Características do pelame de vacas Holandesas em ambiente tropical: um estudo genético e adaptativo

Revista Brasileira de Zootecnia (Impact Factor: 0.36). 08/2003; 32(4). DOI: 10.1590/S1516-35982003000400009
Source: DOAJ


As características do pelame (espessura da capa, comprimento médio dos pêlos, número de pêlos por unidade de área, densidade de massa dos pêlos, ângulo de inclinação dos pêlos com respeito a superfície da epiderme e diâmetro médio do pêlos) foram avaliadas em 973 vacas da raça Holandesa, entre novembro de 2000 e abril de 2001, numa área localizada 20cm abaixo da coluna vertebral, no centro do tronco, tanto nas malhas brancas como nas negras. As amostras de pêlos foram obtidas com um alicate comum adaptado. O método da Máxima Verossimilhança Restrita (REML) foi usado para estimar os componentes de variância e covariância sob modelo animal, sendo empregado o sistema MTDFREML. Os resultados mostraram que as características do pelame preto são diferentes das do branco, quando os animais são criados em ambiente tropical. O pelame preto apresentou-se menos denso, com pêlos mais curtos e grossos devido à maior necessidade de perder calor, enquanto que, o pelame branco é mais denso e com pêlos mais compridos, oferecendo uma melhor proteção contra à radiação solar direta. A seleção de vacas predominantemente negras pode ser uma boa escolha para aumentar a resistência do gado Holandês às condições do ambiente tropical, principalmente à radiação solar, quando esses animais são criados a campo, devido a que a epiderme sob esse tipo de malhas é altamente pigmentada. Tal seleção pode ser facilmente realizada, considerando a alta herdabilidade (h²=0,75) para a proporção de malhas negras. Esta seleção deve ser realizada no sentido de um pelame menos denso, com pêlos curtos e grossos favorecendo as perdas de calor sensível e calor latente.

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Available from: Roberto Gomes da Silva, Jul 04, 2014
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    • "The physiological alterations and differences between the genotypes found in this study do not support the notion that Saanen goats are more adapted to heat on the basis of coat color alone. When comparing different genotypes, other parameters regarding the tegument should be considered, such as pigmentation and thickness of the skin and density, height and length of hairs (Maia et al. 2003; Pereira 2005; Paim et al. 2012). In addition, animals better adapted to warm environments can have increased peripheral circulation and lose heat by convection and radiation (Maia et al. 2009; Cardoso et al. 2010), when there is a thermal gradient between the skin and air (Silanikove 2000; Souza et al. 2008; Silva et al. 2012), besides possessing a larger number of sweat glands, allowing the loss of latent heat (Silva et al. 2010). "
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    ABSTRACT: The aim of this work was to determine the adaptability of Saanen and ½Saanen × ½Anglo-Nubian (½S½AN) goats bred in tropical climates. The study included 30 goats, 15 Saanen and 15 ½S½AN. The data was collected during the rainy and dry seasons. During the whole experimental period, the environment variables were recorded, as well as rectal temperature (RT), superficial temperature (ST), respiratory rate (RR) and heart rate (HR) and milk production (MP). The adaptability coefficient (AC) was calculated for both genotypes. The averages were evaluated by ANOVA at 5 % probability. There was a genotype and period of year effect, as well as the interaction genotype × period of year. Pearson's simple correlation analysis was then carried out between milk production and physiological and environment variables. There was a statistical difference (p < 0.05) between the seasons for RT, ST and RR. RT, RR and HR were lower for ½S½AN than Saanen goats, regardless of the season. MP was greater in the dry season (p < 0.05) (2.52 ± 0.50 kg/day for ½S½AN and 2.41 ± 0.38 kg/day for Saanen) than the rainy season (2.17 ± 0.27 kg/day for ½S½AN and 2.28 ± 0.53 kg/day for Saanen). The MP correlations were very significant (p < 0.05), however low and negative, where it was higher when correlated with RR in Saanen goats. Under the conditions of the present study, it is concluded that the goats were influenced by climatic factors, where the rainy period was more likely to cause thermal stress in the animals.
    International Journal of Biometeorology 11/2013; 58(7). DOI:10.1007/s00484-013-0760-x · 3.25 Impact Factor
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    • "This is probably due to the insulating effect of the fleece which is efficient in impeding the passage of thermal energy between the external environment and the animal and vice versa (Whates and Charles, 1994; Maia et al., 2009). Maia et al. (2003, 2005) noted that hair length and thickness were important traits in animal adaptation in the tropics with a decreasing adaptation with increasing hair length. Short, shiny, fine hair led to better heat dissipation while long coarse hair led to lower heat exchange with the environment (Castanheira et al., 2010). "
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    ABSTRACT: Three genetic groups of sheep (Santa Ines - SI) and their crosses with Texel (TxSI) and Ile de France (IxSI) were tested for heat tolerance in the center-west region of Brazil. Lambs were evaluated twice a day (in the morning with no heat stress and in the afternoon under stressful conditions). As well as physiological traits (heart rate, respiratory rate, rectal temperature, sweating rate), animals were measured for size (height, weight, length, thoracic circumference), blood parameters (red cell and white cell counts), coat colour and thermal indices were calculated. Crossbred animals were longer, taller and were growing faster than the SI. The Texel cross had more animals with rectal temperature above the reference values when compared to the other groups. Animal size measures did not affect most of the traits examined. In terms of blood parameters, the TxSI were more susceptible with higher reactions to heat stress. Most correlations of TR with adaptive skin traits (such as skin temperature and sweating rate) and blood traits were low. Animals with less thermal insulation used less physiological resources to dissipate heat. Texel x Santa Ines animals were, in general, less well adapted than the other genetic groups.
    Small Ruminant Research 05/2012; 104(1-3). DOI:10.1016/j.smallrumres.2011.11.001 · 1.13 Impact Factor
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    • "According to Mader et al. (2000), the comfort zone for feedlot cattle and mature cows ranges from −17.7°C or below in the winter to approximately 23.8°C in the summer. These values depend on body condition (Mader 2003), hair length (Maia et al. 2003), coat thickness (Maia et al. 2005), coat color and plane of nutrition (Mader et al. 2002). Heat is described as a major determinant of animal productivity in a hot environment. "
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    ABSTRACT: Heat stress has important effects on the welfare of livestock. The effects of heat stress in cattle include changes in biological functions and behaviors. The aim of this study was to investigate the behavioral differences between light and heavy feedlot cattle reared in a hot environment. Sixteen male Holstein feedlot cattle were allocated to light (353.8 ± 15.5 kg, n = 8) and heavy (737.1 ± 15.8 kg, n = 8) groups according to their live weight and were kept in a semi-open feedlot barn. The individual behavioral response variables measured were standing, lying, feeding, drinking, ruminating, locomotor activity and elimination (urinating and defecating). The effects of group, day, observation time, replicate and all interactions were included in an explanatory statistical (GLM) model. The data were analyzed using the PROC GLM procedure of SAS. Overall, the heavy cattle spent more time standing (P < 0.001), lying (P < 0.001), and eliminating (P < 0.05) compared to the light group. In contrast, the light group spent more time eating, drinking and ruminating (P < 0.001). Locomotor activity did not differ significantly between groups (P > 0.05). During the day, heavy cattle spent more time standing (at 1600 hours) and less time eating in comparison with the light cattle (P < 0.001) (at 1300 and 1600 hours). Light and heavy feedlot cattle behaved differently in a hot environment. The findings of the study indicate that the welfare of the heavy Holstein feedlot cattle was impacted negatively when the ambient temperature was high (at 1300 hours).
    International Journal of Biometeorology 05/2011; 56(2):297-303. DOI:10.1007/s00484-011-0433-6 · 3.25 Impact Factor
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