Abstract The aim of this study was to evaluate the long-term effects of recombinant bovine somatotropin (rbST) on follicle population and ovulatory follicle development in non-lactating dairy cows. Twenty-one Jersey cows were allocated in rbST (n=11) or control (n=10) groups. On day -60, cows in rbST group received 500 mg of somatotropin (s.c. Lactotropin®, Elanco). On day 0, control and rbST cows received an intravaginal progesterone-releasing device (1.9 g, CIDR®, Zoetis) and GnRH (100 mg, IM, Factrel®, Zoetis). On day 8, cows received PGF2α (25 mg, IM, Lutalyse®, Zoetis) and the CIDR® was removed. Twelve hours after device removal (D8), serum, follicular fluid and granulosa cells samples were collected. Serum and follicular concentration of estradiol (E2) and progesterone (P4) were analyzed. Total RNA was extracted from granulosa cells to measure gene expression of LHCGR, STAR, HSD-3B1, CYP11A1, CYP19A1, CYP17A1, IGFR and PAPPA by real-time PCR. Ultrasonography was performed on days -60, -53, -46, -14, -7, 0 and 8 for antral follicle count. Results were analyzed by repeated measures ANOVA and t-test. There was no effect of rbST treatment on the number of follicles during the 60 days period, as well as no effect on serum and follicular fluid E2 and follicular fluid P4 at the moment of follicle aspiration. There was a reduction in PAPPA (P = 0.006), CYP11A1 (P = 0.04) and CYP19A1 (P = 0.002) mRNA levels in granulosa cells of the pre-ovulatory follicle of rbST treated cows. In conclusion, a single dose of rbST did not have long-term effects on antral follicle population, serum and follicular E2/P4 concentrations in non-lactating dairy cows. Despite that, rbST injection decreased granulosa cell expression of genes related to steroidogenesis in the pre-ovulatory follicle.

RESUMO: O objetivo desse estudo foi estimar a soroprevalência da neosporose e os possíveis fatores de risco em rebanhos (Bos taurus taurus) localizados na mesorregião Noroeste do Rio Grande do Sul, Brasil. Foram coletadas 322 amostras de sangue de bovinos leiteiros, em 18 propriedades localizadas em 17 munícipios desta mesorregião. Um questionário epidemiológico foi aplicado em cada propriedade, contendo questões relacionadas às características gerais dos rebanhos, dados reprodutivos e manejo animal. As amostras de soro foram testadas através do teste de imunoensaio enzimático (ELISA) para Neospora caninum. Os resultados demonstraram uma soroprevalência de Neospora de 88,9% (16/18) entre os rebanhos e 31,1% (100/322) entre os indivíduos. Entre os fatores de risco analisados foi observado que descarte por problemas reprodutivos (OR=0,6), presença de áreas alagadiças (OR=0,5) e venda comercial (OR=0,4) estavam associados a soroprevalência. No entanto, a compra de animais substituídos no rebanho desempenhou um papel significativo na ocorrência da doença (OR=2,2). Os resultados desse estudo sugerem que o Neospora caninum esteve presente nos rebanhos estudados, bem como, existem fatores associados com a soroprevalência nas propriedades da mesorregião do Noroeste do Rio Grande do Sul.

ABSTRACT: The aim of this study was to estimate neosporosis seroprevalence and its associated risk factors in milk herds (Bos taurus taurus) located in the northwestern region of Rio Grande do Sul State, Brazil. Three hundred twenty-two blood samples were collected from dairy cows on 18 farms in 17 cities of this region. An epidemiologic questionnaire was completed for each farm. It consisted of questions about the general characteristics of the herd, reproduction, and animal management. Serum samples were tested for Neospora caninum using a commercial enzyme-linked immunosorbent assay (ELISA) kit. Results indicated a seroprevalence of Neospora in 88.9% (16/18) of herds and 31.1% (100/322) of individuals. Risk factor analyses demonstrated that culling by reproductive disorder (OR = 0.6), flooding (OR = 0.5), and commercial sale (OR = 0.4) were associated with seroprevalence. Nevertheless, the purchase of replacement animals in the herd played an important role in disease occurrence (OR = 2.2). Results of this study suggested that Neospora caninum was present in the studied herds under investigation and that there are risk factors associated with its seroprevalence on the farms of the northwestern of Rio Grande do Sul.