Table 5.

Devices for calving alarm which identify the onset of stage II of parturition, with performance and references.

Event	Sensor Type	Device	N	Application	TI	Device Performance	Factory	References
Vulvar lips separation	Magnetic sensor	Foalert, C6 birth control	22 80 53	Vulva (suture)	0 h	Se = 100; PPV = 95%	Sisteck Srl, Sassuolo, Italy https://www.foalingalarm.net/	Paolucci et al. [53] Paolucci et al. [54] Marchesi et al. [55]
	Magnetic sensor and GPS collar	GPS-CAL	26	Vulva (suture) + neck collar (GPS)	0 h	Se = 100%; PPV = 100%	Sisteck Srl, Sassuolo, Italy SiRF Technology, San Jose, California, USA	Calcante et al. [56]
Device expulsion	Light and temperature	OraNasco®	120 15 117 83	Vagina	0 h	Se = 86.30%	Kronotech Srl, Campoformido, Italy https://www.oranasco.it/	Palombi et al. [57] Rossi et al. [58] Crociati et al. [59] Crociati et al. [60]
	Light	iVET®	167	Vagina	0 h	Se = 78%; Sp = 93%	iVET®-Geburtsüberwachung für Kühe https://www.nrw-agrar.de/projekt/piloterprobung-des-geburtssensors-ivet-bei-milchkuehen-geburtsueberwachung/	Henningsen et al. [61]
	Temperature	Gyuonkei	625	Vagina	0 h	n.a.	Remote Inc., Oita, Japan http://www.gyuonkei.jp/	Sakatani et al. [49]
	Temperature	Vel’Phone®	211 241	Vagina	0 h	n.a.	Medria, Châteaugiron, France https://www.medria.fr/en/solutions/velphone/	Ricci et al. [50] Choukeir et al. [62]
			54		0 h	PPV = 100%		Horvàth et al. [31]

N: number of animals. TI: time interval between calving alarm and parturition. Se: sensitivity; Sp: specificity; Acc: accuracy; PPV: positive predictive value; NPV: negative predicting value; AUC: area under curve; n.a.: not available.