Modern egg production has come a long

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1 Trend and R&D opportunities of laying-hen housing systems On Departments of Agricultural & Biosystems Engineering and Animal Science, Iowa State University, Director of Egg Industry Center, Ames, Iowa 50011, USA Introduction Modern egg production has come a long way from primitive, backyard small flock rearing in the old days to the contemporary sophisticated, environmentally-controlled confinement operations. The environmentcontrolled housing,together with nutritionally balanced diet and continually improved genetics, has made modern egg production remarkably efficient. However, pursuit of high production efficiency alone can no longer satisfy today s consumers. The issue of animal welfare has become a focal point of societal concern and is having some major impact on animal agriculture, especially in Europe and North America. At the same time, food safety, food security, environmental impact and climate change continue to draw increasing attention from government agencies, non-government organizations (NGOs), animal production sectors, research communities and the general public. This paper provides a brief overview of current and emerging housing systems used in egg production, with emphasis on control strategies and research opportunities aimed to improve hen well-being, housing environment, and ultimately sustainability of the operation. about 95% of the total production systems. The CC system is typically divided into two types, according to manure handling practices. One is the high-rise (HR) system, where manure stays in the lower level of the hen houses for certain period of time (typically one year) before a complete removal (generally in the fall after crop harvest and land-applied). The other type is manure-belt (MB), where hen manure is removed frequently (every 1-3 days) from the house into a separate storage or composting facility. Because of the frequent manure removal, MB houses have much better indoor air quality (ammonia NH 3, dust, and odor levels) and lower air emissions to the atmosphere than HR houses (Liang et al., 2005; Green et al., 2008) (Fig. 1). As a result, today in the United States majority (>90%) of the new hen facilities are built as MB houses (Lippi of Chore-Time, Personal Communication, 2010; Fig. 2), even though MB houses cost approximately 50% more than the HR counterparts.realizing the benefits of frequent manure removal on indoor air quality, some producers in mild climate regions are also practicing weekly removal of manure from HR houses. Conventional cage housing systems for laying hens The most predominant egg production system in the world is the so-called conventional cage housing (CC). In the United States, CC houses account for Figure 1 - Ammonia emissions from high-rise or manure-belt laying-hen houses. Manure moisture content (MC) considerably affects its NH 3 volatilization (Li and Xin, 2010), with manure of higher MC emitting larger amounts of NH 3. To further reduce NH 3 emissions of MB houses and improve the ease of manure transportation/ handling, active drying of manure is practiced in most of the MB facilities. One common way is 1

2 using manure-drying air duct situated between the cage floor and the manure belt. Air supply blowers recirculate the indoor air through the air ducts, and the air moves over the manure surface at a flow rate of about 0.85 m 3 hr -1. It is typical that these air blowers run continuously; as a result, considerable amount of electric energy is consumed. Hayes et al. (2012a) monitored the energy use by such blowers and found that they account for 25-60% of the building electricity use. To save energy used on manure drying, a new housing system has been developed and used in some U.S. egg operations. The system contains a so-called drying chamber attached to the exhaust fans. Inside the drying chamber manure belts are zigzagged in tiers and the warm exhaust air from the hen house flows through the tiers, thus drying the manure (Fig. 3). Figure 2 - Trend of new laying-hen houses built in the United States (Source: T. Lippi of Chore-Time, 2010). Nevertheless, majority of the existing hen houses are still in the form of HR (about 65% of the total hen houses in the United States). Ammonia is the predominant noxious gas in poultry houses that can have adverse effects on the health of birds and caretakers and negative environmental impact after emitted to the atmosphere. In the United States, federal regulations exist concerning release of certain gases and particulate matters (known to as the criteria pollutants) into the atmosphere. For animal production, daily emissions of ammonia or hydrogen sulfide (H 2 S) from a facility that exceed 45 kg need to be reported, as required by the U.S. EPA Emergency Planning and Community Right-to- Know Act (EPCRA) ( lcra.html). Although future regulation of ammonia emissions from animal feeding operations under the U.S. federal Clean Air Act remains uncertain, discussion on the topic continues. To reduce ammonia generation and emissions of HR houses, dietary manipulation has been investigated and proven to be quite effective (Liang et al., 2005; Roberts et al., 2007; Li et al., 2012). Specifically, feeding laying hens nutritionally balanced diet with 1% lower crude protein leads to approximately 10% reduction in ammonia emissions from HR houses without adversely affecting hen production performance (Liang et al., 2005). A two-year field study with three commercial HR houses (~255,000 hens each) showedammonia emission reduction of 14% and 39%, respectively, for hen house fed a diet containing 10% (by weight) corn dried distillers 2 Figure 3 - A manure-belt hen house with attached manure-drying chamber (Source: T. Lippi, 2010).

3 grain with solubles (DDGS) and a diet containing 7% EcoCal TM (mixture of zeolite and gypsum) (Li et al., 2012a,b). Alternative housing systems for ling hens Over the past decade intensified movement towards improving animal welfare has led to emergence and increasing adoption of alternative animal housing systems. For egg production, CChousing has been and is continuing to be challenged for its limitation in allowing the hens to exercise their natural behaviors (e.g., perching, wing flapping, dustbathing, foraging). Effective January 2012, the European Union (EU) has banned the use of CC housing for egg production, although, as of this writing, certain EU member countries had not met this requirement. In the United States, an agreement has been reached between the United Egg Producers (UEP) and the Humane Society of the United States (HSUS) that by 2029 CC systems will be phased out and replaced with enriched colony/cage (or other non-cage) housing systems, and the U.S. Congress is yet to act on the nationwide legislation proposal. Alternatives to CC systems include enriched colony/ cage (Fig. 4), single-level floor non-cage (Fig. 5), multi-level aviary non-cage (Fig. 6), and free-range systems. Common features among the alternative housing systems include provision of perches, nestboxes, and dustbathing area (litter or scratching pads). Compared to CC housing, alternative housing systems also provide the hens with much more space (70% 220% or greater) so that hens can flap their wings or move about more freely. Some progressive egg producers, such as J.S. West and Companies in California, have started to use enriched colony systems. J.S. West also offersa 24/7 webcasting of the hens in their enriched colony system for public viewing ( component/content/article/118). Figure 5 - Single-level non-cage henhousing with slats and litter floor. While accommodating natural behaviors of the hens, alternative housing systems are posing some unique issues and challenges that need immediate attention in production management, facility design, systematic research and development. The issues and challenges include, but not limited to: size, type and configuration of certain enrichment elements (e.g., perches); poor indoor air quality (high dust levels in systems with littered floor); need and uniform distribution of supplemental heating in a large hen-house space; floor or dirty eggs; deformation of hen keel bone (presumably arising from contact with hard surfaces in the housing elements); and higher mortality in non-cage production systems (mostly from piling and some from cannibalism). The following sections provide a closer look at some of the issues and challenges/ opportunities that may be considered in production facility design and management, and future research and development. Figure 4 - A schematic view of enriched cage hen housing (Source: Big Dutchman, Inc.). Perches in alternative hen-housing systems Perches are a resource used extensively by the hens. As can be seen from the live video at the J.S. West web site, essentially all the hens are found to 3

4 Figure 6 - A cross-sectional view of an aviary hen-housing system. 4 sit on the perches at night. Variations exist in size, shape and orientation of perches in commercial enriched colony housing systems. For instance, in some cases perches are installed in parallel with the feeder troughs (e.g., Big Dutchman enriched colony system) while in others they are perpendicular to the feeder troughs (e.g., Tecno enriched colony system). The following questions remain to be fully addressed: a) Is there an optimal orientation of perches for the hens? If so, what orientation inside the colony is most conducive to the hen s behavior/ welfare and production performance? b) How high should the perches be to satisfy the hens behavioral needs while minimizing the incidence of crack/check (inedible) eggs? c) How would the relative location of perches to nestboxes affect the use of the nestboxes by subordinate hens in the colony? d) What is the relationship between perch space allowance and incidence of crack/check eggs? e) How does bird genetics affect the aforementioned perch design parameters or relationships? f) How does the size, shape or stability of perches affect their use by the hens and incidence of hen s physical injuries? Nestboxes in alternative hen-housing systems Nest boxes provide a private space for hens to lay eggs. The need for improving and optimizing nestbox design continues. A number of questions remain to be addressed, including, but not limited to: a) What is the minimum nestbox space per hen? b) What is the relationship between nestbox space and eggs laid outside the nestboxes and/or check eggs? c) How important is it to have a pad in the nestbox? d) What is the adequate light level or type in nestbox area? Scratching pad or litter floor in alternative hen-housing systems Scratching pads soiled with hen manure can exist in enriched colony systems. Dirty scratching pads raise concerns of microbiological quality in the production environment, hence egg safety or incidence of other diseases. Research and development should be conducted to investigate means to keep the scratching pads clean. Anecdotal evidence in the field indicates that the size of scratching pads has a considerable impact on their cleanliness. For litter floor systems (e.g., aviary houses), field data have shown that concentrations and emissions of particulate matters (PM 10 and PM 2.5 ) in such systems are considerably higher than those in CC systems (Li et al., 2011; Hayes et al.., 2012b; Fig. 7). The high PM concentrations pose health concerns for birds and workers. There are potential dust-suppressing systems for controlling indoor PM generation in animal housing, such as electrostatic precipitationto suppress dust in broiler housing (Ritz et al., 2006) and oil sprinkling to suppress dust in swine housing (Zhang, 1997). However applicability of such systems in aviary houses is uncertain because electrostatic precipitation may cause the dust to cling onto the housing components, and sprinkling oil would increase the risk of hen physical injuries when moving between floor and tiers. Therefore other methods to significantly reduce dust generation in the non-cage housing systems needed to be investigated. Innovative engineering designs should be investigated. Lighting management in alternative henhousing systems

5 Figure 7 - Diurnal variations and magnitude of particulate matter (PM) concentrations in conventional cage (left, Li et al., 2011) and aviary (right, Hayes et al., 2012) hen-housing systems (note the difference in PM concentration scale). Lighting management plays an important role in hen housing system. In the case of non-cage housing, e.g., aviary houses, proper use of lighting program is key to training the birds to lay eggs in the designated nestboxes, as opposed to be on the litter/manure floor. Simulation of dusk and dawn with dimmable lighting is also more conducive than sudden on/off in terms of waking up the hens in the morning and encouraging them to return to colonies at night. There has been anecdotal evidence that LED (light-emitting-diode) lighting is more conducive to hen egg production, although concrete research data are lacking. Supplemental heat in alternative henhousing systems The lower stocking density in alternative housing systems, as compared to CC housing systems, means lower number of birds per unit housing space, hence less amount of (sensible) heat available from the birds to keep the house temperature in winter season. This can lead to poor indoor air quality or suboptimal thermal comfort in non-cage housing systems (Green et al., 2009; Fig. 8). A simulation analysis by Zhao et al. (2012) indicates that depending on the housing capacity (50,000; 100,000; or 150,000 hens per house), for typical laying-hen building characteristics in the Midwestern USA, balance temperature (i.e., outdoor air temperature below which supplemental heat is needed to maintain the target house thermal conditions 25 o C and relative humidity [RH] of 60% in this case) is 2.6 to 6.2 o C higher for the alternative housing systems than for the CC housing systems. To meet the supplemental heat needs, alternative hen-housing systems, especially the non-cage systems, are equipped with heaters. In the case of Midwestern USA, 2-4 space heaters of 73.3 kw (250,000 BTUhr-1)capacity would be used. However, uniformly distributing the supplemental heat in an aviary hen house of 50,000 birds (20 x 168 m, typical of U.S. operation) can be challenging. Figure 8 - Ammonia (left) and air temperature (right) of conventional cage (high-rise or manure belt) vs. floorraise (FR) hen houses during winter time in Iowa (the letter I after HR. MB or FR stands for inside and O for outside) (Source: Green et al., 2009). 5

6 This is particularly true if the heaters are mounted in the sidewalls, as is the case with some hen houses. One way to overcome this dilemma is to supply the heat, as needed, through the manure-drying air ducts. In this case, the supplemental heaters can be co-located in the rooms where the manure-drying air supply blowers are positioned. Limited field experience indicates that this arrangement works reasonably well. For regions where cold temperature rarely occurs, supplemental heat may be omitted by temporarily allowing the air temperature to drop moderately. Figure 10 illustrates the impact of lowering house temperature setpoint on ventilation curves and balance temperature in an aviary and an enriched colony housing system. As can be seen, a 5 o C drop in house temperature setpointleads to about 10 o C reduction in balance temperature, thus supplemental heat need. Similarly, as shown in Figure 11, allowing temporary elevation in indoor RH will also lower balance temperature and supplemental heat need. A 10% elevation in indoor RH would lower the balance temperature by about 5 o C. However, caution should be exercised when allowing indoor RH to elevate because it may cause moisture condensation and/or development of poorer indoor air quality. It may also create an environment that is conducive to bacterial growth. 6 Figure 9 - Ventilation curves for control of house moisture (dash lines) and temperature (solid lines) in winter seasonand balance temperature (tbal) of conventional cage (CC), aviary, and enriched colony hen housing systems. Indoor temperature = 25 C, indoor relative humidity (RH) = 60%, outdoor RH = 70%. Building constructional characteristics are typical of those used in the Midwestern USA. Housing capacity is 200,000 hens for the CC house; 50,000 for the aviary house; and 50,000 (100%), 100,000 (200%) or 150,000 hens (300%) for the enriched colony house. The birds are either Hy-Line white (W-36) or brown hens (Source: Zhao et al., 2012).

7 Figure 10 - Impact of house temperature setpoint of 15, 20 or 25 C on ventilation rate for control of indoor moisture (dash lines) and temperature (solid lines) in winter season and balance temperature (intersection between temperature and moisture control ventilation curves) of aviary and enriched colony hen housing systems with 50,000 white birds. IndoorRH = 60%, outdoor RH = 70%. The building construction characteristics represent those typically used in the Midwestern USA (Source: Zhao et al., 2012). Figure 11 - Impact of house relative humidity (RH) setpoint of 60%, 70% or 80% on ventilation rate for control of indoor moisture (dash lines) and temperature (solid lines) in winter season and balance temperature (intersection between temperature and moisture control ventilation curves) of aviary and enriched colony hen housing systems with 50,000 white birds. Indoor temperature = 25 C, outdoor RH = 70%. The building construction characteristics represent those typically used in the Midwestern USA (Source: Zhao et al., 2012). Systematic approach to addressing sustainable production systems The subject of sustainable animal production is a complex one because it consists of multiple facets that are interrelated with and affected by one another. These facets include animal welfare, food safety, food security (feeding the world, food affordability), economic efficiency, environmental impact and resource utilization, ergonomics of animal caretakers, and consumer acceptability. For instance, non-cage egg production systems better accommodate natural behaviors of the laying hens than conventional cage housing systems; but they inherently require more resources, from land space to feed energy, than conventional cage housing systems in producing the same amount of eggs. The 7

8 8 increased demand for land space and feed energy translates to higher environmental footprint. The increased capital and operational cost will increase the price of eggs produced, thus affecting food affordability. Similarly, floor-raised hen houses (e.g., aviary houses) inherently generate more aerial pollutants that could have a negative impact on the environment. Engineering means to alleviate certain environmental side effects brought about by meeting the welfare needs of the animals must be an integral part of the system consideration. Currently a multi-disciplinary and multiinstitutional research project is ongoing in the United States that systematically evaluates three laying-hen housing types at a commercial production farm: a) CC with manure belt, b) enriched colony, and c) aviary housing. This 3-year project is evaluating behavior, health and welfare of the hens; environmental conditions and impact (indoor air quality gaseous and particulate matters, air emissions, thermal conditions, energy use), egg quality and safety, worker health and ergonomics, and economic efficiency (production performance, production costs, efficiency of resources utilization, revenue, etc.). The team members include animal behaviorists, avian physiologists, economist, agricultural engineers, human health specialists, immunologists, microbiologists, and poultry nutritionists. Once completed in 2014, the project will yield a set of research-based baseline information that can help guide the U.S. egg industry in decision-making of egg production systems for the future (visit project web site to learn more). This project provides a good model for holistically addressing the multi-facet animal production systems. Closure Egg production systems have undergone considerable evolution from the standpoints of genetics, dietary nutrition and physical environment of production housing. The industry has move from the primitive, unprotectedand low-output backyard flocks to sophisticated, environmentallycontrolled, and high-throughput confinement operations. Today, people s living standards continue to increase, food supplies have become more affordably abundant, and views on animal ethics are changing. As a result, societal forces are mounting to improve animal welfare by allowing animals to exercise their natural behaviors (return to nature). At the same time, as the global population continues to grow, there must be longterm strategic plans in place to feed the growing world while conserving the natural resources and ecological systems for generations to come. This paradox calls for exploration and adoption of truly sustainable animal production systems. In the case of egg production, alternative hen housing systems or management practices are emerging and being adopted. However, certain aspects of the science and technology are lacking, which can lead to unintended consequences, be it animal welfare, food safety, food security, environmental impact or demand for natural resources. A holistic, multidisciplinary approach must be used to address the complexity of sustainable laying-hen housing systems for egg production. References GREEN, A.R., WESLEY, I., TRAMPEL, D.W. and XIN, H. (2009) Air quality and hen health status in three types of commercial laying hen houses. The Journal of Applied Poultry Research 18: HAYES, M.D., XIN, H., LI, H., SHEPHERD, T. and STINN, J.P. (2012a) Electricity and Fuel Usage of Aviary Layer Houses in the Midwestern USA.Transactions of the ASABE (in review). HAYES, M., XIN, H., LI, H., SHEPHERD, T., CHEN, Y., ZHAO, Y. and STINN, J.P. (2012b) Ammonia, greenhouse gas, and particulate matter concentrations and emissions of aviary layer houses in the Midwestern USA. Proceedings of the 9 th International Livestock Environment Symposium, Valencia, Spain. Published by American Society of Agricultural and Biological Engineers, St. Joseph, MI: ASABE LI, H. and XIN, H. (2010) Lab-scale assessment of gaseous emissions from laying-hen manure storage as affected by physical and environmental factors. Transactions of the ASAE 53: LI, H., XIN, H., BURNS, R.T., ROBERTS, S.A., LI, S., KLIEBENSTEIN, J. and BREGENDAHL, K. (2012a) Reducing ammonia emissions from high-rise layinghen houses through dietary manipulation. Journal of the Air & Waste Management Association 62: LI, H., XIN, H., KLIEBENSTEIN, J., IBARBURU, M., BURNS, R.T., ROBERTS, S.A. and BREGENDAHL, K. (2012b) Effects of ammonia-reduction diets on laying-hen production performance and economic efficiency. Poultry Science (In review) LI, S., LI, H., XIN, H. and BURNS, R.T. (2011) Particulate matter concentration and emissions of a high-rise layer house in Iowa. Transactions of the ASABE 54: LIANG, Y., XIN, H., WHEELER, E.F., GATES, R.S., ZAJACZKOWSKI, J.S., TOPPER, P., LI, H. and CASEY, K.D. (2005) Ammonia emissions from U.S. laying hen houses in Iowa and Pennsylvania. Transactions of the ASAE 48:

9 RITZ, C.W., MITCHELL, B.W., FAIRCHILD, B.D., CZARICK III, M. and WORLEY, J.W. (2006) Improving in-house air quality in broiler production facilities using an electrostatic space charge system. The Journal of Applied Poultry Research 15: ROBERTS, S.A., XIN, H., KERR, B.J., RUSSELL, J.R. and BREGENDAHL, K. (2007) Effects of dietary fiber and low crude protein on ammonia emission from layinghen manure. Poultry Science 86: ZHANG, Y. (1997) Sprinkling oil to reduce dust, gases, and odor in swine buildings. Midwest Plan Service Publication AED42:8, Iowa State University, Ames, Iowa, USA. ZHAO, Y., XIN, H., SHEPHERD, T., HAYES, M.D. and STINN, J.P. (2012) Modeling ventilation, balance temperature and supplemental heat need in alternative versus conventional laying-hen housing systems. Proceedings of the 9 th International Livestock Environment Symposium, Valencia, Spain. Published by American Society of Agricultural and Biological Engineers, St. Joseph, MI: ASABE. 9