Several developmental and physiological

XXIV World s Poultry Congress 5-9 August - 2012 Salvador - Bahia - Brazil The importance of the brooding period Summary On HatchTech Incubation Technology B.V., P.O. Box 256, 3900 AG Veenendaal, The Netherlands. Several developmental and physiological processes occur during the important and sensitive brooding period of chickens, which is the first 7 days of a chicken s life. The chicken seems anatomically complete at hatch, but the thermoregulatory, gastro-intestinal and immune system need further development and maturation. Optimal brooding is essential to optimize animal health and contributes to a good performance and survival in later life. The most important brooding condition to control is the body temperature because chickens are unable to regulate their body temperature posthatch. Secondly, feed intake is important and stimulates both intestinal and immunological development. To optimize the brooding period, two systems are developed by the industry: the Patio and the HatchBrood system. In the Patio system, the hatching and growout phase are combined. In the HatchBrood system, brooding conditions are optimized for the first days of a chicken s life. Understanding the specific requirements of posthatch birds and subsequently adjust the brooding conditions is important to improve performance, animal health and welfare. Posthatch development The posthatch period of chickens is called the brooding period and is roughly the first 7 days of a chicken s life. Relative growth of a broiler chicken is largest during the first week of life (Nitsan et al., 1995) and maturation of different regulatory systems occurs during this period (Maiorka et al., 2006; Tzschentke, 2007; Christensen, 2009). First of all, chickens are unable to regulate their body temperature posthatch and react as poikilotherm animals (Romanoff, 1941; Weytjens et al., 1999). When the environmental temperature decreases, the body temperature of a chicken decreases as well. Because the body temperature of a chicken is dependent on the environment in the brooding period, the temperature that the chicken experiences is important. Chickens become homeotherm within 4 to 5 days posthatch, which is called the early brooding period (Romanoff, 1941; Weytjens et al., 1999; Tzschentke, 2007). Secondly, there are major changes in the growth and development of the gastro-intestinal tract (GIT; Noy and Sklan, 1997). The gastro-intestinal tract shows the highest growth rate during the first week of a chicken s life and this growth even exceeds the growth rate of the total body (Sell et al., 1991; Uni and Ferket, 2004). The rapid development of the GIT may indicate the important role of this supply organ in early body development. The chicken must undergo metabolic adaptations (Noy and Sklan, 2001) as it changes from a major lipid diet of the embryonic yolk during incubation to a carbohydrate and protein-rich exogenous diet during the brooding period (Noy and Sklan, 1995; Uni and Ferket, 2004). The digestibility of nutrients increases in the posthatch period (Noy and Sklan, 1997, 1999), which is probably related to the development of the gastro-intestinal tract and the presence of adequate enzymatic activity and sodium cotransporters (Noy and Sklan, 1997, 1999; Sulistiyanto et al., 1999; Uni and Ferket, 2004). Early feeding has been shown to positively affect growth, development and maturation of the gastrointestinal tract and thereby the chicken itself (Noy and Sklan, 1997; Batal and Parsons, 2002; Uni and Ferket, 2004). The earlier the chicken starts to consume feed and water, the earlier its development starts (Noy and Sklan, 1997). In practice, the time between hatch and first feed consumption can be up to 72 hours, because of variations in hatch time, chick handling, and transportation time (Dibner et al., 1998; Noy and Sklan, 2001; Van den Brand et al., 2010). During this period, the chicken has no access to feed and water and can only consume the nutrients of the residual yolk (Noy and Sklan, 1997; Uni and Ferket, 2004). During the last period of incubation, the yolk that is left is retracted in the 1

XXIV World s Poultry Congress 5-9 August - 2012 Salvador - Bahia - Brazil 2 abdominal cavity (Romanoff, 1960). This residual yolk is about 8 to 10% of the total body weight at hatch (Lourens et al., 2005, 2006) and contains mainly lipids (Romanoff, 1960; Noble and Ogunyemi, 1989). In the past, the residual yolk was seen as a lunch box for the posthatch period. It is true that chickens develop slightly after hatch because of yolk utilization (Noy and Sklan, 1999; Molenaar et al., 2010), but this is much lower without access to feed and water (Noy and Sklan, 1997). Furthermore, a delay in feed consumption seems to affect the immunological status of the chicken (Dibner et al., 1998; Juul-Madsen et al., 2004; Bar-Shira et al., 2005). The immune system is not completely developed at hatch (Dibner et al., 1998) and a day-old chicken obtains its passive immunity by absorption of the maternal immunoglobulines of the residual yolk into the bloodstream and transportation of these immunoglobulines to mucosal surfaces where organisms are likely to enter the body (Dibner et al., 1998). When feed consumption is delayed, the valuable immunoglobulines of the residual yolk are absorbed and metabolized for energy (Dibner et al., 1998). This probably impairs the immune status of the chicken and makes the chicken more susceptible for diseases (Dibner et al., 1998). If additionally the brooding conditions are suboptimal and body temperatures become too low, chickens are probably even more susceptible for infections. Optimal brooding conditions The most important factor during the brooding period that needs to be optimized is the body temperature of chickens. With the right body temperature, chickens start eating, drinking, and growing. The range of environmental temperatures in which chickens can maintain their body temperature is narrow (Freeman, 1963) and the environmental and floor temperatures are therefore crucial to maintain an optimal body temperature (Lourens and Kuijpers, 2002; Van der Sluis, 2004). Different studies have shown that chickens survive and grow better when the brooding temperature is high (>28 C; Deaton et al., 1996; Malheiros et al., 2000; Baarendse et al., 2006; Leksrisompong et al., 2009). However, there is hardly any information about the optimal body temperature of chickens (Purswell et al., 2008). In practice, it is shown that a body temperature between 40.0 and 41.0 C in the brooding period is optimal and results in the best growth and development. Within this temperature range, chickens show normal eating, drinking and sleeping behavior. The requirements to obtain an optimal body temperature can differ between flocks. One major factor that affects the brooding conditions is the age of the breeder flock. Chickens of a young breeder flock (<35 weeks of age) are smaller than chickens from a prime (35-50 weeks) or old (>50 weeks) breeder flock, mainly because of the difference in egg size. In general, young breeder flocks produce small eggs that will hatch small chickens. The chickens of young breeder flocks are more sensitive for cold temperatures than chickens of prime and old breeder flocks in the brooding period (Weytjens et al., 1999). The thermoregulatory ability of chickens of a young breeder flock seems to be less developed compared to chickens of a prime or old breeder flock (Weytens et al., 1999). As a consequence, the chickens of a young breeder flock require 24 to 48 hours more to become fully homeotherm compared to chickens of a prime or old breeder flock (Lourens and Kuijpers, 2002). This may be related to the higher surface area to body mass in small compared to large chickens or physiological differences between chickens caused by differences in egg nutrients and/or embryonic nutrient utilization. In practice, it is demonstrated that the environmental and floor temperature in the broiler farm has to be higher for chickens of young flocks compared to chickens from prime or old breeder flocks during the brooding period to maintain body temperatures within the range of 40.0-41.0 C. A second important factor during the brooding period is feed intake. Feed intake stimulates early growth and development (Uni and Ferket, 2004) and it is therefore important that chickens find feed and water easily. In practice, feed is often provided in feeding troughs and on paper at the arrival of the day-old chickens to ensure that the chickens have easy access to feed. Drinking nipples should be at the right height to attract birds to the nipples by the sparkling effect of the water droplets. It should be prevent that birds spoil water, because this can result in wet litter and foot and leg lesions (Houldcroft et al., 2008). Importance of an optimal brooding period Broiler chickens increase their body weight approximately 50-fold within 42 days of age and the brooding period represents 17% of the life span of a broiler chicken (Liliburn, 1998). Because of the short life cycle of broiler chickens, growth and development during the brooding period are

XXIV World s Poultry Congress 5-9 August - 2012 Salvador - Bahia - Brazil important. This is also expressed by the positive relation between body weight at 7 days of age and body weights at marketing age (Nir and Levanon, 1993; Gonzales et al., 2003). As described in the first paragraph, several developmental and physiological processes occur during the brooding period and optimization of these processes are critical to improve animal health and welfare. Optimal brooding conditions improve the intestinal and immune function and thereby increase the health status and survival rate of a flock (Dibner et al., 1998; Uni and Ferket, 2004; Bar-Shira et al., 2005; Lekrisompong et al., 2009). Providing chickens with the correct body temperature is the first step to optimize the brooding period and behavior is a good indicator if chickens are thermal comfortable (Charles, 1986). If the body temperature is not correct, a day-old chicken starts screaming (Lourens and Kuijpers, 2002). If the body Figure 1 - Egg trays in the Patio system with broilers that are hatching. Figure 2 - Broiler chickens in the Patio system during hatching. temperature is too high, chickens start panting (Kaltofen and Dijk, 1984; Charles, 1986). If the body temperature becomes too low, chickens decrease their activity, show more sleep-like behavior, and huddle together (Kaltofen and Dijk, 1984; Charles, 1986; Mujahid and Furuse, 2009). Providing uniform body temperatures throughout the whole flock is the second step to optimize the brooding period. Uniform body temperatures are achieved by uniform environmental conditions and will decrease the number of non-starters and the variation in body weights within the flock (Maatjens, 2010). Uniform brooding conditions improve the uniformity of a flock. Furthermore, optimal brooding conditions may contribute to the reduction in antibiotic usage. Reducing antibiotic usage is an important tool to prevent the worldwide growing resistance to antibiotics of pathogenic bacteria in humans (Cohen, 2009; Van Duijn et al., 2011). When the development of the thermoregulatory, gastrointestinal, and immune system are optimized by optimal brooding conditions, this may positively affect the health status of chickens in later life. This may decrease the outbreak of diseases and the use of antibiotics. However, this hypothesis needs further investigation. Although the poultry industry is more and more aware of the importance of the brooding period, the specific requirements of posthatch chickens and the possible interaction with the incubation process and/or the grow-out period are largely unknown and not intensively investigated yet. Brooding systems Two systems are already developed by the industry to optimize the brooding period of chickens, which are the Patio and HatchBrood system. With these brooding systems, the conditions of posthatch birds can be more optimized and are more uniform compared to traditional broiler farms. In the Patio system, the hatching and grow-out phase are combined (Van de Ven et al., 2009; www. vencomatic.com). The broiler farm receives 18-day-incubated eggs. The chickens hatch on the egg tray, fall into the litter, and have immediate access to feed and water after hatch (Figures 1 and 2). The chickens are kept in the system until the end of the grow-out 3

XXIV World s Poultry Congress 5-9 August - 2012 Salvador - Bahia - Brazil period. The Patio is built in combinations of two rows of about 2.4 meter width. The rows consist of 6 identical levels with litter belts above each other. Every level has its own egg tray-transport system, and feeding and drinking line. At slaughter age, broilers are harvested automatically with the use of the litter belts on which the broilers are housed. Ventilation, heating, and humidification are controlled automatically. Combining the hatching and the growing phase, the Patio system is used as a replacement for the hatcher for the last days of incubation and for the traditional broiler farm. HatchBrood is a system that is designed to optimize the brooding conditions for the first days of a chicken s life (www.hatchbrood.com). After hatching, day-old chickens are placed in the HatchBrood unit. The HatchBrood unit can hold up to 39,600 chickens and is divided in 12 sections (Figure 3). Each section contains dolleys with CradlesTM holding the chickens. Inside the unit, air temperature, relative humidity, and CO 2 are monitored and automatically adjusted to the settings. The CradlesTM inside the HatchBrood unit contain 50 chickens each and have a surface area of 4,000 cm 2 (Figure 4). Each individual CradleTM contains two feed troughs on both sides, which are loaded with feed for the complete HatchBrood cycle. The radiators are equipped with drinking gutters and lights. After 4 days in the HatchBrood system, chickens are transported to the farm. The HatchBrood system is used as an extension of the hatchery and older chickens are delivered to the broiler farm. Conclusion In conclusion, understanding the specific requirements of posthatch birds and subsequently adjust the brooding conditions is important to improve performance, animal health and welfare. 4 Figure 3 -HatchBrood unit with 6 sections on the left side, with the doors closed, and six sections on the right side, with the doors open. Figure 4 - HatchBrood cradle TM with feeding trough and drinking gutter. References BAARENDSE, P.J.J., KEMP, B. and VAN DEN BRAND, H. (2006) Early-age housing temperature affects subsequent broiler chicken performance. British Poultry Science 47:125-130. BAR SHIRA, E., SKLAN, D. and FRIEDMAN, A. (2005) Impaired immune responses in broiler hatchling hindgut following delayed access to feed. Veterinary Immunology and Immunopathology 105:35-45. BATAL, A.B. and PARSONS, C.M. (2002) Effects of age on nutrient digestibility in chicks fed different diets. Poultry Science 81:400-407. CHARLES, D.R. (1986) Temperature for broilers. World s Poultry Science Journal 42:249-258. CHRISTENSEN, V.L. (2009) Development during the first seven days post-hatching. Avian Biology Research 2: 27-33. COHEN, R. (2009) The need for prudent use of antibiotics and routine use of vaccines. Clininal Microbiology and Infection 15:21-23. DEATON, J.W., BRANTON, S.L., SIMMONS, J.D. and LOTT, B.D. (1996) The effect of brooding temperature on broiler performance. Poultry Science 75:1217-1220. DIBNER, J.J., KNIGHT, C.D., KITCHELL, M.L., ATWELL, C.A., DOWNS, A.C. and IVEY, F.J. (1998) Early feeding and development of the immune system in neonatal poultry. Journal of Applied Poultry Research 7:425-436.

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XXIV World s Poultry Congress 5-9 August - 2012 Salvador - Bahia - Brazil resistance against cold exposure in young broiler chickens. Poultry Science 89:716-720. VAN DUIJN, P.J., DAUTZENBERG, M.J.D. and OOSTDIJK, E.A.N. (2011) Recent trends in antibiotic resistance in European ICUs. Current Opinion in Critical Care 17:658-665. WEYTJENS, S., MEIJERHOF, R., BUYSE, J. and DECUYPERE, E. (1999) Thermoregulation in chicks originating from breeder flocks of two different ages. Journal of Applied Poultry Research 8:139-145. 6