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Gene splicing improves pork farm waste

Transgenic plants and animals present us with an uncomfortable paradox. While they may provide very real cost benefits to farmers and environmental benefits for all, they also pose unknowable risks. Whether we support the use of genetically modified animals or not, research is moving ahead. In the last few years, scientists at Ontario's University of Guelph have created Enviropigs™, a line of transgenic pigs containing both mouse and bacterial chromosomes; the pigs cost less to feed and produce less noxious manure.

Genetically engineered enviropigs (Cecil Forsberg)
Genetically engineered enviropigs
Cecil Forsberg

While normal pigs are unable to digest phytate, the naturally occurring form of phosphorus found in feed, bacterial genes inserted into Enviropigs™ allow these animals to produce sufficient phytase enzyme in their saliva to release almost all the phytate phosphorus consumed, for stomach absorption. Farmers raising these pigs would therefore no longer have to add extra phosphorus or phytase enzyme to the diet.

"As the price of oil increases, so does the cost of all components of feed," notes Dr. Cecil Forsberg, head researcher on the project. "Because these pigs utilise practically all of the phosphorus present in a standard diet consisting of corn, barley, wheat and soybean meal, there is a saving of about C$1.14 per pig for supplemental phosphorus, or an equal or greater saving in the cost of phytase." (Other strategies to improve phosphorus absorption focus on crops with phytase in the seeds or containing less phytate.)

Another benefit to these pigs occurs in the small intestine: reduced phytate at this point in the digestive tract decreases the complexes formed between phytate and trace minerals, thereby improving their absorption as well, says Forsberg. Furthermore, farmers will not have high-phosphorus manure to dispose of. According to Forsberg, phosphorus in faeces from young grower Enviropigs™ not supplemented with phosphate was reduced by 75 per cent while that in finisher Enviropigs™ was reduced by 56-67 per cent. The phytase enzyme is degraded in the small intestine by pancreatic proteases, preventing excretion from the pig. Consequently, these pigs produce a fertiliser with a lower content of phosphorus, which is better suited for long-term, repetitive application to agricultural land.

Are we ready?

None of the benefits of transgenic animals such as Enviropigs™ can be realised by farmers until government approves them for use and consumers are comfortable. Although Forsberg's team is ready to submit data in early 2005 for both Canadian and American approval, Kim Brooks of the US's Pew Initiative on Food and Biotechnology notes that the government doesn't have in place a process for approving, let alone monitoring, transgenic animals. Cloning is first on the agenda, and it may be 2006 or 2007 before the first cloned pigs are approved, with approval for transgenic organisms following after. Canada is in a similar position to the US.

Regarding consumer readiness, some answers may be found in a UK Food Standards Agency study called "Consumer Attitudes to Food Standards, Wave 4" conducted in 2003 and released in February 2004. Of all people surveyed, 8 per cent named GM foods as a concern without prompting and, when asked, a further 17 per cent stated these foods were a concern. When given a list, 38 per cent identified GM foods as a concern, as compared to 60 per cent who checked off food poisoning and 42 per cent who identified BSE. However, do these worries affect their choice of what to eat? Of those surveyed, 78 per cent say that their concern over GM foods affects their eating habits either a little or a lot.

The University of Guelph team has been testing these animals extensively since their creation in 1999. Forsberg notes, "The lines of Enviropigs™ that we are studying have health status, growth rates and reproductive characteristics similar to that of conventional pigs (lacking the phytase gene) receiving a diet with supplemental phosphate. Also, the phytase enzyme is produced primarily in the salivary glands, with only trace concentrations (less than 0.1 per cent) in the major tissues such as muscle, liver, heart, skin, etc."

Forsberg sees a need for this type of research because, he says, "If we are going to eat meat, and human population continues to grow, meat production must become more efficient in order to sustain the environment in its current state." Ultimately, no one can provide a guarantee that these pigs will not have a problem that is currently unforeseen. If that occurs, either the use of the animals will be halted, or further genetic research will be required.

Written by: Treena Hein

Date published: March 2005


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