Breed comparison for heat adaptation in rams using multivariate analysis

Authors

  • Carlos Alberto da Cruz Júnior Universidade de Brasília
  • Carolina Madeira Lucci Universidade de Brasília
  • Vanessa Peripolli Universidade de Brasilia
  • Candice Bergmann Tanure Universidade de Brasília
  • Alessandra Ferreira da Silva Universidade de Brasília
  • Adriana Morato de Menezes Universidade de Brasília
  • Alexandre Floriani Ramos Embrapa Recursos Genéticos e Biotecnologia
  • Concepta McManus Universidade de Brasília

DOI:

https://doi.org/10.14393/BJ-v32n1a2016-29741

Keywords:

Canonical average, Discriminant, Principal components, Tree diagram

Abstract

In this study, a multivariate analysis of morphological and physiological characteristics was performed on clinically healthy rams from six breeds (Santa Ines, Bergamasca, Dorper, Texel, Ile de France and Hampshire Down) to determine if these characteristics were able to separate and determine the most important variables in the differentiation of breeds for heat adaptation. To characterize the thermal environment, mean temperature was 23°C and relative humidity ranged between 30.6-55.6%. Morphological and physiological data were subjected to multivariate statistical tests including principal components (PRINCOMP), clustering (CLUSTER), discriminant (DISCRIM), step-by-step (STEPDISC) and canonical (CANDISC) analyses, using the Statistical Analysis System (SAS®). A multiple analysis of variance (MANOVA) was carried out with the variables defined as important by the discriminant analysis. The principal components analysis for biometric characteristics and scrotum-testicle, for physiological characteristics and body temperature as well as the characteristics of the skin and hair explained 60, 70 and 67 % of the total variation, respectively. The dendrogram showed a clear separation between the breeds studied and the existence of two distinct groups, one formed by the Texel and the other by the other breeds, considering all the characteristics used in the study. The most useful morphological parameters to explain heat tolerance were diameter of hair, layer thickness of hair at withers, 12th thoracic vertebra and rump, withers height, thoracic and scrotal circumferences, body weight, anterior and posterior shin perimeters, hair and epidermis brightness as well as the content of red and yellow in the epidermis. Among physiological characteristics, respiratory rate was better than rectal temperature and heart rate to explain changes caused by thermal stress. From the multivariate and variance analyzes it can be concluded that the Santa Ines breed was the most tolerant to heat stress as it presented a highly pigmented epidermis, a shorter hair of larger diameter, the lower layer thickness of hair at withers, 12th thoracic vertebra and rump, the lower temperatures in the testicle and at the 12th thoracic vertebra as well as the lower respiratory rate and rectal temperature value.

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Published

2016-01-20

How to Cite

DA CRUZ JÚNIOR, C.A., LUCCI, C.M., PERIPOLLI, V., TANURE, C.B., DA SILVA, A.F., DE MENEZES, A.M., RAMOS, A.F. and MCMANUS, C., 2016. Breed comparison for heat adaptation in rams using multivariate analysis . Bioscience Journal [online], vol. 32, no. 1, pp. 178–190. [Accessed7 December 2022]. DOI 10.14393/BJ-v32n1a2016-29741. Available from: https://seer.ufu.br/index.php/biosciencejournal/article/view/29741.

Issue

Section

Agricultural Sciences