Effect of diatom supplementation during the nursery rearing of Litopenaeus vannamei (Boone, 1931) in a heterotrophic culture system

Bio-floc shrimp culture systems have been investigated in an attempt to optimize water use and prevent the discharge of effluent into the environment. The importance of microalgae in maintaining water quality and nutrition of the shrimp is well known in conventional systems; however, its maintenance amid bio-flocs and its role in the shrimp performance in this system are still poorly understood. The aim of this study was to evaluate the contribution of diatoms in the performance of Litopenaeus vannamei reared during the nursery phase in intensive system with minimal water exchange. Shrimp (0.31?±?0.10?g) were reared among diatoms, bio-flocs and the combination of the two forming the mixture medium. The survival of shrimp was high in all treatments (90?C97%). However, the shrimp reared among diatoms showed higher weight gain (P?<?0.05) and feed conversion ratio significantly more efficient, reaching a value of 0.47. The results indicate the importance of diatoms in bio-floc culture systems and points out to future research in an attempt to maintain a constant presence of these microalgae in culture medium without requiring successive inoculations.     

Phylogeographic implications for release of critically endangered manatee calves rescued in Northeast Brazil

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A positive growth response to NaCl applications in Eucalyptus plantations established on K-deficient soils

Contrasting responses of Eucalyptus trees to K fertilizer applications have been reported on soils with low K contents. A complete randomized block experiment was set up in Brazil to test the hypothesis that large atmospheric deposits of NaCl in coastal regions might lead to a partial substitution of K by Na in Eucalyptus physiology and enhance tree growth. Treatments with application of 1.5, 3.0, 4.5 kmol K ha⁻¹ (K_1.5, K_3.0, K_4.5, respectively) as KCl, 3.0 kmol K ha⁻¹ applied as K₂SO₄, 3.0 kmol Na ha⁻¹ (Na_3.0) as NaCl commercialized for cattle feeding, and a mixture of 1.5 kmol K + 1.5 kmol Na ha⁻¹ (K_1.5 + Na_1.5) were compared to a control treatment (C) with no K and Na applications. All the plots were fertilized with large amounts of the other nutrients.     

Genetic Analyses for TSV-Susceptible and TSV-Resistant Pacific White Shrimp Litopenaeus vannamei using M1 Microsatellite

Allelic frequency differences at the highly polymorphic MI microsatellite of B20 locus were examined in Taura Syndrome Virus (TSV)-susceptible (Kona) and TSV-resistant (Select) lines of Pacific white shrimp Litopenaeus vannamei . DNA was screened from 1,009 cultured L. vannamei , 166 from the Kona line and 843 (97 broodstock and 746 offspring) from the Select line. A total of 34 different MI alleles were found, 41.2% of which were shared by the two lines, and 58.2% were unique to either line. Only seven (20.6%) of the 34 alleles had similar frequencies in the two lines. The most frequent (22.4%) allele in the Select line (218 bp) was absent from the Kona line. The most frequent (9.6%) allele in the Kona line (236 bp) was not observed in the Select line. Significant genetic differentiation between the two lines was shown using contingency table analysis (X²= 891.20, df = 33, P < 0.0001), the exact test ( P < 0.00001), and F_st, analysis (0.06). Comparison of MI allele frequencies between the TSVresistant Select and TSV-susceptible Kona lines and between the top 12.5% (Top Select) and the bottom 12.5% (Bottom Select) surviving families to TSV challenge in the Select line suggested associations of MI alleles with TSV resistance. These observations suggest testable hypotheses in future experiments aimed at finding genetic markers associated with resistance to TSV and markers that could be used for marker-assisted selection of broodstock.     

Comparison of 2 serologic tests for the diagnosis of porcine proliferative enteropathy

The purpose of this study was to compare results from 2 serological assays at the individual- and herd-level for porcine proliferative enteropathy diagnosis. Cohen’s kappa coefficient (k) was used to measure agreement. The tests tend to show better agreement when used at the herd level.     

A field evaluation of PCR for the routine detection of Babesia equi in horses

We report on a study that evaluated the usefulness of PCR for the routine detection of Babesia equi in horses. The blood from a total of 105 horses comprising both sick and apparently healthy animals were examined for the presence of B. equi using both Wright-Giemsa-stained blood smears and PCR. Microscopic analysis of Giemsa-stained blood smears revealed 10/105 animals positive for Babesia, compared to 16/105 for the primary PCR and 36/105 for the nested PCR. Three of the 10 samples positive by Wright-Giemsa-stain were negative by PCR for B. equi. However, evidence is presented that these samples contained B. caballi and not B. equi. The Wright-Giemsa-stain was shown to identify Babesia in mostly clinically ill animals while the nested PCR detected the organism in a large number of apparently healthy animals. The results of this study suggest that the nested PCR is superior to both Wright-Giemsa-stained and primary PCR methods, and should be considered for the routine detection of B. equi in both healthy and clinically ill horses.     

Prescribed burning of Pinus oocarpa in Honduras I. Effects on surface runoff and sediment loss

The effects of low-intensity prescribed burning on surface runoff and sediment loss were studied in a stand of oocarpa pine (Pinus oocarpa Schiede) in central Honduras. The effects of burning in two seasons were compared on small paired plots on 10°, 25° and 40° slopes. Over a period of almost 2 years, mean percent runoff was 1.73% on the control plots and 5.03% on the burned plots. Mean sediment loss during the same period was 80 kg ha^?1 on the control plots and 1732 kg ha^?1 on the burned plots. The relationship between slope and surface runoff and sediment loss was negative; the effect of slope being masked by variation of other site factors. Recovery from burning was rapid and is attributed to the rapid rate of recovery of the ground vegetation of grasses and forbs which are adapted to frequent burning. Surface runoff and sediment loss on control plots were very low and the increases caused by burning are considered an acceptable alternative to the exposure of the overstory and site to the high risk of wildfires in accumulated fuels. Greater runoff and sediment loss were recorded on the plots burned in February than on those burned in June. As the period November to mid-February offers the greatest number of days with weather conditions suitable for low-intensity prescribed burning, it is concluded that burning for hazard reduction should be conducted as early as possible in this period, in November and December, to permit greater recovery of the ground vegetation before the heavy rains of May and early June.