Hematological parameters and plasma cortisol levels in high-yielding dairy cows in the South of Brazil

Abstract

The metabolic adaptation is an important process to milk production in high-yielding dairy cows. The physiology of hematological and endocrinal changes during the postpartum period is complex and many homeostatic responses are important to achieve the maximum milk production. The hematological status is an useful diagnostic tool to evaluate the general health and the immune system on different stages of the productive cycle in dairy cows. The objective of this study was to evaluate some hematological parameters in different periods of the productive cycle of dairy cows and correlate them with cortisol. Two hundred and ten multiparous dairy cows were selected to this experiment. The animals were distributed by weeks: -3, -1 (60 and 15 days before calving), 2, 5, 8 and 11 (weeks postpartum). The hematological parameters analyzed were PCV (packed cell volume), hemoglobin concentration, total and differential count of WBC (white blood cells). The stress during the periparturient period was evaluated by cortisol levels analyzed by solid-phase radioimmunoassay method. All the hematological and cortisol values were within the normal range for the species. The highest values for cortisol were found during the second week. Hematological changes associated to high stress signs were not observed in the present study and this is probably due to the satisfactory health state during the experiment period and the adequate nutritional and management conditions.