Tillage and crop residue management affect Vertisol properties and grain sorghum growth over seven years in the semi-arid sub-tropics. 3. Crop growth, water use and nutrient balance

The effects of fallow surface management treatments on subsequent growth and yield of grain sorghum were studied during seven cropping periods on a grey Vertisol near Biloela in central Queensland, Australia. Treatments were disc (D), blade (B) and zero (Z) tillage, each with stubble or residue from previous crops either retained ( + ) or removed ( − ) at the start of the fallow period. Treatments were planted to grain sorghum between December and February, following a 7–8 month fallow period.

Plant establishment was significantly (P<0.05) lower in Z than in D and B treatments in five of the seven crops. Average plant establishment over 7 years was about 20% lower in Z treatments. Early crop growth was generally more vigorous in D and B than in Z treatments, but this trend became less pronounced at later stages of growth. Surface cover (stubble+crop) ranged from 46% in Z + to 26% in Z− 5 weeks after planting and from 68% to 57% at anthesis and 62% to 46% at maturity in these same treatments. For the seven crops, annual mean grain yields over all treatments ranged from 1650 to 4490 kg ha⁻¹. Z− had a significantly (P<0.05) lower mean grain yield over the seven crops than all other treatments, which did not differ significantly (P>0.05). Where stubble was retained, yields of D+ and B+ never differed significantly. However, yields from Z+ were significantly higher in three crops than those from D+ and B+ and lower in three other crops. Stubble retention consistently resulted in significantly higher yields than stubble removal in the Z treatment. Crop water use was consistently lower in Z− than in all other treatments. Of the total roots to a depth of 1.6 m, a mean of 28% were found at 0–0.1 m. At 0.1–0.2 m and in deeper 0.2 m increments, the mean ranged from 6 to 11%.

Over 7 years, decreases in soil organic carbon at 0–0.1 m with stubble retained were less than with stubble removed. The differences corresponded to 4.1, 10.0 and 6.2% of stubble carbon inputs in D, B and Z treatments, respectively. Nitrogen removal in grain and stubble, expressed as a fraction of soil total nitrogen at 0–0.2 m plus nitrate-nitrogen at 0–1.6 m, ranged from 43% for D+ to 82% for Z+. Decreases of bicarbonate- and acid-extractable phosphorus at 0–0.1 m each corresponded to between 31 and 50% of the phosphorus removal in grain and stubble.     

Effects of overwinter cover on nitrate loss and drainage from a sandy soil: consequences for water management?

Abstract. A lysimeter study from April 1993 to June 1997 assessed the effects of winter cover crops and unfertilized grass on both the volume of water draining over winter and the amounts of nitrate leached. There were three to five replicates of each treatment in a fully randomized design. The lysimeters were undisturbed monoliths of loamy medium sand, 1.2 m deep and 0.8 m diameter. There were six treatments: sown cover before spring-sown crops (SC), natural regeneration (‘tumbledown’) before spring-sown crops (T), unfertilized grass (UG), bare soil permanent fallow, (PF), winter barley (WB) and conventional overwinter fallow before spring-sown crops (WF). Sugarbeet replaced cereals in 1996 as a disease break, and in consequence no cover was established in SC and T in autumn 1996. Of the four years of the study, two were above-average rainfall, while two were of less than average rainfall. Results are only quoted if statistically significantly different from WB (P=0.10). Over the first winter, NO₃―N losses were similar under UG (26 kg ha^?1) and PF (29 kg ha^?1), due to the slow establishment and growth of the grass. In the following three winters NO₃―N losses under UG were small (c. 6 kg ha^?1), giving an overall mean of c. 11 kg ha^?1. Sown cover crops and T gave means of c. 16 and 22 kg ha^?1 respectively, compared with c. 27–31 kg ha^?1 under PF, WB and WF. Mean NO₃―N concentrations were smallest under UG (4.4 mg l^?1) and SC (10.6 mg l^?1), although both T (13.7 mg l^?1) and PF (12.4 mg l^?1) were less than under WB and WF (15.8–18.7 mg l^?1). Overwinter drainage was greatest from UG and PF, at 239 and 247 mm respectively. In the three winters that cover crops were grown, drainage was decreased by, on average, 30 mm year^?1 compared with WF. However, there were large differences in effects between years, with significant decreases in only one year. We conclude that the widespread adoption of cover crops before spring-sown crops will reduce overwinter drainage in UK Nitrate Vulnerable Zones by no more than c. 2%, compared with no cover before spring-sown crops.     

Effect of adaptation to handling on the circulating Corticosterone concentration of laying hens

1. Single Comb White Leghorn hens were used to determine the effects of adaptation to handling on circulating corticosterone concentrations.

2. Blood samples were collected either by brachial venipuncture (BVP) or by brachial vein cannula (BVC). Half of the birds in each group were first adapted for 1 week to the handling procedure.

3. Adaptation to handling resulted in reduced plasma corticosterone concentrations.

     

Outcomes of thoracic surgery in dogs and cats

Summary: Records of 146 dogs and 41 cats that underwent thoracic surgery at The University of Sydney Veterinary Teaching Hospital were reviewed for age, sex, breed, disease, operation date, periods of pre- and post-operative hospitalisation, use of surgical drains and outcome. Animals were assigned to 16 disease categories, the most common being patent ductus arteriosus, traumatic diaphragmatic hernia and oesophageal foreign body in dogs and traumatic diaphragmatic hernia in cats. Differences were observed between disease categories in all the criteria examined. There were almost equal numbers of male (72) and female (74) dogs, the median (range) age was 2.0 (0.2 to 14.0) years, the median pre-operative stay was 1 (0 to 14) days, the median post-operative stay was 4 (0 to 28) days and the overall survival to discharge rate was 78%.
There were 24 male and 15 female cats (sex not recorded in 2 cats). The median (range) age was 3 (0.1 to 12) years, pre-operative stay 1 (0 to 6) days, post-operative stay 5 (0 to 15) days and the overall survival to discharge rate was 85%. Causes of post-operative deaths among animals in the most common categories are recorded and discussed.     

Effects of an oral superoxide dismutase enzyme supplementation on indices of oxidative stress, proviral load, and CD4:CD8 ratios in asymptomatic FIV-infected cats

This study was designed to test the effect of antioxidant supplementation on feline immunodeficiency virus (FIV)-infected felines. Six acutely FIV-infected cats (> or =16 weeks post-inoculation) were given a propriety oral superoxide dismutase (SOD) supplement (Oxstrin; Nutramax Laboratories) for 30 days. Following supplementation, the erythrocyte SOD enzyme concentration was significantly greater in the supplemented FIV-infected group than the uninfected control group or the unsupplemented FIV-infected group. The CD4+ to CD8+ ratio increased significantly (0.66-0.88) in the SOD supplemented FIV-infected cats but not in the unsupplemented FIV-infected cats. Proviral load and reduced glutathione (GSH) levels in leukocyte cell types did not change significantly following supplementation. Antioxidant supplementation resulted in an increase in SOD levels, confirming the oral bioavailability of the compound in FIV-infected cats. This result warrants further investigation with trials of antioxidant therapy in FIV-infected cats that are showing clinical manifestations of their disease, as well as in other feline patients where oxidative stress likely contributes to disease pathogenesis, such as diabetes mellitus and chronic renal failure.     

Simultaneous isolation and characterization of brush border and basolateral membrane vesicles from bovine small intestine

Purified brush border and basolateral membranes were isolated from homogenized intestinal enterocytes of Holstein steers by divalent cation precipitation followed by differential and sucrose density gradient centrifugation. Alkaline phosphatase and Na/K adenosine triphosphatase served as marker enzymes for the brush border and basolateral membranes, respectively. The brush border and basolateral membrane fractions were enriched 5.1- and 10.1-fold, respectively, over the cellular homogenate. Electron micrographs, obtained with transmission electron microscopy, confirmed the vesicular nature of the membranes and revealed that basolateral membrane vesicles generally were smaller and more irregular in shape than brush border membrane vesicles. The vesicular nature of isolated membrane preparations was confirmed with osmotic activity experiments. Enrichment of brush border and basolateral membrane fractions compared to the initial homogenate and the vesicular configuration of both preparations indicate that the isolated brush border and basolateral membrane preparations were suitable models for evaluating nutrient transport properties of bovine small intestine. The number of transport experiments possible per animal using the membrane vesicle technique is many times more efficient than some other in vitro techniques (i.e., intestinal rings or everted sacs).     

Serological survey of pre-weaned New Zealand fur seals (Arctocephalus forsteri) for brucellosis and leptospirosis

AIM: To conduct a longitudinal serological survey for evidence of Brucella spp and Leptospira spp infection of pre-weaned New Zealand fur seals in a colony on the Otago Peninsula. METHODS: Seal pups were repeatedly captured on a monthly basis from February through to July 2001. Pups were tagged at first capture and a blood sample was taken at each capture event. A total of 163 sera were collected from 118 seal pups. Where sufficient volume was collected, the sera were tested for leptospirosis using the microscopic agglutination test (MAT), and for brucellosis using the competitive enzyme-linked immunosorbent assay (ELISA) for Brucella abortus. RESULTS: None of 128 sera from 101 seals tested positive to the ELISA for B. abortus. All tests for Leptospira interrogans serovars Grippotyphosa, Copenhageni, Bratislava and Leptospira borgpetersenii serovar Ballum were negative at a cut-off of <1/100 dilution. Positive or suspicious titres were found to L. interrogans serovars Canicola and Pomona and L. borgpetersenii serovar Hardjo. The highest titres (12,800) were found to serovar Pomona. The titre to serovar Pomona in one seal rose from <1/50 in March to 12,800 in April and was <1/50 when re-sampled in July. The titre to serovar Pomona in another seal dropped from 12,800 in May to <1/50 in June. These seals also had titres to serovar Hardjo, which rose or fell in the same manner. All suspicious or positive titres occurred in late April and early May, when the pups were approximately 4-5 months old. In June and July, all seals tested were negative. CONCLUSIONS: There was no serological evidence of Brucella infection in the pre-weaned fur seals at the colony. Positive titres to serovars Pomona, Hardjo, or Canicola suggest that a Leptospira species was present at the colony, however isolation or visualisation of the organism is required to confirm this. Care should be exercised when handling New Zealand fur seals to prevent human infection or inadvertent transfer of leptospirosis to another marine mammal species.     

Nasal myiasis in a cat caused by larvae of the nasal bot fly, Oestrus ovis

An 8-year-old desexed male Burmese cat, which lived on a sheep-grazing property in central New South Wales, Australia, was presented following the sudden onset of dyspnoea, moist coughing and violent sneezing. The respiratory distress started several hours after the cat had made an outdoor excursion. Anterior rhinoscopy demonstrated small, white objects moving across oedematous and moderately inflamed nasal mucosa. These were retrieved via a series of vigorous nasal flushes and subsequently identified as larvae of the nasal bot fly, Oestrus ovis. The cat was treated with ivermectin followed by selamectin 7 days later. It went on to make a complete recovery over 2-3 weeks.