Vaccination of Sows and Gilts against PCV2 Diseases: Field Experiences in Europe

Posted in: Welfare by admin on January 1, 2007 | No Comments

Porcine circovirus type 2 (PCV2) has been associated with a number of disease syndromes in pigs, including post-weaning multisystemic wasting syndrome (PMWS), proliferating and necrotizing pneumonia, porcine respiratory disease complex (PRDC), abortion and reproductive problems (Allan & Ellis, 2000). Porcine dermatitis and nephropathy syndrome (PDNS) and a new ear necrosis syndrome have also been associated with PCV2 but today, there is not definitive evidence that PCV2 is the major cause of these syndromes. Since the end of 2004, CIRCOVAC® (Merial), a PCV2 vaccine dedicated to sows and gilts to control PCVD in the whole herd, has been used in several parts of the world. The goal of this paper is to review the large-scale studies of PCV2 vaccination in Europe. PMWS/PCVD are still major causes of impaired economic performance in all parts of the world. Vaccination of the sows with CIRCOVAC® has now extensively, and in various geographic areas, been shown to prevent PMWS mortality and to decrease total mortality in piglets as well as to improve growth and performance of the piglets. The vaccinated herds previously suffering from PCVD were able to recover and to return to a “close-to-normal” performance (even sometimes better than before the PCVD outbreak), due to an almost total reduction of the increase in mortality above the basic non- PCV2-related mortality. In addition, the recent studies presented here confirm the largely reported beneficial effects of CIRCOVAC® in the field on reproduction as well as on the very early period of the piglet’s life. The data regarding reproduction are in contradiction with other recently presented observations in the United States, using the PigCHAMP system (Nerem, 2007), that did not show PCV2 vaccination in 18,000 sows to improve reproduction results, although the tool used is quite similar to the GTE data analysis system. This may have several explanations including a different health status of the herds/sows, a difference in the time frame of the study or a difference in the vaccine used. Vaccination of the sows and gilts with CIRCOVAC® induced major improvements in reproduction parameters, in the piglet performance during the suckling phase as well as impressive improvements in pig heath status and growth for their life span.

Porcine isosporosis: Infection dynamics, pathophysiology and immunology of experimental infections

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Isospora suis, an intestinal protozoan parasite of swine, is the causative agent of neonatal coccidiosis, a disease with high morbidity in affected pig-breeding units and consequently of high economic importance. Infection leads to damage of the mucosal surface in the jejunum and ileum and to non-haemorrhagic diarrhoea. As a result, weight gain of piglets is reduced and secondary infections with other enteric pathogens may lead to increased mortality. Despite its economic and veterinary importance, host-parasite interactions are still poorly understood. To examine these interactions experimental infection models are established using outbred piglets infected with defined numbers of parasites on different days of life. This review discusses the life cycle of Isospora suis and the clinical and parasitological characteristics of porcine neonatal coccidiosis including pathology, and compare the different experimental infection models and the tools for studying Isospora suis in vitro. Moreover, it summarises findings about natural age resistance of pigs against infections with Isospora suis, our current knowledge about immune response to other coccidial infections, e.g. with Eimeria spp. in different hosts, and gives a short overview on peculiarities of the porcine immune system and its development in young animals which may play a role in porcine coccidiosis.

Objects as enrichment: Effects of object exposure time and delay interval on object recognition memory of the domestic pig

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An important non-spatial memory ability not well described in pigs is memory for objects. Knowledge of the robustness of object recognition memory in the pig, including when and how recognition fades, would be useful for pig producers using objects in an environmental enrichment program. While it seems clear that substrates for rooting are utilized by pigs for a greater duration and frequency than objects (Van de Weerd et al., 2006; Scott et al., 2006), and have a greater effect on welfare as indicated by decreased aggression and tail-biting (reviewed by Bracke et al., 2006), objects of all types can provoke some exploration (Van de Weerd et al., 2003). If pigs recognize a repeatedly encountered object as familiar, they would probably not interact with it as they would a novel object. Little is known, however, about how long a pig remembers objects. Therefore, it is the focus of this paper to address object recognition memory in the domestic pig. To better understand the effect of exposure time and delay intervals on pig object recognition memory, a modified spontaneous object recognition test was used to examine object recognition memory in the domestic pig. This test uses preference for a novel object over a previously encountered sample object as indicating recognition of the sample object, and no preference as indicating no recognition. We exposed 5-week-old pigs to different sample objects in their home pens for 10 min and 2 days, respectively. We tested for object recognition memory at various delay intervals after initial exposure by placing littermate pairs in a test pen for 10 min and recording snout contact with a sample object and a completely novel object. At a 1-h delay, half the pairs were tested with the 2-day sample object; the other half received the 10-min sample object. At a 3-h delay, pairs were tested with the opposite sample object. Pairs were also tested with the 2-day sample at a 5-day delay and the 10-min sample at a 6-day delay. We predicted that pigs would show a preference for the novel versus the 2-day sample object at all three delays, but would only prefer the novel object over the 10-min sample object at the 1-h and 3-h delays. Pigs did not show novelty preference in the presence of the 10-min sample object at any delay. Novelty preference in the presence of the 2-day sample object occurred at the 3-hour and 5-day delays, but not the 1-hour delay. The lack of novelty preference when pigs were tested with the 10-min sample object may have been due to failure to habituate to the sample object. Testing in a different location from the initial sample object exposure and retroactive interference from exposure to the 10-min sample object may have contributed to a temporary lack of novelty preference when pigs were tested with the 2-day sample object at the 1-h delay. The finding that pigs retained a memory for the 2-day sample object for at least 5 days suggests that restricting object exposure to less than 2 days may help to preserve the exploratory value of objects rotated among pens.

PCVAD Vaccine Results in Grower-Finisher Units: Practical Evaluation and Considerations

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A severe epizootic of Porcine Circovirus Associated Disease (PCVAD) struck swine herds in Eastern Canada towards the end of 2004. Even though many producers implemented better management practices, PCVAD continued to cause severe economic losses for swine producers. During 2006, Circovac® from Merial, Intervet PCV2 vaccine (no trade name), and Ingelvac® CircoFLEXTM from Boehringer Ingelheim became available in Canada. The first reports on the efficacy of piglet vaccines were very positive. De Grau et al. (2007) reported significant reductions in mortality in 4 independent farm trials using PCV2 Intervet vaccine. Desrosiers et al. (2007) also reported similar improvement with Ingelvac® CircoFLEXTM. In a controlled trial done in 4 finisher barns in Quebec in 2006, mortality was 2.4% in vaccinated pigs compared to 9.5% for non-vaccinated pigs. It is obvious looking at these results that piglet vaccination for PCVAD in the finisher stage significantly reduces the impact of this disease on the herd. However, in the initial stages of the outbreak, the supply of piglet PCV2 vaccines was insufficient to meet demand. As a result, many swine production systems used all of the available commercial products concurrently in order to vaccinate as many piglets as possible. Also, off-label use (e.g. half dosing or administering a single injection of vaccines labelled for use as 2 dose vaccines) became a common practice in an attempt to “stretch” vaccine stores and provide protection to the largest possible number of pigs. Field experience so far suggests that fractional (half) dosing can deliver equivalent mortality rates equivalent to full dose schemes but there may be differences in key economic drivers, such as feed conversion (F/C) and Average Daily Gain (ADG). In an attempt to further examine this question the PigCHAMP data from a 3-site production system were analyzed. Based on the data, and within this system, there appeared to be little difference in performance between full vs. ½ dose Intervet PCV2 vaccinated pigs. However, the data was collected in the field rather than under controlled conditions and represent a relatively small number of groups. Clearly what is needed to clarify this picture is information from case-control studies. Additionally, we must not forget that the majority of the vaccine results obtained so far come from herds where better than average management practices and disease control strategies were in place. Therefore, the decision to embark on the use of off label dosing must be made with due consideration for individual herd factors that may influence the results. Ideally, all farms should have an information system in place to collect objective production information that can be used to both benchmark current performance and analyze the impact of management changes (including vaccine regimens). Given the pivotal role that immune stimulation has been demonstrated to play in the expression of PCVAD (Krakowka et al., 2001), it is critical to take the degree of control of other pathogens into account when designing a PCV2 control program. In PRRSv positive groups, the half-dose regimen had the lowest mortality and FC and higher ADG, whereas in PRRSv negative groups, the full dose regimen had the lowest mortality and FC and highest ADG. Unfortunately, because the data came from uncontrolled studies gathered in the field and the sample size was limited, it’s impossible to draw any conclusions at this time but further research aimed at better defining these impacts would clearly be helpful. The complications introduced by circulating PRRS virus also serves to remind us of the importance of controlling circulating primary pathogens. The system in question is currently engaged in actively managing PRRS virus with the goal of eliminating virus circulation. In the opinion of the authors, PCV2 vaccines are the single most effective tool currently available for the control PCVAD. However, some researchers have already started to raise questions about the “immunological cross-protective capability of single-strain commercial vaccines” (Horlen et al., 2007) and to date our understanding of why PCVAD suddenly became a problem within North America is far from complete. We must not allow the effectiveness of PCV2 vaccines to substitute for good management and long term industry wide strategic planning. The next ‘new’ pig disease may be just around the corner and effective vaccines and control strategies may well be a lot further off.

Emerging Diseases of Africa and the Middle East

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Multifactorial testing of enrichment criteria: Pigs ‘demand’ hygiene and destructibility more than sound

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Environmental enrichment is important for the welfare of farm animals, which are often kept in barren environments (e.g. Young, 2003). In 2001 the European Commission adopted a directive (2001/93/EC) which states that: ‘‘Pigs must have permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities, such as straw, hay, wood, sawdust, mushroom compost, peat or a mixture of such, which does not compromise the health of the animals.’’ The directive leaves considerable room for interpretation, as it is not clear what is proper investigation and manipulation. Furthermore, the value of enrichment material is most likely determined not only by the type of material as listed in the directive, but also by other material properties such as the amount and frequency of material provision, hygiene, destructibility and responsiveness. A semantic model, called RICHPIG, was constructed based on a systematic and formalized analysis of scientific information collected in a database (Bracke et al., 2007a,b). The relative importance of three assessment criteria (destructibility, hygiene and sound) were studied as treatments applied to groups of growing pigs in a 2 x 2 x 2 factorially designed experiment measuring a range of behavioural parameters. The objectives of the study were to examine how the treatments affect pig behaviour, how intensity-related measures relate to AMI, what this means for the relative importance of the three assessment criteria, and by implication to help further validate RICHPIG. These material properties were studied using a specially constructed object consisting of a piece of sisal rope, metal wire and three fixed chain links hanging in the pens. The object was considered to be not destructible (ND), hygienic (HY) and not making sound (NS). After a habituation period of 18 h treatments were applied in that the object was (or was not) made destructible with a partial cut in the rope (DE) and/or was soiled with excreta (not hygienic, NH) and/or was allowed to make a tinkling sound by releasing the chain links (SO). The three treatments were applied in a 2 x 2 x 2 factorial design on a commercial farm in seven replicates using seven different units containing eight pens per unit. At five moments in time, ranging from 18 h before until 1 h after treatment, a range of behaviours was recorded including the frequency-related parameter AMI (animal–material interactions) and four intensity related parameters. Repeated measures ANOVA’s showed significant effects of time and hygiene as well as interactions between time and hygiene, between time and destructibility and between destructibility and sound. Soiling (NH) significantly decreased, and destructibility (DE) significantly increased attractiveness, while sound (SO) was not significant. Only moderate correlations between AMI and the four, intensity related parameters were found, indicating that frequency-related parameters alone may not suffice to determine behavioural importance for animal welfare. This study showed that it is in principle possible to study material properties independent of material type and that it is in principle possible to measure behavioural intensities on a commercial farm. Furthermore, the finding that hygiene and destructibility were more important for pigs than tinkling sounds provided preliminary support for the RICHPIG model.

Nutrient Requirements of Prolific Sows

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The nutrient requirements of modern sows, and the availability of dietary nutrients for sows, are very poorly known in comparison to our knowledge of growing pigs. The number of published research papers in the last 40 years on growing pig nutrition is in the tens of thousands, however, there are only about 800 publications on sow nutrition listed in the Commonwealth Agricultural Bureau database –less than 1% of all publications concerning pigs. If we still don’t know everything we need to about how to feed growing pigs – imagine what we don’t know about sows! The productivity of sows has increased dramatically in the last 20 years, however, the research, upon which current dietary recommendations are based, dates from the late 1970’s to the early 1990’s (ARC 1981, NRC 1998).
In addition, many of the nutrient recommendations for sows are unverified extrapolations from research in growing pigs. Our recent research shows that the current recommendations for both energy and amino acid intake in sows (NRC 1998) are incorrect by a significant margin. The economic benefit to producers of research to revise and update the energy and amino acid requirements of sows is estimated to be worth in excess of $4.50 per pig marketed (Grier et al 2006).

Continuous Vagus Nerve Stimulation Effects on the Gut-Brain Axis in Swine

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Influence of different types of environmental enrichment on the behaviour of finishing pigs in two different housing systems 2. Ratio of pigs to enrichment

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Exploration is a biologically important behaviour used to gain information about the surrounding environment and available resources (Wemelsfelder and Birke, 1997). Pigs have developed foraging strategies that depend on high levels of exploratory behaviour involving the mouth and snout (Arey, 1993). Current EU legislation (Directive 2001/93/EC) requires that ‘‘. . . pigs must have permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities, such as straw, hay, wood, sawdust, mushroom compost, peat, . . .’’. Since the use of most particulate rooting materials in slatted systems can cause difficulties for slurry management, it is necessary to identify other forms of enrichment that meet the requirements of both the animal and the producer within the confines of the system as failure to provide adequate enrichment has been implicated in the development of adverse behaviours. In pens without bedding, exploratory behaviour is redirected towards pen-mates (Beattie et al., 2000; Kelly et al., 2000; Lyons et al., 1995) and pen components (Guy et al., 2002; Lyons et al., 1995). Tail-biting behaviour is also more prevalent under these conditions (Van de Weerd et al., 2005; Scott et al., in press). The aims of this experiment were to assess the effects of: (1) environmental enrichment with either straw bedding or a hanging manipulable toy and (2) the ratio of pigs to environmental enrichment when in the form of a hanging toy, on the behavioural responses and synchrony of behaviour in finishing pigs. One thousand and twenty four (Large White x Landrace) x Large White pigs were housed contemporarily, in 32 pen groups of 32 pigs (16 pens in each housing system), in matched straw-bedded (ST) or fully slatted (FS) buildings from 35 kg to slaughter at 104 kg liveweight. In the ST building, only the straw bedding enriched half of the pens and half received additional enrichment in the form of a single hanging ‘toy’. In the FS house, half of the pens were provided with the same hanging toy, whilst the remaining pens were provided with four such toys. Time spent in toy manipulation was <2% in both housing systems, and did not differ in comparison of the same toy in different housing systems, or the different numbers of the toy per pen within the FS house. Manipulation of straw bedding occupied a much higher proportion of time (21%). In the absence of straw, significantly more investigatory behaviours were directed towards pen components, with a similar tendency in behaviours directed at pen-mates. It was concluded that environmental enrichment in the form of a hanging toy failed to provide the same level of occupation as seen with straw bedding. Since the ratio of pigs to enrichment object had no effect on the level of enrichment manipulation, or on pig or pen-directed behaviours, this difference cannot be attributed to spatial limitation. Functional enrichment should occupy animals to a great extent to prevent them from performing adverse behaviours; therefore the reasons behind the difference in occupation time between straw manipulation and enrichment object interaction require further investigation.

Hyper-Prolificacy and Acceptable Post-Natal Development – A Possible Contradiction

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Although the components of litter size (ovulation rate, embryonic survival and uterine capacity) responsive to genetic selection are well established. However, the reality in existing “hyper-prolific” sows is that increased selection pressure for numbers born has led to indirect negative effects of intra-uterine crowding, reprogramming of fetal development, less efficient post-natal growth performance and adverse effects on carcass quality at slaughter. Therefore, a considerable amount of the variation in growth performance after birth may be pre-programmed during fetal development in the uterus (see Foxcroft and Town, 2004). The effects of prenatal programming on postnatal performance are not limited to effects on muscle development and growth. Harding et al. (2006) showed that the organs most notably affected by pre-natal programming in stillborn pigs with low birth weight were the heart, liver and spleen, with obvious implications for post-natal health outcomes generally. Both birth weight of the individual pig and between litter variation in birth weight are of considerable economic interest for pork production, as post-natal growth in the pre-weaning, nursery and grow-finish stages of production is impaired in low, compared with high, birth weight pigs (see review of Foxcroft et al., 2007). Available results indicate that pigs of low birth weight have poorer carcass and meat quality. Unfortunately, although selection for improved prolificacy has resulted in an increase of litter size at birth in most breeding populations, this has been associated with increased within-litter variation in piglet birth weight, as well as an overall decrease in average birth weight of the litter. The proportion of live-born vs. dead-born pigs within the litters of one population of hyper-prolific French sows suggests that the growth potential of the live-born pigs that survive to weaning will be seriously affected by intra-uterine competition with the increasing number of fetuses born dead. A better appreciation of the characteristics of prolific dam-lines is clearly needed. This information, and an increasing focus on the need to maximize total net revenues per sow in terms of the value of saleable pork products relative to the input costs involved per kg of pork sold, should drive the management of appropriate terminal dam-lines in the future. Ultimately, selection of sows with increased uterine capacity offers the best opportunity for increasing the number of pigs born per litter, without compromising the post-natal growth performance of these pigs. A comparison between the largest and smallest pigs within a litter has most frequently been used to study impacts of birth weight on postnatal growth performance. However, limitations in functional uterine capacity in hyper-prolific sows are predicted to result in prenatal programming effects on entire litters (Foxcroft et al., 2007). If this assumption is correct, then the origins of increasing variance in postnatal growth performance needs to be clarified as the basis for developing selection and production strategies that effectively address the problem. Innovative approaches to addressing the problems, as well as the opportunities presented by pre-natal programming of post-natal performance, will likely be the benchmark of the most profitable pork production systems in the next decade. In particular, these approaches will need to address the possible conflict between continued selection for hyper-prolificacy and increased variance in post-natal growth performance.