Challenges and strategies to manage poultry under stressful environmental conditions
The genetic improvements in poultry birds have provided us poultry stocks with growth and production potentials of the highest magnitude. These production sensitive stocks cannot express their potential without adequate feeding and ideal living conditions. Many physical factors such as social, air, temperature, humidity, light, water, dust, noise and wastes etc. keep disturbing the micro-environment of poultry and make its living conditions harsh and difficult from time to time. These stressful conditions individually and collectively exhibit their impact on the physiological performance, food intake, growth, production efficiencies, well-being and livability of the birds and quality of products obtained from them. The challenges improved by such factors for the poultry managers and producers as well as the managemental and feeding strategies that could be best applied to minimize the impact of these factors on the performance and welfare of poultry birds have been discussed in this paper.
The combined impact of all the external conditions on growth, production, behavior and physiological responses of the animals is referred to as the environmental effect. Over time, the genetic progress has made available the poultry stocks which possesses the growth and production potentials of the highest magnitude. There is a little scope for further genetic improvements. With the efforts of the nutritionists, the nutritional requirements of these genetically superior stocks have been precisely and accurately defined to meet their needs for maintaining highest levels of growth and production. However, in the Genetic-Nutrition-Environment interaction equation, only the provision of ideal environment for these sensitive birds could make the poultry producers able to harness the genetic gains of modern flocks and to get best output from what is fed to them. But unfortunately, environment generally remains overlooked and neglected with most producers, who often do not take seriously the recommendations for improving the environment. With poultry birds, the environment essentially refers to those external conditions, which are found in the bird’s immediate surroundings or the microenvironment. These include the factors such as social, air, temperature, humidity, light, water, dust, noise and wastes. All these factors have thoroughly been investigated, debated and recommendations have been made for their best possible combinations to provide ideal living conditions for poultry birds. The problem with the open-sided poultry houses in most tropical countries is the frequent variations occurring in these environmental factors. As such, the adverse environmental conditions refer to the situations where one or multiple factors that affect the bird’s physiological performance are not managed within ideal limits. In other words, these are stressful conditions that make the living conditions harsh and difficult for the birds and are detrimental for their growth, feed intake, production efficiency, well being and survivability. Some of these factors such as social, light, noise, dust, wastes and air are of smaller magnitude and can be corrected through minor adjustments. However, temperature and humidity are of greater importance, which needs thorough management to prevent huge economic losses. To identify and adopt suitable strategies minimizing production losses under such conditions have always been a challenging job for the poultry producers and managers.
Challenges and Strategies to Correct Different Stressful Conditions
Social Stress : Social stress is a result of overcrowding, non-uniform growth of the flock or fewer number of feeding/watering equipments than required. It is one of the often-overlooked stressor that affects production efficiency and physiological responses. It may occur in layers housed in multiple birdcages and in broilers housed in intensively confined floor pens. Productivity rate generally declines as population size increases and space allowance per bird decreases. The bird’s main response to the social stress interactions of many birds housed in a cage is an increase in the circulating level of corticosterone released from the adrenal gland as a protective mechanism. Koelbeck and Cain (1984) found that the laying hens maintained at 0.094 m 2/bird density had elevated levels of corticosterone than those maintained at 0.373 m 2/bird. In addition, egg production, per cent livability and average body weight were depressed for those birds maintained in floor pens versus those kept in cages. Qubasilar and Aksay (2004) found that the allocation of 5 hens per cage resulted in reduced productive performance and immune response but no differences in stress parameters between the group of one and 3 hens per cage. Thus the number of hens kept per cage and the type of rearing environment (cage v/s floor pens) affect the bird’s productivity and physiological response to social stressors. Similarly, broiler chicks provided 2000 cm 2 floor space showed less agonistic behavior than those provided 667 or 1000 cm 2 (Thomas et al 2004). It is, therefore, important in commercial operations not to overcrowd pens or cages and to provide sufficient number of feeding and watering equipments.
Light related Stress : Proper lighting of poultry houses is one of the oftenly ignored management tool in our country. Proper management of bird’s light environment can maximize egg production of layers and growth of broilers and turkeys. On the other hand, improper light stimulation inhibits egg production and growth. The most common physiological effect of light on growing pullets is the effect of day length on sexual maturity. Sexual maturity in Leghorn pullets and broiler breeders grown under an increasing day length is enhanced and cause egg production and blow out problems in layer house. Sexual maturity is delayed in pullets grown under decreasing day length. Practically, the pullets should be grown under decreasing or constant photoperiod length. In addition to day length, light intensity is also important. High light intensity may cause feather picking and other related problems in pullets, layers, broilers and turkeys grown in light uncontrolled facilities. High intensity of light in brooder house result in disasters for survival of chicks due to the picking during first few days of their life. Since physiological and production responses of poultry are greatly affected by light and lighting programmes, it would be advantageous to use light controlled facilities, if possible. Broiler breeders raised in light controlled facilities will have the advantages of having better control of age at sexual maturity, reduced feed intake with economic savings and better flock uniformity.
For broiler units, light is usually provided continuously for long periods extending up to 23-24 hours/day. Birds do need complete rest. Long exposure of light is thus stressful and particularly under the situation of light failures they become nervous and face stressful moments with elevated corticosterone level in the blood and high mortality due to piling up. Many alternate intermittent lighting programmes have been investigated found to be more promising for better production efficiencies and bird’s welfare (Esmail 2001).
Another aspect recently investigated is the impact of certain coloured light sources on performance and welfare of poultry birds. This has led to the development of electronic coloured light lamps, the use of which not only saves on electricity consumption but also improves welfare and production efficiencies. Rodenburg et al (2004) reported that yellow sodium lighting and green/blue lighting reduced breast smearing while green/blue lighting positively affected footpat lesions and gait score in broilers. Lewis and Morrish (2000) in a review on coloured light conclused that under red illumination turkeys and chickens had inferior growth, more activity and aggressive behaviour than blue or green light. Red light was sexually more stimulatory and blue light had calming effects. Dhaliwal and Nagra (2004) did not observe any significant effect of colour of light on growth and FCR in quails but egg production and egg weight were higher with white fluorescent and fertility was higher with yellow illuminations.
Water/Stress : Water intake is correlated with feed intake. Any decrease in water consumption due to failure in the water supply or lack of watering space lowers the consumption of feed to varying extent depending on the age, and type of chickens, season and degree of water restriction. Regular supply of clean, sanitary and fresh water must, therefore, be maintained. Water temperature particularly in summer months is important. Any contamination of water will influence the performance. Enclosed watering systems is believed to improve feed conversion as the water remains protected from carriers of bacterial contaminants such as dust, litter, feed and faecal materials. Open type waterers remain exposed to such contaminants. These are major contributing factors to poor absorption, diarrhoea and illness. It would require more effort to clean and disinfect the watering system on regular basis, but it certainly leads to better-feed efficiency.
Noise related Stress : It has always been recommended that the poultry rearing facilities should be located away from the noisy areas such as main roads and heavy mechanical industries. But existence of many farms ignoring such recommendations can be seen at many places. The installation of a power generator at an improper location at the farm is generally a common source of noise. There is evidence that the chickens exposed to high level of noise consumed less feed as a result of which weight gain and efficiency of feed utilization are reduced. These effects are mediated through a variety of functional changes in the internal body systems including nervous, endocrine and the gastrointestinal systems. Such changes could be alleviated by proper special arrangements between the chicken house and the source of the noise. In small farms where the land area is a limiting factor, alleviating the noise stress by this means may not be a practical approach. Under such cases, the installation of resonators or exterior application of sound baffles should be considered.
Air Condition (Dust and Gases) and Stress : Air quality is determined by the level of suspended dust particles and toxic gases. Excessive level of suspended dust particles is a result primarily of too dry litter, particularly in dry-hot season. These dust particles damage the lung surface and increase the susceptibility of birds to diseases. On the other hand, high concentration of toxic gases such as ammonia, methane, hydrogen sulphide and carbon dioxide is a result of excessive fermentation of litter due to high moisture content. These gases are lethal at high concentration. Ammonia is the major gas which causes health and production losses. It not only has its potential effects on poultry birds but also affect the caretaker and environment. It is nauseating and causes irritation in the eyes. Continuous high concentration of ammonia reduces the activity of cilia of respiratory trait. A wide range of ammonia concentration (2-30 ppm) is associated with building design and management practices. Current evidence suggests maximum permissible ammonia concentration of 20 ppm in poultry houses. If a cautionary approach is taken to promote welfare, performance and environmental impact, then the permissible concentration should be lowered to 10 ppm (Wathes et al 2004). It is, therefore, necessary to use optimum management measures that can help in the elimination of toxic gases from the house while retaining a certain amount of moisture in the litter to avoid dust problem. This would require controlled air flow in the poultry house through proper ventilation and exhaust system, adequate feeding and optimum manure management.
|Source : IPSACON-2005|