Long‐term selection for increased egg production 1

1. Results are presented of a closed White Leghorn flock selected for increased egg production over a period of 17 years.

2. During the last 7 years a random breeding sample of the production flock served as a genetic control.

3. Regressions of deviations of the production flock from the control flock on years, were highly significant for age at sexual maturity (‐2.18 d), egg production up to 275 d old (3.04 eggs), egg production to 500 d old (5.04 eggs) and egg weight at 14 months old (October) ( — 0.79 g).

4. The heritability of egg production up to 275 d old declined significantly from 0.35 to 0.19.

5. The realised heritability of egg production up to 275 d old was estimated to be 0.14.

6. The genetic correlation between egg production up to 275 d old and production in the residual part of the year was 0.48.

7. The rate of inbreeding in the production flock was 0.515% per generation and the expected rate of inbreeding in the control flock 0.21% per generation.     

Brain and skull lesions resulting from use of percussive bolt, cervical dislocation by stretching, cervical dislocation by crushing and blunt trauma in turkeys

Three experiments were conducted to assess brain damage resulting from percussive bolt shooting and cervical dislocation by crushing (neck crushing) in turkey hens (mean [se] bodyweight 11.4 [0.1] kg); percussive bolt shooting and blunt trauma in turkey toms (13.1 [0.2] kg); and percussive bolt shooting, blunt trauma and cervical dislocation by stretching (neck stretching) in broiler turkeys (3.9 [0.3] kg). Brain and skull damage were assessed using macroscopic and microscopic evaluations and CT. Macroscopic subcutaneous haemorrhage was significantly greater with the percussive bolt in all three experiments (hens P=0.01, toms P=0.02, broilers P=0.0003), and skull fractures were more severe for toms (P<0.0001) and broilers (P=0.03) killed with the percussive bolt versus blunt trauma. In a subsample of turkeys, microscopic brain damage was present in all turkeys killed by percussive bolt shooting (five hens, 10 toms and four broilers) and blunt trauma (nine toms and three broilers), but only in one of four turkeys killed by neck crushing and one of four turkeys killed by neck stretching. Percussive bolt shooting and blunt trauma most likely caused death by directly disrupting brain function, whereas neck stretching and neck crushing probably resulted in death from cerebral hypoxia and ischaemia.     

Antibody response in cattle to oil emulsion rabies and ephemeral fever vaccines

A stable oil emulsion rabies vaccine with a low viscosity was composed by a formula previously employed for Newcastle disease vaccine. Cattle developed high and sustained antibody levels, and guinea pigs were found to be solidly immune after a single injection of this vaccine. Antibody responses in cattle to 2 oil emulsion ephemeral fever vaccines were not satisfactory after a single injection, and severe local reactions were encountered when booster injections were applied.     

Teratogenicity of a mutagenised Rift Valley fever virus (MVP 12) in sheep

A 5-fluorouracil mutagenised Rift Valley fever virus strain, which was shown to be attenuated and immunogenic in cattle and sheep, was evaluated for its ability to cause teratogenic effects in pregnant sheep. A group of 50 sheep at various stages of pregnancy was inoculated with the virus and the pregnancies followed to term. There were two abortions and 14% of the lambs produced by vaccinated ewes showed teratogenic effects, the most prevalent being spinal hypoplasia, hydranencephaly, brachygnathia inferior and arthrygryposis. The foetal malformations of the central nervous and musculo-skeletal systems were mostly consistent with those observed in sheep vaccinated with the attenuated Smithburn RVF strain. The teratogenic effects of MVP12 were not seen in previous experiments by other authors as immunisation of sheep took place in the second to third trimester of pregnancy, when the foetal brain tissue has completed most of its cell division.     

Photosensitivity in South Africa. VI. The experimental induction of geeldikkop in sheep with crude steroidal saponins from Tribulus terrestris

Geeldikkop was induced in sheep by the oral administration of crude steroidal saponins from Tribulus terrestris. Two of the sheep developed typical lesions of geeldikkop, including birefringent crystalloid material in bile ducts and concentric periductal lamellar fibrosis. The clinical pathological changes in these sheep were also consistent with those of geeldikkop: aspartate transaminase and gamma-glutamyl transferase activities in the sera of both were elevated, and one had bilirubinaemia. A third sheep became photosensitive without typical lesions of geeldikkop in the liver or changes in the activities of liver enzymes before euthanasia. The findings of these trials are consistent with reports from abroad that ovine hepatogenous photosensitization, caused by Agave lechuguilla and Narthecium ossifragum, can be induced with crude saponins from the respective plants.     

Pyridoxine (a vitamin B6) and its derivative pyridoxal as treatment for Albizia versicolor poisoning in guinea-pigs

In the course of three experiments it was established that all the toxic effects of a lethal dose of Albizia versicolor pods (greater than 4.5 g/kg) in guinea-pigs could be countered by concurrent subcutaneous injection of pyridoxine (10 mg/kg). This treatment was also successful once severe symptoms had set in. Pyridoxal, on the other hand, was found to be ineffective as a therapeutic agent. The fact that pyridoxal does not counter the action of the toxin indicates an atypical site of action by the toxin as regards the normal pathways which require vitamin B6 as a co-factor.     

THE CONTROL OF BLUETONGUE IN AN ENZOOTIC SITUATION

On account of the wide host range of bluetongue virus and its biological transmission by insects, control of the disease in an enzootic situation is based primarily on the active immunisation of susceptible animals as well as on the prevention of contact between the insect vectors and the susceptible hosts. In spite of their unquestionable value, the egg attenuated vaccines which are currently employed for prophylactic immunisation, have certain shortcomings. The existence of 16 known serotypes of bluetongue virus makes it difficult to achieve a very wide spectrum of immunity in sheep vaccinated once or twice only. The problems which are experienced with the immunisation of lambs born in spring are indicated. The present vaccine can also present problems when used in breeding animals. Furthermore, the costs involved in the annual vaccination of large numbers of animals are considerable. The need for a vaccine for cattle is indicated. Work is also being conducted at present on the development of an inactivated vaccine for use in sheep. The use of novel virological techniques may aid in the future development of absolutely safe and highly efficient vaccines against bluetongue.     

Krimpsiekte and acute cardiac glycoside poisoning in sheep caused by bufadienolides from the plant Kalanchoe lanceolata Forsk

Three toxic bufadienolides , one characterized as hellibrigenin 3-acetate, have been isolated from Kalanchoe lanceolata Forsk. Typical signs of cardiac glycoside poisoning, involving the gastro-intestinal, neuromuscular and cardiovascular systems, could be induced by drenching the milled plant to sheep. Such signs could also be induced by dosing the bufadienolides to sheep or by injecting them into both guinea-pigs (subcutaneously) and sheep (intravenously). The specific paretic syndrome, krimpsiekte , on the other hand, was reproduced only by the repeated intravenous administration of smaller doses of the 2 unknown bufadienolides to sheep. Histopathological examination revealed a mild to severe multifocal cardiomyopathy in sheep receiving plant material or bufadienolides .     

Über die Verwendbarkeit neuartiger Insekticide zur Maikäferbekämpfung

Ohne Zusammenfassung