title: Use of heat tolerance traits in discriminating between groups of sheep in central Brazil.
abstract: The animal and its environment make up an integrated system, where each acts on the other. Tropical regions are characterized by high levels of solar radiation and environmental temperature which may adversely affect animal production. This study carries out a multivariate analysis of physical and physiological traits in sheep in the Federal District of Brazil to test the ability to separate groups of animals and determine which traits are most important in the adaptation of animal to heat stress. The variables studied included coat thickness, number and length of hairs, pigmentation of the skin and coat, number of sweat glands as well as heart and respiratory rates, rectal and skin temperatures, sweating rate, and blood parameters. Five groups of ten animals were used depending on breed (Bergamasca, crossbred, or Santa Inês) or coat color (Santa Inês--brown, white, and black). The data underwent multivariate statistical analyses including cluster, discriminate, and canonical, using Statistical Analysis System--SAS®. The tree diagram showed clear distances between groups studied and canonical analysis was able to separate individuals in groups, especially Bergamasca and white Santa Inês. The canonical correlation redundancy analysis showed that coat reflectance as well as hair length and number of hairs per unit area were the most useful in explaining changes in physiological traits. Skin and coat traits such as hair length, coat reflectance, percentage of epithelial area occupied by sweat glands, skin reflectance and thickness, as well as heart and breathing rates were the most important in separating these groups.
authors.affiliation: Escola de Veterinária, Universidade Federal de Goiás, Goiânia, GO, Brazil. castanheira_m@hotmail.com
authors.forename: Marlos
authors.initials: M
authors.lastname: Castanheira
authors.forename: Samuel Rezende
authors.initials: SR
authors.lastname: Paiva
authors.forename: Helder
authors.initials: H
authors.lastname: Louvandini
authors.forename: Aline
authors.initials: A
authors.lastname: Landim
authors.forename: Maria Clorinda Soares
authors.initials: MC
authors.lastname: Fiorvanti
authors.forename: Bruno Stefano
authors.initials: BS
authors.lastname: Dallago
authors.forename: Patricia Spoto
authors.initials: PS
authors.lastname: Correa
authors.forename: Concepta
authors.initials: C
authors.lastname: McManus
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001831:Body Temperature; D001938:Brazil; D016000:Cluster Analysis; D016002:Discriminant Analysis; D006197:Hair / Q000502:physiology; D006339:Heart Rate; D006358:Hot Temperature; D015999:Multivariate Analysis; D010858:Pigmentation / Q000502:physiology; D056152:Respiratory Rate; D012756:Sheep / Q000145:classification* / Q000502:physiology*; D013545:Sweat Glands / Q000033:anatomy & histology / Q000502:physiology; D014329:Tropical Climate