Better Pork - August 2004The remarkable legacy of Dr. Satoshi Otake
In the space of five years, while completing his PhD at the University of Minnesota, this Japanese scientist has greatly advanced our knowledge of how the PRRS virus can be spread between herds and from pig to pig within herdsby S. ERNEST SANFORD
Dr. Satoshi Otake graduated with his DVM (Doctor of Veterinary Medicine) from the School of Veterinary Medicine, Azabu University, Japan, in 1999. He immediately came over to North America to pursue his PhD with Dr. Scott Dee at the University of Minnesota, where he began intensive investigations into mechanisms of transmission of the PRRS virus. He completed his PhD earlier this year and has now returned to Japan.In the space of those five years, however, he has made a remarkable impact and left us with a tremendous legacy through the explosion of information derived from his studies on the many ways and mechanisms by which the PRRS virus can be spread between herds and from pig to pig within herds.
Coveralls, boots and hands. The first set of transmission studies by Satoshi was aimed at demonstrating which personal biosecurity measures would prevent transmission of the PRRS virus from pig to pig within a herd. He infected four-week-old, PRRS-naïve pigs with PRRS virus. Other investigators then played and rubbed themselves on the infected pigs to ensure that the virus was shed onto their coveralls, boots and their exposed hands. They were also spattered with infected pigs' blood. The contaminated investigators then went into separate isolation rooms housing uninfected pigs after observing certain specific biosecurity protocols.
Group 1/ Direct Contact Group: Without showering or changing coveralls and boots, the designated investigators made direct contact with the uninfected, naïve pigs immediately after working with the PRRS-infected pigs.
Group 2/ Danish Protocol: Immediately after working with the PRRS-infected pigs, the investigators changed coveralls and boots, washed hands, but without taking showers, and then made contact with the uninfected, naïve pigs.
Group 3/ Showers but No Downtime: The investigators changed coveralls and boots, showered but observed no downtime before contacting the PRRS-naïve pigs.
Group 4/ Downtime Observed: These investigators did the same as for Group 3, but also observed 12 hours (overnight) downtime between exposure to the infected pigs and contacting the naïve pigs.
The results of this series of experiments were that only in Group 1 (direct contact with complete lack of observation of any and all biosecurity protocols) was the PRRS virus transmitted to PPRRS-naïve pigs from coveralls, boots and unwashed hands.
Thus, we can conclude that the PRRS virus can be transmitted to susceptible pigs by contaminated fomites such as coveralls and boots, and also via unwashed hands. Minimal biosecurity protocols such as washing hands, even without showering or observing downtimes, were sufficient to prevent transmission of the PRRS virus in these experiments.
Insects and injection needles. Dr. Otake also investigated transmission of PRRS virus by insects and injection needles. Some 300 mosquitoes were interrupted while they were feeding on experimentally PRRS-infected pigs.
The mosquitoes were then transferred over to PRRS-naïve pigs and allowed to complete their feeding. Virus isolation and Polymerase chain reaction PCR confirmed that the PRRS virus had been transmitted to the PRRS-naïve pigs by the mosquitoes.
A similar experimental model was instituted using biting flies. The biting flies were also able to transmit PRRS virus from infected to uninfected pigs.
A follow-up study was conducted to determine just where and for how long mosquitoes and flies are able to keep the PRRS virus alive before transmitting it to other pigs. The gastrointestinal (GI) tract was identified as the source of maintenance of the virus in both the mosquitoes and flies. GI tract viral survival times were six hours for mosquitoes and 12 hours for flies.
A further experiment was set up to demonstrate whether injection needles could do the same as biting insects. Without changing needles in between injections, the researchers vaccinated a group of PRRS-infected pigs with a killed bacterin. They then used the same needles and syringes and continued vaccinating PRRS-naïve pigs housed in isolation rooms. The PRRS virus was subsequently isolated from the previously PRRS-naïve pigs.
This demonstrated that biting insects such as mosquitoes and biting flies, as well as sharp instruments that penetrate the skin, are capable of transmitting the PRRS virus.
Snowballs and mudballs. Dr. Scott Dee took the lead on another series of experiments in which, going through a series of activities that occurs daily on any typical pig farm, the researchers were able to track the PRRS virus in a snowball from one farm, through a truckwash and into another farm more than 50 km away. They successfully transmitted the PRRS virus this way in eight of the 10 replicates conducted in this trial. This, of course, was done in the winter.
Using mudballs in the following spring, they similarly transmitted the PRRS virus from farm to farm through the same series of simulated daily pig farm activities. With the mudballs, however, they were only able to transmit the virus in two of their 10 replicates.
Aerosol Transmission/The "Alaskan Pipeline." Aerosol transmission of the PRRS virus has been a source of heated debate for well over a decade. After several unsuccessful attempts to demonstrate aerosol transmission of the PRRS virus for any distance more than one metre, Drs. Dee, Otake and colleagues were finally able to construct an experimental model showing aerosol transmission of PRRS virus. This was done using a tube, dubbed by Dr. Dee "The Alaskan Pipeline." In this model, viable PRRS virus was transmitted and able to infect PRRS-naïve pigs for up to at least 150 metres along the tube.
Trucks and transport vehicles. Various sanitation treatments of trucks were examined to see which treatment(s) would get rid of PRRS virus after the truck had transported PRRS-infected pigs. Treatment 1 consisted of manual scraping to remove soiled bedding. Treatment 2 consisted of bedding removal, washing and disinfecting. Treatment 3 consisted of Treatment 2, plus freezing and thawing. Treatment 4 consisted of bedding removal, washing, disinfecting and drying.
Only Treatment 4 proved successful in killing the PRRS virus. The experiments showed that if drying was not part of the cleanup protocol, the virus was able to survive. In a follow-up experiment, the PRRS virus was killed when disinfectant consisting of 26 per cent quaternary ammonium chloride combined with seven per cent glutaraldehyde was used after washing but without drying. However, it is still strongly recommended to dry vehicles after washing and disinfecting.
What do we do with this information? Even as the results of these trials were being reported, the industry was responding to the findings.
- Personal biosecurity protocols now have a better scientific base.
- Injection needles are changed more frequently.
- Better attempts are made to control insects.
- Parcels are double-bagged to prevent "snowball/ mudball" transmission.
- Transport vehicles are dried after washing and disinfecting. BP
S. Ernest Sanford, DVM, Dip. Path., Diplomate ACVP, is a swine specialist with Boehringer Ingelheim Vetmedica (Canada) Ltd. in Burlington.
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back Test shows rate of starch digestion needn't be considered for diet formulations
In this experiment, researchers found that, although fibre and DE content differed among the barley and wheat samples, in vitro starch digestibility did not, suggesting that starch for regular barley and wheat samples differing in fibre content is all rapidly degradableby R.T. ZIJLSTRA, J. FLEDDERUS, M.D. DREW
The digestible energy E content of Western Canadian barley and wheat has a large range and this variation is caused by changes in digestibility of energy. Starch is the main source of energy in cereal grains, and starch content differs among samples of barley and wheat, although it is the changes in fibre content that are mostly associated with the changes in energy digestibility.Apart from energy digestibility measured as a percentage at certain points of the gastro-intestinal tract (ileum or total-tract), rates of starch digestibility might also be important to achieve consistent protein deposition rates. Kinetics of starch digestion or degradation might be related to fibre content of cereal samples. This hypothesis was tested using three barley and wheat samples differing in fibre content.
Table 1. Chemical Characteristics of the Barley and Wheat Samples Sample Starch (%) NDF (%) ADF (%) CP (%) DE (kcal/kg/DM) Barley 1 48.6 22.1 5.7 13.6 3180 2 45.5 22.0 8.1 12.8 2997 3 40.8 32.0 11.4 12.8 2567 Wheat 1 54.1 20.91 3.2 19.4 3694 2 46.1 29.3 4.1 18.8 3412 3 43.6 35.7 6.0 19.7 3368 Three barley samples and three wheat samples differing in fibre content were tested for chemical characteristics, DE content, and also in vitro starch digestibility, using the analysis developed by Schothorst Feed Research. It was found that in vitro starch digestibility as a percentage did not differ among the three barley or the three wheat samples. The results suggest that starch in each of the samples was rapidly digestible or rapidly degradable. The DE content of the barley and wheat samples was measured in a total-tract energy digestibility experiment with grower pigs using 96 per cent cereal diets.
Starch, acid-detergent fibre (ADF), neutral-detergent fibre (NDF) and DE content differed among the cereal samples (see Table 1), but crude protein (CP) content did not. These results suggest that the measured DE content was positively related to starch content and negatively related to fibre content.
Thus, we can conclude that, although fibre and DE content differed among the barley and wheat samples, in vitro starch digestibility did not, suggesting that starch for regular barley and wheat samples differing in fibre content is all rapidly degradable. For these cereal samples, rate of starch digestion, therefore, does not have to be considered for practical diet formulations. This project does not exclude the possibility that the rate of starch digestion might be different among samples of cereal grains that, for example, differ in ratio of amylose to amylopectin.BP
Acknowledgements
Sask Pork, Alberta Pork, Manitoba Pork, and Saskatchewan Agriculture Food and Development Fund provided strategic program funding. Project contributors included Danisco Animal Nutrition, Saskatchewan ADF-Agri Value Program, Alberta Agriculture, Food and Rural Development, Canadian International Grains Institute, FeedRite (Ridley Inc.), Degussa, Big Sky Farms, Norwest Labs, and internal funds at Schothorst Feed Research B.V.
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back Figuring out the Ca:P ratio in pig diets
Research shows that swine diets can be formulated containing less total P without sacrificing performance. This results in less P being excreted into the manureby DENISE BEAULIE, RUUARD ZIJLSTRA, MIKE BEDFORD and JOHN PATIENCE
Most of the phosphorus (P) in grains and oilseeds used in swine diets is in the form of phytic acid that is unavailable to the pig and thus excreted into the manure. Inorganic P is usually added to swine diets to meet the animals' requirements, thus increasing diet cost.The phytase enzyme releases the P from the phytic acid, allowing the formulation of diets with less total P. Because the enzyme increases the amount of available Phosphorus (P), the Calcium (C) concentration in the diet may need to be re-examined, since the Ca:P ratio is critical to the utilization of these minerals. Currently, we do not know the optimum Ca:P ratio to use in the presence of phytase.
So an experiment was designed to define the growth response of growing pigs to four levels of a unique, new, phytase enzyme and to determine how critical the Ca:P ratio is in optimizing the use of the phytase enzyme in practical swine diets.
Fifty-four barrows (40.3 ± 1.9 kg) were fed one of 18 different diets (five levels of phytase plus a positive control, at three different Ca:P ratios) for a 28-day growth and digestibility experiment. The corn and soybean diets were supplemented with either 0, 250, 500, 1000, or 2000 units/kg of a novel phytase enzyme. The diets contained 0.38 per cent total P, and either 0.50, 0.60, or 0.70 per cent Ca. The estimated available P at the 0 level of phytase inclusion was 0.11 per cent, which is below the requirement for pigs of this age. The positive control diet was formulated to contain sufficient dicalcium phosphate to meet the pigs' P requirement.
Neither performance (ADG, ADFI, feed conversion) nor P digestibility was affected by the Ca concentration in the diet (P>0.1; data not shown). This was surprising and will be investigated in future studies.
Although the inclusion of the phytase enzyme in the diet improved ADG, ADFI and feed efficiency (P<0.05), this improvement hit a plateau at about the 250 U/kg inclusion level (Figure 1A). Conversely, P digestibility was improved linearly (P<0.001) with each increment of supplemental phytase (Figure 1B). This implies that each incremental increase in phytase addition improved P availability. However, beyond the 250 U/kg level, the pigs did not require or utilize this additional P.
From this, we can conclude that the inclusion of 250 U/kg phytase into diets for growing swine allows the formulation of diets containing less total P without sacrificing performance. This results in less total P excreted into the manure.
For example, increasing the P digestibility of a diet form 18 per cent (without phytase) to 54 per cent (with phytase) would reduce P excretion in the manure from 7.4 g/d to 4 g/d. Moreover, reducing the P content of the manure also improves its N:P ratio, resulting in a manure that is a more balanced fertilizer relative to the needs of crops grown in Western Canada. BP
Acknowledgements
The authors acknowledge with gratitude the strategic program funding provided to the Prairie Swine Centre by Sask Pork, Alberta Pork, the Manitoba Pork Council and the Sask. Ag. Development. Fund.
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back Switzerland: Does "rare earth" from China boost hog performance?
by NORMAN DUNN
Swiss hog producers claim that the use of Chinese "rare earth" in slaughter hog rations over the past year has increased feed conversion efficiency by as much as five per cent and daily liveweight gain by up to 10 per cent. Refined rare earth in that country costs the equivalent of around $10 Cdn/kg and is added to rations at an average 250 mg/kg feed.Rare earth is the name given to a compound of so-called transitional metals with major ingredients including scandium, lanthanum and cerium, mined mainly in western China. It appears to have beneficial effects when added to livestock rations and has been used in Chinese agriculture for 40 years now with claims that it improves weight gain and days to slaughter for a range of animals, including fish, hogs and poultry.
In Europe, rare earth in feed is being hailed by some as a possible substitute for antibiotic growth-enhancers in feed -- additives which are to be banned throughout the European Union by the end of this year.
While Swiss pig producers, in whose country feed antibiotics are already banned, have ploughed ahead with using rare earth in pig feed, neighbouring countries are much more cautious and its inclusion in rations is still not permitted officially.
Trials conducted by LM University in Munich produced results indicating "significant" increases in feed conversion and weight gain for hogs on rations that included the Chinese supplement. The scientists there had to admit, however, that not a lot could be discovered as to how the substance actually worked. The theory so far is that the ingredients lanthanum and cerium in particular have a depressing effect on bacteria, fungal and yeast growth within the hog gut and also seem to boost immunity to disease and reduce inflammation.
But just as everyone was getting excited about its possibilities, Germany's leading animal nutrition scientists within the federal agricultural research institute (FAL) in Brunswick completed rare earth feeding trials with 40 groups each of 20 hogs and found no significant improvements to hog performance.
However, parallel trials at Brunswick with boiler poultry showed that inclusion of rare earth in their rations increased weight gain performance by an impressive seven per cent on average. This means that, in Germany at least, more work is to be carried out on the mysterious effects of Chinese rare earth on hog performance. BP
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back by JANICE MURPHY
Currently unavailable BP
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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