Mr. Bade is a forward looking and enterprising poultry farmer with potentials of becoming one of the champions of our generation of poultry giants. He has a poultry stock with highly superior performance of 92% production in hen day production. The horizon is good and prospects are high as the price of eggs is quite attractive.
Vaccination in poultry is a routine which no farmer will take with levity. Lasota vaccination has come to occupy a prime position in the management of layer poultry due to the significance of Newcastle disease control in egg production. The need to maintain high level titer against the Newcastle is very important and thus the need for routine lasota vaccination during lay.
Inappropriate scheduling of the vaccination (LASOTA VACCINES) results in egg production drops that may result in temporary or permanent cessation of lay which could throw a farmer into a crisis of debt and poor productivity. Some cases result in clinical manifestation of disease due to excessive shedding of viruses in the feaces of the birds.
In spite of keeping all tenets of successful vaccination in poultry, there is a host factor which farmers need to consider before embarking on a vaccination programme. Most times, when all the cold chain and timing of vaccination has been correctly executed, the host factor is very important in vaccination successes.
THE HOST FACTOR: Is the flock prepared to receive the virus (called vaccine) without any calamitous reaction? This reaction could be in form of cessation of lay (temporary or permanent), drop in production, new disease condition, morbidity or outright mortality. Among the important host factors are:
i. Subclinical Conditions: This is when birds are clinically (physically) normal but have a lot more going on in the system without farmers taking notice. It takes the trained eye and sometimes laboratory evaluations to establish a clean bill of health for vaccination preparedness. Among the various conditions are chronic respiratory disease (CRD), stress, and low immunity to particular disease.
Subclinical infections of CRD in vaccinated birds especially with any of the respiratory vaccines such as Newcastle and bronchitis will result in concomitant effect of drop in production or cessation of lay depending on the severity of this condition. The salient condition prior to vaccination may be mild enough to go unnoticed but yet flare up after vaccination, also depending on the strain of the vaccine (hot, virulent, etc.). Also, the level of stress the birds are exposed to determines how they react to the vaccination. It is purely intrinsic individualistic. Different flocks with different measure of stress tolerance and therefore reaction to live vaccination. An overstocked facility will result in unfavorable response to live vaccination. Birds that have just been debeaked, relocated, or starved will display severe and exaggerated response to live vaccination.
ii. Metabolic Conditions: Metabolic conditions such as different levels of fatty liver will absolutely affect response to vaccination. Degenerative conditions are known to be in grades never absolute. A relatively fatty liver could pass without the attention of the farmer. If such birds are subjected to high titred vaccines, they will display production drop which can be very remarkable and long termed. An experienced poultry farmer will agree that fatty liver and “fattyness” is a major condition to contend with in a good performing flock especially at the early productive months. Production crash of 50% production has been documented in many eggs production facilities due to hemorrhagic fatty liver.
iii. Nutrient and Toxins: It has been well documented that flocks at borderline nutrient levels of certain vitamins such as Vit A, Vit C, and Vit C, are likely to have exaggerated response to vaccination which can be ameliorated by the practice of supplementing with generous level of multivitamin. Sometimes, this can be narrowed down to certain vitamins for better effect and cost efficiency.
Also, the role of various levels of certain mycotoxins results in varied levels of vaccination reaction found commonly in farms. An example is T2 toxin, to which poultry is very sensitive. This may at a particular point become present in the feed even at low levels but significant enough to distort the immunity of the flock. It is also noteworthy, that issues may get further complicated by other toxins which interact and overlap in their deleterious effects on the immunity and by implication the vaccination process. This happens commonly between T2 toxins and aflatoxins. This can be avoided by paying special attention to feed mycotoxin levels around vaccination periods. Also, occasional upping of toxins binding elements in water or feeds during vaccination is good effort.
iv. Immune Titre of Birds: At the period of vaccination, it is the absolute norm to check the titre (level of antibody/immunity) before administering vaccines to the birds. There is always an optimum period and also an appropriate strain(type) of vaccine for different scenarios. When the birds are depleted of Newcastle virus titre, they may be producing eggs quite optimally but with relatively high shedding of the virus due to low titre. An introduction of virulent live vaccine at this point will result in in drastic fall of egg production and sometimes mortalities. Newcastle particularly has different strains of the vaccine such as F strain, kamarov, and lasota strain and also clones for discretional use during different times. This is why routine immunomonitoring (checking of blood for immunity factors) before vaccination is important. It is understandable that small scale farmers find this challenging. Some farmers have also devised hyperimmunization through excessive frequency of blind vaccination as a solution but this is equal to groping in the dark. Also, worthy of mentioning is that sometimes live vaccination of highly immunized flock titre results in mopping up of the bird’s high titre (immunity). This opens them up for possible infection later.
In conclusion, vaccination and vaccines are cheap substances and intervention in the flock but they are such small but mighty influencers of success stories in the poultry industry, while all cold chain and adequate preparation and vaccination schedules are in place, the condition of the host animal in receiving the vaccine is the final deciding factor. Critical evaluation of the host before vaccination is key. I call it the “host factor”. It is therefore wise to involve your vet surgeon in the planning and evaluation for vaccination fitness. Mr Bade”s sustainable success in poultry eventually depend on this.
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