INFLUENCE OF THERMAL STRESS ON POST-PARTUM REPRODUCTIVE PERFORMANCE OF CROSSBRED DAIRY COWS

Loading...
Thumbnail Image
Date
2020-05-12
Journal Title
Journal ISSN
Volume Title
Publisher
COLLEGE OF VETERINARY AND ANIMAL SCIENCES, POOKODE WAYANAD
Abstract
Together with increasing productivity of dairy cows, vulnerability to thermal stress (TS) and fertility impairments have become serious concern in the context of ongoing climate change phenomenon. The study was carried out at LRS Thiruvazhamkunnu in Kerala, to elucidate TS influence on reproductive performance of crossbred dairy cows and to identify suitable biological markers for timely intervention. The study involved retrospective assessment of reproductive performance in comparison with climatic variables over a period of six years and prospective investigation of the climatic stress impact on various production and reproduction parameters round the year. Major climatic stress factors showed significant (P<0.001) variation between seasons with highest ambient temperature during summer and lowest in rainy season. Relative humidity was rather high throughout the years so that THI was high enough to cause mild to moderate TS across all the seasons. Corresponding to the extended influence of TS factors, reproductive performance was much below the expected level irrespective of the seasons. Prospective study also showed almost similar pattern of stress impact throughout the year. The biological response assessed based on HSP 70 and Cortisol levels in the serum indicated the prevalence of TS during all seasons with maximum during summer. Respiration rate, rectal temperature and serum MDA level also showed highly significant elevation during summer being the immediate response to stress. However, production and reproduction related parameters showed more or less uniform levels of overall performance between seasons. It is concluded that overall lowered herd fertility is the consequence of TS exposure throughout the year. In spite of more adverse climate during summer, uniform fertility across seasons appears to be due to the adaptation mechanism, reflected by the high level of HSP 70 in the serum. Hence HSP 70 can be used as an effective indicator of TS in crossbred dairy cows.
Description
Submitted in partial fulfillment of the requirement for the degree of DOCTOR OF PHILOSOPHY
Keywords
Citation
Collections