Diagnoses and Treatments in Health-Classified Fattening Herds Rearing Pigs All In – All Out

This study describes diseases encountered, medications used and veterinary involvement in all in – all out finishing herds belonging to one pork production system. The finishing herds had a particular management and housing regime. The pigs originated from health classified farrowing units. Information on 207442 pigs was collected from 595 log books. Altogether 91% of the pigs received no treatments. Four percent of the batches of pigs were given antimicrobial mass medications. The local veterinarian visited the herds on average 2.6 times during the finishing period and made the diagnoses in more than half of the cases. At least one pig was affected with arthritis or tail biting in more than half of the batches, whereas locomotory diseases were recorded in one third of the batches. All other diagnoses were encountered in 1%-13% of the batches. Only a few pigs were treated individually in the affected groups. Antimicrobial drugs were given to 8% and other medicines to 0.7% of the pigs. The diagnosis was missing at least for one pig in 29% of the batches and the information about the medicine use in 8% of the treatments was missing. The study shows that it is possible to rear finishing pigs with only a small proportion of the animals needing treatments. The need of mass medications was low, because infectious diseases affecting the whole herd were uncommon. The recommendations for antimicrobial use given by the authorities had been followed quite well. The farmers and the veterinarians should be educated in order to realise the importance of proper record keeping.


Introduction
Antimicrobial drugs are used in food animals as performance-enhancers, prophylactically to prevent diseases or therapeutically (Blaha 1996, Debeuckelaere & Remy 1996. The usage of antimicrobials has potential adverse effects for the consumer and the population. Abundant use of antibiotics in animals leads to the development of resistant bacteria, which may be passed to humans (Espinasse 1993, Witte 1998. Further, residues of antibiotics may still be present in the meat of treated animals (Van Dresser & Wilcke 1989, Debeuckelaere & Remy 1996. In industrialised countries, the safety and quality of food is increasingly becoming an issue of concern for the consumer (Blaha 1999). Regulatory authorities reduce the risks by monitoring residues at slaughter (Walton 1983), requiring proper testing of medicines prior to authorisation and by developing recommendations for antibiotic use. One of the important factors influencing the probability of antimicro-bial residue occurrence in animal products is the extent of their use (Van Dresser & Wilcke 1989). Intensification of production may lead to loss of attention to individual animals and to the increased possibility of the spread of disease (Noordhuizen & Frankena 1999). It is increasingly necessary to adopt new approaches to food safety and pork quality (Blaha 1999). The pork industry has developed different kinds of quality programs. One way to describe the quality of pork production could be to collect information about medications used, the proportion of pigs needing treatments and how herd health is controlled. Some studies have identified the antimicrobials used in the various phases of swine production based on production, sales and trade information (Espinasse 1993, Björnerot et al. 1996. However, this kind of data gives little information about how, where, when and why antimicrobials are used in swine production (Dunlop et al. 1998a). Only limited information is available about the most common diseases and the medications in different production systems, especially as far as finishing units are concerned (Elbers et al. 1990, Elbers et al. 1992, Blocks et al. 1994. It has been possible to establish national policies for use of veterinary antimicrobials, especially in Scandinavia. In Finland, the Ministry of Agriculture and Forestry published general antimicrobial policy in 1996 (Anon. 1996a) together with recommendations for use to treat specific diseases (Anon. 1996b). In Sweden, guidelines were published in 1990 (Holmgren et al. 1990) and in Denmark in 1997(Pedersen 1997. In 1998, the British Veterinary Association published general guidelines on the use of antimicrobials (Baker et al. 1998). In 1999, a new set of 'global principles' on the responsible use of antibiotics in animals was announced by the World Veterinary Association, the International Federation of Agricultural Producers and the World Federation of the Animal Health In-dustry (Anon. 1999). These guidelines have led veterinarians to reconsider their therapeutic routines. The role of the pork producer is changing from just rearing pigs to being an indispensable part of the food production chain supplying a needed product (Blaha 1999). The swine industry should continue to invest in the maintenance of healthy pig populations aiming to reduce the need for medical treatment (Dunlop et al. 1998b). In Finland a health class and management system in pork production, LSO 2000 system, has been developed (Tuovinen et al. 1997b). The main idea is to produce non-medicated meat. The farmers and the veterinarians are encouraged not to leave diseased pigs untreated, but to treat them individually and to give them an identity to ensure that treated pigs can be refound. Veterinarians play a major role in ensuring responsible and prudent antimicrobial use (Dunlop et al. 1998b) and regular farm visits are an essential part of that control. Further, the swine practitioner needs to support pork producers to provide pigs with quality that meet the demands of the whole chain up to the consumer (Blaha 1997). The objectives of the study were to describe the diagnoses recorded, the medications used and the veterinary involvement in controlling the health and the treatments in the LSO 2000 finishing herds. These herds were controlled to conform certain management and housing requirements. They reared batches of feeder pigs originating from health classified farrowing herds.

Materials and methods
The data for the study was collected between March 1996 and December 1997 from the farmers' log books of all in -all out finishing units rearing batches of minimal disease feeder pigs in Finland.

The piglet producing herds
The farrowing units producing the feeder pigs were certified to be free from major swine pathogens including sarcoptic mange, Mycoplasma hyopneumoniae, progressive atrophic rhinitis and swine dysentery (Tuovinen et al. 1997b). The health status of these farrowing herds was examined by the local veterinarians clinically at least 4 times per year. Bacteriology, serology and/or pathology were used to confirm the diagnosis of clinical signs of the above mentioned diseases. The feedback from the finishing units buying piglets from these farrowing units was constantly used in assessing the disease status of the farrowing units. In addition, Finland is known to be free from some other infectious pig diseases such as swine fever, swine vesicular disease, transmissible gastroenteritis, swine influenza, Aujeszky´s disease and PRRS (Anon. 1998a). Also the incidence of salmonella in livestock has been extremely low in Finland, because of an effective salmonella control program (Anon. 1998a, Anon. 1998b). The feeder pigs had been treated with anthelmintics in the farrowing units approximately one week before transport to the finishing units, which occurred at the average weight of 25 kg. They were also of proven genetic quality (crosses of Landrace and Yorkshire). Usually the feeder pigs were collected from 10-15 farrowing herds in order to make one finishing batch. The feeder pigs were delivered to the pens of the finishing units according to the herd of origin.

The finishing herds
The finishing farms had been classified according to the requirements in the LSO 2000 quality chain (Tuovinen et al. 1997b). These herds were certified to have certain housing and management conditions, which were examined at least every 18 months (Table 1). For example, the effective environmental temperature was calculated. The owners were required to provide the feeder pigs with an effective environmental temperature of at least 22-23°C for one week after the arrival. After that it could be lowered gradually according to the size of the pigs. No routine mass medications (=oral treatment for the whole unit or for a part of the pigs) or antimicrobial feed additives were allowed. In Finland medicines are sold to farmers only by veterinarians or by prescription from pharmacies (Anon. 1998b). The owners of the finishing units and the veterinarians were advised to treat sick pigs individually and ear mark them with an individual number. In case of widespread infection within the unit, mass medication was allowed, but it had to be reported to the animal health service in the slaughterhouse. The owners of the finishing units were advised to ask the local veterinarian to check the herds clinically at least twice during the finishing period, the first one being within one week after arrival of the feeder pigs. The average time in the finishing unit for the study population was 96 days.

The recordings in the finishing herds
The ear number of the pigs diagnosed to have different diseases, the date, the disease code, the code of the person initiating the treatment (owner or the local veterinarian), the duration of the treatments and all medications were recorded in the log book on the day of the treatment by the persons treating the pigs. The pig disease codes of Agricultural Data Processing Centre (Suomen Maatalouden Laskentakeskus) were used in recording the diseases. The codes were combined according to Table 2. The owners of the finishing units were advised to send the log books to the slaughter plant together with the slaughter pigs. All log books which were returned were included in the study.

Log books and overall medical treatments
A total of 595 log books were available for analysis. They consisted of 207442 pigs, which was 79% of all the pigs reared on LSO 2000 finishing farms during the time period studied. The pigs were reared on 152 finishing farms and the median size of one batch was 301 (30-1000) pigs, (minimum-maximum). Altogether 9% (n=18107) of the pigs were either mass-medicated or treated individually. A median of 5% of the pigs per batch were treated. No animals were medicated in 30 batches (5%). A veterinarian visited the herds on average 2.6 times (sd=1.0) during the finishing period. The diagnose was made by the veterinarian in 58% of the cases. The time of the treatment after arrival varied according to Table  3, i.e. Glässer syndrome, infective digestive disorders and oedema disease were diagnosed within a few weeks after arrival, whereas arthritis, locomotory disorders, skin disease, and erysipelas were common 3-4 weeks after arrival. Later tail biting, respiratory diseases and other digestive disorders induced the medical treatments. The animals were medically treated for a median of 5 days (Table 3).

Individual treatments
Arthritis and tail biting were the most common diseases diagnosed in the finishing units, when the percentage of batches with at least one affected pig was studied (Table 4). The median percentage of pigs treated for different diseases in the affected batches after excluding the mass-medicated batches ranged from 0.3% to 3% (Table 4).    The medicines used Altogether 8% (n=17906) of the pigs were treated with antimicrobials either individually or with mass medication. The use of ß-lactam antibiotics (mostly penicillin), tetracycline and the group of lincosamides, macrolides and pleuromutilins were commonly used drugs. The use of trimethoprim-sulpha, enrofloxacin and combinations of several antimicrobials was less common (Table 5). Other medicines than antimicrobials were used for 1450 pigs (0.7% of all pigs): Anti-inflammatory drugs were given for 574 pigs (=3% of treated animals), vitamin E plus selenium for 372 pigs (2% of treated animals), corticosteroids for 338 pigs (=2% of treated animals), antiparasitic drugs for 106 pigs (=0.6% of treated animals) and other medicines for 102 pigs (=0.6% of treated animals).

Discussion
In the present study, 9% of the pigs were medically treated during the fattening period. A majority of the treated pigs were given antimicrobials (8% of all animals) and 4% of the batches were mass-medicated. A few years earlier 19% of the fatteners were medicated and 11% of the batches were given mass medications in the same region (Heinonen et al. 1997). At that time the housing and management of the finishing units were not controlled. However the feeder pigs purchased belonged to the same defined health status in both trials (Tuovinen et al. 1997b). Apparently the introduction of certain production standards and veterinary inspections improved the health status in a positive way. Considerable variation has been found in the use of veterinary drugs between farms. For example, group medication was given in the Netherlands to 69% of the farms because of intestinal disorders and to 84% of the farms because of respiratory disorders (Elbers 1991). The fact that the veterinarians made 58% of the diagnoses must not contradict to the general animal welfare, because the veterinarians visited the farms at strategic time points and certainly at times of accumulated health disturbances. The existence of a strong veterinarian-client relationship is important for proper use of antimicrobials. For example in Canada, only 23% of larger operations participated in herd health programs and only about half of the producers that experienced a disease outbreak in growingfinishing pigs actually consulted a veterinarian (Dunlop et al. 1998b). Information about a specific pig unit, the competence of the managerial staff to apply the antibiotic as prescribed and the previous history of the use of different antibiotics on a farm can only be acquired by a frequent veterinary presence on the farm (Walton 1984). In the present study, the health and the treatments of the pigs were monitored during the monthly visits of the local veterinarians. It is notable that no antimicrobial feed additives were used. The response to them is greater in young pigs and in unhygienic housing (Kunesh & Zimmerman 1994). Withdrawal of feed additives during the fattening period probably meant quite little in the herds studied, because of the high general health status of the herds. Elsewhere, it is very common to use antimicrobial feed additives also for growing/finishing pigs. For example, in Great Britain it was found that 29% of farmers gave them to finishers and 57% to growers (Pearce 1999). The abundant use of antimicrobial feed additives has led to the recommendation that the use of antibiotics as feed additive or for the preventive control of diseases should be prohibited (Debeuckelaere & Remy 1996).
The total avoidance of antimicrobial use is not the ultimate goal, but their scientifically founded use according to the principle 1) tailored to the correct diagnosis and 2) as little as possible, but always the amount that is needed (Blaha 1996). In the present study, the most common diagnoses differed from those made in other systems. The otherwise common infective diseases such as respiratory and digestive disorders affecting the whole finishing batch and needing mass medications were quite uncommon. The pigs could be regarded as individuals and the use of mass medications changed to individual treatments. Animals should be treated individually whenever possible. It is important to get a therapeutic level of drug to the ill pig, rather than to its healthy contemporaries. If the sick pigs are treated individually early in the course of the disease the pathogen load to the healthy pen-mates will be reduced, thereby decreasing the need of further treatments. Another aspect is animal welfare. Individual treatments ensure that each sick pig will be sufficiently medicated. There are various methods to minimise the need of antimicrobials in swine finishing units. Apart from improving the health of the pigs these methods generally improve animal welfare. They include for example all in -all out production, health matching, diminishing the number of source herds by various methods, tracking and eliminating the infection sources and controlling housing and management (Tuovinen et al. 1997c). The all in -all out method effectively interrupts the accumulation of microbes in the piggery. With health matched feeder pigs the pathogen load can be reduced.
In the present study most of the batches originated from 10-15 farrowing units. A decreasing number of farrowing herds supplying the fattening herds has been found to be associated with an increased percentage of drug-free finishing periods (Elbers et al. 1990). Infected farrowing units can be tracked by the help of the finishing units. Sorting the pigs by source herd to the finishing unit pens helps tracking of disease sources and helps to treat infectious diseases effectively without the need to treat the whole batch. The publication of the national antibiotic policy (Anon. 1996a) and recommendations for treatment (Anon. 1996b) published in Finland are likely to have affected the selection of the antimicrobials used. Most of the treatments followed the general policy. However, for example the use of several antimicrobials simultaneously in the case of Glässer syndrome or infective digestive disorders was not according to the recommendations. This paper describes the drug use only in one region. There may be great differences between different regions and veterinarians with regard to the prescriptions (Holmgren et al. 1990). Therefore, the results obtained in a region ought not to be generalised to cover a whole country. Considerably high percentage, 79% of the log books were returned. In the present study the figure should have been higher, because in a quality chain one would have expected better involvement of the farmers. However, no missing log books were requested. The study shows that it is difficult to effectuate control systems employing all farmers. The batches representing the missing log books were, however, not likely to differ from the ones that participated in the study by having more disease problems, because the finishing herds had paid a high price for their minimal disease feeder pigs. Based on our field experience, the farmers were likely to report the disease problems to the slaughter-house in order to claim the dealer about the health of the animals, especially if there were a lot of treatments. Also, the reporting of the treatments did not affect the price of the meat. An obvious limitation in the study was the fact that some of the recordings in the log books were incomplete. The diagnosis was missing at least for one pig in 29% of the herds representing 0.5% of all pigs reared. Similarly, the information about drug use in 8% of the treatments was missing. One would anticipate better record keeping for the farmers and veterinarians of the herds in a quality chain. More education is needed for the farmers and the veterinarians about the matter. They should realise that it is of utmost importance to be able to prove the customers all medicine used in pig production. To conclude, it was possible to rear finishing pigs with only a small proportion of the animals needing treatments. Individual treatments could be used principally, because infectious diseases affecting the whole herd were uncommon. The recommendations for antimicrobial use given by the authorities as part of the national antibiotic policy had been followed quite well in the herds studied. However, the farmers and the veterinarians should be educated in order to realise the importance of proper record keeping in proving the customers all medicine use of the herds if needed.