Influence of blood glucose level on sow traits, farrowing characteristics and piglet parameters in free farrowing sows

Studies have shown that maintaining adequate blood glucose levels can support the farrowing process in crated sows. This study aimed to evaluate the impact of blood glucose levels on sow traits, farrowing kinetics, and piglet parameters under free farrowing conditions. A total of 147 sows were monitored, with blood glucose levels measured at the beginning and end of parturition. In addition, the blood glucose level of the first, seventh, and last-born piglets was evaluated immediately after birth. The mean farrowing duration was 229 ± 86 min, with an average of 16.1 ± 3.6 total born piglets. Blood glucose levels of the sow increased significantly at the onset of farrowing 4.44 ± 0.63 to 4.72 ± 0.79 mmol/L at the end of farrowing. Blood glucose levels of sows at the onset of farrowing were related to the first-born piglet (r = 0.2; P = 0.011) as well as at the end of farrowing with the last-born piglet (r = 0.2; P = 0.018). Sows that consumed their last meal in the evening before farrowing exhibited higher blood glucose level (4.50 ± 0.62 mmol/L; P = 0.009) and tended to have a longer farrowing (238 ± 86 min; P = 0.053) duration compared to those that last ate in the morning (4.34 ± 0.64 mmol/L; 216 ± 85 min). Older sows (≥ 5 litters) exhibited lower blood glucose at the onset of farrowing (4.3 ± 0.6 mmol/L vs 4.6 ± 0.6, P = 0.021) and required more farrowing assistance (62 vs 37%, P = 0.001), having nearly twice as many stillborn piglets as younger sows (1.42 ± 1.5 vs 0.78 ± 1.5). The temperature-humidity index (THI) is a combined index of relative humidity and air temperature, to posit a perceived equivalent temperature. THI correlated negatively with blood glucose at the onset of farrowing (r = -0.16; P = 0.047). No significant correlation was found between blood glucose level and farrowing duration, suggesting that blood glucose levels at the onset of farrowing are not reliable predictors of prolonged farrowing (> 300 min) or dystocia (> 1 h piglet-piglet interval) in free farrowing systems. Overall, while glucose is essential for uterine energy during farrowing, the study concludes that other factors, such as sow age, meal timing, and temperature-humidity index, also play critical roles in farrowing success. Future research should further explore these interactions to enhance sow and piglet performance in free farrowing systems.