Influence of cow and heifer categories on the hematology of Murrah buffaloes (Bubalus bubalis) raised in the microregion of Santarém, Pará, Brazil

The hematological profile is indicated to evaluate the physiological condition of buffaloes, providing information on the functionality of production systems and their response to environmental factors. In tropical regions, such as the Lower Amazon, high temperature and relative humidity can lead to heat stress, affecting hematological parameters. Therefore, the objective of this study was to evaluate the influence of the cow and heifer categories on the hematology of female Murrah water buffaloes (<i>Bubalus bubalis</i>) raised in the Microregion of Santarém, Pará, Brazil. Blood samples were collected from 90 Murrah buffalo females, divided into two categories: heifers (22 to 24 months) and cows (36 to 38 months). A complete blood count was performed, considering the red and white series. The T test was applied to compare the means of parameters between categories (heifers and cows), using the RStudio Desktop 1.3.1093 software. There was a difference in hemoglobin (<i>p</i> = 0.0424), hematocrit (<i>p</i> = 0.0090) and MCV (<i>p</i> = 0.0393) higher in heifers and MCHC (<i>p</i> = 0.0289) in cows. On the other hand, there was no difference for the parameters red blood cells (<i>p</i> = 0.4363), MCH (<i>p</i> = 0.1042) and RBC (<i>p</i> = 0.6722). In relation to the white series, there was a difference in the absolute values of leukocytes (<i>p</i> = 0.0069), lymphocytes (<i>p</i> = 0.0008), atypical lymphocytes (<i>p</i> = 0.0351) and monocytes (<i>p</i> = 0.0477), being higher in heifers than in cows. On the other hand, the segmented ones (<i>p</i> = 0.0002) were higher in cows when compared to heifers. The other leukocyte parameters did not present statistical difference (<i>p</i> > 0.05). Therefore, there were higher amounts of white and red cells for heifers when compared to cows.