Triploidy and intersexuality in adult commercial layers.

The cause of masculinisation of the left ovary and the outgrowth of the vestigial right gonad was investigated in intersexual hens. Tumour-like cell masses, resembling mouse tubular adenomas of the ovary, were observed in the majority of masculinised left gonads. Except for one male and two intersexuals, testosterone concentrations were below detectable levels. For oestrogen, progesterone and the oestrogen : progesterone ratio all differences were significant, except for the difference between the intersex and the male. Histochemically this cell mass showed weak androgen-synthesising activity. These intersexual gonads showed similarities to normal testicular tissue. Karyotyping revealed 3n-autosomes and a ZZW sex chromosome constitution. The early and almost complete absence of cortical follicular structures was most notable and may have been the cause of the sex reversal.

Non-infective factors in the aetiology of synovitis in chickens.

A study was conducted to elucidate the relative susceptibility of broiler breed birds to synovitis and the relative resistance of laying breed birds to this disease. It was shown that difference in structure and chemical composition of fibrous connective tissue can be associated with this difference in susceptibility. A loose structure of fibrous connective tissue (common in broiler breed birds) appears to predispose to synovitis, whereas a compact structure (common in laying breed birds) can be associated with resistance to synovitis. The most fundamental approach to the synovitis problem would be the breeding of broiler breed birds with a compact structure of fibrous connective tissue. However, this approach does not seem to offer favourable prospects in the near future. For the present, synovitis resistance in broiler parents can be enhanced by practising a management scheme aiming at activation of the birds.

A case of Aujeszky's disease virus infection in young chicks.

On a rearing farm with 96,000 birds, 10,000 three and four days old chicks died with nervous symptoms. A virus was isolated from the brains and identified as an Aujeszky's disease virus. The isolate was very pathogenic for chickens up to about 7 days of age, causing mortality after parenteral injection (intracerebral, intraperitoneal, intramuscular) but not after oral, eye drop or spray application. An Aujeszky vaccine virus, made apathogenic by passages in chicken cells for use in swine, had the same pathogenic properties for chicks. The isolated Aujeszky's disease virus is regarded as the agent responsible for the death of the 10,000 chicks on the farm. This virus most likely had been injected in just hatched chicks instead of or together with the Marek vaccine virus. In addition to meningitis, edema, neuronophagia and cuffing of blood vessels with mononuclear cells, haemorrhages were observed in thin sections of brain and spinal cord. After injection of isolate and vaccine virus in the leg muscle intranuclear inclusion bodies were observed in the ganglion cells in the spinal cord. Inclusion bodies have not been described before in pathological conditions of the nervous tissue of chickens.

Contribution to the aetiology of synovitis in chickens, with special reference to non-infective factors. V. Extractability of glucosaminoglycans/mucoproteins from tendon tissue.

A comparative study was undertaken regarding the extractability of glucosaminoglycans and mucoproteins in the tendon tissue of birds highly susceptible to synovitis, viz.broiler breed cocks (BB cocks), and of birds highly resistant to synovitis. viz. White Leghorn hens (WL hens). It was shown that in ;the case of WL hens this extractability decreased in accordance with ageing. In the case of BB cocks such a decrease was not observed. This observation is in support of a working hypothesis which supposes a relatively high degree of interaction between the several components of tendon components of tendon tissue (e.g. collagen and glucosaminoglycans/mucoproteins) in the case of WL hens, and a relatively low degree of this interaction in the case of BB cocks. Moreover the results of this study account for the observation that the tendon tissue of WL hens is more resistant to tensile stress than that of BB cocks, and they indicate that the above interaction is a determinant in the aetiology of synovitis.

Contribution to the aetiology of synovitis in chickens, with special reference to non-infective factors. IV.

The comparative study reported in the present paper was undertaken to collect data on the collagen content and collagen quality of tendons showing high (low) tensile strength levels and a compact (loose) histological structure. It was shown that tendon tissues of these two groups do not differ in this regard. The effect of administering a number of mutrients (known to be essential in collagenesis) was tested during this study. Administration of these mutrients did not prevent synovitis and did not increase tensile strength.

Contribution to the aetiology of synovitis in chickens, with special reference to non-infective factors. IV.

Summary The comparative study reported in the present paper was undertaken to collect data on the collagen content and collagen quality of tendons showing high (low) tensile strength levels and a compact (loose) histological structure. It was shown that tendon tissues of these two groups do not differ in this regard. The effect of administering a number of nutrients (known to be essential in collagenesis) was tested during this study. Administration of these nutrients did not prevent synovitis and did not increase tensile strength.

Infectious proventriculitis causing runting in broilers.

Proventriculitis, runting and poor feed conversion sometimes associated with rachitis, was seen in chickens on a large broiler farm. It was shown that the proventriculitis was caused by an infectious agent.

Contribution to the etiology of synovitis in chickens, with special reference to non-infective factors.

A study of the literature showed that a large number of micro-organisms have been designated as causative agents of synovitis. These micro-organisms cause almost identical clinical pictures. Particular birds are also found to be markedly prediposed to synovitis (broiler breed cocks), whereas the disease only occurs sporadically in other birds (hens of light-weight laying breeds). In view of these findings, a working hypothesis was formulated to the effect that the tendon tissues of birds in which synovitis is a common feature, will show qualitative and/or quanitative deficiencies; this could result in increased susceptibility to infections.

Contribution to the aetiology of synovitis in chickens. With special reference to non-infective factors. II.

The main purpose of the studies reported in the present paper was to test the theory that the tendon tissues of birds predisposed to synovitis, will show qualitative and (or) quantitative deficiencies. The tensile strength (TS) (maximum stress in kg/sq.mm. which can be tolerated by a particular tendon) was adopted as a parameter of the quality of the tendon tissues. The sectional area of a particular tendon per kg. of body weight served as a quantitative parameter. The results of these investigations were in accordance with the theory: the tendon tissues of birds predisposed to synovitis were found to be inferior to those of birds rarely affected with synovitis, both from the qualitative and from the quantitative point of view. These findings will have to be taken into account in future research programmes concerned with synovitis. Only to pay attention to infectious factors in the problem of synovitis means a one-sided approach which will probably fail to provide a definite solution.