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| Maia,Alex Sandro Campos; Silva,Roberto Gomes da; Souza Junior,João Batista Freire de; Silva,Rosiane Batista da; Domingos,Hérica Girlane Tertulino. |
| The objective of the present study was to assess the effective thermal conductivity of the hair coat (k ef, mW.m-1.K-1) of Holstein cows in a tropical environment, as related to conduction and radiation in the absence of free convection. The average k ef was 49.72 mW.m-1.K-1, about twice the conductivity of the air (26 mW.m-1.K-1) and much less than that of the hair fibres (260 mW.m-1.K-1). The low k ef values were attributed mainly to the small cross area of individual hairs, ρef/ρf (17.2% and 21.3% for black and white hairs, respectively). White coats were denser, with longer hairs and significantly higher k ef (53.15 mW.m-1.K-1) than that of the black hairs (49.25 mW.m-1.K-1). The heritability coefficient of the effective thermal conductivity was... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Hair coat; Holstein cows; Thermal conductivity. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-35982009001100022 |
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| Façanha,Débora Andréa Evangelista; Silva,Roberto Gomes da; Maia,Alex Sandro Campos; Guilhermino,Magda Maria; Vasconcelos,Angela Maria de. |
| 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... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Adaptation; Dairy cattle; Hair coat; Tropical environment. |
| Ano: 2010 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-35982010000400020 |
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