Hydrolysis of the wild oat herbicides flamprop-methyl,flamprop-ethyl,flamprop-isopropyl and benzoylprop-ethyl

Kinetic measurements of the hydrolysis rates of flamprop-methyl, flamprop-ethyl,^a flamprop-isopropyl and benzoylprop-ethyl have been carried out and the hydrolysis products analysed. The similarity of the data to that obtained from the hydrolysis of alkyl acetates show that these esters are hydrolysed by bimolecular acyl bond fission in both acidic and basic media. No buffer or salt effects on the rates were observed. The hydroxyl ion rates were approximately 10000 times faster than the protoncatalysed rates, so that optimum stability is found in solutions of pH 4. Equations are given to calculate hydrolysis rates when the pH exceeds 4 at ambient temperatures.     

EFFECT OF POPULATION STRUCTURE AND DENSITY AT STOCKING ON PRODUCTION AND COMMERCIAL FEASIBILITY OF PRAWN (Macrobrachium rosenbergii) FARMING IN TEMPERATE CLIMATES1

During 1978–1980, 18 rearing trials were conducted in 0.25 ha ponds to examine the effects of various stocking strategies on production and economic potential. The strategies tested consisted of stocking: post-larvae only; a mixed population of postlarvae plus juveniles; small juveniles only, at densities ranging from 2.15–8.61 prawns/m². Prawns were fed Purina Marine Ration 25 once daily and seine-sampled at 4-week intervals throughout the 144–168 day rearing periods. Clear relationships between population structure of the stocked prawns and density versus crop yields and estimated revenues were demonstrated. The stocking of postlarvae resulted in lower production levels and less valuable prawns as compared to stocking a mixture of postlarvae + juveniles or juveniles only populations. Also, survival was more variable (range 59.3–84.5%) and lower (mean 69.6%) when postlarvae were stocked. Greater crop yields were achieved at higher densities, however, mean size and unit value of the crop decreased as density increased. Feed conversions were low and averaged 1.4 (range 0.8–2.2) for all trials combined. Preliminary economic feasibility analyses of the various stocking strategies were performed for situations where ponds and associated facilities were already available. The analyses suggested that positive net revenues were possible if a mixed population of postlarvae and juveniles or juveniles only were stocked at about 6.5/m² and seed costs were ∑30/1,000 and the crop was marketed as a combination of large whole.     

The effect of parenteral immunisation on antibody production in the pig colon

Local and systemic antibody production was studied in pigs to compare responses to live and killed bacterial antigen and purified protein antigen, with and without prior mucosal stimulation. Recovery from challenge with live bacteria and intramuscular injection with killed bacteria gave rise to similar high levels of serum IgG antibody, but the ratio of specific IgA to IgG in the colon was significantly higher after infection than following vaccination with killed bacteria. Vaccination with a protein antigen gave rise to serum and local antibody production. Prior feeding of the antigen had a tolerising effect on the serum antibody response, but production of IgG and IgA antibody by the colon was not suppressed.     

Immune responses to intramammary infusion with soluble (ovalbumin) and particulate (S uberis) antigens in the preparturient bovine udder

Pregnant non-lactating cows were immunised by intramammary infusion with killed Streptococcus uberis into one quarter and ovalbumin into another, at one week (group 2) or one week and two weeks (group 1) before the expected date of parturition. A small IgG1 and IgG2 antibody response to ovalbumin was detected in the serum of these cows. There was also a small increase in IgG1 and IgA serum antibody activity to S uberis. In whey the response was restricted to IgA with activity to S uberis. The IgA antibody response to S uberis in group 1 was significantly greater in the quarter immunised with bacteria than that of the control quarters for up to two months after calving. In contrast, the serum IgA response was short or absent in a number of animals.     

An enzyme-linked antiglobulin test for the detection of erythrocyte-bound antibodies in canine autoimmune haemolytic anaemia

A method has been developed which allows identification and quantitation of red cell-bound immunoglobulins and complement in canine blood. The technique utilizes ELISA methodology and the assay identifies cases of autoimmune haemolytic anaemia which are negative by the Direct Coombs test. Further, the amount of antibody present on the red cells shows a close correlation to the haemoglobin level; suggesting that the degree of sensitization of the RBCs influences their rate of destruction. Favourable response to treatment correlates with a decrease in the levels of bound antibody and complement.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. 3. Bermudagrass and clover hays

Five crossbred beef cows (Hereford X Angus, 438 kg), cannulated in the rumen and duodenum, were used in a Latin square experiment to determine the effects of dietary proportions of bermudagrass (B) and clover (C) hays (0: 1, .25: .75, .5: .5, .75: .25 and 1: 0) on digestive function. Feed intake was 85% of ad libitum intake of B alone (1.35% of body weight). Bermudagrass contained 1.88% nitrogen (N), 79.6% neutral detergent fibre (NDF) and 5.2% acid detergent lignin (ADL), and C contained 2.30% N, 55.3% NDF and 6.3% ADL. Molar proportion of acetic increased linearly while propionic acid moved in the opposite direction as B replaced C (P less than .05). Mean particle size of duodenal digesta increased linearly (P less than .05) as B increased, but specific gravity of particles was constant (P greater than .10). Fluid passage rate decreased while volume increased linearly with increasing B (P less than .05) so that ruminal fluid outflow rate increased quadratically (P less than .10). Particulate passage rate ranged from 3.0 to 3.4% h. Apparent ruminal organic matter (OM) digestion was 69.0, 54.0, 53.0, 49.1 and 49.7% for 0, 25, 50, 75 and 100% B, respectively, decreasing quadratically as B rose (P less than .05). Postruminal OM digestibilities as percentages of intake and available OM changed quadratically (P less than .05) as dietary B increased, causing total tract OM digestion to decrease linearly (P less than .05; 73.8, 66.4, 63.1, 60.3 and 58.2% for 0, 25, 50, 75 and 100% B diets, respectively). Duodenal microbial-N flow increased quadratically with increasing B (P less than .05), being 45, 108, 103, 105 and 101 g/d, and microbial growth efficiency increased quadratically as well (P less than .05). True ruminal N disappearance ranged from 69.0 to 79.4% and was not affected by diet (P greater than .10). Ruminal digestibilities of fibre fractions were similar to OM. Little digestive function benefit was achieved by mixing warm season grass and legume hays in diets of maintenance-fed beef cows.     

Hysteretic Responses to Grazing in a Semiarid Rangeland

Ecological systems comprise a complex array of interacting processes that manifest across multiple scales. Effective management of natural ecosystems has to be underpinned by an understanding of how the scaling of these processes influences system integrity and stability. This is particularly true in semiarid rangelands, which display strong relationships between pattern and process that are fundamental to maintaining ecosystem function. Grazing can disrupt the scaling of these relationships and the mechanistic coupling between pattern and process, undermining the health of grazed semiarid rangelands. This is due to possible hysteretic responses in key system components to increases and decreases in grazing disturbance. We used data from a semiarid rangeland in northern Australia to test for hysteretic responses in system components after the removal of cattle grazing. We found an uncoupling of spatial linkages between vegetation and soil moisture in a severely degraded plot that was not evident in less intensively grazed or recovering plots. Recovering plots protected from grazing for 20 yr showed a scale of spatial linkage between vegetation and soil moisture, and soil organic matter and mineralization flush, of a scale much coarser than that of degrading plots. These findings provide evidence for hysteretic recovery from grazing and demonstrate that comparison of the spatial patterns of vegetation and soil properties is essential for capturing the true state of ecological functionality in this system. This has important implications for assessing ecological function in systems typified by strong natural environmental variation or in which data for pristine conditions are lacking.