Better Pork - October 2003
Germany: Blue light boosts performance in hog barns
Trials in Germany have shown that blue-tinted lighting reduces fighting and increases liveweight gain. Next the researchers plan to test it in farrowing pensby NORMAN DUNN
Changing the neon light tubes in a feeding hog building increased average daily weight gain by an average 15 grams in a recent German trial. At the Futterkamp Education and Research Centre, standard lighting was replaced by blue-tinted tubes in a compartment with 96 feeding hogs and performance was compared with hogs in an adjacent compartment where lighting was normal."Blue lighting with a wavelength of around 500 nanometers is already accepted as having a calming effect on humans and is now used in banks and supermarkets in Germany, for instance," explains Futterkamp researcher Christian Meyer. "That's why we decided to try out the idea with hogs. The main aim was to reduce aggression in the pens and thus related problems such as tail biting."
Meyer says the first trial has confirmed the positive effect of blue lighting at 50 lux (a lux is one lumen per square metre) during the day. Compared to the control group there was significantly less fighting amongst pen members and the immediate result was improved performance all-round. Average daily liveweight gain for the control group was under 820 grams but the blue-light hogs averaged nearer 835 grams per head, so time to slaughter was cut by one and a half days. On the slaughter line, hogs that had been kept under blue light had 0.62 per cent higher lean meat than the control group.
Further trials continue and Christian Meyer is now testing the effect of blue light in farrowing pens. "Of course, there is still much more work to be done, but there could well be a future for its calming effect in buildings where weaners from different sources are penned together for the first time. There could be a good case for applying the concept in hog transport wagons to the slaughterhouse and in the lairage, too " he reckons.
The Futtterkamp researchers are also working on whether blue or green lighting has the best calming effect for hogs. "A wavelength of 400 nanometers is getting very near the green sector of the spectrum, which starts at 530 nanograms, so we will be looking at the effects on hog behaviour of this colour too," says Meyer. BP
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Denmark:Charged water jolts feed conversion
by Norman Dunn
Supplying electrochemically activated water (EAW) to piglets for the first two weeks post-weaning resulted in a 40 per cent performance improvement during that period in Danish trials. Tests with 800 piglets by consultant Hanne Maribo, carried our for the National Committee for Pig Production and the Danish Bacon and Meat Council, showed a big boost in weight gain and feed conversion when compared with control groups on standard drinking water.
But what is EAW? "This solution," explains Maribo, " is created through first of all adding chlorine to a saline solution which has a pH modified so that it is slightly lower that that of standard drinking water. We then pass this solution twice through an electrical charging cell."
This EAW solution is then added to the piglets' drinking water at 10 per cent. The process has now been sold to a commercial firm for further development, so the Danish consultant couldn't go into more technical details, except to say that the treatment did a very good job of knocking out at least some micro-organisms in the water. "EAW treatment left the drinking water with zero counts of anaerobic germs and of coli bacteria, although the content of both in the control group's drinking water was significant."
Results so far indicate that the EAW intake only seems to stimulate feed intake and conversion, because there was no difference between the trial groups in mortality rate and diarrhoea incidence. Nor were any significant differences found in the intestine flora of the two groups of piglets after the trial.
Maribo hasn't taken the treatment past the first two weeks post-weaning because the system was sold on at that point as ripe for commercial development. "But I understand that EAW is now being tested with feeding hogs through to slaughter and is also being tried as a component of water used for sprinkling the pigs in warm weather."
In Maribo's work, both EAW piglets and control groups were on conventional drinking water for the remaining four weeks of the weaner growing period. One trial resulted in performance of the two groups of piglets levelling out by ten weeks of age with no significant differences in weight gain and feed conversion over the total growing period. But a second round of the trial, using water that had been treated to reduce a natural high content of iron, gave the EAW piglets a performance advantage which lasted right through to slaughter. BP
For more information, contact Danske Slagterier, Dr Hanne Maribo (website www.lu.dk report No. 578), or Gilbert Hinze at mail@radicalwaters.com.© copyright 2003 AgMedia Inc..
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France:Mobile manure treatment units come to France
by Norman Dunn
Continual tightening of water protection laws by French authorities in the main hog production region of Brittany means that now even 100-sow rearing and feeding units must have a government-approved manure separation and processing system on the farm.
When smaller farms shopped around for the necessary equipment last year, many thought they would have to give up hog production because the capital costs for the required standard of treatment were just too high. But local engineers APV Compost recognised a golden marketing chance and introduced Smelox mobile manure treatment units to carry out regular visits to farms under contract. The system proved so popular that APV had six separate units working within the first year.
The truck-mounted Smelox units can handle up to 100 cubic metres of liquid manure per day and farmers sign a five year contract for treatment of all their hog manure at the equivalent of $15 Cdn per cubic metre. For this outlay, APV delivers the unit when required, along with operators, and guarantees that end products meet the standards required by the local water authority.
The system starts with centrifugal separation of liquids and solids. The solids are dried and carted off the farm for fertilizer production by PVC if so required. Next, oxygen is jetted into the liquid along with additives for oxidation of sulphur compounds, thus reducing much of the odour problem. Also removed in the process is much of the ammonia.
According to the company, heat produced in the process reaches over 250 °C and thus sterilizes the liquid so that it can be safely spread on gardens or farmland. APV claims that the mobile Smelox treatment eliminates up to 90 per cent of ammonia and 75 per cent of phosphor from the liquid.
French farmers are being forced to build manure treatment plants if they want to continue hog production. One way around the problem is a new service featuring mobile manure treatment plants costing the farmers the equivalent of $15 Cdn per cubic metre of manure processed. BP
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Preventing and treating disease through improved intestinal function
Enhancing your pigs' gastrointestinal functions and preventing major intestinal diseases can have a positive effect on growth performanceby JANICE MURPHY
Weaning is a stressful event in the life of a pig. The piglet faces a combination of environmental, social and nutritional adjustments and there is the potential for illness or even mortality as a result of diarrhea.
With restricted use of antibiotics, or complete bans in some countries, researchers are actively pursuing alternative feeding strategies. And they are making considerable efforts to determine what conditions are necessary to optimize the gastrointestinal (GI) ecosystem and so prevent major intestinal diseases in the first place.
The GI tract is a very complex organ and its health and development hold the key to productivity in all domestic livestock and poultry. The tract has two basic functions that are essential to growth and development: acquiring and absorbing nutrients, and maintaining a barrier of protection against infection from microorganisms and viruses.
What changes occur in weaned piglets that predispose them to disease? At weaning, the piglet's diet changes dramatically from sow's milk to a solid ration, so the gut microbes have to adapt very quickly.
The change of diet usually results in reduced feed intake, below the maintenance requirement, during the first week and has a negative impact on the structure of the small intestine, resulting in shortening of the villi (fine projections that increase the surface area and absorptive capacity of the gut). The degeneration of the villi in the small intestine is considered a predisposing factor for postweaning health problems.
Below are some of the most prominent intestinal diseases in pigs:
Postweaning colibacillos is is the most common intestinal disorder immediately post-weaning and is associated with the rapid growth of toxin-producing E. coli in the small intestine.
Swine dysentery is a form of colitis affecting the caecum, colon and rectum of grower pigs and is one of the most economically important intestinal diseases in swine.
Salmonellosis is a concern in the swine industry for two reasons: clinical disease of pigs and contamination of pig products with salmonella serotypes that can infect humans.
Porcine proliferative enteropathies (or ileitis) can be acute or chronic conditions with a common underlying pathological change visible as a thickening of the mucosa of the small intestine and colon (garden hose gut). Economic losses associated with ileitis can result from poorer feed conversion, longer days to market, increased mortality and higher cull rates.
Gastric ulcers in the stomach are common in slaughter pigs and the lesions cause reduced growth performance.
Endo-parasite infection in grower finisher pigs can have major economic impact on pig production through reduced performance. At low levels of infection, parasites like Ascaris suum (roundworms) are known to reduce average daily gain and feed conversion and can even cause mortalities at higher levels.
Recent research in Denmark has focused on feeding strategies to enhance intestinal function. To date, the most successful strategies being used include manipulation of feed composition as well as the use of fermented liquid feed, coarse non-pelleted feed and organic acids.
Danish researchers suggest that the single most important control for the ecosystem in the GI tract, and ultimately for pig health, is the amount and type of substrate available to the microbial population. In theory, this would allow direct control over the processes of fermentation in the GI tract through feed composition. Results to date are inconsistent, but studies have centred on how the fiber, protein and fat content of the diet affect microbial fermentation.
Fermented liquid feed has been a hot topic in Europe over the past five years in the search for alternatives to antibiotics. Feeding fermented liquid feed reduces the pH in the stomach to four or less, which inhibits the growth of bacteria such as coliform and salmonella, and prevents diarrhea. However, growth performance is not improved by using fermented liquid feed, although systems where only the grain is fermented show promise. This may be due to associated improvements in the gut structural components. Results from piglets fed a liquid diet with fermented wheat showed they had higher villus height and higher villus/crypt ratio, suggesting that this may be a way to prevent degeneration of the mucosal architecture after weaning.
Feed processing methods are another factor to be considered. Feeding slaughter pigs coarsely ground feed compared to fine pelleted feed reduces pH of the stomach contents and significantly increases the concentration of organic acids (such as lactic, acetic, propionic and butyric acid) in the stomach. This favours the growth of anaerobic bacteria in the stomach, which in turn produce organic acids. An obvious drawback with feeding a coarse ration is the reduction in performance results.
Adding organic acids to the diet results in inconsistent effects on the GI ecology of pigs, depending on the acid and dose used. The pH along the GI tract tends to be lower after addition of organic acids, but often the effect is not significant. In general, organic acids have a negative impact on bacteria along the GI tract while growth performance is positively affected, with variable results depending on the type of acid and diet used, as well as the dose employed. It is important to note that besides the option of adding acids directly to the diet, the effect can be simulated through fermented liquid feeding or feeding coarse diets, resulting in increased levels of organic acids in the stomach.
The use of fermented liquid feed, coarse non-pelleted feed and organic acids lowers the pH in the stomach, killing off bacteria like E. coli and salmonella so that they do not enter parts of the GI tract where they normally grow and multiply. In this capacity, the stomach acts as a barrier to break the vicious cycle where animals become a source of infection to themselves and others.
Danish researchers suggest that sufficient feed intake is the most important factor in maintaining performance and health of piglets post-weaning.
Piglets that consume creep feed in the farrowing stall are more likely to make the transition early to post-weaning feed intake. The best way to increase feed intake during the nursing phase, to limit problems in the transition phase and beyond, is to increase weaning age from four to five weeks of age (according to experience in Denmark). BP
Source: Jensen, BB, Hojberg, O, Mikkelsen, LL, Hedemann, MS, and Canibe, N. 2003. Enhancing intestinal function to treat and prevent intestinal disease. Proceedings of the 9th International Symposium on Digestive Physiology in Pigs. May 14-17, 2003.
Janice Murphy is Swine Nutritionist with the Ontario Ministry of Agriculture and Food in Fergus. E-mail janice.murphy@omaf.gov.on.ca
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Implementation of COOL could mean loss of much of Ontario swine industry's profitability
Ontario pork will face a price discount and will lose the United States as a reference market from which to create Ontario's base price for market hogs once U.S. country-of-origin labelling comes into forceby RANDY DUFFY and KEN McEWAN
Country-of-origin labelling (COOL) is part of the 2002 U.S. Farm Bill and was passed by Congress with the hope of aiding farmers and ranchers. It is to become mandatory beginning October, 2004, which means that sows bred in November, 2003, and have their litters born on or about April 1, 2004, will be subject to the new law.The potential impact of this legislation is far-reaching for Ontario. Below are some of the key implications from a study done by Ridgetown College for Ontario Pork.
Ontario relies heavily on the U.S. market. A profile of Ontario pork production and exports was generated for 1996-2002 (see Table 1). In 2002, Ontario had total production of 7,367,086 head. Of these animals, only 62.7 per cent were processed within the province, with the rest exported out of the province as live animals (9.1 per cent were shipped to Quebec as market hogs, 22.3 per cent to the United States as feeder pigs and 5.9 per cent shipped south of the border as market hogs). When feeder pig exports, market hog exports, and pork exports were totalled, Ontario ships to the U.S. market approximately 43.8 per cent of its total production (28.2 per cent as live animals and 15.6 per cent as processed pork) based on 2002 statistics. (Note that the 43.8 per cent figure might be slightly underestimated because of the possibility that pork from Ontario market hogs processed in Quebec could be exported to the U.S. marketplace).
Using 2002 figures, Ontario exported 2,076,165 feeder pigs and market hogs worth $128.1 million Cdn. Exports of pork to the United States accounted for a further $311.9 million. When both live pigs and pork exports are combined, Ontario sold $440 million to the United States. Fresh, chilled or frozen pork exports to the United States represent 87.7 per cent of all Ontario exports in 2002. This is a key statistic because presumably the majority of this pork is not destined for the food service sector or used as an ingredient in further processing and thus would be subject to COOL regulations.
Table 1: Trends in Ontario pig numbers and pork production 1996 1998 2000 2001 2002 % of Total
2002% Chge
96-02(i) Pig numbers Pigs processed in Ontario 3,446,071.0 3,358,026.0 4,039,243.0 4,256,837.0 4,620,615.0 62.7 34.1 Pigs processed in other provinces 136,192.0 671,734.0 735,200.0 687,475.0 670,306.0 9.1 392.2 Feeder pig exports to U.S. 253,755.0 585,956.0 793,031.0 1,279,371.0 1,641,448.0 22.3 546.9 Market hog exports to U.S. 710,087.0 1,006,208.0 461,604.0 480,129.0 434,717.0 5.9 -38.8 Total head 4,546,105.0 5,621,924.0 6,029,078.0 6,703,812.0 7,367,086.0 100.0 62.1 (ii) Pork production (tonnes) Pigs processed in Ontario 290,159.2 288,118.6 356,261.2 379,284.2 410,310.6 62.7 41.4 Pigs processed in other provinces 11,467.4 57,634.8 64,844.6 61,254.0 59,523.2 9.1 419.1 Feeder pig exports to U.S. (pork equiv.) 21,366.2 50,275.0 69,945.3 113,992.0 145,760.6 22.3 478.9 Market hog exports to U.S. (pork equiv.) 59,789.3 86,332.6 40,713.5 42,779.5 38,602.9 5.9 -34.6 Total production 382,782.0 482,361.1 531,764.7 597,309.6 654,197.2 100.0 65.3 (iii) Pork distribution (tonnes) Pork exports to U.S. 36,989.3 41,158.2 74,471.0 88,126.2 102,329.6 15.6 176.6 Feeder pig exports (pork equiv.) 21,366.2 50,275.0 69,945.3 113,992.0 145,760.6 22.3 582.2 Market hog exports (pork equiv.) 59,789.3 86,332.6 40,713.5 42,779.5 38,602.9 5.9 -35.4 Pigs processed in other provinces 11,467.4 57,634.8 64,844.6 61,254.0 59,523.2 9.1 419.1 Domestic consumption and other exports 253,169.9 246,960.4 281,790.3 291,157.9 307,981.0 47.1 21.6 Total pork equivalent 382,782.0 482,361.1 531,764.7 597,309.6 654,197.2 100.0 70.9 (iv) Trends in pork distribution (%) Pork exports to U.S. 9.7 8.5 14.0 14.8 15.6 67.4 Feeder pig exports (pork equiv.) 5.6 10.4 13.2 19.1 22.3 250.3 Market hog exports (pork equiv.) 15.6 17.9 7.7 7.2 5.9 -60.4 Pigs processed in other provinces 3.0 11.9 12.2 10.3 9.1 214.1 Domestic consumption and other exports 66.1 51.2 53.0 48.7 47.1 -26.4 Note: Average carcass dress weight (kg) 84.2 85.8 88.2 89.1 88.8 5.5 Source: Statistics Canada, 2003 There are some studies that show Americans prefer to purchase domestic product and would like greater food safety. This is ironic because COOL does not serve any role with respect to food safety. COOL does not change the food safety standards or provide any greater assurances that you will not get sick than before. Evidence of this statement is that the food service industry is exempt from COOL rules.
Canadian pigs face price discount
As for the costs of COOL and whether consumers will be willing to pay a premium for the guarantee that they are a product of the U.S.A., a number of papers prepared within the academic community were reviewed and, as expected, considerable divergence of opinion was found. Much of this seems to revolve around how accurate and verifiable the United States wants the labelling to be. Based on European Union experience, a traceback system implemented under COOL increased on-farm production costs by about 10 per cent.But no matter which cost estimates are most accurate, there will be a cost to the U.S. pork supply chain. This means the costs incurred by U.S. processors to handle Canadian pigs will be greater than zero and presumably greater than those incurred if only American pigs are handled, because there will be a need for additional sorting, segregation and traceability.
An analysis done by Cattle Buyer's Weekly found that U.S. supply chain participants buying Canadian animals would incur COOL costs of $8-13 US per head. U.S. stakeholders only buying American animals would incur costs of $5 a head. Thus, U.S. participants handling Canadian pigs could face an additional $3-8 per head. This means that Canadian pigs destined for the U.S. marketplace will face a price discount in this range to cover the additional segregation and traceability costs associated with handling Canadian product.
How much that discount will be is a discussion point. A significant portion of the pork that leaves the province goes as unbranded, undifferentiated pork. It is very difficult to quantify the impact of COOL on the primal trade because of the various markets served (e.g. no impact on Japanese trade) and the gradual change in the fresh pork business from one of commodity markets to that of value-added.
One of the possible side-effects of COOL is increased supply chain co-ordination and uneven distribution of costs amongst producer groups, giving integrated systems a significant cost advantage. In 2002, the percentage of U.S. hogs procured on the negotiated spot market was estimated at 16.7 per cent, a 50 per cent drop from 1999 levels. It is anticipated that vertically integrated systems already have sufficient records needed for audits. However, producers selling on spot markets are most likely to have inadequate record-keeping systems. The only gain for contract co-ordinated systems versus spot-market purchases from independent suppliers is that the packers have already established communications with the co-ordinated groups.
U.S. consumer trends are difficult to interpret because intentions do not necessarily translate into actual purchases. Research showed that 67 to 73 per cent of consumers preferred to purchase beef with COOL and pay a premium for this information. But when the time comes to actually purchase meat, will American consumers really pay a premium? The success of the many U.S. discount stores, such as Wal-Mart, would suggest otherwise. Nonetheless, with Ontario's heavy reliance on shipping unbranded pork product to the U.S. market, it will take time to develop Canadian brand recognition.
Profits wiped out
The immediate impact will be to drive down the prices of all Ontario pigs (not just those exported) and produce a glut of market hogs and weaners. If, for example, compliance with COOL costs the average Ontario producer $7.50 ahead ($5 US), then much of the profitability within the Ontario industry is gone.The estimated impact on Ontario farm gate sales could be a decrease of $55.3 million Cdn, which would generate a loss of $368 million to the Ontario economy. These figures do not include the price impact of COOL on pork exports. While the size of the price discount on pork sales is not known, the economic spinoff of any discount on Ontario exports could be easily worth $100 million Cdn on top of the $368 million previously mentioned.
Other COOL impacts on the Ontario industry include:
Perhaps the most important impact of all is the loss of the United States as a reference market from which to create Ontario's base price for market hogs. U.S. price equivalency has been one of the pillars of hog marketing in Ontario for well over a decade. The current producer/packer arguments over which U.S.-based price series to use with respect to volume, geographic representation, accuracy of information and the like will no longer happen. Instead, the debate will be about how much is the discount on Ontario pigs and pork shipped to the United States. It should be noted that the lack of the United States as a reference market will affect all pigs raised in Canada, not just Ontario.
- Probable loss of U.S.-based pork trading partners (i.e. fabricators) due to difficulties in keeping Canadian and U.S. products separate. Primal meat cuts quickly lose their identity when they reach the cut floor because of the multiple end uses for the meat (for example, tray-ready products and specialty cuts).
- Greater dependency on Quebec processors because fewer pigs will be exported to the U.S. market. Using U.S. processors to leverage higher prices for Ontario producers will no longer be possible.
- Possible erosion in supply-chain power caused by retailers knowing that Ontario processors have lost access to the U.S. market unless they are willing to accept significant price discounting. Before COOL, Ontario processors could easily move pork product into the United States with no price discount when retailers were not feeling co-operative. This will no longer be possible.
In short, the potential impact of COOL on the Ontario swine industry is large. When total Ontario production is converted to a pork equivalent, Ontario exports approximately 44 per cent of its total production as either live animals or pork to the United States.
There will be also be a cost to the U.S. pork supply chain to implement COOL. If U.S. buyers of Ontario live animals and pork decide the costs are too great to handle, then the loss of any part of its $440 million in exports would be a huge blow to the Ontario swine industry.
Ontario needs to develop a strategy now on how to handle the extra hog marketings expected to occur and begin working on constructing a new pricing mechanism for market-weight animals. BP
Ken McEwan is an economics professor and Randy Duffy is a research associate at Ridgetown College, University of Guelph.
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Post-weaning diarrhea -- did your treatment work?
Figuring out which of several elements in your treatment procedures worked or whether the outcome was due to chance isn't easy in an intermittent disease of this kindby CATE DEWEY
Consider the case of a producer who had an outbreak of post-weaning E. coli diarrhea in an off-site nursery barn. He consulted with his veterinarian, feed salesman and the owners of the sow herds supplying the pigs. Then he implemented the following new procedures:
After implementing these changes, the next group of nursery pigs did not experience postweaning E. coli diarrhea. What worked?
- Antibiotics and acidifiers were added to the water.
- Egg yolk antibody was added to the feed.
- Both the antibiotic in the feed and the disinfectant used in the rooms were changed.
- The pigs were sorted into pens by sow herd source rather than by size.
The veterinarian said it was keeping pigs separated and the water medication. The feed salesperson thought it was the egg yolk antibodies and the new in-feed antibiotic. The producer concluded it was the new disinfectant. But perhaps it was none of the above worked. I worked on a nursery unit with classic postweaning E. coli problems. The best-looking, large pigs died suddenly, appeared dehydrated, had purple bellies and ears and fluid-filled intestines. Other pigs had diarrhea and red, scalded skin under the tail. The diagnostic laboratory cultured large numbers of K88 E coli. No changes were made to the medication or the management of the facility and the problem did not appear in the next group of pigs weaned.
If I had made a medication or management change, I would have been convinced that "my treatment," worked. However, because no change was implemented and the problem resolved itself, I realized that post-weaning E. coli is an intermittent disease.
This farrow-to-feeder pig unit has six nursery rooms that are emptied in an all-out manner, cleaned and disinfected and then filled over a two-week time period. We followed pigs in this barn for the two years after the first outbreak. On four occasions, pigs experienced high morbidity and mortality due to post-weaning E. coli diarrhea. However, only once did the problem occur in consecutive groups of pigs. I believe we can treat post-weaning E. coli diarrhea, but I also know that the disease does not affect each group of nursery pigs.
If we really want to determine what works in combatting a clinical disease problem in a herd, we have to choose one treatment and apply that treatment in a random repeated manner. If the treatment is by injection, we can ear tag all of the pigs, then inject half of the pigs (those with even-numbered ear tags) and leave the other half without medication.
Next, we keep track of how many of the even-numbered pigs and the odd-numbered pigs get sick or die. If the percentage of even-numbered pigs affected is less than the percent of odd-numbered pigs, we may conclude that the treatment works.
If the treatment is given in the feed, then randomly assign pens of pigs to the treatment. Flip a coin to see which treatment the pen gets. If the medication is in the water, you may have to treat alternate rooms.
Let us assume that you are treated post-weaning E. coli diarrhea. You usually put potassium penicillin in the water for the newly-weaned pigs, but the pigs have high morbidity, mortality and culls because of K88 E. coli. You flip a coin to decide how you will assign treatment. The first room gets potassium penicillin and the second room gets apramycin in the water.
If the pigs on potassium penicillin show no signs of post-weaning E. coli, but the second group has severe problems due to E. coli, what do you conclude? That apramycin does not work? That penicillin does work? That neither treatment works? Or that the study needs to be repeated?
What if there was post-weaning E. coli diarrhea in the pigs receiving penicillin, but not in those receiving apramycin? Because we expected apramycin to work and did not expect penicillin to work, the results matched our preconceived response to treatment. What would you conclude? That apramycin does work, so we should use this in all subsequent nursery groups? That penicillin does not work? That neither treatment works? Or that the study needs to be repeated?
The correct answer for both scenarios is the last one. Without repeating the treatment program, we cannot be certain of our conclusions. We don't know if the treatment really caused the lack of clinical problems or was simply due to chance. The next step on your farm would be to continue to rotate rooms between penicillin and apramycin until you see relationship between clinical problems and drug choice.
I realize that you cannot continue to use a treatment program that does not prevent a disease outbreak. However, I also think we cannot conclude that there is an absolute cause-and-effect relationship when a treatment appears to work once. Also, as I mentioned at the beginning, if we implement many new treatments and management changes at the same time, it is not possible to learn which treatment "worked."
In the long run, you may feel obliged to continue with all of the treatments for fear of experiencing the disease outbreak. This can add unnecessarily to the unit cost of pork production. BP
Cate Dewey is a professor in the Department of Population Medicine, Ontario Veterinary College, University of Guelph.
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