Abstract

The aim of the experiment is to demonstrate the effect of potassium and magnesium chloride in reducing heat stress in Holstein cows in the summer by measuring body temperature, respiratory rate, pulse rate and heat tolerance coefficient starting from 1/7/2024 until 1/11/2024, where potassium and magnesium chloride are dosed every 48 hours per cow. 16 multi-season Holstein cows were used and divided into four treatments, each of which includes four replicates. The first treatment, T1, is the control treatment without dosing. The second treatment, T2, is dosed with 10g/48 hours per cow of potassium chloride. The third treatment, T3, is dosed with 2.5g/48 hours per cow of magnesium chloride. The fourth treatment, T4, is dosed with 10g/48 hours per cow and 2.5g/48 hours per cow of potassium chloride and magnesium chloride, respectively, to study the effect of these treatments on Holstein cows suffering from heat stress in the summer. The temperature and humidity index (THI) was calculated during the experiment and the results showed that the cows were under The effect of heat stress during the experiment period negatively affected its physiological performance, as the highest THI value reached 81.88 during the eighth week of August, and the lowest THI value reached 71.56 during the seventeenth week of October. The results of the statistical analysis of physiological characteristics on 13/7/2024 showed that there were no significant differences between the treatments. As for 16/8/2024, the results showed that treatment T4 led to a significant decrease (P≤0.05) in the respiratory rate, which reached 74.00 times/minute compared to treatment T2, which was 94.75 times/minute. On 24/8/2024, the results showed a significant increase (P≤0.05) in the thermal tolerance coefficient of treatment T4, which reached 92.00 compared to treatment T3, which was 83.75. As for 8/30/2024, the results showed a significant increase (P≤0.05) in the pulse rate of treatment T4, which reached 71.00 beats/minute compared to treatment T1, which was 76.00 beats/minute. On 27/9/2024, the results showed a significant decrease (P≤0.05) in the respiration rate in treatment T4. As it reached 48.70 times/minute compared to treatment T3, which reached 64.25 times/minute. As for 25/10/2024, the results showed a significant decrease (P≤0.05) in the respiratory rate in treatment T4, as it reached 37.00 times/minute compared to treatment T1, which was 39.75 times/minute. There was also a significant decrease (P≤0.05) in the pulse rate in treatment T4, as it reached 61.00 beats/minute compared to treatments T1 and T3, which were 68.00 and 71.00 beats/minute, respectively. On 31/10/2024, the results showed a significant decrease (P≤0.05) in the rectal temperature in treatment T3, as it reached 36.82°C compared to treatment T1, which was 38.01°C. Adding 10g of potassium chloride and 2.5g of magnesium chloride during the period of cows being exposed to heat stress had a significant effect on some physiological characteristics, as it reduced the number of respirations, pulse, and rectal temperature, and increased the heat tolerance coefficient during some periods of the experiment.