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Effect of Heat Stress on Blood Parameters in Indigenous Sheep

Dr. M. A. Hashem
Professor
Department of Animal Science, Bangladesh Agricultural University, Mymensingh-2202

Abstract/ Executive Summary:

The research was conducted to study the effect of heat stress on blood parameters in indigenous sheep. Nine sheep were divided into three groups which were almost similar in age, sex and weight. Three groups were divided as zero hour (T₀), four hours (T₄) and eight hours (T₈) heat exposure to direct sunlight. During experimental period temperature–humidity index (THI) value was calculated as 27.09 which indicate T₄and T₈ groups were subjected to heat stress condition for at least four hours and eight hours respectively every day. The amount of red blood cell (RBC), hemoglobin (Hb%) and packed cell volume (PCV%) were increased significantly (p<0.05) with the increase of heat stress but the amount of white blood cell (WBC) had no significant difference (P>0.05) among the treatment groups. It can be concluded that heat stress had significant changes on some blood parameters in indigenous sheep.

Keywords: Heat stress, Sheep, Red blood cell, Hemoglobin, White blood cell, Packed cell volume

Location: Mymensingh

Start Date: 20-04-2011

End Date: 05-06-2011

Program Area: Variety and Species

Commodity: Sheep

Objectives:

The present research work was undertaken to determine the effect of heat stress on blood parameters in indigenous sheep.

Methodology:

The experiment was carried out in goat, sheep and horse farm under the department of Animal Science. Laboratory analyses of the experimental samples were carried out in the laboratory of same department and also in the department of Physiology, Bangladesh Agricultural University, Mymensingh.Nine indigenous sheep which were almost similar in age, sex and weight were selected for the experiment. Means of estimating the severity of heat stress was proposed using both ambient temperature and relative humidity, termed as the temperature humidity index (THI) (LPHSI, 1990; Marai et al. (2007). When temperature is measured (⁰F), the equation to determine THI is as follows (LPHSI, 1990): THI = db ⁰F − {(0.55 − 0.55 RH) (db ⁰F − 58)} where db ⁰F is the dry bulb temperature in ⁰F and RH is the relative humidity (RH%)/100, for sheep and goats. The obtained values indicate the following: values <82 = absence of heat stress; 82 to <84 = moderate heat stress; 84 to <86 = severe heat stress and over 86 = extreme severe heat stress (LPHSI 1990). When the temperature is expressed in ⁰C, the equation of Marai et al. (2001) changes as follows: THI = db ⁰C − {(0.31 − 0.31 RH) (db ⁰C − 14.4)} where db ⁰C is the dry bulb temperature (⁰C) and RH is the relative humidity (RH%)/100. The values obtained indicate the following: <22.2 = absence of heat stress; 22.2 to <23.3 = moderate heat stress: 23.3 to <25.6 = severe heat stress and 25.6 and more = extreme severe heat stress (Marai et al., 2001). Animals were housed in semi-intensive housing system in the Goat, sheep and horse farm of the department of Animal Science. All the sheep were kept in three groups (one group consists of three animals) in the room separated with fence. One group was assigned as control (average room temperature 23.6^?C and relative humidity 65% i.e. zero hour heat exposure), and the rest two groups were served as heat stress such as 4 hours heat exposure from 10 am to 2 pm and 8 hours heat exposure from 9 am to 5 pm. Roughage and concentrate feeds were supplied everyday at adequate amount. A large water trough was provided for each group to supply fresh water available ad libitum. The house was well ventilated and the space per animal was adequate. Cleaning and hygienic management was maintained regularly. The floor, stall, water trough, and feeder were cleaned every day. The faeces were removed carefully from the house. Duration of the experiment :The heat stress period was 45 days, from 20 April 2011 to 5 June 2011. Before starting the collection of experimental data, all animals were subjected for acclimatization with the environment (e.g., daily routine activities) for about two months. All the animals were given 15 days for their psychological and physiological adjustment before starting the real experiment for data collection. Measurement of ambient temperature and relative humidity: The data about ambient temperature and relative humidity of these experimental days was collected from Meteorological Centre, Department of Irrigation and Water Management, Bangladesh Agricultural University, Mymensingh.Determination of blood parameters: Jugular vein was selected for blood collection from all experimental animals by the method described by Schalm et al. (1975). The site of collection was made sterile by using ethyl alcohol to prevent the risk of phlebitis. Immediately after collection into syringe, blood was transferred to sterile test tube containing anticoagulant (4% Sodium Citrate solution) at a ratio of 1:10. Because of time constraint, this blood was then carried out to Physiology Laboratory in an ice carrier and preserved under refrigeration temperature. The sample was then examined for various hematological parameters on the following day. Hemoglobin (Hb) was estimated first after collection of blood. This test was done by Acid-Hematin method. Total erythrocyte count (RBC), total leukocyte count (WBC) and packed cell volume (PCV) were determined as per technique described by Shastry (1983). Body weight, length and heart girth of the animals were also taken. Statistical analysis:The data in this experiment were analyzed statistically using the analysis of variance technique in a computer using SAS statistical computer package programme (1998) in accordance with the principle of Completely Randomized Design (CRD). Duncan’s Multiple Range Test was done to compare variations between treatments.

Source of Information: J. Bangladesh Agril. Univ. 12(1): 91–94, 2014

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From the above study, it can be concluded that heat stress significantly affects on blood parameters i.e. RBC, hemoglobin and PCV levels of indigenous sheep. Further, in depth study is needed to explore more information to minimize the effect of heat stress on blood parameters for both qualitative and quantitative production approaches of sheep meat.

Knowledge Management: Journal