Thermal radiation absorbed by dairy cows in pasture

Author(s)

da Silva, Roberto Gomes ^[1] ; Guilhermino, Magda Maria ^[2] ; Facanha de Morais, Debora Andreia E. ^[1]

Affiliation

^[1] Univ Fed Rural Semi Arido, Dept Ciencia Anim, Mossoro, RN - Brazil

^[2] Univ Fed Rio Grande do Norte, Ctr Tecnol, Dept Agropecuria, BR-59072970 Natal, RN - Brazil

• Document type: Journal article
• Source: INTERNATIONAL JOURNAL OF BIOMETEOROLOGY; v. 54, n. 1, p. 5-11, JAN 2010.
• Web of Science Citations: 22

Abstract

The goal of the present paper was to assess a method for estimating the thermal radiation absorbed by dairy cows (0.875 Holstein-0.125 Guzerath) on pasture. A field test was conducted with 472 crossbred dairy cows in three locations of a tropical region. The following environmental data were collected: air temperature, partial vapour pressure, wind speed, black globe temperature, ground surface temperature and solar radiation. Average total radiation absorbed by animals was calculated as R(abs) 640.0 +/- 3.1 W.m(-2). Absorbed short-wave radiation (solar direct, diffuse and reflected) averaged 297.9 +/- 2.7 W m(-2); long wave (from the sky and from terrestrial surfaces) averaged 342.1 +/- 1.5 W m(-2). It was suggested that a new environmental measurement, the effective radiant heat load (ERHL), could be used to assess the effective mean radiant temperature (T(mr){*}). Average T(mr){*} was 101.4 +/- 1.2 degrees C, in contrast to the usual mean radiant temperature, T(mr) = 65.1 +/- 0.5 degrees C. Estimates of T(mr){*} were considered as more reliable than those of T(mr) in evaluating the thermal environment in the open field, because T(mr) is almost totally associated only with long wave radiation. (AU)

• FAPESP's process: 05/58364-1 - Evaluation of climatic environment for the rearing or dairy cows in region with high levels of solar radiation
• Grantee: Newton La Scala Júnior
• Support Opportunities: Regular Research Grants