Drafts and nesting behaviour
A good straw bed inside the farrowing ark is the most crucial element to achieving a low pre-weaning mortality outdoors. The bed should be high enough to exclude draughts, be flat so as not to impede the piglets’ movement, dry to prevent chilling and straw not too long so piglets do not become entangled. The sow has to have enough good quality bedding material to make a satisfactory nest. If the ark is not well sealed the sow will not establish a good nest as it cannot find a comfortable and sheltered space.
There are two phases to nest building: in the first phase the sow digs a hole and in the second phase it covers the edges and fills it with nesting material. The start of the second phase is determined by the availability of suitable material and the more material available the sooner the nest building is completed (Wischner et al, 2009).
Observational studies have shown that a sow that has not been able to establish a nest to its liking before farrowing will continue the nest building behaviour during the farrowing process, resulting in 16 changes of posture during farrowing compared to 5 changes for sows which have been able to make an adequate nest. Sows given 2kg of straw per day from d.113 of pregnancy spent more time nesting if they were housed in pens than those in crates. The sows in crates also showed higher frequency of quick flops (letting hind quarters fall after kneeling as opposed to lowering down vertically or slightly inclined) after farrowing than those in pens (Andersen et al, 2014). Sows kept in open crates with access to nesting material had higher levels of oxytocin and prolactin 3d before farrowing than those in crates or in open crates with access to sawdust (Yun et al., 2014). Sows in farrowing pens and freedom farrowing pens had shorter farrowing duration and piglet birth intervals than those in crates (Gu et al, 2011).
It is important sows are calm during farrowing and in the following days. Farrowing paddocks tend to be visited once to feed and then, only those paddock with sows recently farrowed or due to farrow, maybe once more. On indoor farms it is not uncommon for farrowing houses to turn into transit points or storage areas and for rooms to be visited often to supervise farrowings, sometimes in a hurry between other jobs. Stress is an antagonist to hormones that support the farrowing process and milk let down (increased caesareans following greater medicalization of the birthing process is well documented in humans (Johanson et al, 2002).
Piglets in the wild learn what they can eat by observing the sow. With feed troughs placed above ground level in farrowing crates to provide the sow sufficient lying space and separate creep dishes for piglets this behaviour is not encouraged. Piglets only start seeing what the sow eats once they are big enough to jump into the trough. On outdoor farms sows are fed in barrels or hoppers which allow the piglets access as soon as they are big enough to leave the farrowing arc. Encouragingly there have already been some trials with two sided sow troughs that allow the sow to eat out of one side and the piglets from the other.
Relationship with the stockworker
If you approach a group of outdoor sows calmly it is not unusual, after a first cautious reaction, for them to approach you to interact and after follow you around the paddock. When there are no corridors or passageways, no solid walls or crates it is practically impossible to make a 200kg plus sow do anything it does not want to. As a consequence, the relationship between the animal and the stockworker is different to that on many indoor units. Positive reinforcement in the way of treats of fee is used to move sows and it is not advisable to try and hurry them in case they scare and bolt, taking with them any electric fencing in their path and, in the worst case scenario, starting a stampede.
Regular positive handling is required to reduce fear responses in pigs and months of positive behaviour is required to reduce fear levels in animals experiencing high levels of fear (Coleman et al, 2000).
Grouping of sows and flight zone
Outdoor dry sows are usually kept at 10 sows per acre (25 sows per hectare) in groups of up to 25-30 sows per paddock. Groups tend to be made at weaning and all attempts are made to not modify them until farrowing and certainly not before 8 weeks in pig. Sows are grouped by parity and size, whenever possible keeping gilts and second parity sows separate. Large groups and dynamic groups are sometimes used but these do not usually appear as calm and settled. Though aggression is not eliminated completely, the extended flight zone in the large paddocks tends to prevent severe bullying and serious body lesions. Dry sow accommodation in intensive systems tends to provide space as dictated by legislation. Obviously the same amount of space cannot be provided indoors, but it can be designed to offer "hiding places" for submissive sows and avoiding dead ends where sows can become trapped between a wall or fence and a dominant sow.