Latent heat loss of dairy cows in an equatorial semi-arid environment

• Published in: International journal of biometeorology Vol. 56; no. 5; pp. 927 - 932
• Main Authors: da Silva, Roberto Gomes, Maia, Alex Sandro Campos, de Macedo Costa, Leonardo Lelis, de Queiroz, João Paulo A. Fernandes
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-09-2012; Springer Nature B.V
• Subjects: Air temperature; Animal Physiology; Animals; Arid environments; Arid zones; Biological and Medical Physics; Biometeorology; Biophysics; Body Temperature Regulation; Cattle; Cattle - physiology; Dairy cattle; Dairy farms; Dairying; Desert Climate; Earth and Environmental Science; Environment; Environmental Health; Evaporation; Female; Heat transfer; Hot Temperature; Latent heat; Least squares method; Meteorology; Original Paper; Plant Physiology; Respiratory Rate; Semiarid environments; Semiarid lands; Surface temperature; Temperature; Vapor pressure; Wind speed; Dairy cows; Thermoregulation; Semi-arid; Cutaneous evaporation; Respiratory evaporation; Tropical environment
• ISSN: 0020-7128; 1432-1254
• DOI: 10.1007/s00484-011-0501-y

The present study aimed to evaluate evaporative heat transfer of dairy cows bred in a hot semi-arid environment. Cutaneous (
E
S
) and respiratory (
E
R
) evaporation were measured (810 observations) in 177 purebred and crossbred Holstein cows from five herds located in the equatorial semi-arid region, and one herd in the subtropical region of Brazil. Rectal temperature (
T
R
), hair coat surface temperature (
T
S
) and respiratory rate (
F
R
) were also measured. Observations were made in the subtropical region from August to December, and in the semi-arid region from April to July. Measurements were done from 1100 to 1600 hours, after cows remained in a pen exposed to the sun. Environmental variables measured in the same locations as the animals were black globe temperature (
T
G
), air temperature (
T
A
), wind speed (
U
), and partial air vapour pressure (
P
V
). Data were analysed by mixed models, using the least squares method. Results showed that average
E
S
and
E
R
were higher in the semi-arid region (117.2 W m
−2
and 44.0 W m
−2
, respectively) than in the subtropical region (85.2 W m
−2
and 30.2 W m
−2
, respectively). Herds and individual cows were significant effects (
P
 < 0.01) for all traits in the semi-arid region. Body parts did not affect
T
S
and
E
S
in the subtropical region, but was a significant effect (
P
 < 0.01) in the semi-arid region. The average flank
T
S
(42.8°C) was higher than that of the neck and hindquarters (39.8°C and 41.6°C, respectively). Average
E
S
was higher in the neck (133.3 W m
−2
) than in the flank (116.2 W m
−2
) and hindquarters (98.6 W m
−2
). Coat colour affected significantly both
T
S
and
E
S
(
P
 < 0.01). Black coats had higher
T
S
and
E
S
in the semi-arid region (41.7°C and 117.2 W m
−2
, respectively) than white coats (37.2°C and 106.7 W m
−2
, respectively). Rectal temperatures were almost the same in both subtropical and semi-arid regions. The results highlight the need for improved management methods specific for semi-arid regions.