Haematological Status of Cows in Different Physiological Stages under Humid Tropic Condition

Background: Baseline haematological data serve as reference for the evaluation of the health status of animals. In cows, physiological stages such as pregnant, calving and lactation represent challenges, which can affect their blood parameters. The prepartum and postpartum periods are important for the productive and reproductive efficiency of cows. There is a transition period involving several physiological adaptations in a short period of time that can lead to health problems, especially metabolic and infectious diseases. The aims of the present study were report haematological reference intervals and identify haematological changes in Gyr x Holstein cows from the humid tropics of Mexico during their prepartum, calving and postpartum stages.Materials, Methods & Results: Body weight, body condition and blood samples of 33 Gyr × Holstein cows were obtained every 30 days as follows: 60 and 30 days prepartum; calving day (0 day); and 30, 60 and 90 days postpartum. Cows were handled according to the production system and conditions established by owners. Feeding was based on intensive rotational grazing on the natural grass Paspalum fasciculatum, and 3 kg animal/day of commercial feed (16% CP), mineral salt and water ad libitum. Haematological variables were measured using an automated analyzer. The haematological reference intervals were obtained using the Reference Value Advisor V21 integrated into Microsoft Excel 2016. This facilitated the calculation of confidence intervals by evaluating the data dispersion and homogeneity. When data were considered with “No Gaussian” distribution, the reference interval and confidence intervals were obtained from the robust method with a Box-Cox transformation of the data. Confidence intervals of the haematological variables were calculated at 90% Variables with Gaussian distribution or transformed were evaluated in one-way analyses of variance using the statistical software IBM SPSS version 22, applying the Tukey test when significant differenceswere detected (P < 0.05). Additionally, Pearson correlation coefficients were estimated between variables. The body condition and body weight of pregnant cows were higher than after calving (P < 0.05), and these variables were positively correlated (r = 0.4, P = 0.01). However, the haematological variables were not associated with the productive variables. The erythrograms of the different physiological stages showed significant differences (P < 0.05) in the packed cell volume (PCV) and mean corpuscular haemoglobin concentration (MCHC) values, whereas the red blood cell (RBC), haemoglobin (HGB) and platelet (PLT) counts; mean corpuscular volume (MCV); and mean corpuscular haemoglobin (MCH) did not present differences among groups. The leukograms showed increases in band neutrophils and monocytes during the calving period (P < 0.05).Discussion: Cows showed a decrease in body condition and live weight after calving. This is attributable to the weight lossfollowing the expulsion of calf as well as liquid and foetal membranes. After this point, cows did not present changes in live weight between 60 and 90 days postpartum. The RBC during all physiological stages was similar with the reported in dairy cows from central area of Mexico and Holstein cows raised in Canada. The RBC and PCV presented a gradual numeric decrease during the prepartum to postpartum periods, causing the increase in MCHC at 30, 60 and 90 days postpartum. Physiologically, it is understood that even when the number of erythrocytes decreases, their function is compensated by increasing their amount of hemoglobin. The leukograms showed statistical differences by increasing the band neutrophils and monocytes after calving, which can associated with calving and the migration of neutrophils to the uterine lumen and mammary glands. The haematological values reported herein can help to establish baseline values that would enable the detection of abnormalities in prepartum and postpartum Gyr x Holstein cows in the humid tropic of Mexico.Keywords: blood values, erythrogram, leukogram, reference data.