Effects of protein-energetic supplementation frequency on growth performance and nutritional characteristics of grazing beef cattle

Two experiments were conducted to evaluate reduced supplementation frequencies for grazing beef cattle in rainy season. In experiment 1, evaluating the nutritional parameters, four rumen-cannulated Nellore bulls (BW = 410 kg) were used. In experiment 2, evaluating animal performance, 48 Nellore bulls (BW = 358 kg) were used. The treatments were as follows: mineral supplement (MS) alone and MS plus protein-energy supplement provided 3×, 5× and 7×/week. Supplementation frequency did not affect (P > 0.05) intake and digestibility. Average daily gain was greater (P < 0.001) to supplementation compared with MS. The supplementation 5×/week resulted in greater weight gain per hectare (9.24) and higher economic returns during the study period (1.64%) compared to other supplementations. Supplementation 5×/week increased animal performance and positively influenced economic returns.     

Influences of Sex and Age on the Hematological Profile of the Jundiá (Silver Catfish) Rhamdia quelen

In this study, sex and age influenced the hematological profiles of Jundiá (Silver Catfish) Rhamdia quelen. Females showed lower levels of hemoglobin, young fish increased lymphocyte counts, and older fish increased hematocrit values. These results indicate that, depending on age and sex, the fish have disparate hematological profiles. For this reason, it is important to consider the sex and age of an R. quelen when examining the impact of environmental and management factors on this species in terms of their hematological profiles.

Received May 24, 2015; accepted March 24, 2016 Published online August 2, 2016     

LED-Induced Chlorophyll Fluorescence Spectral Analysis for the Early Detection and Monitoring of Cadmium Toxicity in Maize Plants

Chlorophyll fluorescence spectral analysis permits detection, monitoring, and evaluation of abiotic stresses upon healthy plants using illumination of a light source in the UV?CVIS spectral range. This technique indirectly assesses the amount of physiological stress caused by photosynthetic damage, specifically damage to photosystem II, in plants. The objective of this study was to detect the toxicity of cadmium in maize plants via spectral analysis of chlorophyll fluorescence. The analysis is noninvasive and nondestructive and is used to follow the temporal evolution of changes in the chlorophyll content and physiological state of Zea mays L. seedlings under cadmium stress. Conventional techniques were also used to evaluate the dry matter production and Cd accumulation in plant leaves. Plants exhibited a notable reduction in dry matter production and chlorophyll levels with the administration of increasing doses of Cd in the nutrient solution. The fluorescence analysis was sensitive to changes caused by Cd in maize plants, detecting damage caused by different treatments before visual symptoms were observed. This technique has a practical application and produces rapid results that can be used in the evaluation of Cd-induced stress in plants and the detection of areas contaminated by this element.     

Temporal and spatial progress of the diseases caused by the crinivirus tomato chlorosis virus and the begomovirus tomato severe rugose virus in tomatoes in Brazil

Efficient management of whitefly-borne diseases remains a challenge due to the lack of a comprehensive understanding of their epidemiology, particularly of the diseases tomato golden mosaic and tomato yellowing. Here, by monitoring 16 plots in four commercial fields, the temporal and spatial distribution of these two diseases were studied in tomato fields in Brazil. In the experimental plots these diseases were caused by tomato severe rugose virus (ToSRV) and tomato chlorosis virus (ToCV), respectively. The incidence of each virus was similar in the plots within a field but varied greatly among fields. Plants with symptoms for both diseases were randomly distributed in three of four spatial analyses. The curves representing the progress of both diseases were similar and contained small fluctuations, indicating that the spread of both viruses was similar under field conditions. In transmission experiments of ToSRV and ToCV by Bemisia tabaci MEAM1 (former biotype B), these viruses had a similar transmission rate in single or mixed infections. It was then shown that primary and secondary spread of ToCV were not efficiently controlled by insecticide applications. Finally, in a typical monomolecular model of disease progress, simulation of the primary dissemination of ToSRV and ToCV showed that infected plants were predominantly randomly distributed. It is concluded that, although the manner of vector transmission differs between ToSRV (persistent) and ToCV (semipersistent), the main dispersal mechanisms are most probably similar for these two diseases: primary spread is the predominant mechanism, and epidemics of these diseases have been caused by several influxes of viruliferous whiteflies.