Limited information is available about risk factors for dystocia in sows, especially in free farrowing systems. A study by S. Gimmel, H. Nathues and A. Grahofer, University of Bern, Switzerland, investigated the influence of sow traits on dystocia in free farrowing systems. The findings were presented at the 11th International Conference on Pig Reproduction, Belgium, 2023.

In this study, 156 crossbred sows were evaluated for backfat thickness, body condition score, and fecal score. In addition, the farrowing process and litter parameters were monitored.

A dystocia event was defined as a piglet-to-piglet birth interval exceeding 60 minutes or sows needing obstetrical intervention. During obstetrical intervention the position, the posture and size of the piglet, the obstruction of the birth canal and the number of uterine contractions were evaluated.

Dystocia was observed in 59 out of the 156 sows evaluated (37.8%). In 27.1% of these sows the cause for dystocia was unknown, while in 23.7% an abnormal position or posture of the piglet was detected, followed by 16.9% uterine inertia and oversized piglets, 15.3% combination of at least two causes and 13.6% obstruction of the birth canal, the researchers said.

Sows requiring obstetrical intervention had significantly longer piglet-to-piglet intervals (25.0 ± 11.8 min vs. 14.9 ± 5.5 min, p < 0.001) and lower backfat thickness (14.9 ± 4.4 mm vs. 16.4 ± 4.0 mm, p = 0.030) than sows not requiring obstetrical intervention.

In addition, sows that expelled the first placental part before the last piglet needed significantly more obstetrical interventions (0.5 ± 0.5 vs. 0.1 ± 0.4, p < 0.001) and had a higher percentage of stillborn piglets (6.5 ± 7.5 vs. 3.7 ± 4.7, p = 0.034), than sows with normal placental expulsion.

This is the first study evaluating risk factors for dystocia in sows accommodated in a free farrowing system. The expulsion of the first placenta and backfat thickness seem to be reliable risk parameters. In addition, the causes and risk factors can also be extrapolated for crated sows, the researchers concluded.

Incorrect progesterone to estrogen ratio

A switch in the progesterone to estrogen ratio at the beginning of parturition is necessary for an increased expression of oxytocin receptors and for myometrial contraction. An incorrect estrogen/progesterone ratio can result in dystocia in sows. Therefore, non-invasive methods are needed to evaluate the hormone status of a sow under practical conditions. Fortunately, the hormonal levels of sows can be detected in the colostrum.

A study by L. Käser, H. Nathues, R. Bruckmaier and A. Grahofer, University of Bern, Switzerland, evaluated the relation between colostrum traits and the farrowing process of sows in free farrowing systems. The findings were presented at the 11th International Conference on Pig Reproduction, Belgium, 2023.

In total, 61 crossbred sows were included in the study. Immediately after the birth of the first piglet a colostrum sample (5 -10 mL) from the first teats was collected. Progesterone, serum albumin and alpha-lactalbumin levels of the colostrum samples were measured in the defatted colostrum samples (colostrum serum). In addition, the farrowing process was monitored, and litter parameters were assessed.

Overall, the median parity of the sows was 3 (minimum 1, maximum 11) and the mean litter size was 15.1 ± 3.8. The birth duration of piglets (first-last piglet) was 241 ± 129 minutes, the mean total farrowing duration (first piglet-last placenta) was 529 ± 276 minutes and placental expulsion duration (first-last placenta) was 353 ± 265 minutes.

The mean progesterone level was 21.9 ± 10.9 mg/mL, the serum albumin was 7.4 ± 1.5 mg/mL and the alpha-lactalbumin concentration was 1.78 ± 1.23 µg/mL.

Colostrum progesterone and the birth duration of piglets were positively correlated (r = 0.30; p = 0.02), as was progesterone with total farrowing duration (r = 0.26; p = 0.04) and the placenta expulsion duration (r = 0.27; p = 0.03).

In addition, progesterone was positively correlated with serum albumin (r = 0.30; p = 0.01) and alpha-lactalbumin (r = 0.41; p < 0.01). No reliable cut-off point for progesterone for the tested parameter could be detected.

This is the first study that evaluated the correlation between specific colostrum traits and the farrowing process in free farrowing systems. The progesterone level in the colostrum could be a parameter to identify sows which are at risk for a prolonged farrowing duration. However, further studies are needed to define a valuable cutoff point for progesterone from the colostrum.