Sprinkler flow rate affects physiological, behavioural and production responses of Holstein cows during heat stress

Abstract

Holstein Friesian cows are known for their high milk yield. They are popular in the commercial dairy  sector of Pakistan. Heat stress is a major challenge for these animals owing to the longer summer season with high ambient temperatures (35 - 40 °C) and relative humidity (30 - 50%) in the area (Butt et al., 2020). Mitigating the effects of heat stress requires substantial investments in energy and water. Spraying dairy  cows with water in the holding pen or at the feed bunk is common practice as it lowers  body  temperature and respiration rate (Kendall et al., 2007; Chen et al., 2013; 2016), and improves feed  intake  and milk yield (Keister et al., 2002). Owing to the recent decrease in global groundwater, studies have  focused on strategies to reduce the use of water to cool dairy cows (Chen et al., 2016). Sprinkler flow  rates  of 1.3 and 4.9 L/min had similar effects on physiological responses of cows to heat load but  produced a 73%  difference in water use (Chen et al., 2016). Similarly, Tresoldi et al. (2019) concluded that  a sprinkler flow rate of 4.9 L/min had poor efficiency compared with 3.3 L/min, as the additional water did not result in increased biologically relevant cooling. These studies were conducted in Mediterranean climates with an average temperature humidity index in the range of 76 to 78. A recent study with Nili Ravi buffaloes revealed a sprinkler flow rate 1.25 L/min was more efficient than one of 2.0 L/min during subtropical summers (Bah et al., 2021). Because water is projected to be scarce in Pakistan by 2030 (Mustafa et al., 2013), holistic strategies for water conservation in the dairy sector are important nationally. The objective of this study was to evaluate the effects of various sprinkler flow rates on the performance of lactating Holstein Friesian cows in a typical corporate dairy farm setting during the subtropical summer. Performance of these cows was assumed to be similar, irrespective of the sprinkler flow rates.