Index of thermal stress for cows (ITSC) under high solar radiation in tropical environments
Tóm tắt
This paper presents a new thermal stress index for dairy cows in inter-tropical regions, with special mention to the semi-arid ones. Holstein cows were measured for rectal temperature (T
R), respiratory rate (F
R) and rates of heat exchange by convection (C), radiation (R), skin surface evaporation (E
S) and respiratory evaporation (E
R) in the north eastern region of Brazil, after exposure to sun for several hours. Average environmental measurements during the observations were air temperature (T
A) 32.4 °C (24.4–38.9°), wind speed (U) 1.8 m.s−1 (0.01–11.0), relative humidity 63.6 % (36.8–81.5) and short-wave solar radiation 701.3 W m−2 (116–1,295). The effective radiant heat load (ERHL) was 838.5 ± 4.9 W m−2. Values for the atmospheric transmittance (τ) were also determined for tropical regions, in order to permit adequate estimates of the solar radiation. The average value was τ = 0.611 ± 0.004 for clear days with some small moving clouds, with a range of 0.32 to 0.91 in the day period from 1000 to 1300 hours. Observed τ values were higher (0.62–0.66) for locations near the seacoast and in those regions well-provided with green fields. Effects of month, location and time of the day were all statistically significant (P < 0.01). A total of 1,092 data were obtained for cows exposed for 1 to 8 h to sun during the day; in 7 months (February, March, April, July, August, September and November), 4 days per month on the average. A principal component analysis summarised the T
R, F
R, C, R, E
S and E
R measurements into just one synthetic variable (y
1); several indexes were then obtained by multiple regression of y
1 on the four environmental variables and its combinations, by using Origin 8.1 software (OriginLab Corp.). The chosen equation was the index of thermal stress for cows, ITSC = 77.1747 + 4.8327 T
A − 34.8189 U + 1.111 U
2 + 118.6981 P
V − 14.7956 P
V
2 − 0.1059 ERHL with r
2 = 0.812. The correlations of ITSC with T
R, F
R, C, E
S, R and E
R were 0.275, 0.255, −0.493, −0.647, −0.818 and 0.075, respectively. Correlations of the index with the physiological variables are presented, and ITSC is compared to three other indexes.
Tài liệu tham khảo
Baeta FC, Meador NF, Shanklin MD, Johnson HD (1987) Equivalent temperature index at temperatures above the thermoneutral for lactating cows. Paper nr. 87–4015. American Society of Agricultural Engineers, St. Joseph, MI
Buffington DE, Collazo-Arocho A, Canton GH, Pitt D (1981) Black globe-humidity index (BGHI) as comfort equation for dairy cows. Trans ASAE 24:711–714
Campbell GS, Norman JM (1998) An introduction to environmental biophysics, 2nd edn. Springer, New York
DaSilva RG (2002) Carga térmica radiante: revisando a técnica de avaliação [Radiant heat load: revisiting its evaluation technique]. Rev Eng Rural (Piracicaba, Brazil) 13:77–84
DaSilva RG, Maia ASC (2013) Principles of animal biometeorology. Springer, Dordrecht, 261p
DaSilva RG, LaScala N, Tonhati H (2003) Radiative properties of the skin and haircoat of cattle and other animals. Trans ASAE 46:913–918
DaSilva RG, Guilhermino MM, Morais DAEF (2010) Thermal radiation absorbed by dairy cows in pasture. Int J Biometeorol 54:5–11
Dewitte S, Crommelynck D, Joukoff A (1997) Maintenance of a long-term total solar irradiance data series. In: Wilson A (ed) Correlated phenomena at the sun, in the heliosphere and in geospace. 31st ESLAB Symposium, 22–25 September 1997. Noordwijk, The Netherlands, p 243–250
Eigenberg RA, Brown-Brandl TM, Nienaber JA, Hahn GL (2005) Dynamic indicators of heat stress in shaded and non-shaded feedlot cattle. Part 1: predictive relationships. Biosystems Eng 91:111–118
Fröhlich C, Lean J (1998) The sun’s total irradiance: cycles, trends and related climate change uncertainties since 1976. Geophys Res Lett 25:4377–4380
Gates DM (1980) Biophysical ecology. Springer, New York
Gaughan JG, Mader TL, Holt SM, Lisle A (2008) A new heat load index for feedlot cattle. J Anim Sci 86:226–234
Hillman PE, Lee CN, Parkhurst A (2001) Impact of hair color on thermoregulation of dairy cows to direct sunlight. Paper nr. 014031 pres. To 94th Annual International Meeting of the ASAE, Sacramento, CA, July 29–August 1
Hutchinson JCD, Brown GD (1969) Penetrance of cattle coats by radiation. J Appl Physiol 26:454–464
Kovarik M (1973) Radiation penetrance of protective covers. J Appl Physiol 35:562–563
Lima LOS (1991) Aspectos genéticos da relação entre a taxa de sudação e a produção de leite em vacas Holandesas [Genetic aspects of the relationship between sweating raqte and milk yield of Holstein cows]. MS Dissertation, São Paulo State University, Jaboticabal, SP, Brazil, 62p
Liu BY, Jordan RC (1960) The interrelationship and characteristic distribution of direct, diffuse and total solar radiation. Sol Energ 4:1–19
Mader TL, Johnson LJ, Gaughan JB (2010) A comprehensive index for assessing environmental stress in animals. J Animal Sci 88:2153–2165
Maia ASC, DaSilva RG, Loureiro CMB (2005) Sensible and latent heat from the body surface of Holstein cows in a tropical environment. Int J Biometeorol 50:17–22
Monteith JL, Unsworth MH (2008) Principles of environmental physics, 3rd edn. Academic, London, 418p
Rencher AC (1995) Methods of multivariate analysis. Wiley, New York, 627p
Shioya S, Terada F, Iwama Y (1997) Physiological responses of lactating dairy cows under hot environments. Eiyoseiri-kenkyuukaiho 41:61–68 [abstract]
Thom EC (1959) The discomfort index. Weatherwise 12:57–60
Unsworth MH, Monteith JL (1972) Aerosol and solar radiation in Britain. Q J Roy Meteorol Soc 99:778–797