4 Dec 2015
Jim Clapp
Job Title
The detection of disease and compromised welfare in growing pigs is becoming more acute because of further intensification restricting the frequency of direct observation, farm animal welfare concerns of the public, and the drive to reduce drug-dependent production.
Subclinical disease is the main cause of economic loss from suboptimal growth rate (Cornou and Kristensen, 2013), while tail biting and fighting injuries from poor welfare (Sonoda et al, 2011) also cause major losses from carcase downgrades and deaths (Valros et al, 2013).
Early detection of clinical or subclinical disease and compromised welfare would allow timely action to be taken, saving money and suffering. Changes in behaviour, described as sickness behaviour (Dantzer, 2004), occur in both frank illness and subclinical disease states in all animals, providing evidence that detailed monitoring of pig behaviour could detect health problems (Berckmans, 2013).
An important characteristic of sickness behaviour is how it reduces a pig’s motivation to be active through suppressing hunger, social, competitive and inquisitive behaviours (Dantzer, 2004), while the diametrically opposite behaviours of hyperactivity and frenzy are the hallmark of tail biting and fighting (Statham et al, 2009).
Studies of normal fattening pigs have shown them to be inactive for 70% of the day, with several active bouts, constituting a mixture of exploratory (15%), feeding (7%), social (7%) and drinking (1%) behaviours (Maselyne et al, 2014).
Research using automated video tracking and digital image analysis of pig activity to detect such changes (Ott et al, 2014; Costa et al, 2014) are problematic in terms of validation, the high equipment costs and its vulnerability to damage from the hostile indoor pig environment (the pigs, dust, ammonia and mice). Thermal imaging to detect fevered pigs (Figure 1; Cook et al, 2015) and microphones for coughing (Exadaktylos et al, 2008) are also prospective technologies yet to be commercially realised. Metering water consumption has shown promise, but is limited to only one aspect of sickness behaviour, while measuring food consumption is similar, but also entails more complex and expensive systems.
Here, a simpler solution is proposed using widely available personal fitness pedometers. But rather than being worn by the pigs, and risk them being eaten, they should be attached (out of reach) on an enrichment toy in the pig pen. Such toys, typically a length of plastic pipe, are common following an EU commission directive (2001/93/EC) requiring pigs to have access to material to enable investigation and manipulation activities (Studnitz et al, 2007).
To model an infection in the pigs, a Glässer’s disease vaccine was administered, which caused a transitory fever (+2°C) with a concomitant drop in water and food intake. This resulted in a significantly reduced total activity (steps) that day (Figure 4).
As an improved refinement, a different pedometer, the Fitbit Zip was selected because the Omron was limited to being read manually and only recording daily totals over seven days (Figure 5). The Fitbit Zip had the advantage of wireless connectivity from outside the pig shed, so avoided disturbing the pigs. Data storage and collection was achieved by online syncing with the Fitbit cloud service. The data graphically presents the toy movement at five-minute intervals and daily totals. Such resolution clearly showed the change in normal daily activity patterns and total daily activity disrupted by vaccine-induced illness.
The pigs showed the typical diurnal pattern of inactivity overnight, even when lights were inadvertently left on. Day activity was restricted between 7am and 7pm, generally with an inactive rest period around noon.
Although hyperactivity from fighting and tail biting were not recoded, an alternative “model” for such activity was successfully created by giving the pigs newspaper to rip up (www.youtube.com/watch?v=dGu0Te3_xmk). A significant increase in recorded pen activity was shown when newspaper was given to pigs at noon, which is usually a low activity time of day (Figure 6).
The pig pen activity recorded using this technique constitutes a combination of active investigation of the enrichment toy and passive movement from pigs knocking it on passing. The toy is best located where the pigs rest – away from water, feed and dunging areas. Pigs often play with the toys while sitting or lying. In larger pens (more than 30 pigs) several enrichment toys can be spread throughout the pen, with a “spider’s web” arrangement linking them to a central activity meter. Toys should be at snout level, but kept clear of the ground to avoid soiling, as faeces makes them unattractive to pigs (Studnitz et al, 2007).
As pigs show a high degree of individual behaviour, each pen of pigs will have a unique activity pattern, making between-pen comparisons inappropriate (Maselyne et al, 2014). However, by monitoring each pen separately, any day-to-day changes in activity will alert farm staff to the potential start of disease and compromised welfare – warranting closer inspection.
The Fitbit Zip can be calibrated to report, via email or text, reduced or increased daily activity using specific thresholds, set appropriately for the pen being monitored – the detection of below threshold activity signifying sickness behaviour, while elevated activity signifying fighting or tail biting.
A refinement that may prove valuable is where daily activity is divided into minutes spent sedentary or in light, moderate or intense activity. Furthermore, such information can be remotely password-accessed by farm and veterinary staff via the Fitbit cloud.
It is proposed the combination of encouraging pig farmers to use enrichment toys, and this relatively cheap and simple method to monitor pig activity, has great potential to both improve welfare and alert farm staff to compromised health and welfare in fattening pigs.
The author wishes to thank Jennifer Murray and Mark Brett of Newcastle University, and Nigel Woolfenden of RAFT Solutions, for their expert help and advice, Newcastle University for providing the pig unit and Innovate UK for funding.
