Dystocia in cows adversely affects calf and dam health and productivity [1]. The incidence of dystocia has been reported to be 3%–22.6% in primiparous dairy cows and 1.5%–13.7% in multiparous dairy cows and is directly associated with an increased rate of stillbirth [2]. Schuenemann et al. [3] proposed that assistance should be provided within 70 min of the appearance of the amniotic sac or within 65 min of the appearance of the feet. Frequent monitoring of cows is essential to detect dystocia, and the prediction of the onset of calving not only ensures timely assistance at dystocia but also leads to labor-saving to manage peripartum cows.

Calving prediction systems based on vaginal temperature and behavioral changes have been applied in clinical settings [[4], [5], [6]]. In addition, wearable gadgets that track changes in skin temperature and tail activity are under development [7,8]. However, even with these methods, failures to predict calving are inevitable. Thus, identifying novel biological parameters that change with the progression of parturition will contribute to the advancement of calving prediction technology.

A rise in fetal cortisol secretion during the prepartum period, which plays an integral part in the induction of calving, elevates placental transfer of cortisol to the dam [9,10]. In addition, blood glucose concentrations are known to rise rapidly during calving due to hypercortisolemia caused by discomfort and stress during parturition [[11], [12], [13], [14]]. Hiew et al. [15] measured blood glucose concentration in cows using a handheld electronic glucose meter to predict calving. As it is simpler, quicker, and more affordable than traditional biochemical assay systems, this point-of-care device is practical. However, even with such a device, frequent blood sampling is required, and continuous monitoring of blood glucose concentrations is practically difficult. Animal welfare should also be a concern because blood sampling is accompanied by pain.

Wearable sensors that measure subcutaneous tissue glucose concentration (tGLU) have recently been developed to assist diabetics in the self-management of their blood glucose concentrations. By affixing a special sensor to the body, these devices enable continuous measurement of tGLU without stressful blood collection. The purpose of this study was to identify tGLU changes in peripartum dairy cows and assess the utility of tGLU as a predictive indicator of calving. In this study, tGLU was measured continuously using wearable sensors during the peripartum period. In addition, the diagnostic capability of tGLU cutoff points to predict calving was assessed.