The aim of this study was to investigate the effect of different dietary levels of concentrate on feed intake, digestibility, ruminal fermentation and microbial population in steers. Eight Nellore steers fitted with ruminal cannulas were used in a double 4 × 4 Latin square design experiment. The dietary treatments consist of four different proportions of concentrate to roughage: 30:70, 40:60, 60:40 and 80:20% in the dry matter, resulting in Diets 30, 40, 60 and 80, respectively. The roughage was corn silage, and the concentrate was composed of corn, soybean meal and urea. Apparent digestibility of organic matter and crude protein showed a linear association with concentrate proportion (p = 0.01), but the increased concentrate levels did not affect the digestibility of fibre. The lowest ruminal pH-values were observed in animals fed with Diet 80, remaining below pH 6.0 from 6 h after feeding, while in the other diets, the ruminal pH was below 6.0 not before 12 h after feeding. After feeding Diet 80, the ammonia concentration in the rumen was significantly the highest. Higher dietary concentrate levels resulted in a linear increase of propionic acid concentrations, a linear reduction of the ratio acetic acid to propionic acid (p < 0.01) and a linear increased synthesis of microbial nitrogen (p < 0.001). The predicted production of methane was lower in diets with greater amounts of concentrate (p = 0.032). The population of methanogens, R. flavefaciens and R. albus decreased with higher concentrate levels, while the population of S. ruminantium increased (p < 0.05). The results indicate that greater amounts of concentrate do not decrease ruminal pH-values as much as expected and inhibit some cellulolytic bacteria without impairing the dry matter intake and fibre digestibility in Nellore steers.

The effect of the essential oils (EOs) of peppermint, Mentha piperita L., and tea tree, Melaleuca alternifolia (Maiden & Betche) Cheel, on the haematological, biochemical, and immunological parameters and intestinal morphology of Nile tilapia, Oreochromis niloticus L., was evaluated. Fish (58.09 ± 5.87 g) were fed 100 mg/kg and 250 mg/kg of each EO and sampled on days 7, 14, 30 and 60 after starting supplementation. The haematological and biochemical parameters were not altered by the supplementation of EOs compared to the control (p > .05). With regard to the immunological parameters, the activation of the complement system of fish fed 250 mg/kg peppermint and 100 mg/kg and 250 mg/kg tea tree EOs were significantly higher compared to the control after 60 days of feeding (p < .05). The complement system plays an essential role in innate immunity and contributes significantly to the acquired immune response; thus, its activation through supplementation with EOs is promising for the formulation of nutritional additives in aquaculture. Regarding intestinal morphology, fish fed 250 mg/kg tea tree EO presented higher villus size compared to all other groups (p < .05), which represents a healthier gut. These fish present a larger intestinal surface, which can result in better absorption and utilization of the nutrients. Based on the responses found in this study, both EOs were considered promising for the formulation of feed additives for Nile tilapia.

Lipid supplementation may adversely affect rumen fermentation, microbial abundance, nutrient utilization and the duodenal flow of fatty acids (FA). In a 5 × 5 Latin square design, 10 Nellore steers with ruminal and duodenal cannulas (292 ± 28 kg BW) were fed one of the five following dietary lipid sources in the concentrate, as follow: (1) no additional fat (WF); (2) palm oil (PO) derived from the Palmaceae plant Orbignya oleifera; (3) linseed oil (LO); (4) protected fat (PF); and (5) whole soybeans (WS). The dry matter intake (DMI) was greater for the animals supplemented with WF than for those supplemented with PO, PF, and WS. The DM digestibility was 11% greater for the animals in the WF group than for those in the PO group. The animals in the PO group had greater duodenal flows of capric (C10:0), lauric (C12:0) and myristic (C14:0) saturated fatty acids (SFA) than did animals in the other groups. The amount of flows of vaccenic acid and total unsaturated acids (UFA) was greater with LO supplementation. The unsaturated fatty acid (UFA) biohydrogenation ratio was greater in the animals supplemented with WS than in those supplemented with PO, LO, and PF. The acetate: propionate ratio was lower in the animals supplemented with PO and LO, at 2.9 and 3.0, respectively. The ruminal flow of particles and rate of fiber degradation were lower with PO supplementation. The proportion of archaea was reduced with the inclusion of PO, LO and PF. PO supplementation resulted in lower total apparent NDF digestibility than did WF, PF, and WS supplementation. Therefore, LO, PF and WS can be used as dietary supplements for grazing cattle without impairing fermentation. The inclusion of PO in the diets of grazing cattle may reduce the number of methanogens and alter fiber utilization.

Trypanosomes are flagellated parasite protozoans that prey especially on wild fish and have recently been described affecting fish in aquaculture. The present study was carried out during a mortality outbreak of Nile tilapia Oreochromis niloticus reared in net cages. Samples of 10 fish in the finishing phase showing unspecific signs, such as anorexia, skin darkening and gill paleness, were analyzed using hemogram, parasitology, microbiology, histopathology, electron microscopy and molecular identification. For microbiological analysis, the kidney was collected aseptically and cultured on tryptone soy agar for 48 h at 30°C. For parasitological analysis, skin, gills, intestinal contents and blood scrapings were examined. Photomicrographs of the parasite were measured. For molecular identification, blood samples were processed and sequenced for amplification of the 18S rDNA gene. Gills, liver, spleen, kidney, heart and intestine were sampled for histopathological processing. The microbiological results indicated that the fish were not infected with bacteria. Scrapings of the skin and gills revealed the massive presence of kinetoplastids, which were also observed in greater numbers than erythrocytes in the blood. Intestines were not affected by endoparasites. The morphometric characteristics indicated the presence of the Trypanosoma genus, which was confirmed in the sequenced samples, where 95% and 98% of the identity were Trypanosoma sp. In histopathology, all organs presented different levels of alteration, accompanied by large numbers of the parasite in small and large vessels. The main findings were the description of mast cell infiltrates in the gill and intestine, as well as multifocal aggregates of melanomacrophages in the liver, pancreas, spleen and kidney. Furthermore, the study addresses the newest features of clinical signs of infected fish and possible causes of infestations and compares the diagnosis of this hemoparasite with other hemoflagellates. To our knowledge, this study represents the first outbreak of Trypanosoma in Nile tilapia in South America. The authors warn of possible new cases of trypanosomiasis in aquaculture, recommending possible forms of containment and biosecurity measures.

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ABSTRACT. The bacterial diversity by 16S rDNA partial sequencing and scanning electron microscope (SEM) of the rumen microbiome was characterized. Three Nellore bovines, cannulated at the rumen, were utilized. Liquid and solid fractions from the rumen content were processed for the extraction of metagenomic DNA and later 16S rDNA amplicons were utilized to construct the WGA library for further clone sequencing. Data were analyzed by MEGA and MOTUR (University of Michigan) softwares. Approximately 97.96% of operation taxonomic units (OTUs) were related to Bacteriodetes phylum and 2.04% of sequences were affiliated to Firmicutes phylum. In the case of Bacteriodetes, the great part of sequences (47.96%) was attributed to Prevotella genus. Bacteroidetes phylum was predominant in rumen content and the Prevotella genus was the most abundant, including diverse species related to this taxon. The bacterial morphological diversity associated to plant fibers was detected by SEM and showed its role in plant biomass deconstruction beyond the detection of microbiological interactions that involved protozoa.Keywords: bacterial community, bacterioidetes, Nellore, Prevotella, taxonomic affiliation.Diversidade bacteriana em rúmen bovino por análise de sequências do 16S rDNA metagenômico e microscopia eletrônica de varredura RESUMO. O estudo foi realizado para caracterizar a diversidade bacteriana por meio do sequenciamento parcial do 16S rDNA total e microscopia eletrônica de varredura (MEV) do microbioma ruminal. Foram utilizados três bovinos da raça Nelore, canulados no rúmen. As frações líquidas e sólidas do conteúdo ruminal foram processadas para extração de DNA metagenômico. Em seguida, amplicons 16S rDNA foram utilizados na construção da biblioteca WGA para posterior sequenciamento dos clones. Os dados foram analisados pelos softwares MEGA e MOTHUR (The University of Michigan). Aproximadamente 97,96% das UTOs foram relacionadas ao filo Bacteroidetes e apenas 2,04% das sequências foram afiliadas ao filo Firmicutes. Para o filo Bacteroidetes, grande parte das sequências (47,96%) foi atribuída ao gênero Prevotella. O filo Bacteroidetes foi predominante no conteúdo ruminal e o gênero Prevotella foi o mais abundante, incluindo diversas espécies relacionadas a esse nível taxonômico. A diversidade morfológica bacteriana associada às fibras vegetais foi detectada por MEV, evidenciando seu papel na desconstrução da biomassa vegetal, além da detecção de interações microbiológicas que envolvem protozoários.

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This study aimed to evaluate the effect of virginiamycin on the metabolism and performance of growing Nellore bulls under low and high gain rates on pasture. In experiment 1, 80 Nellore bulls (age = 12 ± 2 months, body weight = 258 ± 15 kg) were assigned to 16 paddocks in a 2 × 2 randomized block factorial arrangement. In experiment 2, 12 cannulated Nellore bulls were assigned to three 4 × 4 balanced Latin squares. The factors were: (1) mineral salt without or with virginiamycin, and (2) low or high gain rate. No interaction was noted between factors (p > .10). Animals fed virginiamycin had greater average daily gain (14%, p < .01), body weight (11 kg, p = .05), plasma nonesterified fatty acid (20%, p < .01), serum calcium concentration (2.62%, p = .04), and total protozoa (p = .03) and had the same bacterial proportion (p > .27). Animals with a low gain rate had greater serum urea concentration (19.6%, p < .01) and ruminal ammonia nitrogen (62%, p < .01). Thus, virginiamycin increases the performance and changes the metabolism of growing Nellore bulls under low and high gain rates on pasture.