Better Pork - February 2006

Canada is a participant, along with 15 partners from the European Union, in this $8.5 million project, with the latest findings due to be reported in the next few days.

Porcine circovirus type 2 (PCV2) disease and, more specifically, postweaning multisystemic wasting syndrome (PMWS) erupted in epidemic proportions in Ontario and Quebec last fall and winter (see Better Pork, August 2005).

As veterinarians, producers and various segments of the swine industry attempt to find solutions to control this latest disease scourge to afflict our pigs, the same issue is being tackled by a mega-project funded primarily by the European Union (EU).

The project, entitled “The Control of Porcine Circovirus Diseases (PCVDs): Towards Improved Food Quality and Safety,” was launched in December, 2004, and was funded by the EU Sixth Framework Programme in its Food Quality and Safety subsection (http://www.pcvd.org/).

The overriding goal of the project is “to better understand the role of PCV in diseases of pigs” and it is geared towards “generating information on control measures that will have a positive impact on the health and welfare of pigs.” It is also expected to help producers meet consumer concerns about the quality and safety of pork products.

The 16 participating partners represent institutions from across the EU, including the United Kingdom, Denmark, France, Belgium, Sweden, Switzerland and the Netherlands, and one from North America (Canada). The participants’ ranks include epidemiologists, virologists, immunologists, molecular biologists, pathologists, nutritionists and geneticists.

The lead organization and headquarters of the project is Queen’s University in Belfast, with Dr. Gordon Allan as its head. Representing Canada is Dr. John Ellis, virologist at the Western College of Veterinary Medicine, University of Saskatchewan in Saskatoon.

The objectives, listed in order of importance, are:

This multi-disciplinary consortium expects to lay down a platform that will produce answers, not only to this expanding PCV2 disease epidemic, but also to new multifactorial diseases that will no doubt occur in pigs in the future, long after this particular project has ended. The consortium has the expertise to tackle a wide array of current and new diseases. Specific outcomes expected from this project include:

Investments in the project exceed the equivalent of $8.5 million Cdn, more than half of which is funded from the EU Sixth Framework Programme.

We in Ontario and Quebec have only recently started to experience the ravages of the epidemic form of Porcine Circovirus/ PMWS. PMWS, however, has been a devastating disease in most of the EU countries since the start of the millennium. It is obvious from the major accumulation of funds, personnel and resources that have been committed to this PCVD/ PMWS project by the EU governments that they are paying great heed to this disease.

We have already learnt much from their efforts and frustrations in battling PCVD/ PMWS. So far, only partial answers have emerged, but the more investigation and attention paid to the disease, the more we can expect to learn.

At press time (Jan 15) Dr. Gordon Allan, the architect behind this huge consortium, was scheduled to be a keynote speaker at last week’s annual Centralia Swine Conference where he was expected to deliver the consortium’s latest findings and accomplishments. BP

Over the past 15 years, it has become common for swine producers to add pharmacological levels of inorganic zinc to nursery pig diets as a means of improving weight gains and performance.

Since gram positive bacteria are more susceptible to zinc oxide than other microorganisms, researchers have suggested that high dietary levels of zinc oxide may help control E. coli scours and improve gut morphology. Unfortunately, a high dietary level of zinc translates into significant increases in the amount of zinc excreted in manure. So this simple solution to a production issue has created a potential environmental problem. Calculations, based on data gathered in Indiana, for 15- to 18-kilogram pigs fed diets with 23 or 123 parts per million (ppm) of zinc from zinc sulfate indicate that pigs fed the high-zinc diet excreted 61 milligrams of zinc per day, compared to 16 milligrams of zinc per day from pigs fed the low-zinc diet, a 3.8-fold increase in the amount of zinc excreted.

When diets containing 2,500 to 3,000 ppm zinc are fed to weaned pigs, as is commonly done for the purpose of growth promotion, approximately 90 to 95 per cent of the zinc will end up being excreted. Although these high levels might only be fed for a few weeks, the total amount of zinc excreted could approach or exceed the total amount excreted during the entire growing-finishing phase by pigs fed diets containing the NRC recommended level of 100 ppm zinc.

A recent survey of trace elements in Ontario livestock manures indicates that caution will need to be exercised for land application of typical Ontario weaner manure because of high levels of zinc. This study recommended that the swine industry re-examine feeding rates of zinc in order to prevent potential buildup of this metal in soils.

The amount of any given nutrient that is excreted can be influenced by several factors including quality, source and level of the nutrient fed; the level and proportion of other nutrients; processing methods; age, class and nutritional status of animals; and environmental factors. Researchers have been focusing their efforts on identifying other potential sources of zinc for use in nursery diets. Available sources can be divided into two types -- organic (zinc polysaccharide, zinc proteinate, zinc complex, zinc chelate, zinc methionine) and inorganic (zinc oxide). Interest in using organic zinc sources has been growing because they have been shown to have higher bioavailability, resulting in much less supplement being required to achieve similar performance results and significantly less zinc excreted in manure.

To help pork producers make decisions about how to include zinc in nursery pig diets, two experiments were recently conducted by the North Central Regional (NCR-42) Swine Nutrition Committee, across seven university research stations, in the United States. The objective of the study was to assess the effectiveness on growth performance of nursery pigs of feeding pharmacological levels (2,000 to 2,500 ppm) of inorganic zinc as zinc oxide compared to a lower level (500 ppm) of zinc from several organic sources.

In the first experiment, a total of 615 crossbred pigs with an average body weight of 6.3 kilograms and average weaning age of 20.6 days were fed either the basal diet (with 123.5 ppm zinc supplied by the trace mineral premix and grain), the basal diet plus 125, 250 or 500 ppm zinc as zinc methionine, or the basal diet plus 2,500 ppm zinc as zinc oxide. The pigs were fed typical Phase 1 (d 0 to d 14) and Phase 2 nursery (d 15 to d 28) diets.

The results showed that nursery pigs fed diets containing 2,500 ppm zinc as zinc oxide performed better, with greater average daily gain (ADG) and average daily feed intake (ADFI) than pigs fed the control diet during all phases, and better ADG and ADFI than pigs fed organic zinc diets for the duration of the 28 day experiment. Pigs on the zinc methionine diets had a better ADG compared to pigs fed the control during all phases, due mainly to an increase in ADFI (Table 1).

Table 1: Effect of zinc source on performance of nursery pigs
Source	Control	Zinc methionine			Zinc oxide
Added zinc, ppm	0	125	250	500	2500
ADG, grams
0-14 days	268	290	287	292	308
14-28 days	472	489	492	499	524
0-28 days	371	391	389	396	415
ADFI, grams
0-14 days	383	397	394	401	405
14-28 days	793	844	822	840	886
0-28 days	633	633	641	642	642

Since the results of the first experiment showed that pigs fed 2,500 ppm zinc as zinc oxide performed better than animals fed zinc methionine, and because different organic zinc sources may respond differently in weaned pigs, a second experiment was done to determine the effectiveness of different sources of organic zinc compared to the inorganic source, zinc oxide, in nursery pigs.

In the second experiment, six university research stations participated. This time, a total of 624 crossbred pigs with an average body weight of 6.2 kilograms and average weaning age of 20.4 days were used. The basal diet in this case contained 138 ppm zinc supplied by the trace mineral premix and grain. The pigs were randomly assigned to one of eight treatments including the basal diet, the basal diet with 500 or 2,000 ppm zinc as zinc oxide, or the basal diet with 500 ppm zinc as either zinc polysaccharide, zinc proteinate, zinc complex, zinc chelate or zinc methionine.

The results from the second experiment showed that the nursery pigs fed 2,000 ppm zinc as zinc oxide had greater ADG than pigs fed the control diet, and better ADG than pigs fed any of the 500 ppm zinc treatments, over the entire study. Pigs fed 2,000 ppm of zinc as zinc oxide had a greater ADFI than pigs fed any 500 ppm zinc diets, regardless of the source of zinc, throughout the experiment (Table 2).

Table 2: Effect of various zinc sources on nursery pig performance
Source	Control	Zinc oxide		Zinc polysaccharide	Zinc proteinate	Zinc complex	Zinc chelate	Zinc methionine
Added zinc, ppm	0	500	2000	500	500	500	500	500
ADG, grams
0-14 days	215	227	238	215	224	209	213	233
14-28 days	424	420	468	417	427	428	440	434
0-28 days	318	322	352	315	324	317	324	332
ADFI, grams
0-14 days	329	338	348	326	343	310	323	329
14-28 days	728	712	763	698	732	721	725	741
0-28 days	526	523	553	510	535	514	521	537

These results suggest that feeding 500 ppm zinc, whether from an organic or inorganic source, was not as effective at improving ADG as 2,000 to 2,500 ppm of zinc as zinc oxide. In both experiments, it was also evident that there was a large difference in ADG, ADFI and feed efficiency between testing stations. So it is important to consider the effect that other factors like management, facilities and genetics will have on the performance of nursery pigs.

Implementing feeding programs that decrease mineral excretion will be beneficial for the environment and for ensuring the sustainability of pork production in the future, particularly as the industry faces the possibility of restrictions on the feeding of growth-promoting antibiotics. Considering the long-term impact of zinc excretion on the environment, it will be important for researchers to continue to explore the possibility for feeding a much lower level of zinc from an organic source for growth promotion of nursery pigs.

Porcine Reproductive and Respiratory Syndrome (PRRS) costs all sectors of the pork industry big money – the equivalent of $650 million Cdn in the United States and an estimated $100 million in Canada.

Not surprisingly, producers, veterinarians and genetics companies are all starting to get serious about large-scale PRRS eradication. “We can’t have big bugs circulating unchecked and uncontrolled in our population. It is simply too expensive,” says Dr. Doug McDougald, a swine practitioner in the Stratford area.

In November, the American Association of Swine Veterinarians (AASV), which represents veterinarians from Mexico, the United States and Canada, issued the following position statement on PRRS eradication. “Control of the disease via traditional methods has not been effective in all cases. Therefore, it is the position of the AASV that eradication of the disease from the North American swine industry is the long-term goal.”

The AASV plans to partner with various players in the swine industry to start the eradication process at the local, regional and national levels and hopes to obtain funding to support the initiatives as well as share information and technology between all stakeholders in order to meet this goal.

“It is a lot easier to agree that it is necessary than that it is feasible,” says Dr. Peter Davies, Leman Chair of Swine Health and Productivity with the University of Minnesota. “The industry wants to do it, the government wants to do it, but no one has got a big stick,” says Davies.

Biology, technology, management, money and sociology all make the goal of regional eradication seem unattainable. However, Davies says that human nature may provide the biggest barrier of all. “At the end of the day, the psychological barriers end up being bigger than the technological barriers,” he says.

An organized regional eradication program would require investing huge amounts of money in biosecurity, which does not always yield good results. A better understanding of local spread is vital in controlling disease at the regional level. Demography, topography, farm density and climate all play a role in the spread of disease but, says Davies, no one is quite sure how important each of these factors is.

Just as a journey of a thousand miles begins with a single step, eradicating PRRS from a continent starts with one farm. “On an individual herd basis, we can’t live with circulating PRRS virus at the sow, nursery or finisher end,” says McDougald.

Dr. Martin Misener from Linwood Veterinary Services, Linwood, Ontario, agrees. “We have the toolbox to eradicate PRRS at the farm level,” he says, but eradicating the disease on a regional level presents huge challenges, especially in pig-dense areas. “This virus is a very humbling virus. Every time we think we have this thing figured out, it throws another curve at us.”

Misener has changed his PRRS strategy in the past year. One of his clients, who was doing a lot of things right, had 65 per cent of his gestating sows abort when he was hit with PRRS. “It was the worst wreck I’ve seen,” says Misener. The control programs they were using just got blown to pieces. There are strains out there now that are virulent enough to overcome current vaccination strategies.

Culling rate double with PRSS

PRRS on its own is bad. But Ontario producers have been hit with a combination of illnesses, including Post-weaning Multisystemic Wasting Syndrome (PMWS) and a new strain of swine influenza virus (SIV). When these diseases challenge a herd together, the results can be disastrous. McDougald compared two groups of 14,200 pigs in his system – one was PRRS positive, the other negative. The PRRS positive group had a mortality rate of 4.9 per cent in the finishing barn, while the negative group had 2.1 per cent.
The culling rate was double in the PRRS positive group and feed conversion
was also substantially affected. The overall cost of PRRS in this group of
finishing pigs was $115, 000. Even before an organized strategy is in place, McDougald says people can take important preparatory steps. The first is to review and tighten up
biosecurity. “There are almost always things we can do to reduce virus transfer,” he says. Fixing a bunch of little things such as paying more attention to biosecurity and gilt acclimatization can cause the balance to tip in favour of healthier animals. McDougald stresses the importance of building on successes -- less virus circulating in the
herd means less virus to reinfect and cause problems. In his own practice, 11 herds with a combined population of 225,000 sows have begun a PRRS elimination program. From these, 17,000 sows are now producing virus-free pigs. While this is encouraging, to move to a point where he is certain the herds are truly negative will take some time, McDougald explains.

John Otten is the Production Manager for Pig Info, a Stratford-based swine herd management system. He manages 2,500 sows in two herds, one with 1,500 sows and one with 1,000. From these sows, there are three 2,600-head nurseries and 16 contract growers.

Otten knows first hand what it takes to get PRRS out of a barn and how it feels to have the disease get back in. The 1,500-head herd that he manages is located in a pig-dense area of Perth County. His first PRRS outbreak came in December 2003 and a second in October 2004. He was able to clear the sow herd, nursery and finishers of the PRRS virus just before being hit with a different strain of PRRS.

Because the workers had already seen PRRS, they were suspicious when the second strain hit and responded quickly. When they noticed two or three abortions in close proximity, plus a few sows off feed, the barn staff drew blood samples from the aborted sows and took the aborted fetuses to the University of Guelph for analysis.

The second round of PRRS caused more abortions and was harder on the piglets, explains Otten. The mortality rate in the nursery, normally 1.5 per cent, jumped to six or seven per cent.

Otten explains that he has used several different strategies to get PRRS out of the barn without having to depopulate the sow herd. First, he loaded the gilt isolation barn with enough animals of various ages to allow them to get through four months without bringing in any new animals. He also implemented the McRebel program, developed by Veterinarian Monte McCaw at North Carolina State University in 1994. (“McRebel” stands for “Management Changes to Reduce Exposure to Bacteria to Eliminate Losses.”)

The McRebel program is used when the PRRS virus is circulating throughout the farrowing barn and nursing pigs are affected during acute outbreaks. Cross fostering is kept to a minimum and completed before the piglets are 24 hours old. This also means that nurse sows are not used for unthrifty piglets. Sick and unthrifty animals should be humanely euthanized and kept in a freezer for analysis if necessary.

The McRebel program also requires that injections of nursing pigs be kept to a minimum and that the needle is changed between litters. This helps reduce spread of the virus. Biofeedback of piglets, placental tissue and manure must also be stopped until the virus has stopped circulating throughout the farrowing rooms. Strict control of piglet and sow movement between rooms is also mandatory. Farrowing rooms should be operated in an
all-in, all-out basis.

Biosecurity and barn comfort

Successfully implementing the McRebel program requires good motivation on the part of the staff, explains Otten, but he knew his group could handle the challenge. “You can get there fairly quickly, but you need to stick to the McRebel. And the virus will run its course,” he says.

Tight biosecurity was maintained. Every surface in the barn, from rubber boots to the freezer to the medicine bottles, got touched with disinfectant, he says. A good rodent control program was in place and dead stock was taken to a remote area for pick up.
By the time these pigs got to the finishing barn, the staff there knew what to expect and took extra precautions with them.

They paid more attention to barn comfort and were very careful not to stress the pigs in any way. Barn temperature and humidity, especially at arrival, were carefully monitored. The pigs were not chilled and were given extra room in the pens. Staff also elevated the level of medication in the feed when the pigs first arrived, but were able to finish them and send them to market without any feed medication.

Otten and his crew are almost at the end of the second fight with PRRS. Once it is out, they have a protocol in place to keep it at bay. As always, very tight biosecurity measures are key.

They have a separate wash bay for pig movement between inside units. The main transporter has a Standard Operating Procedure for washing and for people movement. They have special vehicle clean-up procedures for veterinarians and managers. Any bagged feed that comes into the unit is wiped down with disinfectant and no boxes are allowed to enter the barn.

While they cannot guard against airborne viruses, they maintain a separate dead stock pick up and vehicles have all inside surfaces cleaned with synergize cleaner. It’s also important to maintain a separate, isolated gilt barn, says Otten. Often overlooked, manure equipment is a vital consideration, especially if it is used at different locations.

After having gone through two bouts of PRRS eradication, Otten is optimistic. He has seen how a motivated staff with good direction can beat PRRS and out-perform herds that never had a break. As for a regional eradication strategy, Otten says, “If veterinarians and
producers work together, we can get rid of this sucker.”

Any kind of eradication strategy at the farm level must take into account the risk factors in order to keep the disease out in the long term, says Misener. A producer located in a very pig-dense area might be better to attempt control measures than to spend a lot of money depopulating.

Misener stresses the need to take care of the top three methods of transmission if good PRRS control is to be achieved. The pigs themselves are far and away the number one risk factor. Defining the disease status of the population is vital. Producers need to know if the herd is shedding virus or not in order to plan an effective strategy, he says.

Transportation is also a key player in transmission. A truck that has carried infected pigs becomes a source of infection itself. Again, knowing the disease status of the animals carried on the truck helps people determine the best way to deal with the truck and where it goes.

Location is the third main risk factor to consider, says Misener. Quebec’s long and narrow farms, with some barns being as close as 500 feet, provide a good example of how important pig location is “They have had a terrible time keeping these viruses out,” Misener says.

Though “an eternal optimist,” Misener advises industry stakeholders not to rush into regional eradication strategies. Areas that do not have high pig densities provide the best opportunity. “Take it slow, be smart and learn from other peoples’ mistakes,” he says.

“We are already well on the way to understanding PRRS,” adds McDougald. Eliminating it on a large scale will require communication, co-operation and sharing ideas between all players and jurisdictions in order to understand this devastating disease better.

Europe launches a mega-project to control PCVD/ PMWS in pigs

by S. ERNEST SANFORD

Finding the right approach to adding zinc to your nursery pigs’ diet

by JANICE MURPHY

Veterinarians gear up to tackle the 'humbling' PRRS virus on a regional level

by KATE PROCTER

Culling rate double with PRSS

Biosecurity and barn comfort