high early mortality and severe reactions to
respiratory vaccines. Such infections may becaused by a variety of bacteria and usually, butnot always, originate at the hatchery. Low litter moisture, water sanitation, proper brooding temperatures, and enclosed drinker systems are effective in reducing these bacterial infections on the farm.

Fungal Infections
     Although fungus spores from a variety of species are common in the broiler house
environment, serious infections are usually
confined to the baby chick and most often
originate in the hatchery. The most significant fungal infection in the chick is aspergillosis, which usually involves the respiratory system. Common signs in the hatchling chick are gasping, sleepiness, and increased mortality. Hatcheries make a concerted effort to prevent aspergillus in the incubation and hatching environment. When aspergillosis is suspected in baby chicks, good brooding practices and culling will help.

Parasitic Infections
     Only one type of parasite, the coccidia, is of economic significance in broiler production. The coccidia are parasites of the cells lining the intestine. Their greatest impact is on growth, feed efficiency and skin coloring. Additives are usually put in the rations for prevention and control of these parasites. The parasites survive in the litter as very resistant cysts and infection occurs when birds peck into the litter. Symptoms may include loss of skin color, diarrhea, passage of undigested
feed, and occasionally by obvious blood in the fecal material. Mortality as result of coccidial infections is rare. Water and litter management, especially in limiting litter moisture, are very effective in reducing economic losses from this group of parasites.

Exotic Diseases
     Certain exotic diseases must be prevented
from entry into any commercial flocks in the
United States. These include, but are not
limited to, exotic Newcastle disease virus and
avian influenza. Extensive surveillance and
avoidance programs are in place at both the
state and national levels. For broiler growers,
bio-security at the farm level is the best insurance for reducing the threat of introduction of exotic diseases. Limit entry and traffic on the farm to only what is absolutely necessary for routine operations. Both diseases mentioned can be devastating in large flocks and could compromise an entire industry.

Farm Management for Disease Control
     In most instances the presence of infectious
organisms does not result in specific or
obvious disease on a flock basis, but rather
results in an added burden on body maintenance requirements of the broiler. In other
words, continuous low level exposure can
cause a broiler flock to have to expend some of
their nutritional intake on limiting the impact
of low-grade infections. These nutritional
expenditures can be in the form of mounting
an immune response, abnormal body temperature swings, reduced consumption
and absorption of feed, and general responses
to stress.
      Generally speaking, our past experience in large-scale broiler production over the years allows us to predict the presence of the significant disease-causing organisms and the industry has developed integrated health
programs that target each of the categories.
However, it remains a common misconception
that the various health programs (i.e., feed additives, vaccines, sanitation chemicals,
etc.) provided at the hatchery, in the feed, or
administered to the chick bear the sole responsibility for flock health. In fact, meeting the needs of the modern-day broiler through
proper flock management is at least as important,
or probably more so, than the integrated

health programs in limiting losses to infectious diseases.
      Often, the difference in broiler performance among houses or farms is the percentage of feed nutrients that go for body maintenance requirements versus growth. In general, feed goes to body maintenance and feather development first and what is left over is available for growth. Therefore meeting the needs of the flock via optimal management limits nutritive requirements for maintenance and maximizes flock performance. Marginal management in terms of improper house temperatures, poor air quality, excessive litter moisture, and generalized stress, will increase disease susceptibility in most flocks and shift feed ingredient utilization from growth to body maintenance. This is why proper management in the grow-out is so important to complement the integrated health programs and provide an invironmental foundation for the flock that will optimize the effectiveness of feed additives, vaccines and sanitation chemicals.
      The brooding phase is especially important. Upon arrival at the farm, the chick must eat and drink immediately. Why? Because rapid feed and water consumption provide the critical nutrients necessary for the development
of tissues and organ systems that allow
maximum performance and health. In most
instances the chick will have been vaccinated with various live viruses that will produce some degree of infection. This is necessary in order to encourage development of the immune system. However, it is critical that the brooding environment provide stress-free, optimal conditions in terms of feed, water, air
quality, house, and litter temperatures, so that chicks can get through this stage as quickly as possible and start growing rapidly. Flocks that are started well will continue to make good growth and fend off disease problems as long as they are given the proper environment for growth.