Validation of triglyceride and glucose index as a rapid diagnostic test to diagnose insulin resistance in pregnant and lactating sows

Context In sows, the development of insulin resistance (IR) during late gestation and lactation favours a productive gap associated with low feed intake during lactation, which is reflected in the herd profitability. Therefore, the development of rapid-use tests to diagnose IR on farms will be very useful.Aims We aimed to validate the triglyceride and glucose (T-G) index as a rapid diagnostic test to diagnose IR in sows during late gestation and lactation.Methods The homeostatic model to evaluate IR (HOMA-IR) was used as a reference. Sixty sows (farrowing 1-5) were selected for blood sampling during late gestation and lactation. In the total number of samples collected (n = 480), the glucose, insulin, and triglyceride concentrations were determined to estimate the HOMA-IR and T-G index. Receiver operating characteristic curves were used to determine cut-off values for diagnosing IR using the T-G index.Key results The highest (P < 0.05) values of HOMA-IR and T-G index were found between Day 110 of gestation and Day 3 of lactation, regardless of the farrowing number evaluated. The area under the curve for the T-G index was 0.83 (95% CI 0.78-0.88). The best overall cut-off point for diagnosing IR by using the T-G index was 4.24 (86% sensitivity and 77% specificity). The association between the T-G index and HOMA-IR was 0.68 (P < 0.0001), regardless of the farrowing number and productive stage (late gestation, early lactation, and late lactation). According to the farrowing number and productive stage, the best cut-off points were 4.21 (sensitivity 86% and specificity 73%), 4.20 (sensitivity 83% and specificity 73%), and 4.20 (sensitivity 88% and specificity 92%) for sow's first and fourth farrowing, and late gestation respectively.Conclusions The T-G index is a reliable field test for IR diagnosis in sows during late gestation and lactation.Implications The T-G index test evaluated for the diagnosis of IR in sows is an approach that could be significantly exploited at the farm level. This test could become a support tool to maximise the productivity of the sow, since the development of IR could be modulated through zootechnical practices.