Abstract
This work aimed to study the annual variation of temperature of the coat surface and other traits of coat in Holstein cows managed in a tropical environment by separately considering black coat and white coat. It was measured the coat thickness (mm) characteristic, hair length (mm), hair number (hair/cm²) and coat surface temperature on 191 crossbred cows with 7/8 and 31/32 Holstein composition distributed in 3 herds in a semi-arid environment. Less dense coats with shorter, flattened hair occurred predominantly in March, a time coinciding to high levels of solar radiation. This type of coat shows low resistance to the flux of latent and sensitive heat through the skin, thus favoring heat loss. The black coat surface temperature was on average 4ºC higher than that of the white one during all the year and its variation followed that of the mean radiant temperature. The models developed to predict the effective thermal conductivity of the coat must take these differences into account because the thermal gradient parallel to the skin surface is not negligible for Holstein cows under the sun in a tropical environment, as well as the other traits.
Highlights
O pelame representa a fronteira entre o ambiente e o corpo dos animais e influencia diretamente as trocas térmicas
This work aimed to study the annual variation of temperature of the coat surface and other traits of coat in Holstein cows managed in a tropical environment by separately considering black coat and white coat
It was measured the coat thickness characteristic, hair length, hair number and coat surface temperature on 191 crossbred cows with 7/8 and 31/32 Holstein composition distributed in 3 herds in a semi-arid environment
Summary
Débora Andréa Evangelista Façanha, Roberto Gomes da Silva, Alex Sandro Campos Maia, Magda Maria Guilhermino, Angela Maria de Vasconcelos. ABSTRACT - This work aimed to study the annual variation of temperature of the coat surface and other traits of coat in Holstein cows managed in a tropical environment by separately considering black coat and white coat. As características morfológicas do pelame, como densidade numérica, comprimento dos pelos e espessura da capa, influenciam diretamente o isolamento térmico proporcionado pelo pelame e podem variar ao longo do ano. Veiga et al (1964) observaram que o pelame de vacas da raça Holandesa apresentava modificações anuais, com substituição dos pelos longos e menos brilhantes, no inverno, por pelos curtos e brilhantes, no verão. Neste trabalho objetivou-se estudar a variação anual das características morfológicas do pelame, além da temperatura de superfície dos pelames preto e branco de vacas Holandesas em ambiente tropical
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