Effect of Dietary Supplementation with Different Sources of Selenium on the Presence of Microorganisms Isolated from Milk

Abstract

Selenium is an essential mineral for cattle health, supporting the immune system and metabolism. Selenium deficiency can impair immunity and milk production. This study aimed to evaluate the effect of dietary supplementation with different sources of selenium on the presence of microorganisms isolated from milk. Thirty-two lactating dairy cows were used, with 120 ± 60 days in milk (DIM), body weight of 700 ± 100 kg, an average body condition score (BCS) of 2.5 ± 0.5, and milk production of 25.0 ± 5.0 kg of milk/cow/day. The animals received dietary supplementation with different sources of selenium — organic (yeast and amino acid), inorganic, and a control treatment — and were monitored for 12 weeks. Milk samples were collected every 28 days and microbiologically analyzed. A randomized block design with repeated measures over time was adopted. The chi-square test was used to assess significance, with a significance level of 5%. Data analysis was performed using the FREQ procedure of the Statistical Analysis System software, version 9.4 (SAS, 2018). Regarding the microbiological analysis, 36 positive isolates of Staphylococcus sp. (p value = 0.426), 1 positive isolate of Streptococcus sp. (p value = 0.388), 3 positive isolates of Enterobacteriaceae (p value = 0.289), and 1 positive isolate of Micrococcus sp. (p_value = 0.388) were detected, with no significant differences among the selenium supplementation treatments. Thus, it can be inferred that, even with the presence of the main mastitis-causing agents in the milk, there was no increase in the somatic cell count (SCC) of the cows, which remained below 200,000 throughout the study. This reflects a good immune response from the cows in the face of contagious and environmental challenges.