[Contamination of the air with microorganisms at various distances from the poultry house]. / Zam'rsenost na v'zdukha s mikroorganizmi na razlichni razstoianiia ot pticharnitsite

Experiments were carried out to establish the microbial contamination of air (including moulds) at various distances from the buildings for raising birds. Results showed that the presence of organisms in the outer air is directly dependent on the microbial contamination of the air in the poultry houses. It was found that the distances between the buildings are too short and the air driven into the premises is of a high bacterial count. Comparative investigations have revealed that the contamination of the air out of the buildings is likewise dependent on the technologic design of the ventilation system. It is concluded that the low contamination of outdoor air is substantiated by an effective system of forced ventilation on the premises coupled with measures lowering the microbial count indoors.

[Comparative study of microbial and mold pollution of the air in locations for poultry-keeping in various technologies]. / Sravnitelni izsledvaniia na mikrobnata zam'rsenost na v'zdukha v pomeshteniia za otglezhdane na ptitsi pri razlichni tekhnologii

Experiments were carried out to establish the microbial and mold contamination of the air on premises where birds were raised following varying patterns of tending and feeding. It was found that on premises for layers, raised in cages, the microbial contamination of the air was 2-3 times lower. The results obtained showed that the main source of air contamination in places where birds are kept is the litter (the other alternative being the floor type of raising). Differences were established in the egg laying, on the one hand, and the forage intake per 'market' egg, on the other, comparing the two types of raising. As all other factors of microclimate were within the normal range of zoohygiene standards, the basic factor which was incriminated to affect both productivity and forage intake per egg was the amount of the microbial flora of the air. Studies have shown that the number of birds per unit of area is an important factor determining the microbial contamination of the air and the health condition of birds.

[Role of vertical transmission and seminal fluid in the infectious leukemia process]. / Roliata na vertikalnoto predavane i semennata technost pri levkozniia infektsiozen protses.

Studied was the occasional role played by vertical transmission of the leukotic infection via the placenta under experimental conditions and in the field. Studies were also carried out to establish the transmission of the infection through the semen as well, using bull semen and test lambs as most susceptible to the virus of bovine leukosis. It was found that at the experimental infection of sheep with the bovine leukosis virus intraplacental infection of part of the fetuses took place. On dairy farms with a widely spread infection (more than 50 per cent) in cattle the newborn calves were found to respond positively immediately after birth and prior to sucking colostrum, having specific leukosis antibodies, though in a low percent. No transmission of leukosis was found with the semen of leujotic bulls.

[Experiments to obtain and use an allergen for the diagnosis of leukemia in animals]. / Opiti za poluchavane i prilozhenie na alergen za diagnostika na levkozata po zhivotnite.

The tested allergen was obtained from a stable cell line FLK which produces leukosis virus type "C" for diagnostics of animal leukosis (cattle, sheep, pigs). It was found that the allergen is strictly specific and induces hypersensitivity of delayed type which is recorded best on the 24th h of injection. The most suitable site to inject the allergen proved to be the tail fold for cattle and sheep and the dorsal part of the ear--for pigs in dose of 0.2 cc. The allergen reaction correlates to a considerable degree with the serologic one (AGDS) but it does not detect all serologic reagents. It detects much larger percent of susceptible animal compared with the hematologic method. Data obtained give grounds to assume that the allergen reaction may be used for quick herd diagnostics of leukosis.

[The effect of microbial contemination of the air on metabolic indices in broiler chickens]. / Vliianie na mikrobnata kontaminatsiia na vuzdukha vurkhu niakoi pokazateli na obmianata na bro-56ileri

Trials were carried out with two groups of birds, White Plymouth times Cornish crosses. A third, control group of birds was also involved in the experiments, reared by the same technology. The only difference consisted in that the air in the premise of the test birds had a lower microbial content which, during the experiments was 2 to 5 times lower than that in the air of the controls. It was found that under the effect of the higher microbial content the blood serum protein drops like the protein content of the liver and heart musculature, the content of free amino acids rises, the amount of triptophane lowers, and the activity of GOT and GPT is enhanced. The birds of the control group show higher enzyme activity so far as the glucose-6-phosphatase of the liver is concerned, lower glycogen content of the liver, and lower blood concentration of glucose. By the end of the trials the broilers of the control group were 50 gr less heavy than the lest birds.

[New trends in the control of enzootic bovine leukemia in Bulgaria]. / Novi nasoki v borbata s enzootichnata levkoza po govedata u nas.

Experimental and literature data as well as personal observations with herds infected with enzootic bovine leukosis have revealed some new aspects that could be made use of in the control of the disease. The more important ones are stated: newborn calves of cows with positive leukosis response can be given untreated colostrum which has been shown to neutralize the virus; in individual regions and Agro-Industrial Complexes where sporadic cases of leukosis have been recorded isolation premises for positively reacting animals could be designed; cows in the last two months of pregnancy do not always give reliable results with the immunodiffusion test, so such animals should not be investigated at that time with this method.

[Importance of saliva and colostrum in leukemia transmission in cattle]. / Znachenieto na sliunkata i kolastrata pri predavane na levkozata u govedata.

Studied was the occasional role played by the saliva of leukotic cows in the transmission of the infection to test lambs along with the role of colostrum as a factor neutralizing the leukosis virus in experimentally infected lambs. It was found that bovine leukosis could be transmitted by the saliva of affected animals. Colostrum that contained hightiter specific antibodies was found to be effective in neutralizing the leukosis virus in newborn calves provided no subsidiary infection took place.

[Micromethod of determining the complement-binding properties of commercial series of the foot-and-mouth disease virus]. / Mikrometod za opredeliane komplement-svurzvashtite svoistva na proizvodstveni serii shapen virus.

Investigations were carried out to establish the possibility of using a micromethod of the complement-fixation test to determine the complement-fixing properties of productional series of the foot-and-mouth disease virus. It was found that the micromethod referred to is an economically profitable and practically simple one. It is readily applicable requiring no particular apparatuses and equipment, is specific, and can successfully be used instead of the routinely employed CFT method. The micromethod suggested is economical, requiring minimal amounts (0.025 cu.c7) of the components taking part.

[Isolation of lymphocyte cultures from leukemic cattle and electron microscopic study of the leukemia virus]. / Poluchavane na limfotsitni kulturi ot bolni ot levkoza goveda na elektronnomikroskopsko prouchvane na virusa na levkozata.

Several methods were employed to obtain lymphocyte cultures from blood samples taken from normal cattle and from cattle affected with enzootic leukosis. Biologic and virologic experiments revealed that the cultures from diseased cattle contained an oncogenic leukosis virus, while those obtained from healthy animals were exempt from such virus. Electron microscopy was applied to study the morphologic aspects of the bovine leukosis virus with a total of 18 lymphocyte cultures. The viral particles noted were shown to have typical configuration and size of type C oncogenic viruses as described in the literature--possessing a central dense nucleotide and double membranes. Seen were also various stages in the development of the virus. Mature virus particles were likewise observed in a stable cell line FLK (percent of the virus) as well as in ultrathin cross sections of the spleen of leukosis-affected animals.

[Specific immunoprophylaxis trials with calves against foot-and-mouth disease]. / Opiti za spetsifichna imunoprofilaktika na teletata sreshtu shap.

Studies were conducted on vaccination of different age groups of calves with monovalent and biovalent vaccine against foot-and-mouth disease using various immunization patterns. The studies showed that passive immunity of calves impedes the building up of solid immunity. It is recommended on the basis of comparative studies of different immunization schemes to vaccinate calves under 6 months of age with double vaccine dose and to revaccinate them 1--2 months later. It was shown that calves aged 6 to 12 months react to vaccine against foot-and-mouth disease as adult animals but revaccination is also recommended to build up solid immunity. The influence is discussed of various factors hindering the building up of solid post vaccination immunity in young animals following vaccination with vaccine against foot-and-mouth disease.