Monitoring environmental conditions on the speed of development and larval migration of gastrointestinal nematodes in Urochloa decumbens in northeastern Brazil.

The study aimed to evaluate the speed of development of gastrointestinal nematodes (GIN) eggs to infective larvae (L3) and its migration under effect of meteorological variables: temperature, rainfall, relative humidity, solar radiation to Urochloa (=Brachiaria) decumbens grass pasture during rainy season, from June to September 2019, and dry season, October to March 2020, in Recôncavo baiano region of Bahia state, Brazil. Monthly, fecal samples obtained from goats with recurrent GIN infection were deposited in six plots of one square meter. In +7, +14 and + 21-days post-deposition, lower and upper strata grass (0-15 and > 15 cm, respectively) and remaining feces were collected and submitted to Baermann's technique modified to perform larval count and identification. Meteorological data were obtained from a local weather station database. The log-transformed larval count results were analyzed regarding the collection day effect, stratum effect, comparing the means by Tukey's test (p < 0.05). Multivariate regression analysis and correlation of meteorological variables with larval counts was performed. In the rainy season, the largest proportion of recovered L3 was concentrated in +7-days post-deposition in the months of June and July, both in the remaining feces and herbage samples, while in August development took place more slowly, after +14-days post-deposition. During the dry season, L3 development only occurred after the first collection in January and February. Lower strata had higher proportion of recovery than in upper strata. Negative correlation was found for solar radiation. Greater rainfall in the rainy season compared to dry season was a favorable condition for high contamination of grass samples. However, reduced vertical migration to upper strata may have been influenced by low temperatures during the rainy season. Regarding the genera present in the fecal samples used in the experiment were found Haemonchus sp., Trichostrongylus sp. and Oesophagostomum sp. Thus, it is possible to conclude that in the region of the study, during the rainy season, there is a rapid larval development and the L3 are able to migrate more effectively to the grass. On the other hand, in the dry season, larval development tends to be slower, with less migration to the grass. Solar radiation can be useful for predicting months with the highest risk of infection. Therefore, prophylactic measures should be employed in goat herds during the rainy season whilst natural reduced pasture contamination in the dry season may favor animal maintenance for a longer time.

Correlation between the natural infection by Corynebacterium pseudotuberculosis in goats and serum progesterone levels and corpus luteum development.

Caseous Lymphadenitis (CLA) is an infectious disease that affects small ruminants, and the bacterium Corynebacterium pseudotuberculosis is its etiologic agent. This disease presents a high morbidity and a great economic impact on goat farming, leading to reduced milk and meat production and reproductive losses. The available data about the influence of C. pseudotuberculosis on the reproductive system were obtained after experimental inoculations. In this way, this study aimed to evaluate the influence of the natural infection by C. pseudotuberculosis on the luteal function and serum progesterone (P4) levels in goats. Sixteen female goats were diagnosed for the presence of C. pseudotuberculosis specific antibodies and divided into 2 groups: CLA positive and negative animals. They were submitted to estrous synchronization, followed by controlled mating. Corpus luteum and serum levels of P4 were evaluated on the 7th and 20th days after mating (D7 and D20). The ultrasonographic results were not statistically different between the 2 groups, as well as serum P4 levels on D7. However, a significant increase in serum P4 levels on the CLA positive group was identified on D20, along with a significant correlation between C. pseudotuberculosis specific antibody production, and P4 serum levels. The result of this study indicates that the infection by C. pseudotuberculosis may influence the reproductive status of female goats through an enhanced production of progesterone.