The aim of this study was to correlate skin temperature assessed through infrared thermography (IRT) with heat and methane production in lactation cows. Six Holstein and Gir (HG) crossbreed and 4 Holstein (H) mid-lactation cows (all primiparous) were evaluated for daily heat and methane production in respiratory chambers, and the IRT images were taken at 9 different body locations every hour during 8 h after feeding, during 5 d. IRT were taken of the anus, vulva, ribs (on the right side), left flank, right flank, right front foot, upper lip, masseter and eye. During the whole trial, cows received the same diet ad libitum and the daily milk yield and feed intake were recorded. The trial lasted 40 d, including previous adaptations of the animals to the respiratory chambers. Correlation analysis showed that daily methane production has strong correlation with IRT taken at the eye 6 h after feeding in HG cows (r = 0.85, P < 0.05) and with IRT taken at the eye 5 h after feeding in H cows (r = 0.88, P < 0.05). Also, heat production showed strong correlation with IRT taken at the right front foot 1 h after feeding in HG cows (0.85, P < 0.05) and with IRT taken at the eye 5 h after feeding in H cows (r = 0.90, P < 0.05). These results were further confirmed using regression analysis. IRT is effective in assessing heat production and methane production in Holstein and Holstein × Gir crossbreed lactation cows (Table 1). Table 1.

Breed1	Regression equation	R2
HG	Methane production = 31,85 × Eye H62 − 723	0.72
Heat production = 660.7 × Foot H13 − 4414.2	0.72
H2	Methane production = 40.19 × Eye H54 − 1036.2	0.74
Heat production = 2282.8 × Eye H54 − 58478	0.82

¹HG = Holstein and Gyr crossbred; H = Holstein. ²IRT taken at the eye on h 6 after the feeding. ³IRT taken at the foot on h 1 after the feeding. ⁴IRT taken at the eye on h 5 after the feeding.