Rank Non-Parametric Correlation Analysis of Indicators of Heavy Metal Transition from Blood to Cow's Milk to Assess its Environmental Safety

Abstract

Correlation analysis constitutes an essential method of statistical processing of the obtained scientific research results. Its proper application using special computer software and reliable results allow practically facilitating the work of the veterinary and livestock service in the production of environmentally safe high-quality cow's milk. The purpose of this study is to analyse the correlation between the content of toxic metals Cd and Pb in the blood and milk of cows using the STATISTICA computer software version 10.0. Scientific and economic experiments were conducted on dairy cows with different types of feeding. All animals selected according to the analogue method in terms of live weight and productivity were divided into three groups: the first control group and the second and third experimental groups. The diet included feeds with an excess of heavy metals, especially cadmium and lead. The high biological activity of pollutants affected their migration from the feed of the diet through the gastrointestinal tract to milk. To reduce intoxication of the animal body, premix “MP-A” was introduced into the main diet of cows of the second and third experimental groups, and in the third experimental group – premix “MP-” and injection of the biological product “BP-9”. First, using the Shapiro-Wilk's W test, the study verified the obtained data from laboratory tests of blood and milk for the concentration of toxic metals, the law of “normal” (Gaussian) distribution, and then the necessary Spearman's non-parametric rank correlation coefficient was selected for calculation. The analysis revealed a high correlation between the variables, which was within r=0.82-0.91 (Cd) and r=0.78-0.96 (Pb) with probability (p<0.05) in animals with different types of feeding. The discovered high correlation allows veterinary medicine specialists to quickly apply measures to reduce the toxic load of the body with elements only by analysing blood for cadmium and lead, and timely prevent the production of low-quality dairy raw materials, including using premix and phytobiopreparation tested in the experiment. Further research is aimed at analysing the correlation between other indicators of the quality and environmental safety of milk and feed, constructing regression equations that will practically contribute to the activities of specialists whose task is to ensure the production of high-quality environmentally safe cow's milk.