Discover how heat stress impacts dairy cows’ feed intake and milk yield. Learn about our research findings and the mitigation strategies to counter these effects.
Who would have thought that weather conditions could have such a profound effect on our dairy supplies? It turns out that heat stress can have a significant impact on dairy production, reducing feed intake and milk yield in cows. This could also lead to changes in milk composition and feed efficiency. However, data examining these effects across various levels of heat stress and different cow populations involved in heat stress studies is limited.
To shed some light on this issue, our research had two primary objectives. The first was to assess the effects of heat stress on dry matter intake (DMI), energy-corrected milk (ECM), milk composition, and feed efficiency (kg ECM/kg DMI). The second objective was to delve deeper into the relationship between these effects and heat stress interventions, as well as individual animal characteristics. For this study, we used meta-analytical approaches.
In the end, data from 31 studies, yielding 34 trials, met the inclusion criteria, providing us with a rich pool of data for analysis. Results showed that heat stress decreased DMI, ECM, and milk protein concentration. Interestingly, however, it did not significantly alter milk fat concentration or feed efficiency.
In the realm of statistical evaluation, a meta-regression confirmed these findings. Reductions in DMI and ECM were linked to rising temperature-humidity index (THI). During periods of heat stress, for each unit increase in THI, DMI and ECM decreased by 4.13% and 3.25%, respectively, in mid-lactation cows.
Our regression models also uncovered a significant interaction between THI and the lactation stage. This interactive component helped explain the substantial variations in the effect sizes of DMI and ECM. We conclude that understanding these relationships and how individual animal characteristics interact with heat stress effects warrant further research.
It’s clear from our findings that heat stress can considerably decrease productivity. This reaches beyond the realm of academic interest and signals a strong need for the implementation of mitigation strategies in heat-stressed herds.
Read more: https://doi.org/10.3168/jds.2023-24059
