Broodiness and Broody Hen Management During Egg Incubation
2022 年 10 巻 p. 337-343
詳細
2022 年 10 巻 p. 337-343
Broodiness behavior is usually seen in avian species. This behavior is dominant in wild birds and indigenous poultry compared to modern egg-laying strains. Eggs laid by indigenous chickens are usually hatched by the broody hens. Due to broodiness behavior, the broody hen sits on a clutch of eggs and incubates them to get offspring. Small-scale farmers generally depend on the broody hen to procure chicks. Like an artificial egg incubator, the broody hen controls temperature, humidity, aeration, and turning by herself. The hatchability of broody hen reported seems similar to an artificial egg incubator. The broody hen might be acknowledged as a natural incubator for operational efficiency and effectiveness. Although broodiness is associated with reduced egg production, it contributes a significant role in enhancing the rural poultry population by supplying chicks. Moreover, the loss of egg production due to broodiness can be minimized through management interventions. The importance of broodiness, broody behavior, regulation of broodiness, performances of broody hens, and their management have been discussed in this study.
Broodiness is a natural behavior to incubate a clutch of eggs for the purpose of getting offspring. Broodiness is usually seen in female birds, but certain male birds and non-avian species also show this behavior [1]. After laying a clutch of eggs, the female birds usually become broody and sit on the eggs to incubate them. The behavioral pattern of broodiness varies in several avian species. The cuckoo bird does not show this behavior, but they lay eggs in the nest of other birds [2]. There are some species where both male and female partners contribute to incubate and take care of offspring. In pigeons, broodiness can be seen in both male and female partners [3]. Broodiness consists of two parts: incubation process and brooding of animals [4]. To complete the broodiness period, the broody hen passes a considerable period of time without egg-laying. As broodiness hampers egg production, the scientists have worked on it and developed layers of non-broodiness character. Due to continuous selection and breeding, the incubation behavior has changed or extinct over the time in several species, but this behavior is essential in wild birds to maintain their existence.
The modern poultry is reared for specific production purposes, either for meat or egg production. In modern poultry industry, broodiness is a nuisance as production loss is associated with this behavior [5]. With the advancement of science and technology, egg incubator has been introduced in the poultry industry to hatch lots of eggs artificially. Along with the modern poultry industry, the rural poultry is also contributing an important role since the beginning of poultry production [6]. In many countries, the rural poultry contributes the maximum percentage of meat and eggs for the nations [7]. The contribution of rural poultry is more intense in developing countries. Usually, the farmers in the rural areas use broody hens to fulfil chick’s requirements without using artificial egg incubators. The broodiness character in indigenous poultry is important for rural poultry production. To hatch the eggs, broody hen provides optimum temperature and humidity to eggs and maintains turning by herself. The broody hens are working like a natural incubator in rural areas. This study will give an understanding about the broodiness and broody hen management. In this review, the importance and role of broody hen have been discussed.
Though broodiness is a natural instinct, there are several factors that might affect intensity of broodiness in avian species.
a) Breed or strain: Broodiness is a heritable trait in poultry [8]. There are hundreds of chicken breeds and varieties in the world having specific broodiness characters. These chicken breeds are generally included into Asiatic, Mediterranean, American and English classes. Breeds of each class possess specific broodiness character. Generally, Asiatic breeds show high broodiness, Mediterranean breeds show low broodiness, English and American breeds show medium broodiness character. The broodiness character also varies among the breeds categorized into egg, meat, dual and ornamental purposes on the basis of their utility [9]. Generally, high egg-laying birds show low broodiness character, meat type birds show high broodiness and dual-purpose birds show moderate broodiness character. b) Age of the bird: Age of bird is related with the intensity of broodiness in the hen. Usually, young birds show less broodiness character. Chicken at age of 41–47 weeks may be suitable for selecting broody hens [10] as the medium aged (40–61 weeks) hens give high hatching percentage compared to early and old aged birds [11]. c) Season of broodiness: The incubation season is also important as both the farmers and broody hens prefer to incubate eggs at a particular period of the year. The highest percentage of hatchability by broody hen was reported during winter season [11]. The farmers prefer October–December for incubating eggs due to availability of feed and high chick survivability during this period [12]. Possibly, photoperiodism plays an important role in regulating egg laying and broodiness character. [13]
The farmers rearing backyard chickens and ducks usually incubate the eggs by broody hens. Egg hatching capability by broody hen is shown in Table 1. The broody hen provides optimum conditions needed for egg hatchability by herself [14, 15]. Egg incubation by broody hen is presented in Figure 1. The activities of broody hen are described briefly: a) Temperature: The body temperature of hen ranges from 40–41 °C. During incubation period, the temperature transfer by broody hen to eggs is about 38–39 °C [16]. To heat transfer, the broody hen undergoes molting processes. Feathers from the underside of hen are molted, the skin becomes thickened and blood flow increases to the skin. The featherless skin becomes warm and transfers the heat to eggs, thus helping the eggs to keep warm [17]. b) Turning: Turning of eggs are important to prevent adhesion of embryo to shell membrane. Research result shows egg turning 24 times a day at 45° angle gives high hatchability when egg is incubated in artificial incubator [18]. Though the frequency and positioning of egg turning are unknown at natural incubation process, broody hen maintains the egg turning by her body movement. The turning is specially done when the hen moves from the nest and return to the nest by her body movement [16]. c) Ventilation: Ventilation of eggs is important and broody hen provides fresh air around the eggs by spreading her feathers [16]. d) Humidity: Humidity of eggs may be controlled by sweating the skin of broody hen or egg itself to maintain humidity for egg incubation [16]. e) Cooling of eggs: Cooling of eggs is also important during egg incubation. Eggs become cooler when the broody hen leaves the nest. In natural incubation period, the hen leaves the nest for about 30 minutes during the first 15–18 days but the hen rarely leaves the nest during the last 3 days of incubation [16]. f) Performs like a brooder: The thermoregulatory system is not developed in newly hatched chicks [19]. Brooding is an important part of poultry rearing to develop thermoregulatory system in chicks. The broody hen works like a brooder. The hen gives warmth to the chicks by sharing temperature from her body. g) Feeding and watering of chicks: The broody hen helps to breakdown large feed particles and share the small feed particles with the chicks (Figure 2). During rearing period, the broody hen teaches their chicks how to eat feed and social interaction which might help them to be more positive and responsible when they will be a broody hen [20]. h) Protects the birds from predator: Most of the birds in rural areas are reared under scavenging conditions. In rural areas, birds have to face the predators such as crows, mongooses, eagles, and foxes surrounding them [21] . The loss of chicken in rural area due to the predators of foxes, crows, mongooses and eagles are remarkable. The mother hen minimizes the loss of chicks during early life of chicks by covering the chicks under her feathers. The broody hen may also influence in the development of chick behavior [21].
Figure 1: Egg incubation by broody hen
Figure 2: Rearing of chicks after egg incubation
The indigenous birds having broodiness character undergo a sequence of behavioral changes to complete the brooding cycle. The behavioral pattern within the brooding cycle is almost consistent and happens sequentially. The cycle starts from the beginning of broodiness behavior to return this behavior after incubation, brooding and rearing, and egg-laying [22]. The broodiness cycle of indigenous hen is shown in Figure 3. To incubate eggs, the broody hen sits on a clutch of eggs (12–17 eggs per clutch) after egg-laying. She incubates chicken eggs for 21 days. After hatching, the mother hen rears the chicks for up to 63–84 days or start egg-laying again. Each cycle covers on average 96–122 days, thus 3–3.5 cycles per year [23, 24, 25]. However, hens with previously experienced brooding show a comparatively shorter brooding cycle [26]. Intervention to improve management may increase the number of cycles from 3 to 6 through shortening total days per cycle from 122 to 68 days [25].
Usually, the indigenous hen starts to incubate their eggs after laying a clutch of eggs. This broodiness character might lead to several changes at behavioral and physiological level of broody hen. The broody hen starts to sit persistently during the last five days before fully broody, show reluctancy to get up off from the nest even there is no eggs in the nest [27]. If she leaves the nest once or twice a day, return quickly after feeding and drinking. The feed and water intake reduce during the broody period [28]. She becomes aggressive and may bite if somebody try to reach near her nest or touch the eggs under her. She fights with other hens or species to protect the eggs in nest [29].
Broodiness is regulated by central nervous system [30]. Several studies reveal the association of hormonal regulation with egg-laying to incubation behavior in birds. The most studied hormones during the incubation period are luteinizing, progesterone and prolactin. These hormones are considered to be related with egg-laying to incubation in birds. The concentration of these hormones varies depending upon the stage of egg production, incubation and rearing of chicks by broody hen. During egg-laying period, the concentration of luteinizing hormone and progesterone in the blood is high. Their concentration decreases during the incubation period (Table 2). On the other hand, prolactin concentration decreases during peak egg production [31] and increases during incubation period [4, 27, 32, 33]. It emphasizes that prolactin induces broodiness [34, 35], and luteinizing and progesterone induces egg production in birds. If a hen become broody, she stops egg-laying and become busy to incubate her eggs. After broodiness period, prolactin concentration decreases sharply [36] and increases the luteinizing and progesterone hormone to initiate egg laying [37]. Again, when nests are allowed the reserve situation happens [35]. Another reported hormone thyroid is probably play important role in losing incubation behavior in chicken like Leghorn breed [38].
| Sources of hatching eggs | Body weight of broody hen (g) | No. of eggs set/hen | Hatching egg weight (g) | Hatchability (%) | References |
|---|---|---|---|---|---|
| Rhode Island Red (RIR) ♂ × Fayoumi ♀ | 800–1100 | 8–17 | Av. 41.3 | 85–89.2 | Azharul et al. [28] |
| RIR ♂ × Fayoumi ♀ | 960–1300 | 10–16 | Av. 42.2 | 83.3 | Roy et al. [39] |
| Deshi, Fayoumi, RIR and Sonali | - | 16 | 35.8–50.5 | 82.2–93.3 | Jahan et al. [40] |
| Deshi | - | 20 | Av. 36.3 | 74.67–100 | Islam et al. [41] |
| Fayoumi, Sonali | - | 12 | 40–42 | 86–90.2 | Miazi et al. [42] |
| Fayoumi ♂ × RIR ♀ | 1585 | - | 40.5 | 87.5 | Barua et al. [43] |
-: not indicated in the original paper
| Broody hens | Hormones (ng/ml) | Laying period | Incubation period | References |
| Bantam chicken | Plasma progesterone | 0.45±0.06 | 0.18±0.04 | Sharp et al. [32] |
| Plasma luteinizing | 2.31±0.17 | 0.87±0.09 | ||
| Plasma prolactin | 122 ±4.4 | 217±12.8 | ||
| White Rock hens | Plasma progesterone | 0.45±0.03 | 0.13±0.004 | Bedrak et al. [33] |
| Plasma luteinizing | 1.64±0.09 | 1.15±0.04 | ||
| Plasma prolactin | 16.43±0.98 | 51.10±1.70 | ||
| Bantam chicken | Plasma luteinizing | 3.76±1.45 | 1.12±0.26 | Lea et al. [27] |
| Plasma prolactin | 24.1 ±10.3 | 78–262.7 |
There are some birds show high broodiness, whereas others show less or non-broodiness character. The hen aged more than one year and having broody characteristics should be selected for this purpose. Keeping some eggs or dummy eggs in the nest for long time may encourage the hen to go broody. The nesting materials should be comfortable for birds. There should be plenty of feed and drinking water near the nest to discourage movement of broody hen. There is a prevalence of ectoparasites such as lice, mites, tick, and flea in backyard chicken, and control of these ectoparasites are important for smooth functioning of broody hen [44]. After egg hatching, the hen becomes engaged to brood and rear her chicks for a long time. Generally, non-broody hen produces more eggs than broody hen, but the compensation of egg loss can be managed through improved management during broody and non-broody period of hen [5]. It is important to rear the chicks separately for quick return of hen to start egg-laying again. Each cycle can be shortened through management interventions like chick separation and practices of creep feeding (Figure 4). The creep feeding play important role to gain high body weight of chicks and reduce chick mortality [45]. As the chicks get older the broody hen gives less time to brood and rear her chicks and return quickly to start egg-laying. If broodiness is not desired, the behavior might be reduced through several interventions from being going a hen broody [46]. Immediately after laying eggs, remove the eggs from the egg laying box. The broody hen should be kept away from the nest after egg-laying. To break the broodiness, there are some practices in the rural areas like placing uncomfortable materials in the nest that discourages the hen from going broody.
Figure 4: Creep feeding (separation of chicks, providing additional feed and management)
Broody hen can incubate eggs efficiently with high percentage of hatchability. She provides optimum temperature, humidity, ventilation and other essentials efficiently to hatch eggs as a natural incubator. After hatching, she broods the chicks and protects them from predators. Though broody behavior reduces egg production, the loss may be minimized through improve management interventions.
The author acknowledges Rushmila Jahan Rupa, student of Faculty of Animal Science and Veterinary Medicine, Patuakhali Science and Technology University for drawing Figure 1, 2 and 4.
