ISSUE FOCUS 40 FEED & ADDITIVE MAGAZINE June 2024 The negative effects of heat stress on dairy cows have been documented. Every year, farmers implement various measures in terms of feed, technology and herd management to minimise the economic losses. The focus is mainly on lactating cows because of the immediate impact of heat stress. Dry cows do not always receive adequate attention despite significant consequences of heat stress on these animals and their offsprings. THE EFFECTS OF SHORT-TERM HEAT STRESS DURING THE DRYING PERIOD The first studies into the impact of heat stress during the dry period began to emerge around five years ago. The final phase of gestation is proving to be particularly critical due to the increased metabolic requirements of the cow associated with the intensive development of the foetus. This period also determines the potential of the next lactation. Drying is of crucial importance for the regeneration and development of the mammary gland. Studies such as those carried out by Tao et al (2011) have demonstrated, using sequential biopsies, that heat stress has a negative impact on mammary cell proliferation. Rising temperatures expose lactating and dry cows to increased risks of metabolic disorders such as reduced feed intake, hormonal instability, and changes to the immune system (Tao et al. 2012; Amaral et al. 2010, 2011). This makes them more susceptible to various infectious diseases. The consequences of heat stress during the dry period can be a 10% to 15% reduction in calf birth weight, a reduction in the quality and quantity of milk produced, and a drop in post-calving performance of up to 20%. This phenomenon is most frequently observed on farms in autumn. Even when temperatures return to normal levels and signs of heat stress disappear, restoring initial performance is often complicated. HEAT STRESS IN DRY COWS Jean Pascard Product Manager for Feed Solution CCPA Group Image 1. In the event of heat stress in cattle, it is imperative to implement corrective measures as soon as possible.
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