Impact of environmental factors on physiological adaptability, thermo-tolerance indices, and productivity in Jersey crossbred cows

Environmental stressors such as temperature, humidity, rainfall, photoperiod, etc. under tropical conditions are some of the important limiting factors for optimum expression of production and reproduction in dairy cows. The present study evaluated changes in cardinal physiological responses, heat tolerance indices, and milk yield in Jersey crossbred cows due to abiotic stress. Climograph was developed using daily maximum and minimum temperatures, humidity, and rainfall at livestock farm over a period of 15 years. Seasons significantly (P < 0.01) influenced cardinal physiological responses and thermal adaptability of Jersey crossbred cows. Diurnal environmental variations between morning and afternoon of the shed caused increase in body temperature, pulse, and respiration rate by 0.59-0.91%, 4.95-7.18%, and 9.73-32.37%, respectively. Thermal adaptability of cows showed significant (P < 0.01) higher deviations from perfect state of adaptability during summer, monsoon, and post-monsoon as compared to winter and spring seasons. The responsiveness and ranking of cows were dissimilar among 3 heat tolerance indices, viz., Iberia heat tolerance index, Benezara's coefficient of adaptability, and Dairy Search Index (DSI). Enhanced respiration rate was the most important observable bio-indicator to poor thermal adaptability. Good thermo-tolerant cows had 8.86% higher (P < 0.05) monthly milk yield per cow than poorly adapted ones. Findings of this study suggest that deviations in cardinal physiological responses across the seasons are very reliable and simple estimates for evaluating levels of thermo-tolerance in crossbred cows.

Effect of heat stress amelioration through open-ridge ventilated thatched roof housing on production and reproduction performance of crossbred Jersey cows

The present study was conducted to assess the impacts of loose house roofing designs and materials on modulation of micro-climate of the cow shed and its influences on production and reproduction performance of lactating crossbred Jersey cows. The control group (T0) was kept in a traditional single-slope asbestos roof shed and treatment group (T1) at a specially designed open-ridge ventilated, double-slope thatch roof shed. Lactation stage, average daily milk yield, and average parity at the beginning of the experiment were kept similar between T0 and T1 cows. The specifically designed T1 shed had significantly (P < 0.05) lower temperature, humidity, and thermal humidity index as compared to the traditional shed (T0). The T1 shed was cooler and more comfortable than T0. Housing significantly (P < 0.05) influenced cardinal physiological parameters of resident cows. Body temperature, pulse rate, respiration rate, and discomfort index were significantly (P < 0.05) higher in T0 as compared to those in T1 cows. Improved housing significantly (P < 0.01) influenced milk yield, composition, quality, and udder health of cows. Daily milk yield depending on parity, monthly milk yield, milk fat, SNF, and protein were significantly (P < 0.01) higher in T1 than those in T0 cows. The milk somatic cell count, modified California mastitis test score, electrical conductivity, and pH of milk samples of T0 cows were significantly (P < 0.0) higher than those of T1. Effect of housing type, parity, and interaction of housing × parity did not cause any significant (P > 0.05) differences in reproductive traits such as service period, break period, calving interval, pregnancy rate, and other cow fertility parameters. Post-partum body condition score and body weight loss did not differ significantly (P > 0.05) between the two groups; however, more loss occurred in T0 than T1. The estimated net profit from housing of cows (N = 20) in a comfortable shed was 2200 kg milk per annum, i.e., 110 kg/cow/annum. The study concluded that a central open-ridge ventilated, double-slope thatched roof design created a favorable micro-environment and it significantly affected cows' comfort index; thermo-comfortable housing significantly reduced the heat stress-oriented drop in milk yield and decline in milk composition, and improved udder health and other milk production traits; however, its impact was non-significant on reproduction and fertility traits in Jersey crossbred cows.