Ontario, Canada

Growing a male turkey out to 18 to 20 weeks of age and beyond represents a large economic investment. If we evaluate mortality, medication costs, weights, feed conversion and condemnations, it is apparent that we are not maximizing potential returns. As part of Hybrid’s commercial database and technical support for customers, we collect and analyze information from growers/ companies. What are most alarming when looking at this data are not the “averages” but the lost capacity of those flocks which fall below the average line. It is not uncommon to see a spread of 50 points of feed conversion, 5 kilos of weight and 15% mortality between flocks which were placed the same week of the year, fed the same feed and sourced from similar breeder flocks. One of the major differences between these flocks is the on-farm management. It must always be remembered that the bird can not change its environment but can only react to it. If the environment is not optimal, neither will the turkey’s performance be. What we get out a flock will be in direct proportion to the quality of input into the flock. Management means doing what needs to be done when it needs to be done. On farm management directly affects the quality of the

product which the processing plant receives. It is always the customer who sets the standard of quality to be achieved. Growers need to meet the needs of both their direct customer, the processing plant and their indirect and ultimate customer : the consumer. Consequently the needs and specifications of the processor include not only those which allow them to produce a safe product such as:

Proper feed withdrawal to prevent fecal contamination

Adherence to correct medication withdrawal

Flock raised under best management practices to reduce food borne pathogens

Flock records to integrate into the plant’s HACCP or ISO program(s) but also those which allow them to produce an economically competitive product :

Product uniformity

Weights within a specified range and anticipated total

meat volume

Good grades

No disease conditions such as breast blisters/buttons or airsacculitis which will slow line speeds or limit product suitability.

This presentation will focus on the respiratory system, as it is the one, which is most commonly compromised and continuously challenged during grow-out. We will look at why problems occur and most importantly what we could be doing to prevent or minimize the impact.

Basics of Bird Breathing

The very high metabolic rate of birds requires a special arrangement for supplying oxygen in sufficient quantities to all tissues. Birds were designed to be very efficient at extracting oxygen and removing air-borne organisms. The respiratory membrane is the most extensive of all tissues that interface directly between animals and their

environment. When a turkey breathes in, the air passes through a long convoluted pathway in the upper airway (turbinates) and the sinuses. Here the air is warmed and particles of dust +/-bacteria and mold are filtered out with clean air being sent

to the trachea. The trachea contains finger-like projections, called cilia which also function to trap bacteria, dust and mold and propel them outwards sending clean air to the air sacs. The air enters the thin walled abdominal air sacs, which act like bellows to propel the air into the lungs as the bird exhales. Air is swept through the lungs by the expansion of the air sacs in inspiration, and out again by their contraction in expiration. In this way the respiratory surfaces in the lung are kept continuously in contact with air whose oxygen content is high. This has been called a 2- stroke system and it allows birds to maximize oxygen extraction into the bloodstream. The air sacs also interconnect with some of the long bones and the vertebrae in the back. They do not function to remove dirt or debris. The domestic turkey does not run, fly to roost or escape from predators, or forage for feed, as did its wild predecessors. The lung of the “selected” turkey has responded to the increase in body size and more rapid growth rate by enlarging the large vessels and small airways at a greater rate than the gas exchange area within the lung. The selected turkey appears to have adequate exchange surface in the lung to support its basal metabolic needs but during times of stress or compromise, these needs are likely not met. This contributes to poor performance and an increased susceptibility to disease challenge. Disease can occur if either the challenge dose of disease causing organism increases or if the turkey’s resistance is lowered.

Basics of Ventilation

The function of the ventilation system is to bring in fresh oxygen, remove carbon dioxide and ammonia, remove moisture, dilute air borne pathogens and prevent large temperature fluctuations. With today’s controlled environmental housing, we should be able to do a better job at providing the optimal environment for our flocks to thrive in. Unfortunately we often don’t consistently achieve this or we knowingly compromise bird health for economics. We can more easily measure the amount of

propane used than we can the amount of damage done to the respiratory system.

It is important to note the following :

Ventilation rates change markedly during the early brooding period and need to be adjusted frequently. The increases are continual on a daily basis, not at the end

of each week.

As the outside ambient temperature increases, ventilation requirements increase dramatically. This is also important during the spring and fall when temperatures during the day will fluctuate, and changes in ventilation must follow accordingly.

Ventilation systems need to be audited periodically to ensure that they are functioning correctly and efficiently. Waiting until you get high condemns due to air sacculitis is too late.

Good air quality is essential to maximizing the potential from the flock. Let’s examine how inferior air quality affects the turkey.

1. Heat.

We are all familiar with heat stress during summer months and have become much better at proactive strategies to prevent losses. Where we often don’t do a good job is

during times of the year when temperatures are fluctuating throughout the day. Anytime we allow birds to pant, we cause air to bypass the upper airways where it is normally filtered and allow the air ( +dust, +bacteria, +mold) to be deposited directly into the abdominal air sacs. The air sacs can not remove this material. It accumulates and as the airsacs become infected, respiration is compromised. Energy, which should be channeled into growth, is now diverted into extra respiratory effort. Heat is also produced by the turkey itself due to muscle activity and growth. This means that the genetic improvements made to produce a heavier turkey can only be realized if that tom is grown at a cooler temperature.

2. Ammonia

Ammonia is a natural by-product of decomposition of turkey droppings in the presence of moisture and heat. Researchers at the University of Minnesota demonstrated a number of years ago the impact of as little as 10 ppm ammonia on the turkey respiratory tract. Ammonia directly kills the cilia present in the trachea. Without the cilia, air-borne dust, bacteria or mold are not trapped and proceed

directly to the abdominal air sacs. Indirectly ammonia affects the immune system by reducing the clearance of E. coli from the air sacs, lungs and tracheas of turkeys. In this case, disease occurs because we have both increased the challenge dose the bird is exposed to and simultaneously decreased their resistance. Continuous exposure to low levels of ammonia is just as damaging as a brief exposure to high levels. Turkeys live in the barn 24 hours a day. Many people who work in turkey barns have become

desensitized to the smell of ammonia and can no longer detect it. Use of ammonia monitors (continuous 24 hour strips, Draeger tubes) are recommended for these

individuals in order to determine whether ammonia levels are too high and when to take corrective action. Ammonia levels are highest after tilling and on used litter. Tilling should only be done when the weather will allow the curtains to be wide open to remove the ammonia that will be produced at the time of tilling. In cold weather till early in the day so that ammonia levels will be lowered prior to

closing the curtains at night. Recent research at the Ontario Veterinary College has

shown that levels of ammonia and bacteria are highest in the litter, 2 weeks after birds are placed in the barn. Airsacculitis condemnations are positively correlated with higher ammonia levels. There are many litter treatment products on the market which function to reduce barn ammonia levels. Strategic application at these times has shown to be beneficial.

3. Dust

Dust is an excellent carrier for bacteria and mold. The upper airways and the trachea are designed to filter inhaled material. Specialized cells called macrophages trap

anything that could not be expelled (coughing, sneezing). They have been compared to garbage cans and consequently when they are full, the trash starts to overflow and cause problems. Dust levels are often highest in grow-out barns during winter months when relative humidity is low and ventilation is minimized to reduce

heating costs. Toxins produced by bacteria have also been detected in poultry house dust. For human health reasons, we recommend wearing a mask while in grow-out barns. We must also consider the effects on the health of the turkey that breathes in the dust for extended periods of time. There are many interactions in the environment, which affect the respiratory system. The worst combination appears to be warm temperatures, ammonia levels greater than 20 ppm and dust levels greater than 8 mg / m 3 . All of these parameters increase when density increases. Once damage occurs in the respiratory tract, bacteria adhere to and colonize damaged epithelial cells. Studies have shown bacteria adhere more easily to viral-infected or

nonspecifically damaged cells whereas, normal cells are resistant to colonization. Bacteria, which are able to colonize the membrane, replicate and invade through the

membrane to the circulation leading to bacteremia. Besides the ability to adhere to damaged cells, some bacteria, most notably, E. coli, can invade from the respiratory tract into the blood across an undamaged membrane under experimental conditions following aerosolization of the bacteria. Osteomyelitis due to Staph aureus has been

correlated with dry dusty barn conditions and the subsequent airsacculitis.

The severity of a viral challenge such as Newcastle Avian Influenza or Avian Pneumovirus on a tom flock, will be directly dependent on the environmental conditions and air quality. Good biosecurity to prevent or lower the challenge dose in combination with good air quality to increase the bird’s resistance will greatly minimize the effects of viruses on a flock and the resultant production losses.

In conclusion, one of the most critical factors in growing heavy toms is consistent, good air quality. Ventilation must be monitored to ensure that air quality is optimal

throughout the grow-out period. Compromises made in ventilation will be reflected in flock performance and economic returns. Any challenge that the turkey has to

respond to takes away from growth and feed conversion.

References:

Fedde, M.R. Respiration, In: Avian Physiology, 4 th ed. P.D. Sturkie, ed., Springer Verlag, New York. Pp.191 – 220. 1986

Nagaraja, K.V.D., D.A. Emery, K.A. Jordon, J.A. Newman and B.S. Pomeroy. Scanning electron microscopic studies of adverse effects of ammonia on tracheal tissues of turkeys. Am. J. Vet. Res. 44: 1530- 1536. 1983.

Noll, S. and D. Halvorsen. Air Quality Parameters – Have They Changed?

Gobbles. Pgs. 15,17. 1998

Timmwood, K.I., D.M. Hyde and C.G. Plopper. Lung Growth of the Turkey, Meleagridis gallopavo: II. Comparison of Two Genetic Lines. Am. J. of Anatomy 178:158-169. 1987