Incidence of dystocia at piglet level in cloprostenol-induced farrowings and associated risk factors

Abstract

Few studies have investigated risk factors for dystocia in swine, although this birthing abnormality can compromise welfare of both sows and piglets by increasing stillbirth rate and decreasing sow productivity. This study aimed to determine risk factors associated with dystocia at piglet level in cloprostenol-induced farrowings. A dystocia event was recorded when a birth interval exceeded 45 $\min$ or when manual extraction was applied. Data were collected from 898 piglets born from 77 Landrace $\times$ Yorkshire crossbred sows, which were induced for farrowing on day 114 of gestation. Generalized linear mixed models (GLMMs) were used to evaluate the association between dystocia and parity, gestation length, litter size, relative birth order (RBO (%) $=$ 100 $\cdot$ birth order/litter size), birth weight, crown rump length, body mass index, ponderal index, piglet's sex, use of oxytocin, and stillbirth. Sows nested in farrowing batches were fitted as random factors in GLMMs. Incidence of dystocia at piglet and farrowing levels was 11.0 % and 75.3 %, respectively. The final multivariate model explained 20.1 % variation of dystocia. RBO had a quadratic effect on dystocia in which incidence of dystocia decreased from RBO $\le$ 40 % to RBO $=$ 60 %-70 %, and then increased to the end of parturition. Piglets with birth weight $>$ 1700 $g$ and stillborn piglets had higher odds of dystocia in comparison with piglets with a birth weight of 900-1700 $g$ (OR $=$ 2.63; 95 % CI $=$ 1.66-4.18) and live-born piglets (OR $=$ 2.62; 95 % CI $=$ 1.12-6.15), respectively. This study indicates that dystocia is very common in cloprostenol-induced farrowings and suggests that the last one-third of parturitions is the most important stage to be supervised, and selection for homogenous litters and moderate high birth weight may reduce the rate of dystocia.