Stochastic variation of system component variables in a network analysis

A deterministic network simulation was reformulated to include the uncertainty of various parameters. Then, by the recording values obtained for each pathway or system in the network for a set of stochastic parameters and then choosing another set of stochastic parameters and recording the values obtained from that simulation, an average value and standard deviation for any system in the network can be determined. In the decision-making process of choosing from one system over another, the manager will have a better understanding of the complex interactions involved by knowing the effects that uncertainty in the system can cause.     

SOME IMMUNOLOGICAL ASPECTS OF A RECENT AUSTRALIAN ISOLATE OF INFECTIOUS BRONCHITIS VIRUS

An infectious bronchitis virus, designated G48, isolated from birds during an outbreak of nephritis in a previously vaccinated broiler flock, overcame the resistance induced in birds vaccinated with 2 commercially available vaccines. Birds vaccinated with the A isolate of infectious bronchitis resisted challenge with this new virus. Cross neutralisation studies revealed that the new virus was serologically distinct from the 4 viruses tested. Homologous antiserum to G48 did not neutralise the other viruses and only antiserum to the A virus completely neutralised the new virus.     

Egg Shell Strength

Three experiments are reported which were designed to measure the relationship that exists between the specific gravity of an egg and deformation of its shell under load and also to determine the extent to which these two egg characteristics are related to shell breakage in the field.

A very close relationship was shown to exist between egg specific gravity and egg shell deformation.

In experiments 1 and 2, measurements of specific gravity and shell deformation were performed upon samples of eggs produced by groups of birds housed in wire‐floored pens and by individual birds kept in battery cages and were found, with one exception, to be significantly related to the incidence of cracking under these field conditions. The one non‐significant correlation was that between egg shell deformation and percentage cracks among eggs from the various pens of birds. However, too much emphasis should not be placed on this latter result because the incidence of floor‐laying in the different pens was not uniform and this increased chance variation in the occurrence of cracking.

In experiment 3 specific gravities and shell deformations were determined on 3000 sound eggs before they were subjected to treatments that simulated the hazards encountered during (a) laying in battery cages, (b) transport in the conventional travelling boxes. Both measurements were found to forecast fairly accurately the probability of a particular egg becoming cracked or remaining sound during the treatments.

The results confirm that egg specific gravity, as measured by the hydrometer method, is a reliable assessment of shell strength and suggest that the measurement of shell deformation is of comparable reliability. Other factors of practical significance that would influence the choice between the two assessments are discussed.     

The effect of varying flock size on the development and subsequent laying performance of floor‐reared pullets

Light‐weight, hybrid pullets were reared on litter in flocks of 400, 800 and 1200 birds per pen. Floor space allowance was held constant at 0–093 m² per bird and other related factors of management were standardised. The different sizes of flock had no significant effect on growth rate or mortality, but individual food consumption was significantly higher in the 400‐bird flocks than in the larger units.

At 18 weeks of age, some of the birds from each treatment were transferred to battery cages and others to deep‐litter laying quarters and records of their performance in terms of egg numbers and size, food consumption, mortality and body weight gain were taken over a period of 1 year. The only consistently significant finding was that birds reared in groups of 1200 tended to produce larger eggs (as shown by market grading) and, when housed on deep litter, to eat more food than birds reared in the smaller flocks.     

Immunoglobulin concentrations in ovine body fluids.

Ovine IgG, IgM and IgA and antisera specific for these immunoglobulins were prepared. The specific antisera were used to estimate the immunoglobulin concentrations in certain sheep body fluids. IgA was shown to be the major immunoglobulin in saliva, lung and lachrymal fluid, tracheobronchial and nasal secretions while IgG was the predominant immunoglobulin in colostrum, milk, bile and serum.     

Response of hybrid muskmelons to polyethylene row covers and black polyethylene mulch

Four commercial and two experimental muskmelon hybrids were grown with four different treatments: (1) bare soil, (2) black polyethylene mulch, (3) clear polyethylene row cover, and (4) a combination of row cover and mulch. The row cover alone afforded slightly better frost protection than the row cover—polyethylene mulch treatment. Daytime temperatures under the row covers averaged 4–5° C above outside air temperatures. Soil temperatures were considerably higher under the row cover—polyethylene mulch treatment than the other treatments.All hybrids commenced pistillate flowering earlier with the row cover treatments than with bare soil or black polyethylene mulch, and the experimental hybrids flowered comparatively much earlier than the commercial hybrids with the row cover—polyethylene mulch treatment. Fruit maturity was 3–9 days earlier for the commercial hybrids and 12–13 days earlier for the experimental hybrids with the row cover—polyethylene mulch treatment than with black polyethylene mulch.The results suggest considerable potential for increasing earliness in muskmelons in northern regions through the use of polyethylene mulches in combination with row covers, and by breeding cultivars more adapted to these cultural methods.     

Immunoglobulins in the serum and nasal secretions of lambs following vaccination and aerosol challenge with parainfluenza 3 virus.

Serial changes in the concentrations of IgM, IgG and IgA were compared in specific pathogen free (SPF) lambs which had been vaccinated with live or inactivated parainfluenza 3 virus (PI 3) by either intramuscular (IM) or intranasal (IN) routes followed by aerosol challenge with PI 3. In the serum, an increase in IgM was associated with the primary antibody response to the aerosol challenge, whereas increased IgG was associated with the secondary antibody response. No changes in immunoglobulin concentrations were observed in the nasal secretions of lambs administered live or inactivated virus IM or IN without adjuvant. Marked increases in IgG were found in the serum and nasal secretions of lambs vaccinated IM with inactivated virus in Freund's complete adjuvant (FCA) and fractionation by gel filtration confirmed that the antibody was associated with IgG in both these fluids.