improvements in many economic traits through the use of reproductive technologies have been a constant for many years. The use of cloning and transgenics are the most recent of these technologies to provide geneticists with additional tools to improve population genetics.
A recent paper prepared by the Council for Agricultural Science and Technology (CAST) in the United States looks at the future of animal agriculture through biotechnology. This detailed report, "Animal Productivity & Genetic Diversity: Cloned & Transgenic Animals," deals with all aspects of these new technologies.
Cloning. Cloning has the potential to assist with the preservation of genetic diversity. The number of species that have been successfully cloned is increasing, but there is still concern regarding the health and potential longevity of cloned animals. It is, however, clearly feasible to use cloning to preserve endangered species.
Cloning has a wide range of potential benefits, including: the multiplication of genetically superior animals in agriculture and companion animals; production of transgenic animals for agriculture and medicine; animal research models; therapies based on human cells; conservation of endangered livestock breeds and species.
Cloning is not likely to be used to produce animals for food, at least not in the near future, since it is too costly and inefficient. Cloning will likely be used to produce breeding stock to generate future animals for food.
Many consumers and some scientists have been skeptical about the safety of cloned animals. Yet the U.S. Food and Drug Administration (FDA) indicated in 2008 that milk, meat and other products from cloned animals are as safe as those from non-cloned animals. Before the introduction in the United States several years ago of rbST, a genetically engineered bovine growth hormone that increases milk production in cows, experts predicted a 20 per cent decline in milk consumption. Consumption levels were never affected.
The CAST paper released in 2009, authored by six scientists and reviewed by additional people across the United States, indicates current costs for cloning cattle as exceeding $10,000 per animal produced. This would limit the use of cloning to breeding strategies.
Transgenics. Whereas a cloned animal is genetically identical to the one from which it came, a transgenic animal is one into which a new gene has been introduced or in which an existing gene has been modified by human intervention.
Applications of transgenic technology can create animals that are better able to combat or resist infection, improve food safety and quality, increase production efficiency, decrease the environmental footprint of livestock production, and introduce new characteristics into the gene pool.
In Ontario, scientists at the University of Guelph have spent over 10 years developing the Enviropig.
This development, still under review by federal regulators, should reduce the environmental impact of pork production as there is less phosphorus in the manure produced. When manure from ordinary pigs is spread on the land, there can be a build-up of phosphorus. The Enviropig excretes much less phosphorus in its manure, which greatly reduces environmental impact.
The Enviropig is a transgenic line of Yorkshire pigs that produces an enzyme (phytase) in its salivary glands and excretes it in its saliva. It is the first genetically engineered animal primarily designed to solve a global environmental problem.
The nucleus herd of these pigs has been developed over seven generations.
Phosphorus levels in manure will be reduced 30 per cent to 70 per cent, feed costs will be lowered and there is no impact on the carcass or nutritional qualities of pork. In 2010, further studies indicated that the Enviropig meets regulatory standards.
Patents have been issued in the United States and China. It will be unfortunate if those countries receive the benefit of this amazing Canadian technology before Canada.
Currently, more than 25 transgenic technology applications are being researched in North America, aimed at the improvement of agricultural production characteristics.
These include the areas of meat production, growth rate, milk production, fibre production, feed conversion, disease resistance, food safety and environmental enhancement.
Genomics. Since the mid-1970s, when scientists figured out how to isolate and interpret gene or DNA sequences, the idea of mapping a genome became a reality. The ultimate aim of farm animal genome research is to gain a better understanding of the genetic control of traits which are of economic, agricultural and biological importance. Genomes comprise a sequence of between one billion (for chickens) and three billion (for cattle) base pairs of DNA, containing some 30,000 or so genes each.
Genomes from pigs, cattle, poultry and other livestock species, which are similar in complexity to those of humans, are being worked on throughout the world. For example, research at Iowa State University in mapping the pig genome is working on data related to genes involved in determining litter size, average daily gain, back-fat, loin eye area and feed efficiency.
Over the past several decades, estrus control, embryo transfer, the freezing of embryos, semen sexing and other achievements have helped to keep animal industries competitive and increased export opportunities for many commodities.
Over the next decade, new research initiatives will enhance animal well-being, improve product quality, increase product safety and decrease the environmental impact of animal production. BF
J.R. (Jim) Dalrymple is a former Ontario government swine specialist and president of Livestock Technology Services Ltd. in Brighton.