In many parts of Subtropical zone, summer is severe with maximum day temperature hovering around 40 C (ie 104 F). There is also shortage of water in summer and since water table goes down, bacterial count in water is high. It is therefore a challenging task to manage poultry in these conditions. During summer, weight gain, FCR, egg production, eggshell quality and hatchability are all adversely affected and mortality is high. Disease incidence is also more because of wet litter, immunosupression, vaccination failures and contamination of drinking water which are common in summer months. Hence in hot weather season, series of special measures in management, nutrition and medication have to be undertaken to minimize the losses

Poultry birds are comfortable when environmental temperature is within the range of 65  to 75 F (18 to 24 C) This is known ascomfort zone (zone of thermoneutrality) as birds do not suffer any ill effects of temperature changes, within this range. Weight -gain, FCR, Mortality and egg production are normal and birds maintain their normal body temperature (104 to 106 F). Chicks up to three weeks age require higher range of temperature 

The upper and lower limits of comfort zone of temperature are called lower and upper critical temperatures  respectively. When environmental temperature reaches beyond  the range of comfort zone, bird tries to adapt and maintain normal body temperature by initiating physiological changes in its body .With extreme changes, in environmental temperatures the efforts for adaptation fail and birds suffer from cold or heat stress as the case be

Cold stress

As environmental temperature dips below lower critical level, cold sensory receptors in the skin are stimulated, pass impulses to  thermoregulatory centre in hypothalamus and that signals contraction of peripheral blood vessels. Thus blood supply to skin is diminished and  sensible  heat loss through skin is prevented. At further lower temperatures birds will not be able  to conserve heat any more and die due to cold stress

Heat stress

With environmental temperature rising higher than upper critical limit, bird responds in the opposite way

i) Peripheral blood circulation (to skin, upper respiratory tract, abdominal muscles. Combs and wattles) increases two to four times. Consequently blood flow to liver intestine, kidneys is reduced

ii) Birds start panting (increase in respiratory and heart rates

iii) Birds stretch the body and take lying position  closer  to litter material and nearer to waterers fans

iv) Water consumption increases by 1.2 to 3.2 times as per outside temperature

The first three responses help in sensible heat loss and the last helps in internal cooling of the body system. However, with prolonged exposure to hot weather, these responses will lead to following harmful effects

A) Reduced blood supply to visceral organs leads to 

i) Poor Wt gain, higher FCR (due to impaired digestion,nd assimilation

ii) Enteritis, reversal of body weight due to SIBO (Small intestinal bacterial over growth

B) Acid base imbalance in the body

There is loss of CO2 because of continuous panting (hyper ventilation) Which results in increased blood pH (alkaloidosis). Kidneys act to restore the acid base balance by renal exchange of bicarbonates with Cl ion. This results in increased excretion of bicarbonates in urine and retention of Cl in plasma and that leads to systemic acidosis. Thus in heat stress initial alkaloidosis changes to systemic acidosis and birds die of acid shock

In heat stress, supplementing diets with Ammonium chloride (NH4Cl) (0.3-1%) + Sodium bicarbonate (1-2%)  is helpful, since Ammonium chloride reduces blood pH and Sodium bicarbonate prevents excessive acidosis

Along with bicarbonates, electrolytes are also excreted in urine because bicarbonates are negatively charged, and Na an K ions (important electrolytes) being positively charged go with it. Loss of electrolytes affects the water balance

C) Water imbalance in the body

Normally Water intake + Water formed  by oxidative metabolism in body

     = 

  Water loss  through urine, faeces and  respiration and evaporation

a)In heat stress water loss is more (60% more) through urine and increased respiration. This results in dehydration (decrease in extra cellular  fluid level), fall in blood volume, fall in blood pressure and increase in plasma osmolality

Body reacts to these changes by releasing Renin from kidney cells and that increases thirst. Anti diuretic hormone (vasopressin) is released from pituitary which reduces urine output by increasing water resorption in renal tubules

Even though birds drink more water, its retention in cells is less because of loss of electrolytes and organic osmolytes (betain, Sorbitol Inositol) as stated above. Negative water balance, prevents internal cooling and hence there is further rise in body temperature.

Supplementation of Betain (osmolyte ) and electrolytes helps in maintaining water balance in the body cells against extra cellular osmotic gradients

D) Immune suppression

In hot weather there is release of corticosteroids from adrenals and also depletion of plasma VitC. and reduction in lymphocyte count. The effect is immune suppression

Tolerance to hot weather

Poultry can tolerate to some extent gradual change of season to summer, but if temperature shoots up suddenly on some days in between, it results in heavy mortality.

It is also  reported that  chicks exposed to higher brooding temperature  during first few days, tolerate heat stress better in later life

Tolerance to heat stress is greatly influenced by Relative humidity in the air. High temperature and high RH  form a deadly combination for poultry . Such conditions prevail in coastal regions of India during August to October months

Symptoms, Post mortem findings and diagnosis of Heat stress

When weather is moderately hot (75 to 80 F)( 24 to 26.7C) , paradoxically , FCR may improve as less energy is required for maintaining body temperature. As temperature rises above 80 F( 26.7 C) feed consumption starts declining. Drop in feed consumption is at the rate of 1.5% for every rise of  1C up to 30C and above  that it is steep being 4 to 5% drop  for every 1C rise.

FCR increases  correspondingly

At 90 F (32 C) and above birds are found  panting continuously, drink more water, prostrate on litter extending the body and there is sudden and heavy mortality occurring  in the later part of the day

In dead birds autolytic changes set in fast and in the post mortem examination of fresh carcasses, engorgement of subcutaneous capillaries, congestion of abdominal and breast muscles(cooked meat appearance), congestion of trachea, combs and wattles may be seen

Diagnosis

In heat stress, intracellular calcium concentration increases which gives rise to efflux of Creatininekinase from cells to plasma. Elevation of plasma creatinine kinase  is indicator of  heat stress in chickens. But routinely laboratory tests are not necessary to diagnose heat stress condition

Prevention of Heat stress in poultry 

  Providing ventilation with cool air

Well located  and well laid out poultry farms, with trees and lawns around and getting good breeze will have lesser problems in summer season. In addition, roof insulation plus increased ventilation by fans would help to withstand  moderate hot weather. Care should be taken to avoid overcrowding and to provide shade to overhead water tanks and pipe system

In extremely hot weather, however, the above measures are not sufficient and  evaporative cooling systems -sprinklers, foggers, or pad cooling-are necessary. These systems work very well especially if relative humidity is low and temperature inside houses  can be brought down by 10 to 15C

Use of fans without evaporative cooling system may be harmful in extreme hot  weather  since it is only hot air that is blown  in to the house

 Daily management to prevent heat stress

In very hot  season, the  following measures are advised

i)  Feed withdrawal from 9am to 4.30 pm.: This is very effective in reducing  heat stress mortality. Feed intake and digestion produce nearly 7% additional heat in the body  which is maximum 4 to 5 hours after feed intake. This should not coincide with hottest part of the day (2 to 3 pm) Birds fasted in the day compensate intake in the night time and it should be seen that lights do not go off in  night

If   biosecurity is poor, feed withdrawal may lead to coccidiosis, necrotic enteritis. Necessary medicines may be kept at hand  in case such eventuality arises

ii)  Drinking Water: Cool Water (at 10-12 C) should be supplied  continuously to birds. Watering space should be doubled. Over head tanks and pipe system should be properly covered to keep the water cool. Birds reject warm water and that accentuates heat stress

Providing fresh cool water (5c) in noon time is very effective  for internal cooling of body (heat sinks) and reducing symptoms of stress

 Preventive treatment through drinking water

a) In moderate hot weather

Ascorbic acid....62.5 mg/litre

+

 Acetylsalicylic acid  62.5 mg/litre 

+

 Sodium bi carbonate  75 mg/litre

+  

Potassium  chloride ( KCl) 125 mg/Litre

b) In heat stress

Vit C  400 mg/ L

+

 Electrolytes 

+

Acetyl salicylic acid  ( Disprin 1 tablet/5 L

+

Sodium bicarbonate  1gr/Litre.......may be used  

 Use of summer feed formula   

In summer, feed should be made more dense with nutrients, Vitamins and minerals to compensate for reduced intake. Thus as the hot season progresses it may be necessary to fine tune feed formula again in mid summer  In addition following  features, which have bearing on heat stress control, should be included in summer feed formula:

a) Crude Proteins. Crude Protein level in feed should not be increased and protein from only vegetable source should be used. Proteins in general and those from animal sources in particular  have higher heat increment values i.e. produce more internal heat in the body 

Secondly vegetable proteins (Soya, Sesame, Sun flower) are  rich in Arginine. Under heat stress arginine absorption is low and  that results in plasma aminoacid imbalance, leading to increased catabolism of amino acids adding to body heat  Hence  vegetable proteins are preferred  in summer

While  keeping protein levels same, crucial amino acids may be increased to compensate for  reduced feed intake

b) Fats: fat should be increased by 2 to 3% at the cost of carbohydrates without changing ME. Fats are good in summer because their  heat increment value is lowest give better cooling effect in body because of higher water content  and fat stimulates feed consumption

c)  Vitamin C: Because of the release of corticosteroids in heat stress, there is increased demand  for Vit C by adrenal glands for controlled production of hormones needed for gluconeogenesis. In heat stress there is also  reduced synthesis and partial depletion of Vit C. Inclusion of Vit C at 150 - 200-400 Gr/ton of feed is recommended in summer months. If included in feed,  there is no need to give ;in water again

d) Sodium bi carbonate: It has positive effect of increasing water intake, and also reducing systemic acidosis. It can also be given through feed instead of through drinking water. In vegetarian feed, inclusion of Sodabicarb at 0.4% (4 kg/ton) + Sodium chloride0.25%( 2.5kg/ton)  would properly balance sodium and chloride levels in feed

e) Betain ( osmolyte) in feed

Betain (0.5 to 1 gr/ton) helps in maintaining water balance in the body cells against extra cellular osmotic gradient. Electrolytes  also have similar action and are better given through water

f) Anti oxidants:

 In heat stress there is excessive oxidative metabolism and release of free radicals in the body. Free radicals damage  all types of biological molecules, and cells of vital organs more so of immune system VitE captures and neutralizes free radicals and its inclusion  at 50 to 100 ppm in feed is advisable. Vitamin C also has antioxidant  property. Similarly antioxidants  namely BHA ,BHT and EQ will protect  fats and oils in feed from oxidative rancidity 

g) Other recommendations:

i) Virginiamycin 15 to 20 ppm in feed  apart from being growth promoter, reduces metabolic heat production, alleviates heat stress and stimulates immune responses

j) Anticoccidials: Nicarbazine and Monensin are contraindicated in summer. The former decreases tolerance to heat and the latter depresses water intake

k) Biotin supplementation at 150 micrograms /Kg feed  is recommended

l) Vit K supplementation is recommended particularly at time of debeaking or if there is threat of coccidiosis because in  heat stress blood clotting time is prolonged

m) Toxin binders :

In wet summer, there is rapid growth and toxin formation in feed. Good quality toxn binders at higher dose should be used in feed

Other associated problems  in summer season

In summer season, apart from hot weather related ones, other associated problems could arise and following precautions are necessary to address them

i) Regular sanitization of drinking water, periodic cleaning of water tanks and flushing pipe system. This is necessary since bacterial counts in water increases in summer due to water table going down

ii) Use of Litter conditioner: In summer, since there is increased intake and excretion of water by birds there is wet litter  and ammonia problems in poultry houses. Hence it is important to maintain litter dry

iii) Vaccination: Strict cold chain should be maintained  during transport storage and administration of vaccines. Vaccination should be carried out during cool hours

v) Immunostimulants should be given for three days following each vaccination

Summary 

Summer is a challenging season  to poultry farming.There is no single solution to hot weather problems and series of  measures are necessary to minimize losses due to heat stress. Among these following FOUR are important and would fairly ensure to preventmajor losses

1)Installation of evaporative cooling system on farms

2)Withdrawal of feed during hot part of day

3)Provision of fresh  cool (5 c) drinkingwater with VitC,Electrolytes and Sodium bicarbonate in hot part of day

4)Use of summer feed formula

In tropical and subtropical countries, the layers are subjected to important heat stress. This heat stress can occur during long periods. The lower feed intake noticed during these periods is the result of the bird’s reduced ability to lose heat. Pullets and laying hens should maintain their body temperature constant by adjusting their food intake according to their ability to lose heat.

The lower growth rates during rearing and the reduced production during lay are only consequences of the reduction in feed consumption when the birds are incapable of regulating their temperature.

The influence of heat and the behaviour of laying hens

A better understanding of the mechanisms of thermoregulation helps us to reduce the impact of heat on growth and production.

- To evacuate extra heat, the bird will increase the heat loss by direct exchange with the immediate exterior environment (air, litter, and radiation). As the environmental temperature becomes more and more difficult and as the upper critical temperature is reached, the body temperature starts to increase.

- Heat elimination is then brought about by respiratory means. Heat loss is reduced as the humidity is increased. A relative humidity above 70 % renders thermoregulation very difficult in hot humid conditions.

- Energy and protein synthesis decrease as soon as the body temperature increases. The production of extra heat during the process of digestion lowers the upper critical temperature, increases body temperature and reduces the resistance to heat.

When the conditions are too severe, there will be a reduction in the quantity of food consumed.

Birds have to match their feed intake to their ability to eliminate the heat produced.

The energy intake is the limiting factor for growth and production.

- The dietary energy level has no effect on growth, thus showing that thermoregulation is responsible for the lower growth.

- During the laying period, energy consumption is not modified by changing the energy level of the diet. Growth and production are reduced at the same time as temperature is increased.- As indication only, because air movement and humidity have effects on thermoregulation:

o Egg weight falls by about 0.4% per °C between 23 and 27°C; above 27°C the decrease is about 0.8% per °C.

o Growth at point of lay is reduced above 24°C, and is extremely low above 28°C.

o Rate of lay is generally only affected above 30°C.

o Feed conversion ratio is minimum at a temperature of about 28°C; above 28°C it increases, because of the fall in production.

The quantity of heat to be lost by convection increases dramatically with increases in ambient temperature. If that is not possible, the mechanisms of thermoregulation come into play gradually with effects on feed consumption.

At high temperatures, the food consumption and production of fully feathered birds are generally lower than of those which are only 50% feathered. This shows that in hot temperatures it is the capability to lose the heat produced, which limits production. As the temperature increases, the thermoregulatory mechanisms, spreading the wings, acceleration of cardiac and respiratory rhythms, are gradually set in motion.

How to reduce the adverse effects of high temperature on growth and laying performances?

As the first effect of high temperature is to increase the heat loss by convection and then via the respiratory route, it is important to increase heat loss:

- By reducing ambient temperature when it is possible (insulation of the roof, reduce the penetration of sunrays in the house, etc…).
- By facilitating heat loss through convection (cages design, …).
- By increasing speed of air movement.
- By cooling the air.
- By providing a cool water: Water is an important tool for the chicks to evacuate part of the heat. The cooler the water the better the birds can tolerate high temperatures.

Providing a cool water to the birds will increase their consumption and reduce the quantity of energy to be removed (1,5 % for a reduction of 10 °C of water temperature).

Both in rearing and in production, growth and laying performances can only be maintained by facilitating heat loss and/or by allowing the birds to consume their food the cooler part of the day at which time they can more easily lose the specific heat of digestion (extra heat).

In rearing period:

The growth is affected when the birds approach full plumage. It is therefore important to arrange it so that excellent growth and uniformity is obtained during the first 5 weeks.

- One extra feeder and one extra open drinker compared to normal conditions have to be available.

- The growth during the first weeks of age is also related to light duration. So, a slow step down lighting programme will help to boost feed consumption and growth. The reduction of light duration done in the evening will allow the birds to eat early in the morning during the cooler part of the day and help the bird to lose easily the specific heat of digestion before hotter part of the day.

- As the pullets are not able to adapt their feed intake to the energy level during the first 5 weeks, a starter feed rich in energy and in protein will help the growth. A starter feed in crumbs during this period will encourage feed intake and growth.

After 6 weeks:

- As 25 % of the maintenance requirement is devoted to eating the food, a uniform texture  75 % of the particles between 0,5 and 3,2 mm) will reduce the energy needed.

- Giving the feed early in the afternoon will encourage feed consumption of large particles size (low energy needed) before the light off. Fine particles will be easily eaten in the morning. This meal feeding will encourage the development of the digestive tract and help the increase of consumption at start of lay.

- If the birds are not obtaining the bodyweight at a given time, one should be delaying the change of feed (starter to grower and grower to developer).

A too low bodyweight at start of lay will lead to post peak dips, risks of high mortality in production with some prolapse, and poor quality and persistency later on in production.

- A too early light stimulation will lead to post peak dips. No light stimulation is necessary before 2 % of lay. Light increase is managed to meet increase of production.

- In order to obtain pullets with enough reserves, a pre lay feed during 2 weeks before 2 % of lay with 2 % of Ca is advised. The addition calcium should be in particles to avoid negative effect of powder on feed consumption.

In production period:

- As during the rearing period, the impact of high temperature will be reduced if feed intake is encouraged during the cooler part of the day. All increase of light duration after 2 % of lay is advised in the morning.

- 2 hours of light from 2 % of production can be gradually placed in the middle of the night to encourage feed intake (so growth) and to provide Calcium during the intensive shell deposit.

- Giving lights from 4 to 20 hours and at night from 23 hours to 1 o'clock in the morning appears to be the programme adopted in most hot countries, between latitudes 20° north and 20° south.

Feed during production period:

- To avoid any under-consumption at start of lay, the use of a similar energy level in production as during the second part of the rearing period will not penalize feed intake.

Energy level during production period should be constant throughout the laying period.

- Addition of fats during the laying period has some advantages: the feed becomes more palatable with a lower heat increment. Shell thickness and egg weight seems to be improved. Production is maintained and feed efficiency improved.

- 75 to 80 % of the amino acids assimilated by a chicken are used directly for the production of egg material. So, amino acids requirements for optimum production have to be covered. Amino acids content in the feed should be adapted to real feed consumption noticed.

- The attractiveness of a feed depends to a large extent on its texture. In theory, presenting food in crumb or pellet form, will lead to an increase in food consumption, provided that the technology and the raw materials used give the hens access to a good quality crumb.

- In a hot climate, a diet with good texture help to reduce the degree of under consumption observed in summer conditions. For this reason, we advise having a diet with a minimum of 75 to 80 % of the particles between 0.5 and 32 mm diameter.

Management of egg quality in hot climate:

These previous tools will help to improve the growth and the feed consumption of the future layers and layers. This should lead to an improvement of the production and the liveability. To optimise the egg quality, it is also important to take care of the quantity of calcium in the diet according to the age, the size of the calcium provided.

To limit the natural deterioration of the egg quality throughout the laying period, four majors points have to be it is important to take into account the following aspects:

- To insure that the bird has developed good reserves of calcium before the first egg
- To insure that calcium is available during the shell formation
- To provide a optimum size of limestone during the shell formation period
- To adapt quantity of limestone according to the age

The obtention of the right bodyweight associated to the utilisation of a pre lay feed the 10 days before the first egg will encourage the development of the calcium reserves in the medulary bone and therefore the egg quality during the second part of the laying period. The prelay feed is an intermediate feed between developer and layer feed. The calcium content should be 2% with 50 % of this amount in particles (from 2 to 4 mm).

The intensive deposit of calcium occurs during the last part of the day and during the night. Calcification is completed for 80 % of the birds 2 to 3 hours after light on. Higher will be the feed intake and the calcium intake in the afternoon, higher will be the calcium deposit and therefore stronger should be the egg shell. An adapted feeding timetable reduces the mobilisation of the calcium from the medulary bone. The introduction of a period of light in the middle of the night improves the shell quality by allowing the hen to replenish her calcium reserves.

Eggshell quality depends to a large extent on the quantity of calcium remaining in the gizzard at the end of the calcification process and, therefore towards the end of the night. By using a limestone with a particle size between 2 and 4 mm, say 2 – 4.5 mm, the hen has calcium available at the end of the night, thanks to a progressive solubilisation of the calcium.

The increase in the level of calcium in the feed is justified by the increase in the weight of the egg shell and the fact that calcium from medulary bone is less available during the second part of lay.

Conclusion:

The harmful effects of heat, which affect both growth and production, can be reduced considerably by recognising the physiological requirements of the birds.

The conception of the laying house, the water temperature provided, the lighting programmes, the feeding timetables, the feed content and presentation are additional measures which allow to reduce the problems cause by high temperatures. But the results obtained depend to a large extent on diligent everyday care of the birds.

References:

Bougon (1996) Report to Itavi Seminar1996

Buyse et al (1993) British Poultry Science 34 : 699 – 709

Gabarou et al (1998) British Poultry Science 39 : 79 - 89

Grizzle et al (1992) British Poultry Science 33 : 781 - 794

Leeson et al (1997) Commercial Poultry Nutrition 2nd Edition

Lewis et al (1996) British Poultry Science 37 : 279 - 293

Morris (1995) British Poultry Science 36 : 763 - 769

Morris (1967) Environmental Control in Poultry Production. Carter (Ed.):15–39

Xin et al (2002) British Poultry Science 81 : 608 – 617

Zollitsch et al (1996) International Symposium on Requirements of Poultry and Swine. Ed. Rostagno Joly (2003) ISA technical bulletin

Keeping Birds Cool in Hot Weather

As warmer weather approaches, the threat of heat  stress increases. Poultry producers need to anticipate this and have housing  and management procedures ready to respond. Effective summertime management  is crucial for growers to achieve maximum weight gains and optimum feed  conversion while preventing bird loss due to heat exhaustion. The following is a  summary of some steps to be taken during hot weather ventilation. The month and  year of the full newsletter on each of these topics are listed in parenthesis at the  end of each section and can be found at http://www.poultryventilation .com

Air Speed Distribution

Air speed is the most effective way to cool birds in  hot weather and ensure optimum performance. Modern houses are designed for  air speeds of 500 to 600 ft/min. In theory, the distribution of air speed  should be=20 equal across the length of the house. However, interior side wall  construction and equipment placement have been shown to significantly impact wind  speed distribution down the length of the house. Solid side wall houses with a  smooth surface have better wind speed distribution versus those with posts. Air  speed along the side walls has been found to be as much as 200 ft/min slower  than the air speed in the middle of the house.

Bird Distribution

When more birds are in one end of the house than the  other bird performance is reduced. In addition to the increased competition for  water and feeder space, the heat load in the house can be very different from  front to back. Timely installation of migration fences and use of appropriate  fence materials are key to maintaining bird uniformity down the length of the house. Not all materials make good migration fences. While most materials will  do a good job of minimizing bird migration down the house, they can cause  dead air spots on the downwind side of the fence, resulting in heat stressed birds and increased mortality. Plywood fences resulted in the largest dead spot = whereas=20 the ten inch black plastic drain pipe has a smaller yet still significant dead spot. Wire shelving material works best with no dead spot and relatively  no wind resistance.

Nighttime Cooling

During hot weather, night-time bird management is  just as important as the daytime management. Even in the best broiler houses,  some heat build up is going to occur on hot days. During that time, bird body  temperature may rise, but does not increase enough to result in panting. It is these  days, as well as days that birds end up panting that nighttime cooling can  have enormous impacts on bird performance. Just because birds are not panting  does not mean that they are not hot. In addition to that, some people feel = that when temperatures drop at night, it is an opportunity to reduce the number of  fans running for utility savings. However, the small amount saved on the = electricity bill will not compare to what is lost in performance. A recent study conducted by the USDA in Mississippi demonstrated the importance of running fans at night.The study showed that providing 300 ft/min was better than no fans running but stated that 550 ft/min provided the best results with increased weight  gain and better feed conversion. The money it costs to run the fans during the  last two weeks should be considered a good investment. The increased weight gain  and better feed conversion will definitely yield a good return on that  investment

Equipment and House Maintenance

The whole ventilation system is dependent on the fans  which create the negative pressure to pull air into the house. Fan belts and  pulleys should be checked routinely because as they wear down, fan blade speed and subsequent movement will be reduced. Fan shutters should be cleaned  regularly. Dirty shutters will make it harder for the fans to move air, reducing their efficiency. Testing house static pressure is just as important for hot  weather as it is for cold weather. Provided that the fans are in good repair,  house static pressures that are low after conducting a test indicate air leakage. Any air leaking through cracks or holes is not being pulled through cool  cell pads.This will result in larger temperature buildups from front to back and = hurt=20 overall house performance, as well as result in poor bird uniformity. The evaporative cooling system should receive regular maintenance as it adds = to the=20 effectiveness of cooling birds by tunnel ventilation. Dirty pads will = restrict air flow making it harder for the fans to pull air into the house. Not only will this hurt fan efficiency and increase fan wear and tear, but bird cooling will be significantly reduced.


Good  management and routine maintenance are important components of hot weather broiler production. Simple steps and attention to detail will ensure that houses  are running optimally and that birds are managed correctly