Table 1.

Studies showing relationship between surface (measured by infrared devices) and ambient temperature in healthy pigs

Source	N	Breed	Approx. weight (kg)	Surface area(s)	Thermal Window (X: yes)	T ambient [°C]	Regression Constant, T 0 [°C] ( A )	Regression coefficient, b ( A )	Correlation (r) and goodness of fit (R 2 ) ( A )	Remarks
Henken et al. [30]	16	Norwegian, Finnish and Dutch Landrace and Great Yorkshire	26	Lumbal area		11-26	22.5–25.9	0.37–0.47	r = 0.83–0.91 (**)	(B)
Wendt et al. [34]	89		7–60	Ear base	X	12–30	28.5	0.263	r = −0.68 (***)	(C)
	147		160–222				27.6
Loughmiller et al. [2]	4	Crossbred	30	Loin		10–32	24.8	0.40	R2 = 0.97 (***)
Collin et al. [35]	8	[Large White × Landrace] × Piétrain	15–35	Interscapula region		23–33	29.3	0.29	(**)	(B)
Savary et al. [36]	9		50–70	Ear base, abdomen (caudal) and upper medial side of legs	X	12–18	30.6	0.36	(***)
				Carpus, tarsus, shoulder, knee and elbow			25.2–27.1	0.48
Costa et al. [37]	12		8	Part of body with the highest temperature	X	22–36	30.8	0.20	R2 = 0.44 (***)
			11		X	16–28	33.7	0.20	R2 = 0.57 (***)
Malmkvist et al. [31]	39	Danish Landrace × Yorkshire	>200	Eye	X	15–25	32	0.2	(***)	(B)
				Snout			28.7	0.3
				Udder (caudal)	X		32	0.2

^AT_skin = T₀ + b*T_ambient , where T₀ = regression constant [°C], b = regression coefficient ( = T_skin increase per 1°C increase in T_ambient). **:P < 0.01 and ***:P < 0.001.

^BEstimations performed by author of this article.

^CBased on thermocouple temperature measurements, not IR.