Better Pork - April 2005

Breaking down the technical barriers to quick boar stud testing for PRRS

A Minnesota vet has developed an innovative and relatively innocuous method of obtaining blood samples from boars. Together with faster lab turnaround, this can help shorten the time between infection and detection of the infection in boars in a stud
by S. ERNEST SANFORD
As more and more boar studs eliminate PRRS from their resident populations and are stocked with PRRS-naïve boars, it has become critically important to do vastly increased testing to ensure and certify that the boars in the stud remain PRRS-negative.

This is no easy task. First, the testing has to be elevated to a level whereby false positives and false negatives are virtually eliminated. Second is the necessity of having increasingly rapid turnaround times.

Both of these technical barriers have been scaled over the last two to three years. Highly sensitive PCR methodologies and real-time PCR testing have increased diagnostic accuracy. Some diagnostic laboratories now offer faster turnaround, with either same-day or next-day results on PCR tests, depending on arrival time of the diagnostic samples.

Yet another limitation, however, that has nothing to do with laboratory accuracy and turnaround time, is the length of time between when the first boars in a stud become infected with the PRRS virus and the appearance of the virus in the semen. The technical difficulty here is that, although the first few boars that become infected will be viremic (PRRS virus circulating in their blood) within 24 hours of infection and can remain so for two or more weeks, there is no set time when virus will appear in their semen. Furthermore, shedding of the virus into the infected boar's semen is intermittent and can trail its first appearance in the blood by several hours or even days. The intermittent nature of virus in the semen is even more unnerving because of the possibility of the virus being absent in the particular sample chosen for testing but being present in the sample taken just before or just after.

Dr. Darwin Reicks, swine veterinarian at the Swine Vet Center, St. Peter, Minn., has cleared this hurdle with introduction of an innovative and relatively innocuous method of obtaining blood samples from boars. A few readily available materials are needed and include:

  • A two-millilitre blood sample tube with snap-cap.

  • 0.9 per cent sterile saline (250 mL bottles) sample tube.

  • A swab (a Dacron swab rather than the routine cotton swab is recommended).

  • A 20 or 22 gauge 1/2" or 3/8" single-use disposable needle.

That's all that's needed -- plus the boar, of course -- and now the job can be done. The sample is collected at the time of semen collection. The boar mounts the dummy as usual and the following procedure is carried out:

  • Prepare materials and have them ready.

  • Add 0.75 millilitres of saline to the snap-cap tube.

  • Identify the boar's ear vein.

  • After ejaculation starts, prick the boar's ear vein with the needle.

  • Smear blood liberally onto the Dacron swab.

  • Place blood-smeared swab into the sample tube.

  • Break swab off, leaving tip in the tube.

  • Close sample tube with its snap cap.

  • Veterinarian submits sample to the lab for PCR.

Table 1. Time of first PCR detection of PRRS virus from ear swab versus semen over the first six days after infection.
Days Swab Semen
1 & 2 95% 10%
3 & 4 100% 50%
5 & 6 100% 70%
ALL 98% 43%

One of the main objectives of this approach is to shorten the time between infection and detection of the infection in boars in a stud. The shortening of detection time could make it possible to do a test and removal before too many boars become infected, thus saving the entire stud from having to be depopulated. At a minimum, this boar swab technique is far more sensitive than semen for detecting PRRS-infected boars.

Table 1 shows a comparison of the sensitivity of PCR PRRS detection rates between the ear swab method and semen. The ear swab method clearly detects the PRRS virus 95 per cent of the time in the first 24-48 hours after infection, compared with 10 per cent over the same time period for semen. BP

S. Ernest Sanford, DVM, Dip. Path., Diplomate ACVP, is a swine specialist with Boehringer Ingelheim Vetmedica (Canada) in Burlington. esanford@bur.boehringer-ingelheim.com

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Better Pork - April 2005

What effect does crowding have on fully and partially slatted floors?

A study by the Prairie Swine Centre suggests that crowding resulted in a reduction in average daily gain, there was no evidence that a fully or partially slatted floor made any difference
by T. DONE, S.M. HAYNE and H.W. GONYOU
Floor space allowance remains one of the more contentious issues in the debate on modern farm practices and animal welfare. It is generally believed that space requirements for maximum growth will vary with housing conditions.

The Code of Practice recommends that pigs on partially slatted floors be provided with more total floor area than those on fully slatted floors. However, some research has suggested that there are no differences in the effect of crowding with these two floor types. This study was conducted to gain a better understanding of space required for pigs housed on either fully or partially slatted floors.

Four blocks of 216 grower pigs (average initial weight, 37 kg) were assigned to two floor types (full or partial slats) and three levels of floor space allowance (0.38, 0.54, and 0.78 square metres per pig). The lowest space allowance was discontinued after the grower phase.

The space allowance coefficients, where k = area (m2)/BW (kg).667, were approximately 0.025, 0.036, and 0.052 for the grower phase (to 58 kg), and 0.026 and 0.037 for the remaining treatments in the finisher phase (to 95 kg). Pigs were fed ad-libitum a series of mash diets from wet/dry feeders. Within each block, pigs were assigned to two pens (18 pigs per pen) within each floor type and space allowance combination. Pens were balanced for sex within pens.

Average Daily Feed Intake (ADFI) was not affected by floor type or floor space allowance in either the grower or finisher phases. Average daily gain (ADG) tended to be less on partially than on fully slatted floors during the grower phase (1.036 vs. 1.072 ( 0.010 kg/d, P = 0.08), but did not differ in the finisher phase. Pigs on the lowest floor space allowance grew slower than pigs on the other two space allowance treatments (1.013 vs. 1.067 and 1.083 ( 0.010 kg/d, for 0.38, 0.54, and 0.78 m2/pig, respectively; P = 0.001) during the grower phase. ADG tended to be reduced by crowding during the finisher phase (0.953 vs. 1.001 ( 0.013 kg/d, for 0.54, and 0.78 m2/pig, respectively; P = 0.06). There were no significant interactions between floor type and space allowance.

From this, we can conclude that, although crowding to a space allowance coefficient of 0.026 resulted in a reduction in ADG, there was no evidence that this effect differed depending on whether the floor was fully or partially slatted.

Strategic funding for this study was provided by Sask Pork, Alberta Pork, Manitoba Pork, and the Saskatchewan Agriculture and Food Development Fund. Project funding was provided by NSERC and AAFC.BP


T. Done, S.M. Hayne and H.W. Gonyou are researchers at the Prairie Swine Centre, Saskatoon.

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Better Pork - April 2005

THE STORY BEHIND CANADA'S PIG PRODUCTION EXPANSION

Over the past decade, the percentage of Canadian production going to the United States has jumped dramatically - from 24 per cent in 1995 to 42 per cent in 2003
by RANDY DUFFY
Pig production in Canada has increased significantly during the past several years. Similarly, the markets where this production ultimately ends up in and the form that it does so have also changed.

Total pigs produced are the sum of pigs processed in Canada, plus live exports to the U.S. of feeder pigs and slaughter weight pigs.

In 1999, Canada produced approximately 22.9 million pigs. Of this total, 18.8 million (82 per cent) were processed in Canada, while about 4.1 million were exported to the United States (18 per cent). These exports were split approximately 50:50 between feeder pigs and slaughter weight pigs. It should be noted that these slaughter weight figures include market hogs, cull breeding stock and F1 breeding stock intended as replacement animals.

In 2004, Canada produced 31.3 million total pigs, of which 22.8 million were processed in Canada (73 per cent) while 8.5 million were exported to the United States (27 per cent). Of the exports, 5.6 million were feeder pigs and 2.9 million were slaughter weight animals. The mix between feeder pigs and slaughter weight animals is now about two-thirds feeder and one-third slaughter weight.

Pigs processed in Canada and live exports have both increased during this period. Pigs processed in Canada are up 21 per cent while live exports are up 107 per cent. Total production is up 37 per cent.

Where are pigs produced in Canada?
If we look at the almost 23 million pigs processed in Canada in 2004, we see that Quebec accounts for 34 per cent, with Ontario next at 23 per cent and Manitoba third with 18 per cent. Rounding out the top five provinces are Alberta with 15 per cent and Saskatchewan at six per cent.

In actual pigs processed, the top five provinces stack up as follows: Quebec, 7.8 million; Ontario, 5.3 million; Manitoba, 4.0 million; Alberta, 3.5 million; Saskatchewan, 1.3 million. These five provinces account for almost 22 million pigs or 96 per cent of the Canadian total.

What provinces export live pigs?
If we look at the 8.5 million live pigs exported by Canada to the United States in 2004, we can see that the largest number came from Manitoba, which accounts for 58 per cent of the total. Next is Ontario with 31 per cent, while Saskatchewan is third with six per cent. Alberta has five per cent while British Columbia, Quebec and the Atlantic provinces combined account for less than one per cent of the Canadian total. In actual pigs exported, the top four provinces are: Manitoba, 4.9 million; Ontario, 2.6 million; Saskatchewan, 500,000; Alberta, 400,000 million. In all, Canada exported about 8.5 million live pigs to the United States in 2004, an increase of 107 per cent compared to 1999.

How is Canada's total production distributed?
The distribution of Canada's total pig production in 1995 is based on approximately 17.3 million total pigs produced in Canada that year. Of that total, 65 per cent, or about 11.2 million pigs, were consumed domestically. The remaining 35 per cent was exported, 25 per cent as pork and 10 per cent as live pigs. Of the 25 per cent of production exported as pork, about 56 per cent (or 14 per cent of total production) went to the United States and the remaining 44 per cent (11 per cent of total production) went to all other countries. Canada's dependence on the U.S. market to sell pork and live pigs was about 24 per cent of total production.

How does this compare to today?
Complete figures for 2004 are not yet available, but Graph 5 shows the distribution of Canada's total pig production in 2003. This is based on approximately 29.7 million total pigs produced in Canada that year. Of that total, 40 per cent of total production or about 11.9 million pigs were consumed domestically. The remaining 60 per cent was exported as either pork or live pigs -- 35 per cent as pork and 25 per cent as live pigs to the United States. Of the 35 per cent of production exported as pork, about 49 per cent (or 17 per cent of total production) went to the United States and the remaining 51 per cent (or 18 per cent of total production) went to all other countries. Canada's dependence on the U.S. market to sell pork and live pigs was about 42 per cent of total production. It would initially appear that less pork was being consumed in Canada in 2003 compared to 1995. However, even though the domestic consumption share of total production has decreased (from 65 per cent to 40 per cent), the actual number of pigs this represents has increased slightly from about 11.2 million to 11.9 million pigs.

Canada's dependence on the U.S. market has increased significantly, both in terms of pork exports and live pig exports. In 2003, about 42 per cent of total production was sold to the U.S. market, up from 24 per cent in 1995. The share of U.S. pork exports in terms of total pork exports to the world has declined slightly from 56 per cent in 1995 to about 49 per cent in 2003. It is estimated that this share will further decline in 2004. The United States remains the main market for Canada's production, but this is starting to be offset by increasing pork exports to other countries in the world, notably Japan and Mexico.

To summarize, Canada exported about 60 per cent of its total production in 2003 either as pork or live pigs. This is a significant increase from 1995, when about 35 per cent of total production was exported. In 1995, 24 per cent of Canada's total production was exported to the United States as pork and live pigs, compared to 42 per cent of total production in 2003.

Where do Canadian pork exports go?
Total Canadian exports for the period January-November 2004 were 872,316 metric tonnes, a 2.6 per cent increase from the same period in 2003. The United States has the largest share at 42 per cent, followed by Japan (22 per cent) and Mexico (7 per cent).

Exports to Japan, Mexico, China, Taiwan and South Korea have all increased over 2003 in terms of the number of metric tonnes exported. This is good news for Canada as hopefully this trend continues and Canada can become less dependent on the U.S. market as the main buyer of Canadian pork and live pig exports. BP


Randy Duffy is a research associate at Ridgetown College, University of Guelph.

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