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| Author(s): |
Rodrigo de Andrade Ferrazza
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Botucatu. 2017-01-17. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Medicina Veterinária e Zootecnia. Botucatu |
| Defense date: | 2016-12-22 |
| Advisor: | João Carlos Pinheiro Ferreira; Elizabeth Moreira dos Santos Schmidt |
| Abstract | |
Heat stress reduces the reproductive efficiency in dairy cows. Follicular fluid (FF) contains proteins involved in the follicle activity and cell differentiation and oocyte maturation. The characterization of the proteome of FF may contribute to a better understanding of the physiological mechanisms involved in folliculogenesis and impairment of reproductive function during heat stress. In the first experiment, the FF proteomic profile of cows at different stages of follicle development (pre-deviation, deviation, dominance and pre-ovulatory) was evaluated and the association of proteins with intrafollicular concentrations of steroid hormones was tested. Twenty-two differentially expressed proteins (P < 0.05) were found among the follicular categories, with deviation being a critical time-point in the determination of protein expression. In addition, three proteins were correlated (P < 0.05) with the intrafollicular concentrations of estradiol, while sixteen were correlated (P < 0.05) with the local concentrations of progesterone. The canonical pathway analysis identified the activation/inhibition of the pathways associated with acute phase response, coagulation system, complement system, liver X receptor and retinoid, and production of nitric oxide and reactive oxygen species. In the second experiment, the effect of heat stress on the expression of cow FF proteins was tested. In the experimental model validation, we observed that the continuous exposure to heat stress affected thermoregulatory mechanisms,leading to a marked increase in respiratory rate, followed by an increase in rectal temperature. The influence of environmental variables from the previous day on physiological parameters and dry matter intake were more important than the immediate effect and ambient temperature represented the most determinant factor for heat exchange. Although prolonged exposures to heat stress indicate an adaptive adjustment, in this study the acclimation process was only partial. The follicular growth of cows exposed to heat stress was affected and may be partly explained by the altered expression of the FF proteins. The 28 differentially (P < 0.05) expressed proteins in FF from heat stressed cows were closely associated to the immune function and the coagulation cascade pathways. Such findings indicate potential molecular mechanisms and signaling pathways involved in folliculogenesis and reduction fertility observed during the summer. (AU) | |
| FAPESP's process: | 13/20083-8 - In vivo study of the factors involved in the establishment of follicular dominance and atresia in Holstein cows and the effect of heat stress on these phenomena |
| Grantee: | Rodrigo de Andrade Ferrazza |
| Support Opportunities: | Scholarships in Brazil - Doctorate |