Computer-implemented method for identifying a farm animal having an impairment of regulative capacity in response to metabolic stress comprising: a) assessing the value of the nonlinear domain heart rate variability component L MAX of a farm animal based on a heart beat interval data set obtained for said farm animal; b) comparing the value of L MAX assessed according to (a) with a species specific threshold of L MAX; whereby said farm animal is identified as having an impairment of regulative capacity if its value of L MAX is below said species specific threshold, wherein the method further comprises determining the species specific threshold of L MAX by performing the following steps: i) determining the values of the nonlinear domain heart rate variability component L MAX of at least two farm animals of the species to be assessed based on heart beat interval data sets obtained for said farm animals from a feed-ad-libitum -period (L MAX ad libitum); ii) determining the values of the high frequency domain parameter of heart rate variability of the same at least two farm animals as in (i) based on heart beat interval data set obtained for said farm animals from a feed-ad- / ibitum- period (HF ad libitum); iii) determining the values of the high frequency domain parameter of heart rate variability of the same at least two farm animals as in (i) based on heart beat interval data sets obtained for said farm animals from a fasting -period (HF fasting); iv) determining the difference between HF ad libitum and HF fasting (ΔHF) for each of the at least two farm animals; v) linear regression ΔHF versus L MAX ad libitum; vi) determining the species specific threshold of L MAX in that the value of L MAX ad libitum corresponding to ΔHF = zero in the linear regression according to v) represents the species specific threshold of L MAX. a) assessing the value of the nonlinear domain heart rate variability component L MAX of a farm animal based on a heart beat interval data set obtained for said farm animal; b) comparing the value of L MAX assessed according to (a) with a species specific threshold of L MAX; whereby said farm animal is identified as having an impairment of regulative capacity if its value of L MAX is below said species specific threshold, wherein the method further comprises determining the species specific threshold of L MAX by performing the following steps: i) determining the values of the nonlinear domain heart rate variability component L MAX of at least two farm animals of the species to be assessed based on heart beat interval data sets obtained for said farm animals from a feed-ad-libitum -period (L MAX ad libitum); ii) determining the values of the high frequency domain parameter of heart rate variability of the same at least two farm animals as in (i) based on heart beat interval data set obtained for said farm animals from a feed-ad- / ibitum- period (HF ad libitum); iii) determining the values of the high frequency domain parameter of heart rate variability of the same at least two farm animals as in (i) based on heart beat interval data sets obtained for said farm animals from a fasting -period (HF fasting); iv) determining the difference between HF ad libitum and HF fasting (ΔHF) for each of the at least two farm animals; v) linear regression ΔHF versus L MAX ad libitum; vi) determining the species specific threshold of L MAX in that the value of L MAX ad libitum corresponding to ΔHF = zero in the linear regression according to v) represents the species specific threshold of L MAX. i) determining the values of the nonlinear domain heart rate variability component L MAX of at least two farm animals of the species to be assessed based on heart beat interval data sets obtained for said farm animals from a feed-ad-libitum -period (L MAX ad libitum); ii) determining the values of the high frequency domain parameter of heart rate variability of the same at least two farm animals as in (i) based on heart beat interval data set obtained for said farm animals from a feed-ad- / ibitum- period (HF ad libitum); iii) determining the values of the high frequency domain parameter of heart rate variability of the same at least two farm animals as in (i) based on heart beat interval data sets obtained for said farm animals from a fasting -period (HF fasting); iv) determining the difference between HF ad libitum and HF fasting (ΔHF) for each of the at least two farm animals; v) linear regression ΔHF versus L MAX ad libitum; vi) determining the species specific threshold of L MAX in that the value of L MAX ad libitum corresponding to ΔHF = zero in the linear regression according to v) represents the species specific threshold of L MAX.