Oxidative stress is higher in replacement gilts than in multiparous sows.
The recent success obtained in term of increasing the litter size of sows has not correlated with a reduction of replacement rate. There is thus an increased economic demand for gilts with optimal reproductive potential and longevity. Unfortunately, replacement gilts are known to be more susceptible to diseases and less productive than multiparous sows. While it is straightforward to identify the physiological failure which leads to the removal of a gilts from the herd, identification of the underlying molecular reasons for the occurrence of these events continues to be more challenging. Interestingly, reproductive performance, resistance to diseases and longevity could all be largely affected by oxidative stress. To investigate if oxidative stress conditions could account for the poor performance and longevity observed in replacement gilts in comparison to older multiparous sows. Three distinct groups of 15 F1 conventional Yorkshire x Landrace sows were formed based on their similar age and parity. These groups were primiparous gilts (group 1), third parity sows (group 2) and fifth parity sows (group 3). All animals were slaughtered during the post-ovulatory period of the estrous cycle and blood as well as tissues samples were collected and frozen at -80°C. Principal biomarkers of oxidative damage to proteins (Carbonyls) were analyzed in plasma and liver samples using ELISA procedures. Specific mRNA expressions of the major antioxidants glutathione peroxidases 1 and 4 (GPx1, GPx4) as well as superoxide dismutases 1 and 2 (Sod1, Sod2) were monitored in liver and kidney samples by quantitative RT-PCR. Specific enzymatic activities of glutathione peroxydases and superoxide dismutases were measured by spectrophotometric assays. The plasmatic concentrations of protein carbonyls were significantly different between the three groups with the higher concentrations being observed in gilts (P ≤ 0.001). The mRNA expression levels of GPx1 and GPx4 were also significantly increased in the liver of primiparous gilts when compared to multiparous sows (P ≤ 0.05) while no differences were observed in kidneys (P > 0.10). Sod2 enzymatic activity was found to be higher in the liver of primiparous gilts than fifth parity sows (P ≤ 0.05). It is well established that the expression and activity of antioxidants increase in response to oxidative stress. Taken together, our results indicate that replacement gilts sustain significantly higher oxidative conditions than multiparous sows. Current findings may contribute to the design of nutritional regimens that will increase the productivity of gilts by counteracting oxidative stress.Keywords: oxidative stress, gilts, longevity.