FARROWING BEHAVIOR AND STILLBIRTH IN 2 ENVIRONMENTS - AN EVALUATION OF THE RESTRAINT-STILLBIRTH HYPOTHESIS

A total of 59 farrowings were studied in either a conventional, narrow farrowing crate (0.43 m wide) or a much wider alternative design with sides spaced 1.2 m apart at the sow's standing height but narrowing n ear the floor to limit the sow's lying area. Using video recording, we monitored each ''birth interval'' (i.e. the period between two succes sive births) and noted the interval's length, the sow's posture and po stural changes during the interval, and whether the interval ended wit h a live-born or stillborn piglet. The wide and conventional crates di d not differ significantly in median interval between piglets (15.9 ve rsus 16.0 min, respectively), incidence of stillbirth (5.8 versus 7.0% ), in any measures of posture or postural change, or in piglet surviva l and weight gain to 3 days of age. Sows were most active during the f irst two birth intervals; as farrowing continued they made progressive ly fewer postural changes and spent more time lying. Sows differed gre atly in the frequency of postural changes and the time they spent in d ifferent postures; however, these measures were largely unrelated to s tillbirths, except that stillbirths were rare if the sow sat during mu ch of the interval (P < 0.001). Birth intervals were longer, on averag e, before a stillbirth (median of 34 min) than before a live birth (13 min; P < 0.001). The greater incidence of stillbirths late in the far rowing was associated with a greater proportion of long birth interval s late in the farrowing, and greater likelihood of stillbirth even for shorter and medium intervals. Stillbirths were more common in longer farrowings (P approximate to 0.01). evidently because these tended to involve larger litter sizes and more long birth intervals of over 60 m in. However, the proportion stillborn in a litter was not correlated w ith median birth interval. The results of this and related studies sug gest that greater freedom of movement in the farrowing environment doe s not consistently produce shorter duration of farrowing or a lower in cidence of stillbirth. Published by Elsevier Science Ltd.