Herbage Responses and Performance of Mature Horses Grazing Warm-Season Perennial Grass-Legume Mixed Pastures

Legume-grass mixtures may be a useful alternative to nitrogen-fertilized grass monocultures, but pasture and animal responses have not been assessed for pastures grazed by horses in Florida. This 2-yr study compared pasture and horse responses of continuously stocked, mixed pastures of rhizoma peanut (RP, Arachis glabrata Benth) and bahiagrass (BG, Paspalum notatum Flüggé) receiving 30 kg nitrogen (N)/ha (RP-BG) compared with BG pastures fertilized with 120 kg/N ha (BG-N) or with no N (BG-No N). Herbage mass was similar among treatments in 2020 and for most evaluation days in 2019. In 2019, stocking rate (AU/ha) was greater in BG-N (3.9) than in RP-BG (3.7) and BG-No N (3.1). In 2020, BG-No N (2.6) had the lesser stocking rate compared with BG-N (2.9) and RP-BG (2.9), with RP-BG not differing from BG-N. Herbage crude protein (CP) and digestible energy were similar across treatments in 2020, but they were greater for BG-N and RP-BG than BG-No N at some evaluation days in 2019. Except for CP, treatment did not affect nutrient digestibility by horses. Digestibility of CP was greatest for RP-BG in the late season. In the RP-BG treatment, proportion of RP in the pasture (~29%) was not affected by sampling date, and RP comprised 18.4% of the diet. Nonetheless, no differences were observed among treatments for body weight and condition score. The results indicate that intercropping legumes into warm-season perennial pastures can improve some measures of nutritive value and maintain horses’ body condition with similar stocking rate as N-fertilized bahiagrass pastures, while contributing to development of sustainable grazing systems for horses with reduced off-farm nitrogen inputs

A Novel Technique to Label Cover Crop Biomass Using Stable Isotopes

Stable isotopes can be used as tracers for carbon and nitrogen pathways being a great tool to track nutrients in integrated systems. The objective of this experiment was to understand the partitioning of 15N and 13C within cover crop plants when they were labeled with stable isotopes, using chambers under field conditions. Cover crops were planted at the University of Florida, North Florida Research and Education Center-Marianna, located in Marianna, FL. Treatments were four cover crops, in which one was considered a typical cover crop system and the other three consisted of an integrated crop-livestock system with or without the inclusion of legume or different nitrogen fertilizer rates grazed every two weeks. All treatments were replicated three times in a randomized complete block design. Two chambers were built and placed in each plot to label the cover crop plants. For the 15N labeling, 15N2-labeled urea (98 atom% 15N) was applied at a rate of 0.5 kg N ha-1 only once. The target amount of 13CO2 (99 atom% 13C) was determined considering a 20% enrichment of the CO2 concentration present inside the chamber’s volume. The 13CO2 labeling was performed for 28 consecutive days. The labeling technique using chambers and stable isotopes to enrich cover crop species worked under field conditions for both, grass and legume species. Moving forward, this labeling technique can be a useful tool to track nutrient pathways, especially litter decomposition in diversified integrated crop and livestock systems under different management practices

Establishment and cryptic transmission of Zika virus in Brazil and the Americas

Transmission of Zika virus (ZIKV) in the Americas was first confirmed in May 2015 in northeast Brazil1. Brazil has had the highest number of reported ZIKV cases worldwide (more than 200,000 by 24 December 20162) and the most cases associated with microcephaly and other birth defects (2,366 confirmed by 31 December 20162). Since the initial detection of ZIKV in Brazil, more than 45 countries in the Americas have reported local ZIKV transmission, with 24 of these reporting severe ZIKV-associated disease3. However, the origin and epidemic history of ZIKV in Brazil and the Americas remain poorly understood, despite the value of this information for interpreting observed trends in reported microcephaly. Here we address this issue by generating 54 complete or partial ZIKV genomes, mostly from Brazil, and reporting data generated by a mobile genomics laboratory that travelled across northeast Brazil in 2016. One sequence represents the earliest confirmed ZIKV infection in Brazil. Analyses of viral genomes with ecological and epidemiological data yield an estimate that ZIKV was present in northeast Brazil by February 2014 and is likely to have disseminated from there, nationally and internationally, before the first detection of ZIKV in the Americas. Estimated dates for the international spread of ZIKV from Brazil indicate the duration of pre-detection cryptic transmission in recipient regions. The role of northeast Brazil in the establishment of ZIKV in the Americas is further supported by geographic analysis of ZIKV transmission potential and by estimates of the basic reproduction number of the virus

Persistent detection of Zika virus RNA from an infant with severe microcephaly – a case report

Abstract Background Zika virus (ZIKV) is a recently emerged arbovirus, which infection during pregnancy is associated with a series of congenital malformations, collectively denominated Congenital Zika Syndrome (CZS). Following infection, ZIKV RNA has a median duration period of 10 days in plasma and up to 6 months in semen in immunocompetent adult individuals. Moreover, ZIKV is able to replicate and persist in fetal brains and placentas, consequently, infection is associated with pregnancy loss, albeit the pathogenic mechanisms are still unknown. Case presentation Here we report a CZS case of an infant born during the ZIKV outbreak in northeast Brazil, the child presented recurrent episodes of seizures with prolonged presence of ZIKV RNA on the central nervous system (CNS) and blood. ZIKV RNA was identified and partially sequenced from a sample of cerebrospinal fluid (CSF) obtained from the infant with 6 months of life, and later from another sample after the infant completed 17 months of life. Commonly congenital infections were discarded based on STORCH (syphilis, toxoplasmosis, rubella, cytomegalovirus and herpes simplex virus) negative laboratory results. Presence of specific ZIKV antibodies on both mother and children confirmed the association of severe microcephaly and ZIKV infection, diagnosed after birth. Conclusions Altogether, our data raise the possibility that CZS cases may result in prolonged viral presence, these findings could be useful for therapy and diagnostic recommendations