June, 2000 . Volume 23, Number 5 
NCSU Extension Swine Husbandry
June, 2000 . Volume 23, Number 5 GENETICALLY MODIFIED ORGANISMS IN ANIMAL PRODUCTION
A topic that has been receiving a lot of press lately is the introduction of genetically
modified organisms (GMOs) into our food chain. For nonscientists, the technology behind
genetic modifications is bedazzling, which is the reason for fear among many. Even for
scientists, genetic modification of living organisms may raise some serious questions about
ethics. On the other hand, genetic modification of organisms opens some interesting
possibilities for improving productivity and better tailoring products to the demands of
the consumer.
Mankind has manipulated the genetic composition of animals and plant as long as farming has occurred (and probably even before that) through selection. Genetic modification technology offers the opportunity to change the boundaries and allows a different type of selection.
GMOs in animal production
The following examples of GMOs may have an impact on animal production.
Vaccines: Vaccines are typically administered through an
injection, a process that is laborious for the producer and stressful for the animal. Also,
in large production settings there is a real risk that hired labor 'forgets' to vaccinate
animals. Edible vaccines would be an attractive alternative to vaccination by injection.
In the human arena, several products have already been discussed, including a banana that
contains an edible vaccine for cholera. The philosophy is that each third-world village can
have one such banana tree which, if fed to the local children, ultimately would lead to the
elimination of cholera. For swine, similar vaccines are possible and are actually under
development (e.g., a TGE vaccine).
Microorganisms: GMOs are being developed in many different fields. For
example, bacteria and fungi are being modified to produce drugs, enzymes, vitamins, and
other materials of interest. Products made by these microorganisms or even crude
preparations made by these bacteria already have a place in animal nutrition.
Examples of GMO products are phytase, non-starch polysaccharide degrading enzymes (such as
xylanase and beta-glucanase), and vitamin B12. Many of these products are
processed so that the final preparations are free of genetic material. The end products ar
the same as naturally occurring compounds, so it is hard to perceive them as GMOs.
The impact that these products have on animal nutrition are obvious. Animal feed will less
expensive as the ingredients are cheaper. Or more nutrients will be derived from the feed
because it has been made more digestibility.
It is expected that new enzymes will enter the market over the years to come, but little
information is available as to the nature of these enzymes. Research publications on
mannanases and proteases likely to be derived from GMOs have already appeared in the press.
Plants/feed sources: Many genetically modified plants are being introduced
into the market. For example, in Canada alone over 500 different plants were submitted for
regulatory review in 1999. Of these, however, only 20 were listed potentially altering
nutritional composition. Although further details were not provided, it is likely that the
majority of these 20 involved nutritional characteristics of interest to human nutrition,
such as altered fat composition or increased vitamin contents.
A recent article by Monsanto actually suggests that crops targeting animal nutrition are not
likely to become mainstream. The reasons for this are the difficulty in rewarding the crop
farmers for these products as such products would require identity preservation through the
production chain. In addition, as stacking genes is still technically challenging, farmers
are likely to find a better value in some of the insecticide or herbicide-resistant crops
than in, low phytate or high lysine corn, for example (although these products have been
talked about by Optimum Quality Grains and Dupont).
For example, corn with 0.1 percent extra lysine has an estimated extra value per hectare of
$20 under ideal conditions. Such corn, however, has to be identity preserved so that this
value has to be split between the animal producer, the grain handlers, the crop farmer, and
the seed producer. Bt corn, on the other hand, is expected to improve the margin per
hectare with $38.50, all of which goes to the farmer.
It is thus much more likely that 'super high' lysine corn will be developed in which the
lysine content is so high that it can be purified and sold to compete with lysine produced
through fermentation. Although this route would require identity preservation as well, it
would be much easier to justify this cost since the value of the end product is much larger
while the land area required to grow this crop is much smaller.
Crops that are finding their way into the marketplace are low phytate corn and soybean meal
(some of which are non-GMO products). The obvious advantage of these crops is the improved
phosphorus utilization, thus reducing phosphorus excretion. Again, the economic benefits of
such crops are rather low as phytase, a very expensive feed additive, can achieve similar
results.
As for lysine, it is more economically attractive means to reduce the phosphorus problem by
developing plants that express extremely high levels of phytase with the objective of this
phytase or the whole plant could be used as the phytase supplement, rather than phytase
obtained through fermentation. Such phytase sources are under development.
Other GMO crops targeting animal production are low-fiber feedstuffs. Fiber is well known
to increase the digestive effort and to reduce digestibility, and plants low in this fiber
(specifically nonstarch polysaccharides such as stachyose, raffinose, mannose, xylans and
beta glucans) should yield more digestible and metabolizable energy and protein and less
manure.
Animals: An innovation that received a large amount of press coverage was the
phytase producing pig produced by the University of Guelph, Canada. Researchers inserted the
phytase gene so that the pig produced phytase in its saliva and could now break down plant
phytate (the `enviropig'). This is an interesting technical demonstration but its value
should be questioned in light of consumer concerns about GMOs and in light of economics.
Microbial phytase currently costs approximately $.50 per pig, and new phytase supplies
(such as high-phytase soybeans) are likely to further decrease this cost. In addition,
low-phytate crops are being introduced, and all these solutions to the phosphorus problem
are less likely to lead to consumer problems than genetically modifying the pig itself
while likely being more economically attractive on top of it.
Selected references
Engel, K-H., G.R. Takeoka, and R. Teranishi (1995) Genetically modified foods - safety issues. American Chemical Society symposium series 605, 243p
http://www.agbioworld.org links to many sites focusing on biotech issues (both pro and con)
Liu, K. (1999) Biotech crops: products, properties, and prospects. Foodtechn. 53:42-48
Reichhart, T., D. Butler, A. Abbott, D. Dickson, and A. Saegusa. (1999) Long-term effect of GM crops serves up food for though. Nature 398:651-653
Trewavas, A. (1999) Much food, many problems. Nature 402:231-232.
Theo van Kempen
At the Northeastern Regional Pork Conference the top 10 practices for
pork producers to follow in order to avoid a problem during a DWQ inspection were outlined
by Ms. Daphne Cullom from the Washington Regional Office of the Division of Water Quality.
Her top ten list was as follows:
10. Have a readable freeboard marker in your lagoon.
9. Record freeboard levels weekly.
8. Allow no over application of nitrogen.
7. Maintain a suitable vegetative cover on lagoon dikes and walls.
6. Maintain vegetative cover crops on all fields that match the crops outlined in your plan.
5. Have current soil and water analyses + 60 days of the irrigation event.
4. Maintain complete, accurate, up-to-date irrigation records including nitrogen balance for each field.
3. Report within 24 hours of first knowledge of a) freeboard < 19 inches, b) discharge,
c) over application; excess of plant available nitrogen (PAN), and d) deterioration of
lagoon dike walls.
2. Be honest with the DWQ inspector.
1. Follow your certified animal waste management plan and general permit to the best of
your ability.
Todd See
Effects of feeding spaces and availability of water in the feeder on pig behavior and
performance were evaluated by Gonyou and Lou (J. Anim. Sci. 78 (2000), pp. 865-870).
Twelve different feeders were classified into two groups depending on the number of
feeding spaces (single-space and multiple-space) and the availability of water (dry and
wet/dry). The feeders represented a wide range of feeder designs available commercially,
thus preventing confounding of results due to specific features (other than those under
study) of a particular feeder. Effects of feeder design on pig performance over a 12-week
period are shown below.
| Item | ||||
| ADG, g/d | ||||
| ADFI, kg/d | ||||
| Gain/Intake | ||||
| Carcass, % lean | ||||
| * Difference in Dry versus Wet/dry (P < 0.05). | ||||
Presence of water within the feeder increased feed intake (ADFI) and daily gain (ADG) by
approximately 5%, but reduced % lean in the carcass. The formulation of diets to be used
in Wet/dry feeders may need to be adjusted to account for increased feed intake and gain
and to avoid a decrease in carcass lean. Number of feeding spaces did not affect
performance, indicating that 12 pigs (12 pigs were used per feeder in this experiment)
could be fed from a single feeder space without detrimental effects on performance. Effects
of feeder design on feeding behavior are shown below.
| Item | |||||
| Duration of easting, min/d | |||||
| Feeder visits, no./d | |||||
| Occupancy rate of feeder, % | |||||
| Occupancy per feeder hole, % | |||||
| * Difference in Dry versus Wet/dry (P < 0.05). abc Values with a different letter within a row are different (P < 0.05). |
|||||
Pigs spent less time eating form a Wet/dry feeder compared to the Dry feeder and occupancy
rate was reduced for Wet/dry feeders. Pigs spent less time eating with fewer feeding spaces,
but occupancy rate was increased with fewer feeding spaces. The authors concluded that
productivity could be maintained at feeding space occupancy rates of 80%. At least 12
pigs could be maintained on a single-space feeder. The number of pigs that can be maintained
per feeding space for a Wet/dry feeder would be greater because of the reduction in eating
time and occupancy rate.
Eric van Heugten
The Pork Industry Handbook is now available on CD-ROM. The CD includes 138 fact
sheets developed by various authors selected on the basis of their expertise in subject
matter areas. In this format, the Pork Industry Handbook can easily be searched,
and many of the fact sheets include color photos, video, www links and spreadsheets. All
phases of pork production and marketing are covered in this project, which was coordinated
on a national basis in an attempt to supply uniform information.
Purchase of the CD includes updates for a 3-year period. To obtain an order form, contact
your local county livestock agent or email your name and address (or fax number) to
Carla_Mckinney@ncsu.edu, and we will send a form to you.
Todd See