TDK conference 2017

Chronic lameness is one of the most common stressors of dairy cows, therefore is a matter of grave concern of animal welfare. Long lasting pain (stress) leads to numerous hormonal and physiological changes which strongly affect the milk and meat yield and also the reproductive abilites and immunity of cattle.

The aim of this research was to assess those physiological responses which are given to acute stress triggered by ACTH load in cattle suffering from chronic stress (lameness).

We selected 11 chronic lame and 11 non-lame (contol) animals (lactation number: 4,1 ± 1,0 vs. 4,3 ± 1,6; DIM: 190 ± 78 vs. 167 ± 73, milk yield: 31,8 ± 3,6 vs. 32,1 ± 7,0). On the first day of research we examined the hoofs and collected blood, hair and urine samples from each individual to evaluate the general health status. In the blood and urine samples, glucose, beta-hydroxibutyric acid, FFA, AST, urea, haptoglobin levels were measured along with pH and net acid excretion of urine; cortisol and DHEA levels of the hair samples. On the 2nd and 3rd day blood samples were taken 30, 15 and 0 minutes prior to administering 60µg synthetic ACTH (Tetracosactide), after which new samples were taken 10, 20, 30, 40, 60, 120 and 240 minutes later. Then we assessed the cortisol concentrations of these blood samples. During the experiement we were also recording HRV by Polar heart rate monitors attached to the thorax of each animal.

Locomotion score of lame animals was higher (4,2 ± 0,7 vs. 1,6 ± 0,5), where we observed sole ulcer, interdigital phlegmone, toe necrosis, unlike to non-lame animals. There was no difference in metabolic indices of the two groups, but the hair samples showed higher cortisol concentration (10,2 ± 2,5 vs. 7,8 ± 2,2) indicating chronic stress. There were no differences in cortisol concentrations in plasma samples prior to (baseline) and after ACTH administration (maximum value, amplitude of the response, area under the curve, return to the baseline and time to reach peak value). We used the HF (high frequency component) of the calculated HRV values to examine the parasympathetic tone. Lame cattle had lower HF baseline values which indicates that standing was painful, causing stress for the animal. After injecting ACTH both groups showed HF-decrease, but it reached its minimum and returned to the basic value with delay in lame animals.

According to our results, chronic stress triggered by lameness does influence the HF component of HRV, but does not affect the responsiveness of the adrenal cortex.