The objective of this study was to evaluate and compare physical parameters in groups of sheep with different phenotypic characteristics in the Centre-west region of Brazil. Five groups of sheep, with nine animals per group, were selected, three groups of Santa Inês animals with different coat colours (white, brown and black), one group with crossbred animals (Santa Inês × Bergamasca) and one group with animals of the Bergamasca breed. The following traits were evaluated: coat thickness, number and length of hair, pigmentation level in the coat and the skin as well as the percentage area of sweats glands in the skin tissue, carried out by histological analysis. The number of hairs and the area of sweats glands were not significantly different between the evaluated groups. The Bergamasca breed showed low pigmentation of the skin and long hairs. The levels of pigmentation of the hair and of the skin were highly correlated. Between the Santa Inês groups, the group with white hair showed the better parameters for heat adaptation, while the brown hair group showed the lower heat adaptation when compared with another hair breed groups.
Resumo -O objetivo deste trabalho foi avaliar medidas corporais associadas à tolerância ao calor em bovinos. Utilizaram-se 64 animais das raças naturalizadas Curraleiro (15), Mocho Nacional (7), Crioulo Lageano (7), Pantaneira (14) e Junqueira (11), e 26 animais de duas raças comerciais: Nelore (15) e Holandesa (11). Foram analisados dados sobre comprimento corporal, perímetro de canela, altura de cernelha, perímetro torácico, espessura da pele, espessura do pêlo, número de pêlos, comprimento de pêlos, pigmentação da epiderme e pelame. A raça Curraleiro apresentou menor perímetro torácico, tendo diferido das outras raças, principalmente da Mocho Nacional. As raças Crioulo Lageano e Pantaneira apresentaram maior espessura de pêlo; a raça Mocho Nacional apresentou maior espessura de pele. Os resultados obtidos demonstram que as raças Curraleiro e Junqueira são mais tolerantes ao calor que as demais raças naturalizadas.Termos para indexação: adaptação, bioclimatologia, medidas corporais, tolerância ao calor. Body traits associated with heat adaptation in naturalized Brazilian cattle breedsAbstract -The aim of this work was to evaluate physical aspects of heat tolerance in cattle. Sixty-four animals from five naturalized breeds were used, including Curraleiro (15 animals), Mocho Nacional (7), Crioulo Lageano (17), Pantaneira (14) and Junqueira (11), as well as twenty-six animals from two commercial breeds: Nellore (15) and Holstein (11). Measurements on shoulder height, girth, body length, cannon bone circumference, skin and hair thickness were analysed as well as hair density and hair and skin pigmentation. Girth in Curraleiro was significantly smaller than in other breeds, especially Mocho Nacional. Crioulo Lageano and Pantaneira had the thickest hair and Mocho Nacional the thickest skin. Curraleiro and Junqueira were shown to be the most heat tolerant of the naturalized breeds.
Adaptability can be evaluated by the ability of an animal to adjust to environmental conditions and is especially important in extreme weather conditions such as that found in tropical Brazil. A multivariate analysis using physical and physiological traits in exotic (Nellore and Holstein) and naturalized (Junqueira, Curraleira, Mocho Nacional, Crioula Lageana, and Pantaneira) cattle breeds was carried out in the Federal District of Brazil to test and determine which traits are important in the adaptation of animal to heat stress as well as the ability of these traits and statistical techniques to separate the breeds studied. Both physical and physiological traits were measured on three occasions and included body measurements, skin and hair thickness, hair number and length, pigmentation, sweat gland area as well as heart and breathing rates, rectal temperature, sweating rate, and blood parameters. The data underwent multivariate statistical analyses, including cluster, discriminate, and canonical procedures. The tree diagram showed clear distances between the groups studied, and canonical analysis was able to separate individuals in groups. Coat traits explained little variation in physiological parameters. The traits which had higher discriminatory power included packed cell volume, shoulder height, mean corpuscular volume, body length, and heart girth. Morphological and physiological traits were able to discriminate between the breeds tested, with blood and size traits being the most important. More than 80% of animals of all breeds were correctly classified in their genetic group.
Heat stress is considered a limiting factor for sheep production. We used information from physiological characteristics linked to heat tolerance to determine whether infrared thermography temperatures were able to separate groups of animals and determine the most important variables in this differentiation. Forty-eight four-month-old male lambs from eight genetic groups were used. Physiological (rectal temperature–RT, heart rate–HR, respiratory rate–RR) and blood traits, infrared thermography temperatures, heat tolerance indices, body measurements, weight and carcass traits were measured. Statistical analyses included variance, correlations, factor, discrimination and regression. Observing the correlations between physiological characteristics (RT, RR and HR) with temperatures measured by infrared thermography, regions for further studies should include the mean temperature of flank, nose and rump. Results show that there are strong relationships between thermograph measurements and RR, RT and HR in lambs, which are suggested to be directly correlated with heat tolerance capacity of the different genetic groups evaluated in this study. The assessment of body surface temperature measured by the thermograph could be used as a noninvasive tool to assess heat tolerance of the animals.
Existem diversas opções de genética de ovinos para os sistemas de produção, desde recursos genéticos locais (geralmente adaptados as condições ambientais) até raças especializadas. O cruzamento é uma alternativa para explorar a heterose e complementariedade entre as raças. Este estudo avaliou oito grupos genéticos obtidos a partir do cruzamento entre Santa Inês (SI), Poll Dorset (PD), Dorper (DO), East Friesian (EF), Primera (PR), and White Dorper (WD). SI e PD foram usados com raças paternas e maternas, enquanto as demais foram usadas apenas como raças paternas. Quarenta e oito cordeiros foram avaliados para altura da cernelha, perímetro torácico, comprimento do corpo e da garupa e espessura da pele, bem como peso de carcaça fria e peso dos cortes comerciais como pescoço, fralda, paleta, pernil, costela e lombo. Os animais Santa Inês demoraram mais tempo para atingir o peso de abate (30 kg) que as cruzas com Dorper e Poll Dorset. Os animais 87PDSI, 75PDSI e DOPD apresentaram maior peso dos cortes comerciais e maior rendimento de carcaça. O uso da raça Santa Inês, uma raça localmente adaptada, como raça maternal em sistema de cruzamento apresentou resultados similares ao uso de Poll Dorset, uma raça especializada para produção de carne. Esses resultados destacam a utilidade dos recursos genéticos locais em sistema de produção intensivo. Poll Dorset é a raça paterna recomendada para o cruzamento com matrizes Santa Inês em sistema de produção intensivo.
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