Because of poor pellet quality and reduced pellet hardness, up to 50% fines have been reported in the poultry pellet feed under field conditions. These incidents of high levels of fines in the field are not only associated with poor live weight and FCR but also have huge dusting potential, which can pose a threat of respiratory disease in today’s hyper producing broilers too. The fines in the feed are inhaled by the birds and while exhaling these settle in various parts of air sacs, specially thoracic air sac, where air stays for longer period. This causes difficulty in breathing for the birds and hence, could lead to deficiency of oxygen in their blood. While processing of feed makes it more readily digestible by animals, it also becomes easily digestible for molds as well. After pelleting and bagging, mold spores appear almost immediately within 12-24 hours in the feed under field conditions. The moisture content of the feed usually ranges from 10-12 percent. When such a feed is exposed to environment and retained in the pans as uneaten leftover for a day or more, before it is consumed in automated feed system, it gets heavily contaminated with mold spores. Birds fed with lots of fines in feed with increasing mold spores infestation and placed in environments contaminated with aerosolized conidia (mold spores), may show significant pathology after only a short duration of exposure. Anatomy and physiology of the avian lung-air sac system are strikingly different from that of the bronchoalveolar lung of mammals. Avian air sacs are particularly prone to contamination because they are submitted to an airflow that favours particle deposition. Mold spores are small enough, 2-3 μm in diameter, to bypass initial physical barriers and disseminate deeply in the respiratory system.
It has been suggested that the dust created by the fines of the feed and mold appeared in the stale feed get inhaled by the birds during increased number of pecking, leading to irritation and reduced efficiency of the airways.
Poor air quality, environment dust and respiratory diseases also imapires the perfusion capacity of chicken lungs, creating an imbalance between oxygen supply and the oxygen required to sustain rapid growth thus predispose birds to ascites by causing respiratory damage Ascites is a disease, which causes death in poultry apparently because of fluid retention. Ascites is commonly known as “water belly”. There is no known cause and no apparent cure. There are theories that the amount of heat in the early days of the chicken or turkey’s life, or stress, may be the cause of ascites, but there is no significant data to support these theories. However, invention with antifungal agents to reduce the symptoms associated with ascites and preventing mortality from the disease confirms the role of mold and its spores as a major causative factor for the ascites.
Recent development on Ascites Syndrome (AS) has confirmed that Ascites is not caused by the increased O2 requirement of a fast growth rate but by an impairment of the O2 supply needed to sustain the fast growth rate of these hyper producing birds.
The commercial broiler of today represents the culmination of dramatic changes over the past 60 years. Genetic selection processes that focused mainly on production traits putting heavy pressure on the bird’s cardio respiratory system and immunity. Birds already low in immunity coupled with impaired immune system when fed on dusty feeds with invisible molds, do not succeed in eliminating inhaled dust or mold spores at the site of air capillaries causing development of loosely attached plaques overgrown by connective tissues. These plaques or necrotic debris in the respiratory tract can obstruct the trachea or bronchi or fill up the air sacs to impair the O2 supply.