Heat Stress Impacts on Lactating Cows Grazing Australian Summer Pastures on an Automatic Robotic Dairy
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Date
2020-05-17
Journal Title
Journal ISSN
Volume Title
Publisher
animals
Abstract
The objective of this study was to measure the impacts of summer heat events on
physiological parameters (body temperature, respiratory rate and panting scores), grazing behaviour
and production parameters of lactating Holstein Friesian cows managed on an Automated
Robotic Dairy during Australian summer. The severity of heat stress was measured using
Temperature-Humidity Index (THI) and impacts of di erent THIs—low ( 72), moderate (73–82) and
high ( 83)—on physiological responses and production performance were measured. There was a
highly significant (p 0.01) e ect of THI on respiratory rate (66.7, 84.7 and 109.1/min), panting scores
(1.4, 1.9 and 2.3) and average body temperature of cows (38.4, 39.4 and 41.5 C), which increased as
THI increased from low to moderate to high over the summer. Average milk production parameters
were also significantly (p 0.01) a ected by THI, such that daily milk production dropped by 14%
from low to high THI, milk temperature and fat% increased by 3%, whilst protein% increased by 2%.
The lactation stage of cow had no significant e ect on physiological parameters but a ected (p 0.05)
average daily milk yield and milk solids. Highly significant (p 0.01) positive correlations were
obtained between THI and milk temperature, fat% and protein% whilst the reverse was observed between THI and milk yield, feed intake and rumination time. Under moderate and high THI, most
cows sought shade, spent more time around watering points and showed signs of distress (excessive
salivation and open mouth panting). In view of the expected future increase in the frequency and
severity of heat events, additional strategies including selection and breeding for thermotolerance
and dietary interventions to improve resilience of cows need to be pursued.
Description
Research Article
Keywords
milk production, panting scores, respiration rate, thermal camera
Citation
Osei-Amponsah, R.; Dunshea, F.R.; Leury, B.J.; Cheng, L.; Cullen, B.; Joy, A.; Abhijith, A.; Zhang, M.H.; Chauhan, S.S. Heat Stress Impacts on Lactating Cows Grazing Australian Summer Pastures on an Automatic Robotic Dairy. Animals 2020, 10, 869.