|dc.description.abstract||In comparison to grower/finisher pigs, relatively little is known about the effects of space allowance on nursery pigs. Because nursery pigs overlie, it has been hypothesized that the relative space allowance (k value) which is appropriate for finishing pigs may overestimate the requirements of nursery pigs. Therefore, the objective of this study was to determine the effects of space allowance on piglet behaviour, growth, and welfare. The study was completed in four blocks over four seasons using 1200 newly weaned pigs. Pigs were housed at six space allowances (k values: 0.0230, 0.0265, 0.0300, 0.0335, 0.0370 or 0.0390), in groups of 10 or 40 pigs/pen. All pigs were weighed weekly, and pen size was adjusted based on the predicted average body weight of pigs the following week. Overhead cameras were used to record group behaviour for eight hours on one day in weeks one, three and five. The percentage of animals standing, sitting, feeding, lying (sternal or fully recumbent) and overlying was recorded at 30 min intervals. The behaviour of four focal piglets per group (all female) was recorded continuously using the same footage as described for group observations. Videos were observed continuously for eight hours per day to measure feeding and drinking behaviour in focal pigs in weeks one, three and five. Salivary cortisol samples were collected from focal pigs in weeks one, three, five and six.
The results were analysed using Proc Mixed and Proc Glimmix procedures in SAS (9.4) with fixed effects of density, group size and week. Overall, growth (ADG) and G:F ratios were not affected by changes in space allowance. Although there tended to be an effect of space allowance on ADG in week five (P = 0.054), no clear relationship to changes in space allowance was observed. Pigs were observed sitting more (% frequency of observations) at lower space allowances (frequency of observation (%) sitting: k = 0.0230: 43.54% vs. k = 0.0390: 31.18%. SEM = 4.05, P = 0.004). Fully recumbent lying is known to be a more restful posture and was higher at higher space allowances frequency of observation (%) fully recumbent: k = 0.0230: 49.13% vs k = 0.0390: 53.88%. SEM = 5.01, P = 0.049). As pigs aged the frequency of standing, sitting and feeding behaviours increased over time (P < 0.05). Pigs spent more time overlying in week one than in weeks three or five (P < 0.001). Space allowance had a significant effect on feeding behaviour time budgets, with pigs at lower space allowances eating more meals per day, but of shorter duration than those given higher space allowances (average bout duration: k = 0.0230: 76.8 s vs k = 0.0390: 99 s. SEM = 0.02, P = 0.003). Pigs at low space allowances also spent less time feeding compared to those at higher allowances (total feeding duration: k = 0.0230: 45.99 vs k = 0.0390: 50.83 min. SEM = 0.04, P = 0.038). The number of drinking bouts/day was highest at the lowest space allowance, while mean duration of drinking bouts was highest at the highest space allowance (drinking bouts per day: P = 0.037, average bout duration: P = 0.002). Group size had a significant effect on feeding bouts/day and drinking behaviour. Pigs in groups of 10 ate fewer meals but tended to have longer meals (Feeding bouts/day: P = 0.026; Average bout duration/min; P = 0.071) and pigs in groups of 40 spent more time drinking with longer bouts (P <0.01 for total drinking duration and drinking bouts/day). Salivary cortisol levels were also affected by space allowance, with pigs at higher space allowances having significantly higher cortisol levels (P = 0.025; SEM = 0.03), possibly because of higher activity levels.
In conclusion, although there was no effect of space allowance on production performance, reductions in space resulted in pigs changing resting (fully recumbent lying) and sitting postures which are related to space sharing and welfare. Moreover, lateral recumbency increased and overlying reduced over time, which suggests that effects of space restriction are greatest as pigs approach nursery. Therefore, on the basis of postural changes, the hypothesis that nursery pigs require less space than grower/finisher pigs due to overlying are not supported.||