Effects of electrical stimulation on the behavior and production performance of postpartum sows

Electrical stimulation has emerged as a promising technique to save crushed piglets. But only the individual parameter of electrical stimulation was considered in the excessive response of sows. In this study, a systematic investigation was conducted to determine the response of the effectiveness and startle index of sows under different body positions and stimulated voltages. An evaluation was made to clarify the electrical stimulation on the production performance of sows. The field experiment was conducted at a farrowing house in Shandong Province, China, between November and December of 2022. A total of 72 healthy first-born sows were selected and then randomly assigned to 12 treatment groups, with six sows in each group. The waist, flank, and thigh root were selected as the stimulated positions. Electrical stimulation was applied at voltages of 1200, 1600, 2000, and 2400 V, resulting in a total of 12 treatments. The hair was removed from the stimulated positions of all experimental sows, in order to ensure that the positive and negative electrodes of the electrical stimulation device were in close contact with the pig's skin. An electrical stimulation was administered, when the sow side lying. Their body behaviors (lie, sit, stand, and jump) and sounds (silent, grunt, bark, squeal, and bite) were synchronously recorded by a mobile phone camera. An optimal combination was determined for the most appropriate electrical stimulated position and stimulated voltage. The feed intake and growth rate of piglets were measured to verify the impact of appropriate electrical stimulation on the production performance of sows. Two treatment groups of five sows were randomly assigned to the total of 10 healthy first-born sows with a minimum of 12 functional nipples. The newborn piglets were fostered within the first 24 hours after birth. There was no significant difference in the litter weights (P>0.05). Furthermore, the electrical stimulation was applied daily on each lying sow between 08:00-17:00 in the treatment group within the first three days post-partum. There was no intervention in the control group. All sows were fed three times per day from day 8 to 21 of the lactation (weaning age). The results demonstrate that the effective response rate and the startle index of the test sows showed an upward trend, as the voltage increased. The effective response rate of the test sows was below 50% at stimulated voltages of 1200 and 1600 V. However, the effective response rate exceeded 75% in 2000 and 2400 V. Compared with the voltage of 1 200 V, the probability of effective response of the sows under these voltages (2000 and 2400 V) increased by about 21.645 and 52.366 times, respectively, which was extremely significant (P<0.01). The effective response rate of the waist was 70.8% for the stimulated positions, which was higher than the flank and thigh root by 20.8%. The probability of effective response of the waist was nearly 3 times higher than the flank. Lower voltage was negligible to stimulate the standing response of sows. But, the maximum startle index of the sows exceeded 60% at a stimulated voltage of 2400 V. It inferred that the risk of stress reactions of saws increased their production performance. The maximum startle index was lower than 60% at 2000 V. Therefore, electrical stimulation of 2000 V can be recommended to place the electrical stimulation device on the waist, according to the effective response and startle index. The production experiment demonstrated that the feed intake per day (5.50 kg) and weaning litter weight (58.91 kg) of the experimental group under the appropriate electrical stimulation parameters were slightly higher than the control group, which were the average daily feed intake (5.45 kg) and weaning litter weight (58.42 kg). But the differences were not significant (P>0.05). The appropriate parameters (2000 V, waist) had no statistically significant effect on the reproductive performance of sows. These findings can provide valuable reference and data support for the development and application of equipment to rescue piglets.