The state of the adrenal cortex in cows with different levels of productivity and their breed affiliation

Purpose: the goal is to study the condition and functional reserves of adrenal cortex in cows with different levels of dairy productivity and their breed accessories.

Materials and methods. In the first experience, the object of the study was cows of a holstered black-motley breed with a high and relatively low level of milk productivity (n = 10 in each group). The second experience was carried out on four breeds of lactating cows: Holsteinated black-made, red-made, Montbeliard and Jersey (n = 10 in each group). The blood of animals were taken from the tail vein 1 time per month during lactation to morning feeding. In both experiments, in the third month of lactation, all animals were performed by a two-time functional load of ACTH (dose – 0,5 units / kg of alive mass intramuscularly). After one hour, blood selection was performed and re-injected by adrenocorticotropic hormone in the same dose. After the second introduction, the ACTH was selected through 1.2 and 3 hours. The calculation of the index of the functional activity of the adrenal cortex was carried out according to the JACN = K₂ / K₁ formula where K₁ is the level of cortisol 1 hour after the first load, K₂ is the level of cortisol after the second load of the ACTH.

Results. In the 1st experience of the highest values, the level of cortisol reached a 3 month lactation. In a highly productive group, the level of cortisol was 86,1 ± 5,3 nmol / l, and in the low product group 74,5 ± 5,7 nmol / l. At 8 months, the lowest cortisol concentration levels are fixed, followed by an increase of 10 months. Differences between groups on 2, 3 and 4 months of lactation are noted as statistically significant (p<0,05). After the load of the ACTH, an index of the functional activity of the adrenal cortex (JACN) was established - in the first high productive group, it was 1.42, and in the second less productive group it was lower and amounted to 1,04.

In the 2^nd experience at the peak of lactation, which also corresponded to 3 months, the level of cortisol concentration increased from a holstered black-motley breed, Mont Belärd, Red-motley and Jersey to 79,3 ± 5,5; 70,2 ± 3,7; 80,3 ± 3,2; 80,5 ± 3,6 nmol / l, respectively. For 8 months of lactation, this figure decreased with the subsequent increase of the 10th month. After establishing Jacnes in a holstered black-motley breed, Montbeliard, red-motley and jersey recorded the following indicators: 1,21; 1,24; 1,18 and 0,89, respectively.

Conclusion. The studies have indicated that in all periods of lactation relative to the high level of cortisol recorded in cows with a higher level of milk productivity. When comparing different rocks, it was established that the limit of the functioning of the adrenal glands in the cows of the Jersey breed was implemented after the first functional load of the ACTH, which gives reason to consider it less stress-resistant with respect to rocks a holstered black and motley, red-motley and monobeldam.

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