EFFECT OF HIGH ENVIRONMENTAL TEMPERATURE ON PRODUCTION AND HAEMATO-BIOCHEMICAL PARAMETERS OF INTENSIVELY REARED DAIRY COWS

Abstract

The dairy sector is one of the most important components of the livestock sector in Bangladesh. The demand of milk for the growing large population in Bangladesh is increasing day by day. The number of dairy farms is increasing gradually as well. Bangladesh is a country situated in sub-tropics and has a hot and humid environment. The seasons of this country vary in the temperature and humidity. The high temperature and humidity of the dairy cow shed and also cow itself can impact on the milk production and blood parameters. However, there is very limited information on the effect of heat stress on the production and blood profile of intensively reared dairy cattle. Therefore, this study was conducted in the intensively reared Chattogram military dairy farm to reveal the effect of heat stress on the production and to know the effect of heat stress on the haemato-biochemical parameters of dairy cattle. For this, a three-month-long study was conducted in Military Farm Chattogram, at Chattogram Cantonment, in Chattogram district. A total of 90 cows were selected based on the lactation at the end the month of February. Lactation-wise production data, the temperature of the ambient, shed, and rectal temperature of each cow were recorded by digital thermometer for three months, from March 2022 to May 2022. The average milk production of each cow as per lactation was calculated in Excel sheets. Milk parameters like fat, solid non-fat (SNF), and total solids (TS) were analyzed weekly in the experimental area. Blood samples were collected from 72 cows for hematological and biochemical assays after the end of the study on May, 2022. Routine hematological parameters were analyzed and a few selected serum biochemical parameters were assayed. The study revealed that the rectal temperature of cows at 3rd (101.90 ±0.3°F) and 5th (101.99 ±0.4°F) lactation increased in the month of April, whereas, increased rectal temperature of 4th lactation (101.91 ±0.4 °F) was observed in cows at May. There was significant difference of rectal temperature between different months of 4th and 5th lactating cows. Results showed that the increased average environmental (100.21± 0.4°F) and rectal temperatures (101.82± 0.4°F) were observed in May. There was no significant difference between the average rectal temperatures and environmental temperatures of cows at different months recorded during the study period. It was found that, the highest milk production was achieved in all cows of 3rd (12.12 ± 3.53 liter), 4th (12.83 ± 3.26 liter), and 5th (11.71 ± 2.86 liter) lactation during March. However, xiii average milk production decreased in April and May in all lactation groups and the variation was significant. Milk analysis data showed that the fat% significantly increased in April (3.82 ± 0.19 %) and May (3.99 ± 0.19 %) than March (3.69 ± 0.39 %). Whereas, SNF% significantly decreased in April (8.71 ±1.53 %) and May (8.58 ± 0.19%) than March (9.46± 0.25 %). Total Solids% insignificantly decreased in April (12.59 ± 1.60 %) and May (12.57 ± 0.27 %). The hematological analysis revealed that, there was significant variations of white blood cells (WBC) among different lactations with higher number of WBC was found during 5th lactation (11.50±3.03 10³/µL). Irrespective to months, across the blood samples, all of the hematological parameters were found to be within normal value range; except in case of mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentrations (MCHC) where majority of the cows showed higher than normal (49% and 57% samples, respectively). Blood serum biochemical analysis revealed that glucose, sodium and calcium were found to be higher in the 3rd lactation animals whereas albumin and chloride were higher in the 4th lactation. Total Protein (TP), Phosphorus, ALT (Alanine Transaminase) and AST (Aspartate Transaminase) were higher in 5th lactation animals where AST was significantly higher than other lactation. Phosphorus was found to be higher across all blood samples with 60% samples had higher than normal reference range. The study can conclude from the findings that the ambient temperature directly affects the body physiology of cows—reflected by the increased rectal temperature and decreased milk production —and the milk components especially SNF and Total solids. It also affects the older cows (5th lactation) than the younger animals (3rd lactation) which is reflected through the changes of hematological parameters (especially WBC) and biochemical parameters (especially AST). Therefore, there could be possible effect of the ambient temperature on the heat stress of dairy cows and optimum environmental temperature is necessary for the better production and body physiology of intensively reared dairy cows