Management strategies for forage rape (Brassica napus L. cv Goliath): Impact on dry-matter yield,plant reserves,morphology and nutritive value

Limited information is available on the grazing management principles of forage rape (Brassica napus L.), particularly in relation to grazing height and intensity and the impact of these on dry-matter (DM) yield and nutritive value. A glasshouse study was undertaken to investigate the effect of three defoliation heights (plant height at harvest; DH: 40, 70 and 90 cm; L, M and H DH respectively) and three defoliation intensities (height at which plants were cut; DI: 5, 20 and 35 cm of residual height; H, M and L DI respectively) on forage rape (cv Goliath) yield and nutritive value at two harvests (harvest 1, H1 and harvest 2, H2), and the impact of nitrogen (N) and water soluble carbohydrate (WSC) reserves on regrowth. Increasing DH from L to H increased estimated total DM yield (H1 plus H2) from 0.5 to 4.6 t DM/ha but DI did not affect yield. Dry-matter yield was optimized at 90 cm DH, but greater nutritive value was achieved by harvesting at lower levels of DH. Despite high in vitro DM digestibility (IVDMD; 852–889 g/kg), harvesting at 90 cm DH could not meet the protein requirement of lactating dairy cows and harvesting at lower levels risks nitrate poisoning. Our results indicate the optimum DH may be between 70 and 90 cm DH, and 20 and 35 cm DI, which requires further studies.     

Establishment techniques affect productivity,nutritive value and atmospheric N2 fixation of two sunn hemp cultivars

Nitrogen fertilization is a common practice for sustaining forage production in forage systems in southeastern United States. Warm-season annual legumes may be an alternative forage to warm-season perennial grasses that do not require N fertilization. Sunn hemp (Crotalaria juncea L.) is a fast-growing, warm-season annual legume native to India and Pakistan. The objective of this 2-year study was to assess the herbage accumulation (HA), atmospheric N₂ fixation (ANF) and nutritive value of sunn hemp. Treatments were the factorial arrangement of two sunn hemp cultivars (“Crescent Sun” and “Blue Leaf”), three seeding rates (17, 28 and 39 kg seed/ha) and seed inoculation (inoculated or non-inoculated seeds), distributed in a randomized complete block design with four replicates. Crescent sun had greater HA (3,218 vs. 1764 kg DM/ha) and ANF (41 vs. 25 kg N/ha). Blue leaf had greater crude protein (CP) (188 vs. 176 g/kg) and in vitro digestible organic matter (IVDOM) concentrations (564 vs. 531 g/kg) than crescent sun. Non-inoculated seed had greater CP than inoculated seed, 188 and 177 g/kg, respectively, and inoculation did not affect HA. Intermediate seeding rate (28 kg/ha) decreased HA (2002 kg DM/ha), while HA from high and low seeding rates (17 and 39 kg/ha, respectively) did not differ (2,863 and 2,615 kg DM/ha respectively). Planting non-inoculated crescent sun at 17 kg/ha seeding rate is a feasible management practice to produce sunn hemp in subtropical regions; however, inoculation should always be recommended for proper establishment.     

Cylindrospermopsin effects on cell viability and redox milieu of Neotropical fish <Emphasis Type="Italic">Hoplias malabaricus</Emphasis> hepatocytes

Cylindrospermopsin (CYN) is a cyanotoxin that is cytotoxic to a wide variety of cells, particularly to the hepatocytes. In this study, the toxic effects of purified CYN were investigated in primary cultured hepatocytes of Neotropical fish Hoplias malabaricus. After isolation, attachment, and recovery for 72 h, the cells were exposed for 72 h to 0, 0.1, 1.0, 10, and 100 μg l^?1 of CYN. Then, cell viability and a set of oxidative stress biomarker responses were determined. Catalase, superoxide dismutase, glucose-6-phosphate dehydrogenase, and glutathione S-transferase activities were not affected by exposure to CYN. Concentration-dependent decrease of glutathione reductase activity occurred for most CYN-exposed groups, whereas non-protein thiol content increased only for the highest CYN concentration. Lipid peroxidation, protein carbonylation, and DNA damage levels were not altered, but reactive oxygen species levels increased in the cells exposed to the highest concentration of CYN. Cell viability decreased in all the groups exposed to CYN. Thus, CYN may cause a slight change in redox balance, but it is not the main cause of cell death in H. malabaricus hepatocytes.     

Immunostimulatory effects of dietary poly‐β‐hydroxybutyrate in European sea bass postlarvae

The stable production of high‐quality fry in marine aquaculture is still hampered by unpredictable mortality caused by infectious diseases during larval rearing. Consequently, the development of new biocontrol agents is crucial for a viable aquaculture industry. The bacterial energy storage compound poly‐β‐hydroxybutyrate (PHB) has been shown to exhibit beneficial properties on aquatic organisms such as enhanced survival, growth, disease resistance and a controlling effect on the gastrointestinal microbiota. However, the effect of PHB on the developing immune system of fish larvae has so far not been investigated. In this study, the effect of feeding PHB‐enriched Artemia nauplii on survival, growth and immune response in European sea bass (Dicentrarchus labrax) postlarvae was examined. Amorphous PHB was administered to 28‐day‐old sea bass postlarvae over a period of 10 days. The survival and growth performance were monitored, and the expression of 29 genes involved in immunity, growth, metabolism and stress‐response was measured. While the expression of the insulin‐like growth factor 1 (igf1), an indicator of relative growth, was upregulated in response to feeding PHB, the larval survival and growth performance remained unaffected. After 10 days of PHB treatment, the expression of the antimicrobial peptides dicentracin (dic) and hepcidin (hep) as well as mhc class IIa and mhc class IIb was elevated in the PHB fed postlarvae. This indicates that PHB is capable of stimulating the immune system of fish early life stages, which may be the cause of the increased resistance to diseases and robustness observed in previous studies.     

Vaccination of pigs with the S48 strain of Toxoplasma gondii – safer meat for human consumption

As clinical toxoplasmosis is not considered a problem in pigs, the main reason to implement a control strategy against Toxoplasma gondii (T. gondii) in this species is to reduce the establishment of T. gondii tissue cysts in pork, consequently reducing the risk of the parasite entering the human food chain. Consumption of T. gondii tissue cysts from raw or undercooked meat is one of the main sources of human infection, with infected pork being considered a high risk. This study incorporates a mouse bioassay with molecular detection of T. gondii DNA to study the effectiveness of vaccination (incomplete S48 strain) in its ability to reduce tissue cyst burden in pigs, following oocyst (M4 strain) challenge. Results from the mouse bioassay show that 100% of mice which had received porcine tissues from vaccinated and challenged pigs survived compared with 51.1% of mice which received tissues from non-vaccinated and challenged pigs. The presence (or absence) of T. gondii DNA from individual mouse brains also confirmed these results. This indicates a reduction in viable T. gondii tissue cysts within tissues from pigs which have been previously vaccinated with the S48 strain. In addition, the study demonstrated that the main predilection sites for the parasite were found to be brain and highly vascular muscles (such as tongue, diaphragm, heart and masseter) of pigs, while meat cuts used as human food such as chop, loin, left tricep and left semitendinosus, had a lower burden of T. gondii tissue cysts. These promising results highlight the potential of S48 strain tachyzoites for reducing the number of T. gondii tissues cysts in pork and thus improving food safety.     

Computed tomographic myelography of a foal with discospondylitis and extradural spinal cord compression due to a vertebral abscess

A one‐month‐old Quarter Horse colt presented with progressive gait abnormalities and weakness. The foal was ataxic at presentation. Radiography identified focal endplate irregularities and lysis at C6–7. Radiographic diagnosis was discospondylitis. Computed tomographic myelography was performed immediately following euthanasia and identified an extradural compressive spinal cord lesion corresponding to the site of discospondylitis. Post mortem examination findings included abscess formation at the C6–7 intervertebral space with osteomyelitis extending into the adjacent physes and subchondral bone of caudal C6 and cranial C7. The vertebral abscess extended into the ventral spinal canal at C6–7 and was identified as the cause of extradural spinal cord compression. Salmonella sp. was cultured and isolated from purulent exudate at the intervertebral space. Computed tomographic myelography has not been previously reported for assessment of discospondylitis in horses and was successful at accurately characterising spinal cord compression in addition to osteolytic changes associated with discospondylitis.     

Nitrosylhemoglobin as a Potential Bioactive Storage form of Nitric Oxide (NO)

Veterinary Research Communications -     

Secondary Stress Responses in Juvenile Brazilian Flounder,Paralichthys orbignyanus,throughout and after Exposure to Sublethal Levels of Ammonia and Nitrite

This study investigated the secondary stress responses of Paralichthys orbignyanus exposed to ammonia and nitrite and after recovery. Fish were exposed to 0.12, 0.28, and 0.57 mg NH₃‐N/L, or 5.72, 10.43, and 15.27 mg NO₂‐N/L for 10 d followed by the same time length for recovery. Ammonia‐ and nitrite‐free water was used as a control treatment. Blood samples were collected after 1, 5, and 10 d of exposure and after recovery. Fish exposed to ammonia presented lower and higher glucose levels after 10 d of exposure and recovery, respectively. Ammonia induced initial and transient ionic disturbances and metabolic alkalosis. Nitrite exposure caused hyperglycemia, increased plasma K⁺ levels, and respiratory alkalosis, whereas metabolic acidosis was observed after recovery. Increased proportion of monocytes and/or granulocytes and reduced number of lymphocytes were demonstrated in fish exposed to 0.28 mg NH₃‐N/L (Day 1) and 10.43 mg NO₂‐N/L (Day 5) and after recovery in the 0.28 and 0.57 mg NH₃‐N/L treatments. Exposure to ammonia decreased the proportion of granulocytes on Day 5. In conclusion, exposure to concentrations at 0.12 mg NH₃‐N/L and 5.72 mg NO₂‐N/L provoked physiological disorders in Brazilian flounder. Nonetheless, fish exposed to 5.72 mg NO₂‐N/L following a 10‐d recovery period showed complete resumption of homeostasis.