Assessment of the correlation between thermal stress and mineral status during late gestation in cross bred dairy cattle

Abstract

In a hot, humid tropical state like Kerala, the production of crossbred dairy cattle is severely impacted by thermal stress. To implement appropriate mitigation strategies and achieve sustainable production, it is crucial to assess the level of stress and its relationship to physiological changes, particularly when both thermal stress and metabolic stress occur during the late gestation stage. Hence this study was formulated for the assessment of the correlation between thermal stress and mineral status during late gestation in cross-bred dairy cattle. Two distinct sets of six healthy Holstein Friesian crossbred cows (Frieswal) from the 210th day of gestation to the day of calving were selected from the University Livestock Farm and Fodder Research Development Scheme, KVASU, Mannuthy for the present study. The first set included six animals commencing their 210th day of gestation in December, serving as the control group (season Ⅰ). The second set consisted of another six animals commencing their 210th day of gestation in March (season Ⅱ). Thus, the late gestation period of these animals fell in the period of elevated temperature humidity index (THI) (Jisha, 2020). The animals were maintained at standard feeding (ICAR, 2013) and management practices for the entire study period. Clean drinking water was provided ad libitum. During the study period, ambient temperature and relative humidity were collected. Inhouse temperature, inhouse relative humidity, inhouse floor temperature, respiration rate, rectal temperature, and skin temperature (forehead, ear, neck, forelimb, hindlimb, and udder) were recorded at 10:00 A.M., 2:00 P.M., and 5:00 P.M. The blood was taken on 210th, 240th, and 270th days of gestation. The blood samples were collected from the animals two times at the beginning of the 8th and 9th months and from newborn calves. The meteorological and physiological parameters were recorded on three-day intervals from the 210th day specifically at 10:00 A.M., 2:00 P.M., and 5:00 P.M. till the day of calving. All the climatic parameters were significantly elevated in the heat-stressed season (season Ⅱ) compared to the season Ⅰ. In season Ⅱ, there was a significant increase in respiration rate, rectal temperature, and skin temperature. 93 Minerals like Cu, Se, Fe, and Co showed a significant difference. Biochemical parameters like glucose, total protein, albumin, and globulin did not show a consistently significant change. Also, a significant increase in thyroxine (T4) during the heat stress period was noted. Even in the low THI period, the animal started responding to variations in temperature. Microenvironment manipulations like intermittent wetting, ventilation, and forced ventilation as well as mineral supplementation could be adopted for alleviating thermal stress in the terminal stage of gestation in dairy cows for optimizing production in the subsequent lactation period and also the health of the calf born. This observation also pointed to the fact that the thermoneutral zone of different categories of dairy cattle corresponding to different physiological states has to be reassessed with continuous monitoring of physiological parameters in a climate-controlled environment.