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.
Product Manager for Feed Solution
CCPA Group
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.
THE EFFECTS OF LONG-TERM HEAT STRESS ON OFFSPRING
Research suggests that the deleterious effects of post-traumatic stress can be perpetuated over several generations. This phenomenon, known as transgenerational programming, highlights the lasting consequences of heat stress. Exposure of cows to heat stress at the end of gestation (particularly during the last trimester) can compromise the development of the mammary gland, not only in the cow itself, but also in the unborn calf. This results in a reduction in future milk production capacity during the dairy career. Studies have shown that calves born to heat-stressed mothers can produce up to 5 kg less milk per day in their first lactation than those born to mothers not exposed to high temperatures.
As well as having an impact on milk production, calves exposed to heat stress in utero show a reduction in longevity of 11.7 months (Laporta et al; 2020).
Heat stress in calves, even during the prenatal period, can significantly influence their health, growth and, ultimately, their future milk yield.
PREVENT THE CONSEQUENCES OF HEAT STRESS WITH THERMOPLUS®
In Mexico, the CCPA group tested the distribution of Thermoplus® around calving time. The results of this test were associated with a more favourable start to lactation.
Thermoplus® was administered for 24 days prior to farrowing and for the first 100 days of lactation. The batch receiving the Thermoplus® solution got off to a more promising start, with milk production 10% higher. Distribution before calving showed positive effects from the very first days of lactation.
Thermoplus® is a specific plant- and mineral-based premix designed to reduce the adverse effects of heat stress on dairy ruminants. A trial published in the Journal of Dairy Science in 2023 revealed that, in addition to improved milk production (in terms of milk volume and rate), animals fed Thermoplus® showed a reduction in stress markers and a lower body temperature.
We recommend using the adjuvant Thermoplus® for all the animals in the herd:
• Dairy cows and dry cows: 40g per day via a mineral or specific feed
• Calf: 6.5g per 100 kg live weight
Our trials show a return on investment of more than 3.
