Acclimatization response to a short-term heat wave during summer in lactating Brown Swiss and Holstein Friesian cows
Author(s)
Date Issued
2025
Type
article
Volume
12
Journal
Abstract
Introduction: Dairy cows are highly susceptible to heat stress, raising concerns
about animal welfare, production efficiency, and economic losses. Previous
studies suggest that Holstein and Brown Swiss breeds exhibit different levels
of thermal tolerance, but their short-term adaptive responses require further
investigation.
Methods: This study aimed to evaluate breed-specific physiological and
productive responses to a 4-day natural heat wave in 40 lactating cows (20
Holstein, 20 Brown Swiss) from the same commercial dairy farm, homogeneous
for days in milk, body condition score, parity, and energy-corrected milk
yield. Before the heat wave, cows experienced at least 48 h in thermoneutral
conditions. Physiological parameters were recorded three times daily (4:00 AM,
3:00 PM, and 8:00 PM). Blood samples were collected before the heat wave (D1,
4:00 AM, thermoneutral conditions) and at the warmest moment of the fourth
day (D4, 3:00 PM, heat stress conditions).
Results and Discussion: The heat wave negatively impacted physiological
parameters in both breeds. Rectal temperature increased daily from 4:00 AM
to 3:00 PM (p < 0.01), with Holstein cows showing consistently higher values
than Brown Swiss (p < 0.01). Respiration rate reached its lowest point at 4:00
AM each day (p < 0.01) but remained elevated at 8:00 PM, despite decreasing
THI, indicating accumulated heat load. While both breeds followed a similar
trend, Holsteins exhibited a greater capacity for overnight recovery compared
to Brown Swiss. Regarding productivity, Brown Swiss cows maintained stable
milk yield (MY) from D1 to D4, whereas Holsteins showed a progressive MY
decline throughout the heat wave (p < 0.01). Most blood parameters showed no
significant breed differences (p > 0.05), but heat shock protein 70, a key regulator
of thermal adaptation, exhibited an increasing trend in both breeds (p < 0.01),
appearing earlier than other physiological indicators of heat stress.
Conclusion: This study, conducted under identical conditions, highlights distinct
breed-specific responses to short-term heat stress. The findings suggest that
Brown Swiss cows may be more resilient to heat stress in terms of productivity,
while Holsteins show better nighttime recovery. Further research should explore
additional physiological and molecular markers to better characterize breed
differences and improve heat stress mitigation strategies in dairy farming.
Project(s)
PRIN-2022 grant from Italian Ministry of University and Research (Resiliency to heat stress: a system biology approach, CUP: J53D23010270006).