Porcine Circovirus Associated Disease (PCVA)… a “Double Bogey”

Posted in: Welfare by admin on January 1, 2006 | No Comments

Symptoms of PCVAD include: gross lesions; microscopic lesions; hallmark lymphoid lesions; immunohistochemistry; main confirmatory test; serology; ELISA, IFA; PCR; quantitative, nested, multiplex; virus isolation; sequencing; and antigen capture ELISA.
An assessment was done on boars using ELISA or IFA to determine PCV2 status because naïve incoming boars may represent a risk. Producers must consider exposing naïve boars to PCV2, either by Vaccination or PCV2 positive (by PCR or Antigen Capture ELISA) feces from resident boars 5 weeks prior to bringing them into the main stud. In order to assess the breeding herd use ELISA or IFA to determine PCV2 status. Naïve incoming gilts may represent a risk. Consider exposing naïve gilts to PCV2 by vaccination or planned exposure (fecal feedback, mummified fetus feedback, cull sow exposure). In order to assess the nursery or finisher pigs confirm that PCVAD is a problem by histopath and IHC; use ELISA or IFA to determine when maternal antibodies wane and to determine when seroconversion occurs; do PCR on pooled serum (or saliva) to further define time of infection; do some PCV2 sequencing so you have a historical record of the system. If morbidity and mortality are unusually high, use sequencing to determine if the PCV2 in the system has changed. PCV2 isolates that are genetically highly homologous may differ in virulence. These differences may explain differences in clinical manifestation of PCV2 associated diseases. An experiment was done to determine the effects of host genetics on susceptibility to PCV2-associated disease and lesions. It was concluded that 3/19 (15.8%) Landrace pigs developed PMWS whereas none of the Duroc or Large White pigs developed PMWS. There was significantly more severe lymphoid depletion in tonsils and lymph nodes of Landrace pigs. The Landrace pigs used in this study appear to be predisposed to PCV2-associated lymphoid depletion and PMWS. Reproduction of severe disease and lesions typical of PMWS in CDCD pigs co-infected with PCV2 and PRRSV resulted in a 90% mortality in coinfected group, no mortality in singular PRRSV group and less severe disease and lesions in PCV2 only group (40% mortality). PCV2 and PPV coinfected conventional SEW pigs had increased incidence and severity of clinical signs characteristic of PMWS. There was also a significantly higher incidence and more severe lymphoid depletion observed in coinfected pigs. The PCV2 coinfection Model characterized severe disease by coughing, dyspnea, lethargy and decreased growth. Dual infected pigs had significantly more severe lung lesions and a significantly higher number of genomic copies of PCV2 in sera at 14 and 21 DPI. They also had more severe lymphoid depletion and higher amounts of PCV2 antigen in lungs and lymphoid tissues. A field trial looked for evidence for immune stimulation induced progression of PCV2 infection to PMWS. They found PMWS in 42.9% of the vaccinated pigs versus 10.7% in the group treated with normal saline. This work provides evidence that the efficacy of PRRSV vaccines can be decreased when administered to PCV2- infected pigs. Based on field evidence, we suspect that PCV2 infection may similarly decrease the efficacy of other vaccines administered between 6-14 weeks of age. The use and the appropriate timing of M. hyo vaccination is an effective tool in reducing the production losses associated with PCV2 and M. hyo-induced respiratory disease complex. Another experiment confirmed that the use of CTC (Aureomycin®) in the feed for 2-4 weeks at an approximate dose of 22 mg/kg body weight is a highly effective tool in reducing the production losses associated with PCV2- and M. hyoinduced respiratory disease complex. In order to control PCV2-Asscociated Diseases confirm PMWS/PCV2 by histopath, IHC; identify and control concurrent viral infections; minimize effects of M. hyo. with commercial vaccines and/or antimicrobials; aggressively treat other bacterial coinfections; determine if there is an association of increased PCV2-induced disease with the use of certain vaccines or timing of vaccination; use anti- inflammatory drugs; pulsing the group with spray dried plasma protein; pull sick pigs; focus on decreasing stress and improving pig comfort; use effective disinfectants (Virkon-S) between groups; consider a change in pig genetics; and use PCV2 vaccines. These are all ideas that will help control the outbreak of PCV2 in swine barns.

Monitoring production, health and marketing of indigenous Tswana pigs in Ramotswa village of Botswana

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Evaluation and comparison of four methods of ranking horses based on reactivity

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Horses’ reactivity was scored using four different methods. Their responses to: isolation from group mates, exposure to an unfamiliar object, passing an unfamiliar object down a hallway was each assigned a subjective emotional score. During each test, the behaviour of the horse was videotaped and the heart rate was recorded. In order for a test to be considered valid, there had to be a demonstrable reaction to the isolation or novel object in terms of the horses’ behaviour or heart rate between horses that were tranquilized and those that received a sham tranquilization. The change in behaviour had to be observed in a minimum of 75% of the trials. There was not a difference in the heart rate of tranquilized and control horses that were passed to a novel objects has they moved down the hallway. As well, during the test only 52% of the trials resulted in the horses exhibiting a change in their behaviour. Therefore, passing by an unfamiliar object while walking down a hallway is not an effective technique at assessing horses’ reactivity. Isolation and an unfamiliar object were both effective stimuli to assess a horses’ reactivity. The most accurate method of assessing the reactivity was the heart rate response. In terms of behaviour, the most reliable indicator was walking when exposed to an unfamiliar object and the number of times a horse defecated in response to isolation. Based upon the heart rate response, isolation and exposure to an unfamiliar object resulted in similar physiological responses and similar reactivity scores. However, the behaviour measurement rated the reactivity of the horses differently. The heart rate and behaviour of horses exposed to an unfamiliar object had comparable reactivity scores, while isolation created some variation between the reactivity score assigned based upon the heart rate or behavioural response. Thus, scoring a horse’s reactivity is more accurate when using the response to an unfamiliar object. The subjective emotion scores were moderately correlated with the heart rate and isolation and with walking scores, in response to an unfamiliar object. The subjective emotionality score were not as accurate as the heart rate and behaviour response to an unfamiliar object. The most accurate way to assess the reactivity of a horses is to used both physiological and behavioural measurements, or by using multiple behavioural measurements.

Happy pigs are dirty! – conflicting perspectives on animal welfare

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Animal production in developed countries has changed considerably over the last 50 years. In Europe, the changes have been brought about by public policies favouring more abundant, cheaper food. As a result of these policies animal production became much more efficient, as measured by the cost of producing each egg, each kilogram of meat, each litre of milk, and so on. The pressure for efficiency has more recently become market-driven, with competition between producers and between retailers to sell food as cheaply as possible. It has thereby acquired its own momentum. In many ways, this can be viewed as a success story. Thus consumers in the developed world are able to buy animal products at prices that are low relative to those charged in the past. Efficiency has been achieved by intensification. Farms have grown in size and now keep more animals per unit area. Farming methods have been automated. Beyond automation, other features of contemporary animal farming reduce labour costs – consider, for example, cages and other types of housing designed to control the behaviour of the animals and thus make their management easier. Animals have also been bred to produce meat, milk and eggs faster and with lower feed inputs. Over the last 30 years or so public awareness of what is done to farm animals in intensive animal production has grown (Appleby, 1999). This has led to responses and initiatives by various individuals and agencies concerned with agriculture and its role in the economy and society at large. Initiatives to deal with animal welfare issues have been taken by farmers’ organisations, by professional organisations such as those representing veterinarians and animal scientists, by several of the ancillary industries involved in animal production, and by various retailers and fast food chains. People with a background in modern animal production will probably have a bias towards focusing on the average. That bias is bound to be ingrained in the thinking of someone whose professional aim is to optimise commercial income. This takes us to the main topic of this paper. Different stakeholders will take different views of the ethical issues that underpin welfare measurement, and this has a number of important implications. Let us not forget that the starting point of the growing awareness of animal welfare within animal production was public concern. If it turns out that the public, or a significant section of it, views animal welfare in a way that significantly differs from the way in which it is viewed by scientists and those working in animal production, then there are likely to be problems. These problems will have to be dealt with. Otherwise initiatives to improve animal welfare may backfire. The ethical discussion of what constitutes a good animal life must be linked to public discussion of the assessment of farm animal welfare. Concepts like ‘animal welfare’ and the ‘good animal life’ are the outcome of an ongoing process of social construction. Consequently they can be seen as results of a political struggle between different interest groups, each of which tends to promote a particular definition. Those within the pig farming and food sector who wish to play a productive role in future developments should be open to the views found among the public. They should allow concepts such as that of ‘natural living’ a prominent place in the discussion. Failure to do so may result in a social controversy like the one witnessed in relation to food biotechnology in the past decades.

Avoid the Tiger in the Woods: Audit your Biosecurity

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Biosecurity is protecting your herd against the introduction of biological agents. There are many areas that need to be addressed such as the facility itself. How far are the closest pigs? How many? Is the driveway gated with “No Entry” signs? Are there feed spills? Are the doors locked? Is there a rocked perimeter or standing water? Has there been any rodent baiting? You must also look at the source of your replacement animals, how are the animals hauled to the facility? Who takes care of isolation? Feed? Manure? Maintenance? Who is the source of your semen, how is it delivered? Do you know who comes and goes from the farm? Is there posted downtime requirements? Is the staff routinely trained on biosecurity? Who is in charge of communication with service personnel and shower facilities? Other areas that need to be checked are the load-inout facilities; supplies and maintenance, and the handling and removal of dead animals. Most importantly always quiz the farm employees because the weakest link needs to be identified. Most breakdowns in biosecurity are due to the lack of communication to employees. This is the only way to find out what really goes on at the farm.

Intestinal Uptake and Metabolism of Threonine: Nutritional Impact

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Amino acid metabolism by the splanchnic tissues, which include the liver and
the portal-drained viscera (PDV), determines amino acid availability for protein
deposition in peripheral tissues and thus whole-body growth. Threonine, lysine
and methionine are the first limiting amino acids in milk-based and cereal diets
of growing pigs. Studies have shown that both dietary essential and nonessential
amino acids are extensively utilized by intestinal tissues for the
generation of energy, protein synthesis, and other biosynthetic purposes.
Threonine, with 60-80% extraction in first-pass of the dietary intake, is the
single most utilized essential amino acid by the PDV. This can most likely be
attributed to the incorporation of threonine into membrane-associated and
secretory mucosal glycoproteins, the so-called mucins, which are an important
component of the protective mucus covering the gut epithelium. In pigs, mucin
represents 11% of the basal endogenous ileal losses of protein with threonine
contributing approximately 30% to the total amino acid content. Thus, the
secretion, recycling, and loss of intestinal mucins have a substantial impact on
the maintenance requirement for threonine. Factors that increase the
production of mucin will increase threonine requirements and consequently,
decrease the availability of threonine and energy for growth and production.
Furthermore, the availability of threonine may limit intestinal mucin synthesis
and therefore reduce gut barrier function. This highlights the importance of
threonine for maintaining intestinal integrity, which is essential for regulating
dietary amino acid supply for the whole body

Cortisol, behavioral responses, and injury scores of sows housed in gestation stalls

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Sow housing systems have always focused on efficient utilization of space. Housing design affects the welfare status of sows at any stage of growth or production. The restriction placed on freedom of movement of pregnant sows has been a major welfare criticism leveled at individual stall housing. While it is presented as one of the main criteria for evaluating the welfare of animals, freedom of movement is arguably the most controversial design criterion for housing systems. The limited space in stalls is reported to reduce the ease with which the sow can change posture, and can cause injury and discomfort. It is important to note that the adequacy of space allowance depends on space available relative to the size of the pig. Depriving animals of opportunities to walk and turn around may affect their health, performance, and overall welfare. Most of the commercially available stalls provide the minimum space required for average sized sows and have similar design and measurements. The size of sows, nevertheless, varies considerably, depending on age, genetics, feeding level, and stage of gestation, and effective space available to a sow may become inadequate with advancement of pregnancy. Also, the welfare status of sows may not be static throughout their stay in the gestation housing system. Factors such as: separation from piglets, change in accommodation, and restricted feeding may contribute to an initially low welfare status of sows in stalls. The sow may adjust to the situation as the stay continues. In late gestation, the sow may be compromised by the relatively smaller space available with increasing body size. Stress associated with advanced gestation may cause further compromise. Though confinement in stalls has been viewed as adversely affecting welfare, the manner in which the compromise in welfare progresses during the course of the stay in the stalls has not been studied in detail. The present study, therefore, aimed to assess the welfare status of sows housed in stalls through measurement of injury scores, salivary cortisol concentrations, and behavior during the initial (day 5), middle (day 56) and late (day 108) stages of gestation. Timelapse video recording for 24-hour periods was used to observe their behavior on each day. Salivary cortisol concentrations were assessed using adioimmunoassay. Injuries were scored individually and added to provide a total injury score (TIS). It was concluded that Cortisol concentrations were lower on gestation day 56 than on other days, and TIS was higher on day 108 than on days 5 and 56. Time spent lying was highest on day 108. Sows spent more time on exploration and active behavior on day 56 than on days 5 and 108. Time for the transition from sitting to lying was higher on day 108 than on day 56. Frequencies of overall postural change and of standing or sitting to lying and lying to sitting were highest on day 5. Frequency of lying to standing was higher on day 5 than on day 108. Body weight was negatively correlated with time spent on exploration and active behavior and standing, and positively correlated with time spent lying. Therefore, the welfare of sows in gestation stalls appears to be more compromised during early and late stages of gestation. Providing larger sows with larger stalls might improve welfare.

PRRSV Transmission and Biosecurity Update

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Eradication of PRRS is possible on an individual farm basis, however; re-infection via local spread of the virus is a frequent event. Proof of knowledge on the routes of PRRSV transmission and biosecurity is necessary before large-scale eradication efforts can begin. The specific aims of this study are to assess the efficacy of three levels of biosecurity on reducing the risk of PRRSV transmission to naïve pig populations; to evaluate the role of season on PRRSV area spread; to estimate the frequency and significance of observed routes of PRRSV transmission and to compile a bilingual PRRSV-biosecurity manual summarizing routes, intervention and monitoring protocols for use on commercial farms. After five replicates the preliminary results for the high level facility is that all samples collected remained negative. The results from the medium level facility confirmed evidence of RNA in aerosols with subsequent infection of pigs. In the low level facility evidence was confirmed of RNA in marked flies with subsequent infection in pigs and there was no evidence of RNA in externally collected samples and no infection of pigs. Other preliminary results conclude that during the cool weather in June there was an outbreak of the PRRS virus; however, there was minimal spread during the hot weather in July. The next studies to be conducted will be large-scale, long-term demonstration projects under controlled field conditions.

Antigenicity and variability of membrane proteins of Mycoplasma hyopneumoniae, causing agent of enzootic pneumonia in swine

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Enzootic pneumonia is a chronical respiratory disease caused by Mycoplasma hyopneumoniae. It results in considerable economical losses for the swine industry in America and Europe. This disease delays growth of the infected pig and reduces its immunity, decreasing the efficiency of vaccination programs, particularly against pathogens of the respiratory tract. Together with strict husbandry, the controlled administration of antibiotics is used against M. hyopneumoniae. But the latter methods is costly and raises the problem of antibiotics resistant pathogens. Vaccination appears an interesting alternative. The searchers wanted to identify membrane proteins of M. hyopneumoniae that could trigger protective immunity. The searchers developed tools for making a subunit protective vaccine. Recombinant fusion proteins of three M. hyopneumoniae membrane proteins (p46, p65 and p97) were produced by genetic engineering with E. coli. These recombinant proteins were used for the development of monoclonal antibodies and diagnostic tests. Also, the recombinant proteins were administered to young piglets to assess their immunity response. The recombinant protein p46 seemed to be a good target antigen for serological diagnostic tests. Furthermore, the recombinant proteins p46 and p97 proved to be very strongly antigenic (more than p65), as shown by the results of a challenge infection with a virulent strain of M. hyopneumoniae. The lungs of pigs vaccinated with the recombinant proteins showed significantly less lesions than those of non-vaccinated pigs, threee weeks after the challenge infection. This research represents an important step towards control of M. hyopneumoniae in swine, particularly with regards to subunit vaccines developed with recombinant proteins.

Using Floor Cooling as an Approach to improve the Thermal Environment in the Sleeping Area in an Open Pig House

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In pig production, heat stress can be extremely detrimental to welfare and production over a range of thermal conditions. The results of heat stress may range from decreased feed intake and growth efficiency, reproduction and even hyperthermic death. In order to alleviate heat stress, many cooling systems for pig housing have been developed in recent years (Gates et al., 1991; Panagakis et al., 1996; Eigenberg et al., 2002). In China, the approaches such as the fan and pad cooling system (mostly used for growing/finishing pigs), the drip cooling system (mostly used for gestating sows), and the underground tunnel air-cooling system has been used (Liu et al., 1997; Dong et al., 1998, 2001; Ma, 1997). Those systems were mainly designed and applied in confined pig production buildings. Although the indoor environment is improved, common problems of the cooling systems during operation arise, such as increasing humidity, wet and dirty floor, noise level, etc., which will damage pig health and decrease pig production. Many of those cooling systems cannot be used in an open type pig house. Pig production systems with open structures and free access to an outdoors area are very common in China. The thermal conditions in these types of pig housing are very much dependent on the weather. In hot weather, feasible and effective cooling systems will be in great demand to provide a comfortable environment for the pigs. Generally, on hot days pigs may cool themselves by wallowing or enjoying water sprinklers (Heitman et al., 1962), and they may seek protection from the sun in the shade (Heitman et al., 1962; Blackshaw & Blackshaw, 1994) if shading facilities are available. They may also attempt to increase their heat loss by moving away from hot places to a cooler area or to a place with higher air velocity, by changing their lying posture from the belly to the side, or by avoiding having body contacts with other pigs (Geers et al., 1986). By rolling from side to side in a wallow or a damp place, the pigs may benefit from the evaporative heat loss via cooling their moist upper skin and conductive heat loss via contact in water. Since pigs spend more time resting than any other domestic animals, i.e. about 80% of the time daily (Haugse et al., 1965), relaxation and sleep are very important for pig health and growth rate. Therefore, a cooling system to meet the lying demands of pigs in an open type house under hot weather conditions is essential for the optimal production as well as for the welfare of pigs. Experiments were conducted to compare the floor temperatures and to observe the lying behaviour of pigs in the sleeping area of the buildings with and without floor cooling system. The results showed that, without the floor cooling system, the floor temperature was nearly the same as the air temperature in the open pig house. With the floor cooling system, the floor temperature of the sleeping area was controlled at 22–26 °C, even though the air temperature was as high as 34°C, which improved the comfort of the pigs in the sleeping area. The pig lying behaviour was greatly affected by the floor temperature. More than 85% of the pigs were lying in the sleeping area when the floor temperature was below 26 °C, while only 10–20% of the pigs were lying in the sleeping area when the floor temperature was about 30 °C, and hardly any when the floor temperature was above 33 °C.