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    • br Removal of therapeutic doses of antibiotics from Marek s

    2023-12-21


    Removal of therapeutic doses of m-Chlorophenylbiguanide hydrochloride from Marek’s Disease Vaccines The impact of this change seems to vary widely among operations, probably dependent on the pre-existing quality of hatching egg production, hatchery sanitation, hatchery management, and brooding management. Increases in 7-day mortality of 0.5 to 1.0 percentage points or more over the pre-existing baseline appear to be common. Unfortunately, there is no simple non-antibiotic alternative to overcome these issues. Nevertheless, most of this loss can be recouped by diligence and attention to detail. Hen houses must be managed to produce a nest-clean hatching egg. Items to consider may include lighting, ventilation, litter management, nest space, nest placement, nest management, egg collection practices, gut health management, and pest control. Farm egg storage, egg pickup, and transport facilities and procedures should be clean and designed to minimize egg sweating. Egg disinfection should not be necessary for dry nest-clean eggs. All aspects of hatchery cleanliness and maintenance are critical. Areas of focus include: egg trucks; egg coolers; incubator and hatcher halls and machines; egg trays and racks; hatcher baskets; processing equipment (in ovo injection machines, separators, processing belts, reusable chick boxes, vaccination equipment, etc.); wash water temperatures and water, detergent and disinfectant flow rates and usage in tray and basket washers; and chick delivery vehicles. Hatcher and setter hall ventilation capacity, temperature, and humidity should be controlled to maximize machine ventilation and minimize the work that the machines must do to maintain stable incubation parameters. The machine manufacturer should be consulted for advice and assistance on ventilation, maintenance, and operation of their specific machines to minimize the hatch window and produce the highest quality chicks. Constant monitoring of set and pull times should be used to produce a chick that is neither wet and “green” nor “overdone” and dehydrated. Continuous bacteriological monitoring using swabs, contact plates, and samples of room air and humidification water is a useful quality control procedure. Fumigation of eggs and fumigation of hatchers may be necessary, especially in the early stages of transition to RWA/NAE production. Formaldehyde is effective but controversial, and there are other alternatives for fumigation such as hydrogen peroxide that can be helpful. Proper brooding management becomes even more critical in RWA/NAE production.
    Coccidiosis
    Necrotic Enteritis and Dysbacteriosis NE is typically associated with coccidiosis, so adequate control of coccidiosis will prevent most clinical problems with NE. Subclinical NE and dysbacteriosis may still be an issue in both vaccine-only and chemical coccidiostat programs even in the absence of clinical coccidiosis. It is now generally accepted that NE results from the clonal expansion of virulent strains of Clostridium perfringens possessing netB toxin and other virulence factors, which strains are normally present only in small numbers (Timbermont et al., 2011). This expansion is in turn usually due to disruptions in normal gut homeostasis that allow nutrients (especially protein) to reach the lower gut, and that disrupt the normal inhibitory flora. The following interventions therefore have been suggested to help control NE in RWA/NAE programs. Crude protein should be restricted, and the protein should be highly digestible and of high biological value to minimize residual protein reaching the lower gut. The use of all-vegetable diets may make crude protein restriction difficult, in which case the use of crystalline amino acids to limit crude protein while still achieving ideal amino acid profiles may be beneficial. The use of proteases also may be an aid (Bedford, 2000). Since fishmeal and high levels of meat and bone meal have been used to induce NE in experimental models, it has been suggested that animal proteins should be avoided and that vegetable diets may be necessary or at least advantageous. Low quality animal proteins with biogenic amines, rancid fats, and clostridial spores are a risk even in conventional production and should be avoided in either system and especially in RWA/NAE systems. However, when permitted, it is possible that high quality animal proteins with high biological value, at moderate inclusion rates, could be used to advantage in RWA/NAE production to meet protein and essential amino acid needs while restricting crude protein levels. Fish meal has high levels of zinc, glycine, and methionine, all of which are conducive to C. perfringens blooms, so it should be used with caution (Williams, 2005).