Vegetation Cover, Composition, and Yield as Influenced by Soil, Litter and Grazing Intensity

Three pastures located 2.5 miles southwest of Hays were selected to determine the relationship of vegetation to depth of soil and different intensities of grazing. The pastures were classified as non-grazed, moderately-grazed, and heavily-grazed according to past use. Sites with deep and shallow soil were selected in each pasture to study in detail vegetational variations with respect to differences in soil and grazing intensity. When soil depth was less than 12 inches, soils were considered shallow and depths greater than 12 inches were considered deep. Ten quadrats, one square meter each, were selected on deep and shallow soil of each pasture. A detailed study of vegetation and soil differences was made by studying the following factors: basal cover and composition, monthly yield of vegetation, growth of grasses in height, counting of forbs with three feet by one foot rectangle, textural classification of soil, amount of organic matter and soil pH, amount of mulch, and utilization of vegetation by livestock. Basal cover increased with increased intensity of grazing. Deep and shallow soils of the heavily-grazed pasture had the highest basal cover when compared with the same type of soils of the non-grazed and moderately-grazed pastures. Composition of the species also varied according to the depth of soil and intensity of grazing. On deep soil of the non-grazed pasture, big bluestem was dominant while little bluestem dominated the shallow soil. On deep soil of both moderately- and heavily-grazed pastures, buffalo grass, blue grama, and side-oats grama were the dominants. Blue grama, hairy grama, and side-oats grama were dominant on shallow soils. Production of vegetation, mulch, and per cent organic matter was greater on deep and shallow soils of the non-grazed pasture as compared to the moderately- and heavily-grazed pastures. Deep soil of all three pastures produced higher vegetation, mulch, and organic matter than the shallow soil. Percentage of organic matter was higher in the 0-to-6-inch layer than the lower 6-to-12-inch layer of soil in each type of soil and pasture. Organic matter content was greatest in deep soil than in shallow soil of each pasture. Utilization of vegetation by livestock than the mode rarely-grazed pasture was 54.8 per cent while in the heavily-grazed pasture utilization was 77.8 per cent

Sensitivity to Antibacterial Agents Associated with Envelope Changes in Escherichia coli

Gram-negative bacteria are resistant to many hydrophobic antibacterial agents due mainly to the fact that their outer membrane acts as a very efficient permeability barrier against the entry of such compounds. Sensitivity to hydrophobic, cationic and 4-quinolone antibacterial agents was investigated using strains altered in outer membrane permeability due to the effects of cationic permeabilisers, Col V plasmids and mutations affecting outer membrane proteins. The cationic agents N-(2-pyrimidinyl)piperazine, 4,5,6-triamino pyrimidine, 1,4-diaminopiperazine, methylglyoxyl bis(guanyl-hydrazone), spermidine, agmatine sulfate, 1,3-diaminoacetone,3,3’-diaminobenzidine and 1,4-diaminobutanone were found to considerably enhance the growth inhibitory effects of novobiocin. In constrast, the agents 1,3-diaminoguanidine, triethylenetetramine, tetraethylene pentamine, N,N,N’ ,N’ -tetramethy 1-p-phenylenediamine and formamidine disulfide had no effect on novobiocin activity. Diaminoacetone also enhanced the activity of erythromycin, rifampicin, nalidixic acid, bacitracin, serum, polymyxin B, hydrogen peroxide and hexanoic acid (at pH 4), but failed to have any significant effect on the inhibitory activities of rifamycin, fiisidic acid, vancomycin, oxacillin, nafcillin, nitrofurantoin and deoxycholate. The growth inhibitory activity of EDTA and hexanoic acid were partially reversed by diaminoacetone. Magnesium ions were found to reverse novobiocin acitivity and also to compete with the enhancers of novobiocin activity. Inhibitory effects of the DNA gyrase inhibitors norfloxacin and ofloxacin were unaffected by the cationic agents diaminoacetone and methylglyoxyl bis(guanyl-hydrazone), but that of flumequin was significantly increased by both the cationic agents. Norfloxacin and ofloxacin are hydrophilic and amphoteric compounds respectively and hence use the porin pathway for entry into the Gram-negative cell. Flumequin, on the other hand is the most hydrophobic of these three DNA gyrase inhibitors tested, and may enter the cell via one of the other two pathways. It seems that the cationic agents act as permeabilisers of hydrophobic agents and therefore act at the surface of the cell ie. at the outer membrane; the possible mechanism of this effect is discussed. The effects of the ColV plasmids ColV,Ia-K94, ColV,Ia-K94 TnlO, ColV-K30, ColV-8 and ColV-41 were investigated on sensitivity of their E.coli K12 host strain to various antibacterial agents. Plasmids ColVJa-K94, its derivative ColV,Ia-K94 TnlO and ColV-41 were found to considerably increase the sensitivity of their host strain to erythromycin, rifampicin, gentamicin, novobiocin, but only to flumequin (and some to ofloxacin) out of the five 4- quinolones tested. Plasmid ColV-8 sensitised its host to most of the quinolones tested whereas plasmid ColV-41 conferred no effect on the sensitivity to these agents. With ColV,Ia-K94, colicin V and its immunity component, transfer components and an unidentified factor were found to contribute towards the observed increased antibiotic sensitising effect. I propose that the increased antibacterial agent sensitivity effect associated with the presence of most of the Col V plasmids is due to a change in the proportion of the outer membrane components and possibly also due to changes in LPS structure, but not due to any specific uptake system encoded by these plasmids; ColV-8 may however provide an additional route of entry for the quinolones. Novobiocin was found to be very active at low pH and this change in activity may be related to an observed change in its conformation at pH 5. On the other hand, novobiocin may be using a different pathway of entry into the cell at pH 5. This latter concept was investigated using strains containing mutations in the various major outer membrane proteins eg. porin proteins and those involved in the iron-assimilation system

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Influence of Homogenization Conditions of Buffalo Milk on the Recovery of Milk Constituents and Yield of Mozzarella Cheese

Mozzarella cheese making involves losses of milk constituents, especially during plasticizing stage of cheese curd. Buffalo milk is considered more suitable than cow milk for Mozzarella cheese making, especially in terms of colour, yield and stretch property of resultant product. Homogenization of milk reduces the losses of milk constituents, increases its whiteness and is expected to render superior flavor to cheese. The fat globule size for buffalo milk is larger and the cheese tends to be firmer and chewy as compared to cow milk counterpart. Homogenization of buffalo milk is of significance in this regard since it can improve the color, recovery of milk constituents culminating in higher cheese yield, a mellower product with lower tendency to oil-off during baking applications. Since the conditions of homogenization affects the recovery of milk constituents, it was decided to study temperature and pressure of homogenization on such aspect including cheese yield.Homogenization of standardized buffalo milk at 55 or 65oC and 4.90 MPa (P2) pressure is found beneficial with regard to recovery of milk fat, while use of lower pressure i.e. 2.45 MPa (P1) at above temperatures is found beneficial for protein and TS recoveries. P2 pressure is more beneficial than P1 pressure in improving the fat recovery in buffalo milk Mozzarella cheese. There is an improvement in the yield of Mozzarella cheese with an increase in homogenization pressure. The yield of Mozzarella cheese prepared using buffalo milk homogenized at P2 and P1 pressure (at 65oC) was 17.00% and 16.10% respectively. The recoveries of milk fat, protein and TS and per cent yield for control cheese was 83.68%, 84.10%, 56.74% and 14.53% respectively