## 4 Discussion  
Our research shows a higher difference between the rectal temperature and the eye temperature than the difference reported by [PERSON] et al. [37]. This could be due to the measurements of the whole eye in our research, while [PERSON] et al. [37] observed only the eye caruncle. The eye caruncle is the most suitable place for measuring the temperature of dairy cows. However, is it very problematic to create high-quality pictures and media in order to evaluate the eye caruncle. The blood vessels in the milk cow's body expand more, and the ST of the dairy cow's body rises at the same time, as well as the temperature of the lacrimal caruncle of the eye, which is in accordance with the results of the authors [PERSON] et al. [1], who devoted themselves to the evaluation of the most advantageous place for observing the eye temperature of a dairy cow depending on the microclimatic conditions of a housing facility. From the above, it can be understood that it is important to obtain an algorithm for evaluating the influence of THI, the AT in the environment, as well as the influence of RH, which is in line with the knowledge of the authors [PERSON] et al. [42]. [PERSON] et al. [47] recorded lower IRT temperatures measured at the eye (2-7 \({}^{\circ}\)C) compared to RT. Other studies involving European breed animals housed in controlled environment facilities reported differences of 3-5 \({}^{\circ}\)C between body ST determined by IRT and RT [17]. [PERSON] et al. [32] and [PERSON] et al. [48] observed variation (5 \({}^{\circ}\)C) in IRT temperatures between different body regions. As stated by the authors [PERSON] et al. [49]; [PERSON] et al. [30]; and [PERSON] et al. [50], an update of THI critical thresholds is based on physiological responses for dairy calves, heifers and cows. As stated by the authors [PERSON] et al. [49]; [PERSON] et al. [50]; and [PERSON] et al. [51] (most THI critical  
Figure 4: Relationship between the THI and the values of the difference between rectal temperature and eye temperature of dairy cows. Dots represent individual recorded values. Red solid line represents linear regression. Dashed lines represent the level of significance 0.05.  
thresholds were based on rectal temperature and respiratory rate. Therefore, we can conclude that it is also important to update and supplement knowledge for a better determination of the influence of THI parameters on RT and ET parameters. Our conclusions are consistent with the work of other authors. [PERSON] et al. [18] draw attention to the need to ensure stable atmospheric conditions during thermography, as even a slight fluctuation in temperature (<0.8 \({}^{\circ}\)C) on the body surface of an animal can lead to an increase in incorrect diagnoses. As shown in our measurements, AT and THI are positively correlated, and RH is negatively correlated in the object, to the difference between RT and ET. As stated by [PERSON] and [PERSON] [39] and [PERSON] et al. [40], it was found that IRT temperatures in the area of the lacrimal caruncle of the left eye can be correlated with body temperature, which essentially serves as a surrogate for body temperature. Here, we want to emphasize that it is important to map how individual parameters affect the environment of RT and ET. Consequently, one can determine whether this method is suitable for monitoring the animal's health or the THI's impact on animals' welfare. However, we must not forget that measuring the RT can cause stress in dairy cows, and thus, those measurements can change the RT as reported by [PERSON] et al. [52]. The results achieved by [PERSON] et al. [8] are also in similar agreement, which also point to the possibility of using IRT to measure the body temperature of dairy cows. At the same time, they point to the fact that ambient temperature, relative humidity and THI influence the accuracy of non-contact measurement using IRT.