Background Approximately 50% of sows are slaughtered each year, but management of cull sows is not well described.
Methods We aimed to describe how cull sows are sent to slaughter using a questionnaire survey emailed to 885 Danish pig farmers, including questions about the use of pick-up facilities (either a designated pen used for reasons of biosecurity and practicality, in a special part of the barn, where pigs are kept in the last hours before being loaded onto a commercial truck, or a stationary vehicle kept outside the buildings and used for the same purpose) and evaluation of fitness for transport.
Results A total of 360 farmers answered all questions, constituting a homogeneous group of middle-aged, experienced males. The management of the sows seemed rather variable, for example regarding choice of pick-up facility, its available resources, actions taken when sows were not fit for transport and sow conditions leading to doubt about fitness for transport. Special condition transport was only reported rarely, and rejection of sows due to lack of fitness for transport, by drivers or veterinarians at the slaughterhouse, was only rarely experienced.
Conclusion These findings may be used for formulation of hypotheses for future studies in this area characterised by welfare challenges, potentially leading to science-based recommendations relevant for animal welfare, productivity and biosecurity.
- animal welfare
- cull sow
- animal transport
- livestock driver
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In commercial pig production, up to 50% of the sows are slaughtered each year.1–3 Internationally, pig production is characterised by increasing herd sizes and changes in the slaughter industry towards fewer and larger slaughterhouses. Consequently, transport distances from farm to slaughter are increasing (as discussed by Lambooij4).
The movement and management of cull sows through the pre-slaughter logistic chain is not well described, and may differ considerably between countries (see Blair and Lowe5 for a recent description of US practice). In addition, it may involve a number of potential challenges for animal welfare, production and biosecurity. For example, based on French slaughterhouse data, Decaudin et al 6 reported a positive relation between time (counted in 10-hour intervals) spent off-feed in the interval from leaving the farm of origin and until slaughter, and the likelihood of whole-carcass condemnation. Across countries, a large proportion of sows are culled directly after weaning of the piglets,7 8 and are thus lactating on the day of slaughter.9 Modern lactating sows are, due to the large litter sizes and high genetic potential for milk production, sensitive towards heat stress,10 especially close to weaning, where milk production is peaking.11 Hence, sending sows to slaughter may involve thermal challenges, especially for lactating sows, and hyperthermia has been suggested to be among the main reasons for cull sow mortality upon arrival to slaughterhouses.12
A third challenge when sending sows to slaughter is the vulnerable clinical condition of some of the sows. Typical reasons reported for sow culling are reproductive problems, reduced health and age.13 14 Hence, as a consequence of the productive life in the herds, cull sows may be weak or prone to injuries, and thus less fit for transport than other types of pigs.15 Recently, we reported that 11% of 522 sows from commercial Danish sow herds, examined before being sent for slaughter, had decubital shoulder ulcers, 55% had at least one wound on the body (excluding the shoulder ulcers), 31% had superficial skin lesions and 26% had udder lesions.9 In Denmark, drivers of commercial pig transport vehicles share the legal responsibility for the fitness for transport of the animals with the farmer.16 Hence, it is possible for drivers to reject sows from entering their vehicle based on their evaluation of the sows’ condition. In addition to the obligations of the farmer and the driver, the fitness for transport of animals sent to slaughter is also checked by a veterinarian upon arrival to the slaughterhouse.
The journey to the slaughterhouse may be a challenge as well. Even though almost all research on the transport of animals has been conducted on fit and healthy individuals,17 cull sows are often mentioned as being more vulnerable to transport stress than other types of pigs.15 18 Recently, we reported significant deterioration of the clinical condition of cull sows after transport (up to 8 hours) to slaughter,19 such as increased occurrence of wounds, superficial skin lesions and changes in gait score. Similarly, higher mortality during or shortly after transport has been reported in sows than in slaughter pigs or weaners.12 20 Hence, some countries maintain special transport regulations for cull sows compared to other types of pigs (eg, in Denmark, cull sows are not considered fit for more than 8 hours of transport16 21). In addition, in their guidelines for animal transport, The World Organisation for Animal Health specifically mentions the vulnerability towards transport of cull sows compared to other types of pigs.22 However, there are also examples of regulation regarding pig transport where sows are not considered different than the other types of pigs (eg, in the European Union23).
It is clear from the above that care must be taken when managing cull sows from farm to slaughter. In this light, it may seem paradoxical that only few studies have focused on the different aspects of the pre-slaughter logistic chain for sows, and that science-based guidelines for drivers, farmers or veterinarians in this area are scarce.
The aim of the present study was to describe different aspects of the management of cull sows on the day they are sent to slaughter in Denmark, including the use of pick-up facilities and the assessment of fitness for transport. This knowledge was achieved by the use of an online questionnaire distributed to all pig farmers sending sows to the largest commercial sow slaughterhouse in Denmark.
Materials and methods
The target population was sow herd owners in Denmark, of which there are approximately 1200.24 An invitation to complete the questionnaire was emailed to all farmers that deliver sows for slaughter at Danish Crown (Danish Crown, DK-8900 Randers, Denmark) (n=885), which is the largest slaughterhouse accepting sows, slaughtering approximately 6200 sows/week. The invitation explained the background and purpose of the study, guaranteed confidentiality and included a link to the survey (SurveyXact, Ramboll, Aarhus, Denmark). The invitation was sent to the farmers from the Pork Cooperative Supply of Danish Crown, but otherwise the company did not have any influence on the choice of or formulation of the questions. No reminders were sent to non-respondents.
The questionnaire (shown in table 1) consisted of 18 closed and a few open questions. Here, we report the results of the closed questions, of which the initial four were demographic focusing on age, gender, experience and role at the farm. As part of the development of the questionnaire, it was tested online by two pig farmers. The estimated time to answer the questionnaire was less than 10 min.
The results of the questionnaire survey were subjected to descriptive statistical analyses and presented as proportions of answers, means, and when applicable the variability was expressed as SD or ranges.
Demographic information about the respondents
In total, 360 farmers answered all questions (response rate 41%) and were included in the study. Of the respondents, 94% were men, and the mean age was 50 years (SD: 9; range 24–76 years). Among the respondents, 94% were herd owners, 4% were managers, 1% spouses of herd owners and 1% employees. Almost all respondents (94%) had more than 10 years of experience, 3% answered that they had 6–10 years of experience, 2% had 1–5 years of experience and only 1% had less than 1 year of experience.
Frequency of and number of sows sent to slaughter
When asked about the frequency of sending sows to slaughter and the number of sows sent the last time, answers were relatively heterogeneous. Thirty-three per cent of the respondents reported sending sows to slaughter once a week, 42% every other week and 25% less often. Only one farmer sent sows more than once a week. The number of sows sent to slaughter the last time varied considerably from 0 to 75 with a mean of 11 (SD: 9). Farmers reporting 0 sows may have sent gilts or boars, or may have skipped one shipment of sows from their pre-agreed contract with the slaughterhouse to send sows regularly.
Fitness for transport
The farmers were asked about the main conditions causing doubt about fitness for transport of their sows, choosing between 11 options, where they could select as many as they liked. The last option was ‘other’ allowing the respondents to write their own suggestions. As can be seen from figure 1, lameness (80%) and shoulder ulcers (47%) were the most frequently selected options. The 19 respondents (5%) answering ‘other’ mentioned the following conditions: Actinomycosis in udder (where slaughter is recommended by the industry to limit spreading of the pathogen), hoof abscesses, healed shoulder ulcers, sore legs, foul smell, swelling around ear tag and crooked legs. Six respondents reported that they rarely or never experienced doubt and two reported that all sows (or nearly all sows) from their farm could be slaughtered.
Table 2 lists how often the respondents experienced that a driver or the veterinarian at the slaughterhouse rejected one of their sows due to poor fitness for transport. If a driver rejects a sow, she will be killed on farm or kept in a hospital pen to recover and regain fitness for transport. If the veterinarian rejects a sow, she will be killed on the ramp of the slaughterhouse and the farmer and/or driver will be legally charged for transporting an unfit animal. The farmers that had sows rejected by either drivers or veterinarians at the slaughterhouse were asked about the conditions causing the rejections. The proportion of respondents reporting each of the 11 options is shown in table 3. Lameness and shoulder wounds were the main reasons, but sows who were too thin was also mentioned by 11% of the farmers as a reason for sows being rejected by veterinarians at the slaughterhouse.
According to Danish law, sows that are slightly injured or slightly sick can be sent to slaughter, but then require special conditions during the journey, for example, the use of extra bedding and partitions to separate them from the rest of the load. The farmers were asked how often their sows were transported under special conditions. Among the 360 respondents in this survey, 50% never used this option, 24% used it but less than once per year, 18% used it no more than once per year, 7% used it more than once per year and only 1% used it at least once per month. Farmers were also asked about whether such special conditions would benefit some sows. Here, 45% of the respondents answered that some sows would benefit from this type of transport, whereas 55% answered that no sows would benefit.
On-farm management of cull sows
The farmers were asked what actions they would typically take in cases where sows were in a condition where the farmer was not certain if the sow was fit for the intended transport to slaughter (table 1). The farmers could choose between five different options and could select more than one option. Here, 34% of the respondents selected two and 30% selected three options. Killing sows on-farm when in doubt about their fitness for transport was selected by 54% of the respondents, 59% placed sows in a hospital pen to recover, 54% consulted their veterinarian and 43% waited until the next delivery, hoping that the sow’s condition would have improved. None of the respondents selected the ‘I send them anyway’ option.
Typically, the commercial truck picking up the sows visit more than one herd on the way to the slaughterhouse. Hence, sending sows to slaughter is a hazard in terms of biosecurity and farmers may use different types of pick-up facilities, aiming to limit the contact between the driver and his vehicle (often filled with sows from other herds) and their own herd. Typical facilities are a designated pen in a special part of the barn or a stationary vehicle kept outside the buildings. When asked what kind of pick-up facility they used, the most frequent answer was a stationary transfer vehicle (76%). A room at the farm designated for pick-up was used by 16% of the respondents. A few farmers used an outdoor pen or other facilities depending on whether they were first on the route of the truck or not. A single farmer answered that he drove the sows himself.
The reported waiting time in the pick-up facility is shown in table 4, split according to whether the respondent used stationary transfer vehicles (n=275) or a designated pick-up room (n=58). The rest of the categories (outdoor pen or other facilities) were left out due to low representation. When using stationary transfer vehicles, the majority of the farmers reported waiting times of less than 30 min and less than 3% reported waiting times exceeding 1 hour. Among farmers using designated pick-up rooms, 27% reported waiting times exceeding 1 hour.
The next question focused on the provision of resources for the sows while they were waiting to be picked up by the truck. In table 5, we report only answers from respondents that used a stationary transfer vehicle or a designated pick-up room. In the stationary transfer vehicles, provision of bedding, cover/roof and partitions was reported by more than half of the farmers, while water was only reported by 4%. In the designated pick-up rooms, provision of partitions was the resource most often reported (by 62%), whereas the reporting of none of the other options exceeded 50% (table 5).
The farmers were asked to what extent they believed that weather conditions could affect the behaviour of the sows while they were waiting to be picked up and/or during the transport. Across all respondents, 22% answered that the weather did not have any influence at all, 59% that the weather could have a slight influence, 14% that it had some influence and 5% answered that the weather had large influence on the behaviour of the sows while waiting to be picked up and/or during the transport.
The aim of this study was to describe management of Danish cull sows on the day the sows are sent to slaughter, including pick-up facilities and the evaluation of fitness for transport. This knowledge was obtained by use of an online questionnaire distributed to all pig farmers sending sows to the largest sow slaughterhouse in the country. Overall, the results suggest that how sows are managed and sent to slaughter seems to be somewhat variable. For instance, in terms of frequency and number of sows sent, available resources in the pick-up facility and in terms of actions taken when farmers were not certain about the sows’ fitness for transport. Despite the large variation in the number of sows sent per week and farm, the mean number was relatively low, which highlights the need for a truck to visit more than one farm on the way to the slaughterhouse. In the present study, farmers were not asked whether they experienced doubt about fitness for transport, but were asked about clinical conditions underlying their potential doubt. In addition, the results clearly showed that special condition transport was reported to be used only rarely, and that rejection of sows due to lack of fitness for transport, by drivers or veterinarians at the slaughterhouse, was only rarely experienced.
Despite the respondents being a homogeneous group (experienced, middle-aged, males) their answers were not homogenous at all and show that different management strategies are used. The phase of sow production covered by this study—the cull phase—has received limited research attention except for studies about the economic aspects of culling strategies.3 7 14 As we will argue further below, future studies should examine whether certain types of management of cull sows can be recommended in terms of animal welfare, productivity and/or biosecurity.
The actions typically taken by farmers in cases of uncertainty about the fitness for transport of a sow varied considerably. This aspect of cull sow management clearly involves dilemmas in terms of productivity and animal welfare (as discussed by Cockram17). In the present dataset, 54% of the respondents reported to kill sows on farm if the fitness for transport was questionable. Knowing that the clinical condition of cull sows may deteriorate during transport to slaughter,19 this choice seems advantageous from an animal welfare point of view. However, if the condition of a given sow does live up to the legal requirements for fitness for transport, killing her on farm may be considered an ethical problem due to the human food wasted,25 as well as an economic problem for the farmer. Recently, the possibility for on-farm emergency slaughter26 or the use of smaller-scale mobile slaughter facilities27 have been suggested to be an alternative to transport to slaughter for compromised dairy cows, but to the best of our knowledge, no such development is taking place regarding the slaughter of cull sows.
As an alternative to on-farm killing of sows where fitness for transport was questionable, 59% of the respondents reported that they used designated hospital pens, thereby allowing the sows to recover and be slaughtered later on. This choice may be advantageous in terms of animal welfare (the sow is not transported until she is fit for the intended journey), and productivity (the meat will be used for human consumption). It is however, noticeable, that 43% of the respondents stated that they waited until the next shipment to see if the sow had regained fitness, and 30% answered ’yes’ to all these three options. Hence, most farmers chose more than one option, and at present the underlying reasons behind these are not clear. Only recently, the special needs of sick pigs, and the potential advantages from the use of hospital pens have received scientific attention.28 29 At present, the reported choices of the farmers cannot be evaluated, and studies are needed to clarify these areas, especially for clinical conditions typically reported in cull sows such as lameness, prolapses or shoulder ulcers.
Unexpectedly, only 19% of the farmers responded that they believed that the weather had moderate or major influence on the behaviour of the sows while waiting in the stationary transfer vehicles or during transport. In addition, only 4% of the 275 farmers using stationary transfer vehicles and 48% of the 58 farmers using designated pick-up rooms reported that they offered the sows access to water while waiting. None of the respondents reported ‘ongoing lactation’ as a clinical condition causing doubt regarding fitness for transport even though lactating females show increased sensitivity to heat stress.10 Based on recent evidence from Thodberg et al, 19 temperature seems to be a risk factor for the deterioration of the clinical condition of cull sows during transport to slaughter. Similarly, hyperthermia has been suggested to be among the main reasons for cull sow mortality upon arrival to slaughterhouses.12 If larger studies conducted under conditions relevant for Danish pig production involving use of pick-up facilities and transport can confirm the negative effects of high ambient temperatures, there seems to be a need to pursue this research area to solve this welfare challenge, for example, by provision of water. Based on the responses of the farmers in the present study, it may be advisable to suggest to farmers that they pay attention to the weather, the provision of water during longer waiting periods before pick-up and the increased risk of heat stress in lactating sows, when it is decided which sows to send to the slaughterhouse on a given day.
One clear finding of the present study was that the rejection of sows due to lack of fitness for transport, by drivers or veterinarians at the slaughterhouse, was only rarely experienced. Hence, despite earlier reports on relatively low agreement between drivers, farmers and veterinarians in terms of assessment of fitness for transport in cull cows,30 the present results suggest that the assessment of fitness for transport in cull sows are aligned across these professional groups.
When in doubt about fitness for transport, the respondents most frequently reported lameness as the underlying clinical condition. Additionally, lameness was reported as the condition most often leading to rejection of sows by drivers of pig trucks and veterinarians at the slaughterhouse. In a recent Canadian review on fitness for transport in livestock (covering pigs, cattle, horses and sheep), evaluated by the Canada Agricultural Review Tribunal following enforcement action by authorities due to non-compliance with local regulation for fitness for transport, lameness in pigs is the most frequently reported cause of rejection as well.17 In the European regulation for animal transport, it is stated that ‘Animals that are injured or that present physiological weaknesses or pathological processes shall not be considered fit for transport and in particular if they are unable to move independently without pain or to walk unassisted’.23 In Denmark, the recent guidelines from the Danish Veterinary and Food Administration regarding fitness for transport of cattle and pigs state that ‘Animals that walk normally and take support on all four legs are fit for transport. Animals showing signs of minor lameness and/or walking impairment may only be transported if they are not experiencing further suffering during the journey. These animals should be transported under special conditions, such as the use of extra bedding, short journeys, direct transport to destination or while segregated from other animals. Animals that cannot walk unsupported or are severely lame or showing severe walking impairment cannot be transported’ (translated from Danish31). Even though it may seem relatively simple to recognise these categories, a recent study among farmers, veterinarians and drivers of cattle trucks, showed limited agreement in their evaluation of lameness in cows shown on video clips—within as well as across professional groups30). Such lack of alignment in the assessment of the walking ability of sows might explain some of the situations reported in the present study, where sow farmers experienced rejection of one of their sows. However, increased gait score has been reported in cull sows after transport to slaughter19 as well as after a 24-hour stay in a designated pick-up room.32 Despite being statistically significant, these changes were minor, but it cannot be excluded that the sows reported as having been rejected by drivers or veterinarians at the slaughterhouse, had changed their walking ability during the waiting in the pick-up facilities or during transport. Future studies of experiences from drivers of sow trucks (they are the only professional group seeing the animals both before and after transport) may clarify this.
Not only lameness but also shoulder ulcers created doubt about fitness for transport (mentioned by 47% of the respondents) in the present study. Shoulder ulcers are pressure sores commonly observed in the shoulder region of lactating sows kept in farrowing crates.33 34 The lesions are most likely painful.35 36 Danish regulation regarding the acceptance of sows with shoulder ulcers for transport is based primarily on the diameter of the lesion, which can be evaluated using a simple meter giving clear indications as to whether a given shoulder ulcer is negligible, minor or major, and only sows with major ulcers are considered unfit for transport.37 Recently, Thodberg et al 19 reported that shoulder ulcers in cull sows changed clinically (reddening and increased bleeding) after transport to slaughter, and such changes may underlie the doubt of the farmers. However, in the data presented by Thodberg et al,19 none of the involved shoulder ulcers evolved from subclinical to clinically evident, and only relatively mild deteriorations in their clinical appearance were reported.
One area in the present questionnaire survey where answers were almost dichotomous was the question about potential advantages of special condition transport. Here, farmers answered almost 50:50 yes or no to the possibility for some sows benefitting from the use of separation from other sows. Recently, Cockram17 reviewed the scientific literature on fitness for transport in livestock, and stated that the effectiveness of the mitigation measures to avoid additional suffering likely to be associated with transport of a compromised animal are questionable, and that there are different views about the types of conditions that constitute a compromised animal.
The mean number of sows reported to be sent from each herd, and thus the need for the commercial trucks to visit more than one herd on the way to the slaughterhouse emphasises the hazard of sow transport in terms of biosecurity. In the present study, farmers were not directly asked about biosecurity initiatives (as done by eg, Oliveira et al 38 39). Almost 80% reported to use a stationary transfer vehicle to deliver their sows, thereby limiting the biosecurity hazard, because the truck (carrying driver and animals from other herds) did not come near the buildings of the farm or the staff. The use of stationary transfer vehicles has received very limited scientific attention. In addition, it is not clear what these transfer vehicles mean in legal terms as they are not commercial trucks for the journey to the slaughterhouse but at the same time not permanent housing either. Consequently, a stay in a stationary transfer vehicle (if less than 2 hours) is not included in ‘transport duration’ according to Danish regulation.16 Even though most of the respondents in the present study reported relatively short stays in the transfer vehicles, it is worth noting that we previously reported a high occurrence of fighting and a very limited occurrence of resting for sows kept in stationary transfer vehicles for as short as 5 min.40 The available knowledge regarding the use of this biosecurity tool is very limited, and at present potential consequences of a stay in such a vehicle in terms of animal welfare or productivity are not known.
In conclusion, this paper is the first to report on different aspects of the management of cull sows on the day they are sent to slaughter, including the use of pick-up facilities and the evaluation of fitness for transport. Overall, different management strategies of cull sows were used. The present findings may be used for formulation of hypotheses for future studies in this area and potentially lead to science-based recommendations relevant for animal welfare, productivity and biosecurity.
The authors wish to thank Marie Gry Bodenhof Hansen and Hans Jørgen Tellerup, Danish Crown, for assistance with the distribution of the questionnaires to the farmers. In addition, we thank the two anonymous farmers, who tested an initial version of the questionnaire and all respondents for their cooperation and time.
Funding This study was supported by a grant from the Danish Green Development and Demonstration Program ’SOTRANS – Optimized transport of cull sows – improved animal welfare and meat quality’ (Journal number 34009-17-1284) and a grant from the Danish Pig LEVY Fund.
Competing interests Danish Meat Research Institute receives financial support from the Danish Meat Industry, but with no direct link to or influence on the current work.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Access to data can be granted after request to first author.
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