i) Persistency of Anti-Ranikhet Material Antibodies in newly Hatched Chicks.
Ranikhet disease is a great handicap to the poultry development because of the associate heavy mortality, even upto 100%. A series of experiments have been conducted to evolve vaccines to control this disease and at present LaSota (a lentogenic strain) and R2B (mesogenic strain) are commonly used in India for vaccine production. Subsequently, a ND Killed vaccine has also come into use for producing a persistent immunity especially in Breeder flocks and to ensure transfer of sufficient level of maternal immunity in newly hatched chicks.
In presence of high levels of maternal antibody, vaccine administrated does get neutralized and does not evoke sufficient immune response. It is, therefore, that we should have the knowledge about how long the maternal immunity persist in the newly hatched chicks. The Institute has been raising the commercial broiler, commercial layer, Layer parent and cockerel flocks for practical experience of the student in poultry rearing. These flocks have been used for this and it has been found that the maternal antibody levels are quite high in all these flocks upto 7th day age, in a few flocks tested even upto 15th day at a protective level. It therefore suggests that delaying the primary vaccination from the presently suggested 4 to 7 days to 10th day may improve the vaccination response. (In all the experiments as Ranikhet, antibody levels are titrated by Haemagglutination â€“ Inhibition test.)
ii) Minimizing the Expenses on Ranikhet Vaccination in Commercial Broilers.
With the introduction of ND Killed vaccine, it is a general practice to vaccinate the commercial broiler chicks at 4 to 5 days with LaSota intraocularly and ND Killed vaccine subcutneously and again boostered with LaSota through D/W at about 20-25 days. One dose of ND Killed vaccine for a broiler chick costs 40 paise. It was, therefore thought that if giving LaSota vaccine alone in two doses could reduce the vaccination cost. A series of trials were made on different commercial LaSota intraocularly, through drinking water or by subcutaneous injection and compared with ND Killed vaccine on 25th day. It was found that giving LaSota vaccine by injection on 25th day induced good immune response considered as protective and plus this protocol could save an amount of 30 paise per bird in vaccination expense. Such types of vaccinations have been done at this Institute over a few years and no outbreak of clinical or subclinical Ranikhet disease has appeared at this Institute.
These experiments therefore suggest that giving LaSota vaccination first 10th day intraocularly and booster dose on 25th day by injection may protect the flock against Ranikhet virus.
iii)Evolving Vaccination programme against Infections Bursal Disease in Broiler Flocks.
Infectious Bursal Disease has emerged as a very serious in recent years and has caused heavy mortality in poultry. Different types of vaccines are available and are in use against this disease. These vaccines are lukert (mild), Intermediate Standard, Intermediate plus and killed.
Different protocols of permutations and combinations of these vaccines have been used in broiler flocks at this Institute, but none proved quite successfully. A protocol seems to be successfully only to turn out to be unsuccessful later on.
Parent flocks are regularly vaccinated against this disease and at times the disease also appeared in these flocks, causing heavy economic losses. Testing for the maternal antibodies in commercial broiler chicks by ELISA test have invariably shown poor antibody levels, many times at a level less than 500 which is considered to be a protective titre. Even vaccination by different protocols using these vaccines have rarely induced good antibody responses and the outbreaks of disease with heavy mortality have occurred.
It is therefore that as yet we have not arrived at a definite protocol to be followed. The reason for this is perhaps due to different levels of maternal antibody in different flocks. However, our recent experiments suggest that vaccination by Lukert Strain to one-day age chicks along with Marekâ€™s disease vaccine by subcutaneous injection and giving IBD Killed vaccine in 0.2 ml dose on 4th day age may prove to be effective.
Similarly even in layer flocks, no vaccination programs had been found quite successful. However, we were tried quite a different protocol in layer parent flock consisting of lukert Strain vaccination in the hatchery by subcutaneous injection along with Marekâ€™s disease vaccine, IBD Killed vaccine by injection on 4th day, IBD Intermediate Standard intraocularly on 12th day, IBD Intermediate plus vaccine on 24th day and IBD Intermediate Standard vaccine on 35th day both through drinking water. The antibody response tested were found satisfactory.
However, the biological material keeps on changing and therefore further work is needed for controlling this disease more effectively.
iv) Testing of Escherichia coli Bacteria Sensitivity to Various Anti-microbial Agents
Escherichia coli organism is commonly involved in setting up the conditions as omphalitis and colibacillosis in young chicks, especially those reared on litter system. At this Institute, organism has been isolated at various times and their sensitivity tested.
The studies indicated that all these strains were quite susceptible to bactenil, pelwin, nicoli, amoxycillin, nalidixic acid and enrofloxacin. Therefore, these studies indicate that any of these drugs may be used alternately to control these conditions, whenever the facilities to test for sensitivity are not available.
v) The Institute offers short-term courses and therefore within a short time stay of students it may not be possible for use to show them the actual cases of disease or different conditions. Therefore, wherever such conditions occur, attempts are made to preserve the pathological specimens in 10% formalin. About 100 specimens have been collected.