The application of wool as a biosubstrate to assess the impact of various strontium levels on the biological characteristics and productive qualities of dairy cattle under conditions of increased technogenic load

Strontium is a natural component of aquatic and terrestrial ecosystems. However, due to anthropogenic activity, strontium concentrations locally increase to levels that create a potential environmental risk and can lead to disturbance of the elemental status and productive qualities of farm animals. In this regard, the aim of this study was to study the elemental status and productivity of Holstein cows with different levels of Sr in wool, bred in environmentally unfriendly areas of the Southern Urals. The studies were carried out among the Holstein cows whose wet weight was within 505-535 kg. The lactation stage was 30-50 days after calving. Dairy productivity was 18.8-31.4 liters per day. The research was carried out in Agrofirm Industrial LLC, Orenburg region. The animals were divided into three groups depending on Sr concentration in their coat. The range of Sr concentrations in the coat of cows Group I was from 0.716 to 1.69 mu g/g, Group II - from 1.82 to 3.68 mu g/g, and Group III - from 3.81 to 7.23 mu g/g. When comparing the chemical elements concentrations in the coat among the groups under the experiment, it was found that an increase in Sr level was accompanied by the significant change in levels of Ca, K, Mg, P, Se, Mn, Cd, Ni, B. Moreover, as Sr content increased from the minimum to the maximum value, there was occurred a decrease in Cu concentration by 10.9-25.3 %; Zn - by 11.1-21.2 %, and As - by 10.0-30.0 %. The ratios calculated with the Spearman's rank correlation for the experimental animal groups revealed a reliable correlation between Sr concentrations and concentrations of Cu, Se, and Zn in the coat. As Sr content in the coat increased, there was a change in the indicators of the antioxidant status of the blood serum, which was expressed via an increase in the level of malondialdehyde by 2.2 and 2.6 times. The cows with Sr content in coat lower than 1.82 mu g/g exceeded the analogues of Groups II and III in daily productivity calculated based on milking - 1 % milk by 32.8 and 32.3 %, respectively.