Efeito da aplicação de lipopolissacarídeo intrafolicular sobre o desenvolvimento folicular e momento da ovulação em fêmeas bovinas

Abstract

The objective of this study was to evaluate the effect of intrafollicular lipopolysaccharide (LPS) administration on follicular diameter, moment of ovulation, ovulatory rate, as well as the corpus luteum diameter, and progesterone production in the subsequent phase of estrous cycle in dairy cattle. The study was conducted in two experiments using hormonal synchronization protocols. Eighteen Jersey cows were divided in two groups (control or LPS). Cows in treated group received 1 µg/mL of LPS intrafollicular and were evaluated by ultrasonography every 12 hours to assess follicular growth, moment of ovulation and posterior luteal size. In Experiment 1, it was evaluated the effect of LPS on dominant follicle and the results demonstrated that follicular growth was not disturbed by intrafollicular LPS administration. In Experiment 2, it was evaluated the LPS effect on preovulatory follicle and the results demonstrated that LPS delays follicular growth (P=0.02), increases follicular blood flow (P=0.05), delays ovulation (P=0.03; Control: 78.0 ± 4.90 h vs LPS: 106.0 ± 13.02 h) and reduces ovulatory rate (P=0.03; Control: 100% vs LPS: 66.6%). Corporal temperature was not affected 24 hours after LPS administration (P=0.7), demonstrating that LPS could have a local effect in the ovarian follicle. However, despite of different follicular growth, ovulatory diameter (P=0.1) and moment of estrus (P=0.6) were not different between groups. Luteal area and the serum progesterone concentration were not affected. The current study was the first experiment to evaluate the local effect of LPS at follicular level in vivo. The results demonstrated that LPS induced a follicular response, delaying follicular growth, ovulation moment and reducing ovulatory rate, indicating that infectious process can affect fertility in cattle.