Particle formation by ion nucleation in the upper troposphere and lower stratosphere

Unexpectedly high concentrations of ultrafine particles were observed over a wide range of latitudes in the upper troposphere and lower stratosphere. Particle number concentrations and size distributions simulated by a numerical model of ion-induced nucleation, constrained by measured thermodynamic data and observed atmospheric key species, were consistent with the observations. These findings indicate that, at typical upper troposphere and lower stratosphere conditions, particles are formed by this nucleation process and grow to measurable sizes with sufficient sun exposure and low preexisting aerosol surface area. Ion-induced nucleation is thus a globally important source of aerosol particles, potentially affecting cloud formation and radiative transfer.     

Egg shell deformation: Field comparison of two measurement devices 1

Two devices for measuring shell deformation were compared. One was the original Schoorl and Boersma apparatus, the other a device developed by Voisey and Foster.

It was found that the two machines were of similar precision but gave different absolute values for the same egg. This was thought to result from a systematic error in the Schoorl and Boersma machine.

The Voisey and Foster machine was found to be easier to use but the time required to take each measurement was 2 1/2 times that for the Schoorl and Boersma apparatus.     

Genetics of hatchability and its components and some production traits of chickens 1

Twenty‐egg samples from individual pullets belonging to four closed pedigreed populations were incubated to obtain hatchability and embryo mortality data. Egg production, egg weight and body weight data were obtained from the same pullets and comprehensive variance and covariance analyses were performed on the entire body of data. A slight but consistent genetic relationship was noted between hatch‐ability and egg production, mainly due to the influence of embryo viability during the final 12 d of incubation.

Limited evidence existed suggesting negative genetic correlations between egg size and hatchability. It is suggested that this relationship may be of the curvilinear type and this is substantiated by some data from a population selected for increased egg size.

The results are discussed from the viewpoint of their possible significance in practical breeding programmes.     

Variance and covariance of hatchability and some of its components in the chickens

Samples of 20 hatching eggs from each of 2004 individual pedigreed pullets were incubated and hatchability recorded. Unhatched eggs were examined for evidence of embryo development and classified as infertile, early embryonic death (died 0–10 d) or late embryonic death (died 11–22 d). Variance analysis yielded a mean heritability value for hatch of all eggs of approximately 0.30. Heritability values for early and late embryo mortality were subject to larger errors but there was a tendency among the estimates of h ² ₈ for late embryo mortality to be higher than those for early embryo mortality.

The genetic correlations between hatchability and both early and late embryonic mortality were high and negative as was to be expected from part × whole correlations. However the genetic correlation between early and late embryonic mortality was also consistently positive indicating common genetic determination of these two independent traits.     

The measurement of egg shell strength: a comparison of four methods

A variety of methods exists for assessing egg shell strength. For practical field use, a method is desired which is relatively rapid, easy to use and cheap. It must demonstrate differences between experimental varieties or nutritional treatments with sufficient precision that decision makers can rely on the results. A study has been made of eggs from 10 inbred lines of White Leghorns using non‐destructive deformation, beta backscatter count, deformation at failure, force at failure, shell stiffness and shell thickness to estimate shell strength.

A comparison of these methods indicated that under the conditions of this experiment, backscatter count yielded low coefficients of variation and did not demonstrate differences between inbred lines. The other methods showed differences between lines with non‐destructive deformation possessing an acceptable combination of precision, ease of operation and cost. Deformation and force at failure and egg shell stiffness required expensive non‐portable apparatus but stiffness was nevertheless thought to be a useful parameter. Direct measurement of shell thickness was acceptable but necessitated breaking the eggs.     

Vaccine efficacy against Ontario isolates of infectious bronchitis virus

Infectious bronchitis (IB) is an economically important viral disease with worldwide distribution. Every country with an intensive poultry industry has infectious bronchitis virus (IBV). The virus rapidly spreads from bird to bird through horizontal transmission by aerosol or ingestion. Sentinel bird studies were carried out in southern Ontario and IBV has been isolated from layer flocks. Genetic analysis of the S1 region of the strains showed that they were not vaccine related. The pathogenicity of selected Ontario variants of IBV isolates was studied and the subsequent work was to determine the degree of protection against field isolates provided by a commonly used vaccine MILDVAC-Ma5 in Ontario. The protection was evaluated by challenging immunized chickens with the respiratory (IBV-ON1) and nephropathogenic (IBV-ON4) viruses. The mean vaccine efficacy for IBV-ON1 was 66.7% indicating that a Massachusetts serotype vaccine would provide some protection against IBV field isolates.     

Pathogenicity of infectious bronchitis virus isolates from Ontario chickens

Infectious bronchitis (IB) is one of the important viral diseases of chickens, and in spite of regular vaccination, IB is a continuous problem in Canadian poultry operations. In an earlier study using sentinel chickens we determined the incidence of infectious bronchitis virus (IBV) in Ontario commercial layer flocks. The objective of this study was to determine the pathogenicity of 5 nonvaccine-related IBV isolates recovered from the sentinel birds. The clinical signs, gross, and histological lesions in specific pathogen-free chickens indicated that all 5 isolates caused mild lesions in the respiratory tract. An important finding of this study was the significantly lower average daily weight gain among virus-inoculated groups of chickens during the acute phase of infection. Based on sequences of part of the S1 gene IBV-ON2, IBV-ON3, and IBV-ON5 formed a cluster and they were closely related to strain CU-82792. IBV-ON4 had 98.7% identity with the strain PA/1220/9, a nephropathogenic variant.