Impact of Water Stress on Maize Grown Off-Season in a Subtropical Environment

During the last decade, the production of off‐season maize has increased in several regions of Brazil. Growing maize during this season, with sowing from January through April, imposes several climatic risks that can impact crop yield. This is mainly caused by the high variability of precipitation and the probability of frost during the reproduction phases. High production risks are also partially due to the use of cultivars that are not adapted to the local environmental conditions. The goal of this study was to evaluate crop growth and development and associated yield, yield components and water use efficiency (WUE) for maize hybrids with different maturity ratings grown off‐season in a subtropical environment under both rainfed and irrigated conditions. Three experiments were conducted in 2001 and 2002 in Piracicaba, state of São Paulo, Brazil with four hybrids of different maturity duration, AG9010 (very short season), DAS CO32 and Exceler (short season) and DKB 333B (normal season). Leaf area index (LAI), plant height and dry matter were measured approximately every 18 days. Under rainfed conditions, the soil water content in the deeper layers was reduced, suggesting that the extension of the roots into these layers was a response to soil water limitations. On average, WUE varied from 1.45 kg m⁻³ under rainfed conditions to 1.69 kg m⁻³ under irrigated conditions during 2001. The average yield varied from 4209 kg ha⁻¹ for the hybrids grown under rainfed conditions to 5594 kg ha⁻¹ under irrigated conditions during 2001. Yield reductions under rainfed conditions were affected by the genotype. For the hybrid DKB 333B with a normal maturity, yield was reduced by 25.6 % while the short maturity hybrid Exceler was the least impacted by soil water limitations with a yield reduction of only 8.4 %. To decrease the risk of yield loss, the application of supplemental irrigation should be considered by local farmers, provided that this practice is not restricted by either economic considerations or the availability of sufficient water resources.     

Prevalence of Yeasts and Mycelial Fungi in Bovine Parasitic Otitis in the State of Minas Gerais,Brazil

Infestations by rhabditiform nematodes and acarids of the genus Raillietia are considered the primary causes of external otitis in cattle in tropical regions. Recently, yeasts of the genus Malassezia have been associated with a relatively high percentage of otitis cases, but the occurrence of other yeasts and mycelial fungi has not yet been reported in the literature. This work studied the presence of fungi in the ear canal of 45 cattle with external parasitic otitis. The results were positive for yeasts of the genus Malassezia in 31 (68.9 %) of the 45 cultures in Mycosel medium supplemented with olive oil. The 45 cultures in Sabouraud dextrose medium revealed the growth of seven (15.5 %) yeasts of the genus Candida, five (11.1 %) Rhodotorulamucilaginosa, two (4.4 %) fungi of the genus Aspergillus and eight ‘Micelia sterilia’. Future studies may confirm and elucidate the importance of these agents in the aetiology of bovine otitis.     

The role of metallothionein and zinc in hepatic copper accumulation in cattle

The role of metallothionein (MT) and zinc (Zn) in hepatic copper (Cu) accumulation in calves from a region in North-West Spain has been investigated. In this region there is intensive pig farming, and animals with liver Cu concentrations above normal are not uncommon. Concentrations of hepatic MT were not related to Cu accumulation but were strongly dependent on the Zn status of the animal. When analysing the metal content bound to MT it was observed that Cu-MT values, in the same way as Zn-MT, were directly correlated with MT concentrations in the liver, indicating that although Cu is a poor inducer of MT synthesis, it can compete with Zn for MT binding sites. The ability of Cu to displace Zn from MT is highly dependent on the Cu:Zn ratio in the cell, Cu being the main metal in MT at the higher levels of Cu exposure in Galician cattle. In spite of this, the percentage of the total hepatic Cu bound to MT is very low in these animals, indicating that cattle have a very limited capacity to accumulate Cu-MT in the liver, and may therefore have a greater susceptibility to Cu toxicosis.     

Morphometric and quantitative evaluation of the NADH-diaphorase positive myenteric neurons of the jejunum of streptozotocin-diabetic rats supplemented with acetyl-L-carnitine

Summary In this study we investigated the effect of the acetyl-L-carnitine (ALC) supplementation on the myenteric neurons of the jejunum of rats made diabetic at the age of 105 days by streptozotocin (35 mg/kg body weight). Four groups were used: non-diabetic (C), non-diabetic supplemented with ALC (CC), diabetic (D), diabetic supplemented with ALC (DC). After 15 weeks of diabetes induction the blood was collected by cardiac puncture to evaluate glycaemia and glycated haemoglobin. Next the animals were killed and the jejunum was collected and subjected to whole-mount preparation to evidence the myenteric neurons through the histochemical technique of the NADH-diaphorase. The neuronal counts were made in 80 microscopic fields, in tissue samples of five animals of each group. The profiles of the cell bodies of 1000 neurons per group were analysed. Diabetes induced a significant increase in the area of the cell body and decrease in the number of NADH-diaphorase positive myoenteric neurons. ALC suplementation to the diabetic group promoted smaller hypertrophic effects and less neuronal loss than in the myoenteric neurons of the diabetic rats, and in addition diminished the body weight decrease and reduced the fasting glycaemia.     

Risk of postnatal exposure to Sarcocystis neurona and Neospora hughesi in horses

OBJECTIVE: To estimate risk of exposure and age at first exposure to Sarcocystis neurona and Neospora hughesi and time to maternal antibody decay in foals. ANIMALS: 484 Thoroughbred and Warmblood foals from 4 farms in California. PROCEDURE: Serum was collected before and after colostrum ingestion and at 3-month intervals thereafter. Samples were tested by use of the indirect fluorescent antibody test; cutoff titers were > or = 40 and > or = 160 for S neurona and N hughesi, respectively. RESULTS: Risk of exposure to S neurona and N hughesi during the study were 8.2% and 3.1%, respectively. Annual rate of exposure was 3.1% for S neurona and 1.7% for N hughesi. There was a significant difference in the risk of exposure to S neurona among farms but not in the risk of exposure to N hughesi. Median age at first exposure was 1.2 years for S neurona and 0.8 years for N hughesi. Highest prevalence of antibodies against S neurona and N hughesi was 6% and 2.1 %, respectively, at a mean age of 1.7 and 1.4 years, respectively. Median time to maternal antibody decay was 96 days for S neurona and 91 days for N hughesi. There were no clinical cases of equine protozoal myeloenchaphlitis (EPM). CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to S neurona and N hughesi was low in foals between birth and 2.5 years of age. Maternally acquired antibodies may cause false-positive results for 3 or 4 months after birth, and EPM was a rare clinical disease in horses < or = 2.5 years of age.     

Otitis in cattle, an aetiological review

Otitis externa in cattle has a significant impact in tropical and subtropical regions, and the aetiological agents are predominantly rhabditiform nematodes and mites of the genus Raillietia. Its prevalence is higher in mature and Zebu cattle. In advanced clinical cases there can be irreversible and fatal neural lesions. Ear infection in calves has been associated with concurrent respiratory diseases and mixed infection. The principal reported agents of otitis in calves are bacteria such as Actinomyces spp., Corynebacterium pseudotuberculosis, Escherichia coli, Haemophilus somnus, Pasteurella multocida, Mannheimia haemolytica, Pseudomonas spp., Streptococcus spp. and Mycoplasma bovis. The control and treatment of bovine otitis is not standardized and there is little evidence-based support for the diverse treatments available in the literature.     

CD86 molecule is a specific marker for canine monocyte-derived dendritic cells

In this study, canine monocyte-derived dendritic cells (cMo-DC) were produced in presence of canine GM-CSF (cGM-CSF) and canine IL-4 (cIL-4), and they were characterized by their dendritic morphology, MLR functionality and phenotype. We noticed that cMo-DC were labelled with three anti-human CD86 (FUN-1, BU63 and IT2.2 clones), whereas resting and activated lymphocytes or monocytes were not stained. CD86 expression was induced by cIL-4 and was up-regulated during the differentiation of the cMo-DC, with a maximum at day 7. Furthermore, cMo-DC were very potent even in low numbers as stimulator cells in allogeneic MLR, and BU63 mAb was able to completely block the cMo-DC-induced proliferation in MLR. We also observed that cMo-DC highly expressed MHC Class II and CD32, but we failed to determine their maturation state since the lack of commercially available canine markers. Moreover, cMo-DC contained cytoplasmic periodic microstructures, potentially new ultrastructural markers of canine DC recently described. In conclusion, this work demonstrates that the CD86 costimulatory marker is now usable for a better characterization of in vitro canine DC.     

Morphoquantitative aspects of NADH-diaphorase myenteric neurons in the ileum of diabetic rats treated with acetyl-L-carnitine

In this work, we investigated the effect of the acetyl-L-carnitine (ALC) supplementation (200 mg/kg/day) on the myenteric neurons of the ileum of rats made diabetic by streptozotocin (35 mg/kg, i.v.). Four groups were used: diabetic (D), diabetic supplemented with ALC (DC), control (C) and control supplemented with ALC (CC). After 15 weeks of diabetes induction the animals were killed and the ileum was collected and subjected to whole-mount preparation to evidence the myenteric neurons through the histochemical technique of the NADH-diaphorase. The density of neurons seen in 12.72 mm2 of ileum showed no difference among the groups, although in group D it was 22% smaller than in group C, while group DC was 9% smaller to group CC. The profiles of the cell bodies (PC) of 1000 neurons per group were analysed. The neurons PC in group D decreased (P < 0.0001) when compared with other groups and increased (P < 0.0001) when compared with group DC. The incidence of neurons with a PC inferior to 200 microm2 was larger in group D. The frequency of neurons with a PC higher than 200 microm2 in group DC was close to those seen in groups C and CC. We concluded that ALC eases the loss of neurons and makes the incidence of myenteric neurons with a PC higher than 200 microm2 similar to the control rats.