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Physiological responses of lactating cows under grazing and indoor feeding conditions in the tropics

Published online by Cambridge University Press:  12 July 2002

S. PRASANPANICH
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
S. SIWICHAI
Affiliation:
Dairy Farming Promotion Organization of Thailand, Muaklek, Saraburi, 18180, Thailand
K. TUNSARINGKARN
Affiliation:
Institute of Health and Research, Chulalongkorn University, Bangkok, 10330, Thailand
C. J. THWAITES
Affiliation:
Department of Animal Science, School of Rural Science and Natural Resources, The University of New England, Armidale, 2351, Australia
C. VAJRABUKKA
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand

Abstract

The study reported examined the physiological changes between two groups of 6 Friesian-cross cows in mid-lactation; one group grazed outdoors without shade, the second group was housed indoors in an open-sided barn and fed cut-and-carry forage from the grazing area. All cows were machine-milked at 05.00 and 15.30 h daily. At 14.00 h dry bulb temperatures averaged 29·5 °C outdoors and 29·0 °C indoors whilst black globe temperatures were 36·2 and 29·5 °C respectively. Relative humidity averaged 76% outdoors and 72% indoors, and the temperature-humidity indices were 79·1 and 78·3, respectively. Cows in the outdoor group had higher rectal temperatures (40·4 v. 39·0 °C; P<0·01), respiratory rates (87·9 v. 62·9 breaths/min; P<0·01) and skin temperatures (41·2 v. 38·2 °C; P<0·01) than those indoors, but lower haematocrit (26·2 v. 34·9%; P<0·01) and haemoglobin levels (10·4 v. 13·2 g/100 ml; P<0·01). Cows in the outdoor group had a higher sweating rate than those indoors (559·7 v. 68·6 g/(m2×h); P<0·01), largely due to a high radiant heat load (as indicated by slightly higher black globe readings). The results of the current study show that the barn used in this study was effective in protecting cows from solar heat. Further field studies to determine the effectiveness of lower cost strategies to reduce heat stress, including showers and shade that can be accessed by grazing cows, are needed.

Type
Research Article
Copyright
© 2002 Cambridge University Press

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