Effect of thermal stress on basic seminal characteristics of Gyr bulls

Autor(es)

Freitas, Anielly de Paula ^[1] ; Ferreira dos Santos, Guilherme Felipe ^[2] ; Fernandes, Andre Rabelo ^[3] ; Mendonca, Gabriela Geraldi ^[2] ; Paro de Paz, Claudia Cristina ^{[1, 2]} ; Vercesi Filho, Anibal Eugenio ^[4] ; El Faro, Lenira ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Ribeirao Preto Med Sch, Av Bandeirantes 3900, BR-14049900 Ribeirao Preto, SP - Brazil

^[2] Anim Sci Inst APTA SAA, Beef Cattle Res Ctr, Rodovia Carlos Tonanni, Km 94, BR-14160900 Sertaozinho, SP - Brazil

^[3] Tech Superintendent Brazilian Assoc Dairy Gyr Bre, Praca Vicentino Rodrigues Cunha 110, BR-38040971 Uberaba, MG - Brazil

^[4] Ctr Genet & Anim Reprod, Rua Heitor Penteado 56, BR-13380011 Nova Odessa, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: INTERNATIONAL JOURNAL OF BIOMETEOROLOGY; v. 64, n. 10, p. 1649-1656, OCT 2020.
• Citações Web of Science: 0

Resumo

The objective of this study was to evaluate the influence of thermal stress indices and minimum temperature on the semen quality of dairy Gyr bulls and to determine whether the minimum night temperature is able to balance the thermal stress that occurred during the day. A total of 922 semen samples were collected from 391 bulls aged between 15 and 49 months, which participated in progeny pretest trials, from December 2011 to April 2017. Semen characteristics (ejaculate volume, gross motility, sperm motility, sperm vigor, sperm concentration, and percentage of total defects) and scrotal circumference were analyzed. Meteorological data were recorded daily by the National Institute of Meteorology. The analyses were carried out using mixed models. The following fixed effects were included in the model: test, month of sample collection, scrotal circumference, the age of the bull at sampling as covariate (linear regression), and the climatic variables (equivalent temperature index {[}ETI], temperature and humidity index {[}THI], or minimum temperature). The effect of the bull nested within the test was included in the model as a random effect. Two periods were considered to evaluate the effect of the climatic variables on sperm quality: 7 days before collection (period 1) and the day of collection (period 2). There was an effect of ETI on sperm vigor and concentration in both periods and on volume and percentage of total defects only in the second period. The THI exerted a significant effect on volume in both periods and on sperm motility and concentration only in the second period. There was an effect of the minimum temperature on ejaculate volume, sperm motility, sperm concentration, and percentage of total defects only in the second period, which corresponds to the day of semen collection. Taken together, the results show that there was sufficient thermal stress to negatively affect semen quality. However, the minimum temperature during the night was a significant factor that balanced these negative effects of THI and ETI on semen traits of Gyr bulls. (AU)

• Processo FAPESP: 16/17517-4 - Modelos de Norma de Reação para estudo da interação genótipo x ambiente em rebanhos da raça Nelore
• Beneficiário: Anielly de Paula Freitas
• Modalidade de apoio: Bolsas no Brasil - Doutorado