Waveguide surface plasmon resonance studies of surface reactions on gold electrodes.

We describe the fabrication and characterisation of gold-coated graded index channel waveguide sensors designed for simultaneous electrochemical and surface plasmon resonance studies. The active sensing electrode area is a thin gold film between 0.5 and 5 mm in length and 200 microm wide deposited on top of a 3 microm wide waveguide which forms one arm of a Y-junction while the other arm of the Y-junction serves as a reference. Using these devices we have measured simultaneously the changes in transmittance through the device whilst carrying out cyclic voltammetry in either sulfuric or perchloric acid solution or during the deposition of an UPD layer of copper at the gold surface. In all cases we obtain stable and reproducible results which demonstrate the very high sensitivity of the devices to sub-monolayer changes occurring at the gold electrode surface. The response of these integrated optoelectrochemical devices is discussed in terms of a numerical model for the propagation of light within the waveguide structure.

Selection for heterosis from crossbred populations: estimation of the F1 heterosis and its mode of inheritance.

The heterosis inheritance backcross evaluation technique (HI-BET) is proposed as a selection strategy for developing a pair of complementary strains from a crossbred population descended from a F1 population possessing considerable heterosis. These complementary strains are expected to produce a strain cross superior to the F1 population from which they were derived. In the first stage of an experimental evaluation of HI-BET, Australorp and White Leghorn hens were compared with their F1, F2 and F1 by parental breed backcross populations for a range of egg production traits. The substantial heterosis for survivors' egg production and total egg mass was largely lost in the F2 and backcross populations indicating that this heterosis was mainly due to parental epistasis. The uneven distribution of residual heterosis in the backcross populations suggests that about two-thirds of this parental epistasis was inherited from the White Leghorn line. As the Australorp line was substantially superior to the White Leghorn line for survivors' egg production and total egg mass, it most likely contained additive genes for both these traits that were not present in the White Leghorn line. It is suggested that HI-BET should be an effective strategy for incorporating these additive genes into the White Leghorn line, together with some brown egg shell genes if also desired, as a means of further improving the performance of the F1 cross.

Selection for heterosis from crossbred populations: comparison of the F3 and backcross populations.

An experimental evaluation of HI-BET (heterosis inheritance backcross evaluation technique) involving the comparison of the performance of F3 and backcross (BC) families with common sires is described. These crossbred populations were derived from an F1 cross between Australorp and White Leghorn fowls with substantial heterosis for egg production variables. There was considerable evidence for the presence of a statistically significant sire family by population type interaction for survivor's total egg mass. The ranking of sires varied substantially depending upon whether they were being assessed on the performance of their F3 or their BC daughters. The BC population yielded substantially higher sire component heritability estimates for egg weight, egg production and total egg mass than did the F3 population. For the latter two traits, this improvement in the correlation between genotype and phenotype is in accordance with the expectations of HI-BET. It is concluded the HI-BET should be effective strategy for selectively focussing upon the non-additive genes that are only present in one ancestral line at a high frequency, whilst ignoring non-additive genes unique to the other ancestral line.

The fine structure of the proximal growth plate of the avian tibia: vascular supply.

The vascular supply to the proximal tibial growth plate of the 7 weeks old chicken is described using various vascular markers. In addition the ultrastructure of metaphyseal and epiphyseal vessels as well as their supporting tissue is reported. The metaphyseal arterioles terminate in large calibre vessels which have occasional endothelial gaps and no basement membrane or supporting cells, and therefore could be classified as venous sinusoids. In contrast the epiphyseal arteriole terminates in a capillary-venule plexus lined by an attenuated and fenestrated but continuous endothelium. This paper definitively establishes that communication of epiphyseal and metaphyseal vessels across the avian growth plate does not occur. The eosinophilic streaks which often join these two vascular supplies have been described ultrastructurally and would appear to be remnants of the 'retreating' epiphyseal vessels.

The cholesterol content of eggs produced by Australian egg-laying strains.

1. Eggs laid by the various strains entered in the 25th New South Wales Random Sample Layer Test were analysed for cholesterol content when the hens were 30, 45 and 60 weeks of age. 2. The strains differed in cholesterol content per gram of yolk and per egg. However most of the variation in cholesterol content per egg was attributable to strain differences in egg weight and in the proportion of yolk per egg. 3. Since 1 g of yolk contains approximately 6.7 times more energy and requires approximately four times the deposition energy of 1 g of albumen, the relation between the proportion of yolk within an egg and efficiency of egg production from food was considered. 4. It is recommended that comparisons of egg-laying strains and investigations into the efficiency of egg production from food should include an estimate of the proportion of yolk in the eggs.

Effects of restricted feeding in the growing and laying periods on the performance of White Leghorn by Australorp crossbred and White Leghorn strain cross chickens.

1. The effects of restricted feeding in the rearing and laying periods on the performance of three White Leghorn cockerel by Australorp pullet crossbred strains and one White Leghorn strain cross were studied in two experiments. 2. After feeding ad libitum in the rearing period, mean body weights of the three crossbred strains at 20 weeks of age were 1.75, 1.66 and 1.55 kg and that of the White Leghorn strain cross was 1.40 kg. The differing restrictions during rearing reduced mean body weight at 20 weeks by 14 to 33% and increased the time to sexual maturity by 8 to 23 d. 3. All restriction regimes during rearing increased mean egg weight and tended to reduce mortality in the laying period. Optimum hen-day egg number over 64 weeks of lay was obtained following mild restriction (14% body weight reduction) of the two heavier strains or ad libitum feeding of the lighter strains. Over 48 or 64 weeks of lay, egg number per hen housed (at 18 to 20 weeks of age) was optimised after moderately restricting (14 to 21% body weight reduction) the crossbred strains or feeding the White Leghorn strain cross ad libitum. 4. Over 64 weeks of lay, mortality was reduced from 19.3% to 10.5% in the lightest crossbred strains, in which a high proportion of deaths were associated with Marek's disease and lymphoid leucosis, by restriction during rearing. 5. Restricting food intake by 7 or 8% throughout the laying period reduced hen-housed egg number and mean egg weight of all four strains. The reduction in hen-day egg number associated with food restriction during lay was less for the heavier strains that had also been restricted during rearing. 6. Metabolisable energy intakes required to support maximum production over 64 weeks of lay were 1.23 to 1.36 MJ/d.

The incidence and importance of tibial dyschondroplasia to the commercial broiler industry in Australia.

1. To survey the relationship between tibial dyschondroplasia (TD) and the down-grading of broiler carcasses three processing plants representing the major breeding and growing organizations in Australia were visited. 2. The incidence of TD for the three flocks examined varied from 14 to 35%. In the flock with the highest incidence of TD there was a direct relationship between the presence of TD and down-grading of carcasses due to leg abnormalities. 3. A genetic analysis was carried out on one of the parent lines of the breeding group with the highest TD incidence. The genetic correlation between body weight and TD incidence at 7 weeks of age was negative, suggesting that continued selection for increased body weight should lead to a reduced incidence of TD. Since this conflicts with usual expectations, possible reasons, including a within-line genotype by environment interaction, are discussed. 4. Because of the substantial genetic component associated with TD, screening of breeding cockerels for its presence if strongly recommended.

Further studies with a sex-linked lethal gene in the fowl.

1. The ladykiller (lk) gene has been located on the sex chromosome of the fowl. It is 4.2 map units distant from the feathering rate locus (k) and 11.2 map units distant from the dwarf (dw) locus. 2. Most of the embryonic mortalities associated with this gene occurred between 3 and 4 d of incubation.

The inheritance of tibial dyschondroplasia in broilers.

A breeding programme to develop a line of chickens with a high incidence of tibial dyschondroplasia (TD) from Australian broiler stock is described. Despite the absence of a control flock, this programme has demonstrated that selection in a broiler population can rapidly increase the incidence of TD. There was consistent circumstantial evidence of the presence of a major sex-linked gene, the recessive allele of which is associated with an increased incidence of TD. The realised heritability estimates (obtained in the absence of a control flock) consistently exceeded 1.00, suggesting the presence of an environmental trend favourable to the onset of TD over the four generations of this investigation. There was a high maternal component or dominance genetic component, or both, for the inheritance of TD in the final generation, suggesting that environmental factors associated with the female parent line may influence the incidence of TD in broilers.

Partitioning of variance and estimation of genetic parameters for various bristle number characters ofDrosophila melanogaster.

Phenotypic variance for each of several bristle number characters (abdominal, sternopleural, second and third coxal) was partitioned using both hierarchal and dialled designs. Heritabilities and genetic correlations were estimated from parent-offspring regressions and correlations and half-sib correlations.A high proportion of the genetic variance for abdominal bristle number was due to epistatic and sex-linked gene action, but most of the genetic variance for the other characters was additive autosomal.The genetic correlations among sternopleural, and second and third coxal bristle numbers were all high, but that between abdominals and sternopleurals was low, while those between abdominals and either second or third coxals were virtually zero. An appreciable proportion of the covariance between abdominal and sternopleural bristle numbers was non-additive genetic.The diallel method gave more reliable estimates of genetic parameters when non-additive or sex-linked genetic variation was present.