Assessing Sow Preference for Scratching Enrichment and Effectiveness in Farrowing Crates

Effective enrichments for farm animals are increasingly important to address public concerns about farm animal welfare and improve the welfare of the animals we raise. The public’s concern has increased in recent years as the management and care that farmers give their animals has become more apparent to them. Some of the conditions in which animals are kept are emotionally not appealing to the public. One such condition is farrowing crates for sows and piglets. The sows are confined in a small space with no social contact and cannot perform nesting behaviors. Farrowing crates are widely used though, as they allow farmers to handle piglets without fear of sow aggression, meet individual sow nutritional needs, and personalize care. Piglet mortality due to crushing is also decreased with crate use. Sow welfare in farrowing crates can be improved through environmental enrichments. Enrichments improve welfare by increasing species-specific behaviors, creating a more complex environment, reducing abnormal behaviors, and increasing an animal’s ability to cope with stressful situations. For pigs, different enrichments have been shown to decrease stereotypies, like sham chewing and bar biting, decrease harmful redirected behavior towards pen mates, like tail biting and belly nosing, increased exploratory behavior, and increase positive affect. Straw has been found to be the best enrichment for pigs because it allows them to perform motivational behaviors such as rooting, foraging, and nest building. It is also complex, manipulatable, destructible, and ingestible, which are important attributes of effective enrichments. Unfortunately, straw cannot be used in farms that have slurry systems, as the straw will fall through the slats into the pit below and cause drainage issues. This includes farrowing crates. There have been a few studies on alternative enrichments for sows in crates, like cloth tassels, but they are not as effective as straw and are rarely used on farm.

Most enrichments target pigs’ motivations to forage, root, graze, or build nests. Pigs perform other behaviors and may have other motivations that enrichments have not targeted yet. One such behavior is scratching. In a semi-natural environment, pigs will rub against trees and bushes. In confinement, pigs rub on fences, walls, and even allow people to scratch them with their hands. There have been no recorded studies done on scratching enrichment for pigs. Many studies have been done in the dairy industry exploring rotating brushes. These brushes have been implemented successfully on commercial farms and are used by cows to groom and scratch themselves. A similar device may allow pigs to also satisfy their itch. Our aim is to provide scratching enrichment to sows in farrowing crates. Since there have been no studies recorded on scratching enrichment or scratching in pigs in general, several steps had to take place before addressing the topic for sows in crates. The first project’s aim was to see what materials pigs prefer to scratch on and their willingness to use such an enrichment.

The first project consisted of 2 experiments. Exp. 1 was a pilot study where 5 different materials on scratch posts were presented to a pen of gestating sows. The scratch posts were constructed from polyvinyl chloride (PVC) pipes, boards, and a gate post. Five different materials were attached to the boards: white, soft, long-bristled brushes (White Brush), red, hard, short-bristled brush (Red Brush), black, short-bristled, astro-turf-like mat (Plastic Mat), colorful coir, hard, short-bristled mat (Fiber Mat), and blue, plastic, large-round-bristled combs (Plastic Combs). The 8 sows received all 5 scratch posts in their pen for a habituation day and then 7 d of testing. During testing, video was continuously recorded from which 2 behaviors were collected; scratching and interacting. Sows scratched the most on Plastic Mat followed by Fiber Mat, Plastic Combs, and Red Brush. The White Brush was scratched on the least. The top 3 preferences were chosen to proceed to Exp. 2.

Experiment 2 for sow preference was performed on several pens (N=14) of sows and gilts with Plastic Mat, Fiber Mat, and Plastic Combs to narrow the preference down to 2 materials to proceed to the farrowing crates. The experiment was carried out in repetitions. Each repetition tested 4 pens at a time. The scratch posts were modified from Exp. 1 and each material was placed in a pen. Due to material destruction only 2 repetitions were carried out, both ending a little early (N=8). During the first repetition (Rep 1), sows ate and destroyed all the Plastic Combs within 2 d. The Plastic Comb scratch posts were pulled from the study and the second repetition (Rep 2) only had the Plastic Mat and Fiber Mat represented. An observation was made that one of the pens in Rep1 had extra feed on their floor and were not destroying their materials as fast as the other pens. So for Rep 2, more modifications to the scratch posts were made and the sows were given a little extra feed. The scratch posts were still destroyed in Rep 2 proving that the sows’ hunger and motivation to perform oral manipulations overwhelmed scratching behaviors. However, from the data that was collected sows spent more time and more frequently interacted with the Fiber Mat compared to the Plastic Mat. They more frequently and spent more time interacting than scratching with the enrichments but scratched on both enrichments the same amount of time and frequency (Durations: F_1,112.6 = 13.63, P = 0.0003; Frequencies: F_1,111.9 = 19.72, P < 0.0001).

The plastic and fiber mats were presented to sows in farrowing crates for the second project by default. Sows (N=18) of parities 2 (P2) and 3 (P3) were housed for 25 d and assigned no enrichment (Control) or to a scratch pad treatment of plastic mats (Plastic) or fiber mats (Fiber). All were assessed for lesions, abnormal behaviors, eating and scratching behaviors, and time spent in different postures and behaviors. Scratching bouts occurred in short durations and were intermittent throughout the day. Parity 2 Plastic sows scratched for a longer total duration than P2 and P3 Fiber sows, P3 Plastic sows, and P2 Control sows (F_2,11 = 11.94, P = 0.002). Parity 2 Plastic sows also displayed scratching bouts more frequently than all except P3 Control sows (F_2,11 = 18.46, P = 0.0003). There were no body lesion differences between treatments (P > 0.05). Abnormal behaviors (P > 0.05) and proportion of time spent in different postures (F_2,94 = 0.0003, P = 0.999) did not differ among treatments.

In conclusion, if a sow is experiencing hunger while in gestation pens this motivation may be overwhelming any other behavior needs. Scratch posts were destroyed and eaten. In this sort of environment, focusing on an enrichment that meets the need to forage and root would be more successful. Sows still scratched on the posts, so their preference and scratching use was still recorded to an extent to proceed to the experiment in farrowing crates. In farrowing crates, plastic scratch pads may be a suitable enrichment as they increased the natural behavior of scratching and did not increase abnormal behaviors. More research is needed to refine the scratch pad design and identify additional measures needed to examine the suitability of scratch pads as a form of environmental enrichment for sows in farrowing crates. In addition, the behavioral characteristics and sows’ underlying motivation for scratching need to be studied because very little is known about scratching behavior of sows. If sows are motivated to scratch, and scratching helps improve their welfare, then scratching enrichment may be beneficial to sows and farmers.