The use of infrared thermography as an indicator of methane production in hair sheep.

Infrared thermography may be an alternative technology for measuring the amount of CH₄ produced and has the advantages of low cost, speed and efficiency in obtaining results. The study's objective was to determine if the infrared thermography is adequate for predicting the emission of CH₄ in hair sheep and the best time after feeding to carry out the measurement. Twelve Santa Inês lambs (females, non-pregnant, with twelve months old and mean body weight of 39.3 ± 2.1 kg) remained for two days in respirometric chambers, in a semi-closed system, to determine the CH₄ production. The animals were divided into two treatments, according to the diet provided. During this period, seven thermographic photographs were taken, at times - 1 h, -0.5 h, 0 h, 0.5 h, 1 h, 2 h, 3 h, 5 h, and 7 h, according to the feeding time, defined as 0 h. CH₄ production was measured over 24 h. Thermographic images measured the maximum, minimum, average and point temperatures at the left and right flanks. The temperature difference between the left and right flanks (left minus right) was calculated each time. Pearson correlation coefficients, multiple regression and principal component analysis were carried out in SAS^®. The best prediction of emission intensity of CH₄ (kg of CH₄ per dry matter intake) was obtained at 3 h after feeding: CH₄/DMI = 13.9016-0,38673 * DifP² + 3.39089 * DifMed² (R² = 0.48), using the difference between left and right flanks for point and average temperature measures. Therefore, infrared thermography can be used as an indicator of CH₄ production in hair sheep three hours after feeding.