Effect of Farming Condition on Postnatal Growth and Development of Lymphoid Organs and Tissues in Deshi Chicken (Gallus domesticus) of Bangladesh

Deshi or native chicken is a major local chicken breed in Bangladesh. This breed is being reared in Bangladesh for a long period of time and it has contributed about 19.75 and 25.06 per cent of total meat and egg production, respectively (Dutta et al., 2013). Most of the farmers, particularly village women reared these chickens. For this reason, these chickens are usually regarded as a “Walking Bank or Bank Coin” for the rural poor families. These chickens are frequently reared in free range farming system where they scavenge for feeds during the day time and are confined at night. They usually take kitchen waste, seeds, grains, garden leftover, insects, green grasses and all other human refusal that would otherwise go to waste. Attaining approximately 1.0 kg at 6 months of age in free range farming system (Rahman et al., 2003; Islam et al., 2012), their body weight also increases if being reared in intensive farming system (Ershad, 2005). The lymphoid organs of chicken, viz. bursa and thymus and tissues, viz. spleen and cecal tonsils, plays significant roles in the prevention of disease occurrence (Khalil et al., 2002; Tizard, 2013). Studies on the lymphoid organs of chicken have revealed that the growth and development of lymphoid organs and morphology and functions of tissues are related with the growth of chickens (Ciriaco et al., 2003). In turn, the growth rates of chickens are related with their rearing systems (Ershad, 2005).
                 
Many scientists have studied the postnatal growth and development of lymphoid organs in different high yielding birds like Broiler chicken (Nagy and Olah, 2010; Khenenou et al., 2012; Khan et al., 2014), White Leghorn chicken (Betti et al., 1991; Del Moral et al., 1998; Kozuka et al., 2010), Aseel chicken (Haseeb et al., 2014), CARI Shyama and Vanaraja chickens (Jain et al., 2010), Guinea fowl (Onyeanusi et al., 1994) and Geese (Gulmez and Aslan, 1999). A few number of research were conducted on gross and histomorphology of the postnatal lymphoid organs of deshi chickens in Bangladesh (Khalil et al., 2002), with the results being compared to broiler chickens as well as other high yielding chickens. The reports on postnatal growth and development of lymphoid organs of deshi chickens reared in intensive farming system are scanty. Some authors have also reported that due to scavenging nature, the postnatal lymphoid organs of deshi chickens contain more immunocompetent cells than that of high yielding chickens (Khan et al., 2007; Islam et al., 2012). Therefore, from economic, nutritional and immunological point of view, this study was conducted to explore the effect of farming conditions on the postnatal growth and development of lymphoid organs and tissues in deshi chickens of Bangladesh.

Rearing of chicken
 
A total of 40 day-old non-descriptive deshi chicks were collected and categorized into two groups of 20 each. Subsequently, the chicks were reared in both scavenging (traditional or free range system) and intensive farming system up to 180 days in Chittagong district (sub-division) of Bangladesh according to Banerjee (1978).
 
Collection of lymphoid organs and tissues
 
The chickens were routinely collected at D₁ (day-1), D₃₀, D₉₀ and D₁₈₀ and then sacrificed by ‘halal’ method. After separation of lymphoid organs and tissues (bursa of Fabricius, thymus, spleen and cecal tonsil), samples were washed with normal saline solution.
 
Morphometry
 
Color and shape of lymphoid organs and tissues were recorded after collection. Weights of individual lymphoid organs and tissues were measured in grams (g) by using a sensitive electronic balance (Mettler Toledo B154, ± 0.001 g, China). The height of bursa of Fabricius; length of thymus, spleen and cecal tonsils and the width of bursa of Fabricius, spleen and cecal tonsils were measured in centimeter (cm) using slide calipers (0-150 digital caliper, Shinko Denshi Co. Ltd, Japan) and calibrated scales.
 
Tissue processing
 
For histological study, sections of the tissue samples were fixed in 10% neutral buffered formalin for a period of 72 hours followed by processing and staining with H and E stain according to Gridley (1957).
 
Histomorphometry
 
For obtaining histomorphometric data, fivephotomicro-graphs were taken from each age group of lymphoid organs and tissues of both SDC and CDC by using a photomicroscope (AmScope Trinocular Compound Microscope, Model T490 B-MT). AmScope image measuring software (x86, 3.7.3036 version) was used for measuring the actual length, height and width of respected lymphoid organs and tissues and was expressed in micrometer (µm).
 
Data analysis
 
The recorded data in excel sheet (Microsoft Excel-2007) were transferred to statistical software, STATA-13 (STATA Corp., Texas, USA) and unpaired sample t-test was done to compare means of different variables between two chicken groups (SDC and CDC). A p-value of equal to or less than 0.05 (P≤0.05) was considered as significant for this test and results were expressed as Mean ± SD.

Morphometry
 
Bursa of Fabricius
 
In the present study, the mean weight, height and width of bursa in both SDC and CDC gradually increased from D₁ to D₉₀ and the highest mean values of those parameters (2.04 ± 0.11 g, 1.48 ± 0.08 cm and 1.04 ± 0.11 cm, respectively) were found at 90 days old CDC (Fig 1). The respective values for highest weight, height and width of bursa were 3.0 g, 3.0 cm and 2.0 cm, in 120-150 days-old Hybrid chicken (Getty, 1975), 1.95 g, 0.6 cm and 0.31cm, in 70-80 days-old Broiler chicken (Khenenou et al., 2012) and 3.8 g, 5.0 cm and 0.7 cm, in 180 days-old Duck (Sultana et al., 2012). It was also found that the mean weight, height and width of this organ were significantly(P≤0.05) higher in all ages of CDC except day-old (D₁) chicks as compared with SDC (Fig 1). This higher weight, height and width of bursa in CDC may be due to their higher growth rate in the intensive farming system as compared with SDC in the free range scavenging system. Jain et al., (2010) pointed out that the size and shape of bursa depend on the species, breed and even farming conditions of the birds. In D₁ chicks, the parameters of bursa of both CDC and SDC were analogous owing to their relatively equal body weights in both the farming conditions. The mean weight, height and width of bursa decreased at D₁₈₀ in both SDC and CDC, indicating the involution of this organ by that age. Involution of bursa started by D₁₄₀ in Broiler chicken (Khenenou et al., 2012), >150 days in White Leghorn chicken and >180 days in Duck (Getty, 1975). Hence, in the present study, the size and involution of bursa in both SDC and CDC varied according to the species and breed.
 

 
Thymus
 
Data in Fig 2 showed that the morphometric parameters of thymus viz. number of lobes, weight and length increased significantly (P≤0.05) with advancement of age from D₁ to D₁₈₀ in both SDC and CDC. These results partially differed from the reports of Getty (1975) who observed that the number of lobes, weight and length of thymus in White Leghorn chickens increased up to D₁₂₀. This dissimilarity may be due to the breed difference. In both SDC and CDC, the number of lobes in thymus varied according to age, with no difference in the same age. Average mean number of thymic lobes on each side of neck was 4.40 to 6.40 in both SDC and CDC, which partially agreed with previous reports of 3-8 on each side of neck in Domestic fowl (Hodges, 1974; King and McLelland, 1984), 6-7 in Guinea fowl (Onyeanusi et al., 1994) and 5-9 in Geese (Gulmez and Aslan, 1999). This partial discrepancy may be due to the variation in species. Contrarily, the mean weight and length of thymus were significantly (P≤0.05) higher in all age groups except day-old chicks of CDC as compared with SDC. This inconsistency with the advancement of age may be attributed to their rearing environment. Comparatively similar weight and length of thymus was found at D₁ chicks in both SDC and CDC as their body weights were relatively equal in both scavenging and intensive farming conditions.
 

 
 Spleen and Cecal Tonsil
 
The mean weight, length and width of spleen (Fig 3) and cecal tonsil (Fig 4) in both SDC and CDC also increased from D1 to D180 in accordance with the reports of Getty (1975), who described that the weight, length and width of spleen and cecal tonsil in White Leghorn chicken also increased with the advancement of age. In the present study, the mean weight, length and width of spleen and cecal tonsil were significantly (P≤0.05) higher in all age groups (except D₁ chicks) in CDC as compared with SDC. The CDC was reared in intensive farming condition where ad-libitum feed and water were supplied thus, their growth rates were higher than SDC. For this reason the mean weight, length and width of spleen and cecal tonsil were higher in CDC than that of SDC. Ciriaco et al., (2003) reported that the mean weight, length and width of lymphoid organs of Hybrid chickens depend on the farming condition as well as their weight gain. In day-old (D₁) chicks of both SDC and CDC, the mean weight, length and width of spleen and cecal tonsils were relatively similar as their relatively equal body weights in both scavenging and intensive farming conditions. On the other hand, maximum mean values of weight, length and width of spleen (3.06 ± 0.18 g, 2.26 ± 0.16 cm and 1.62 ± 0.08 cm, respectively) were found at 180 days-old CDC. Previously reported respective highest mean weight, length and width were 3.0-4.5 g, 2.0-3.0 cm and 1.0-2.0 cm, in 120-150 days-old Hybrid chicken (Getty, 1975), 1.974 ± 0.04 g, 18.93 ± 0.39 mm and 13.45 ±  0.34 mm, in 28 days-old Broiler chicken in Bangladesh (Khan et al., 2014) and 0.18 g, 0.94 cm and 0.68 cm, in 90-120 days-old indigenous Duckling in Bangladesh (Sultana et al., 2012). This dissimilarity may be due to the difference in species, breed and age as reported by Jain et al., (2010) who noticed that the color, weight, length and width of lymphoid organs of Hybrid chicken depended on the breed, age, sex and rearing environment.
 

 

 
Histomorphometry
 
Bursa of Fabricius
 
The comparative histomorphometrical data of bursa of Fabricius are shown in Table 1. The number of mucosal folds in the present study varied from 6-12 (Fig 5), whereas the number of mucosal folds was 12 in Domestic fowl (King and McLelland, 1984), 12-14 in Helmeted Guinea fowl (Onyeanusi et al., 1993), 11-13 in Geese (Gulmez and Aslan, 1999), 8-16 in both CARI Shyama and Vanaraja breeds of poultry (Jain et al., 2010) and 11-13 in Hybrid chicken (Betti et al., 1991). The mucosal folds of the bursa was covered by pseudostratified columnar epithelium except at the apex where it was covered by simple columnar epithelium (Fig 5). Some authors have reported that the surfaces of mucosal folds were covered by pseudostratified columnar epithelium (Hodges, 1974; Onyeanusi et al., 1994) but the others have reported, they were covered by both simple columnar and pseudostratified columnar epithelium (Jain et al., 2010). Jain et al. (2010) found that the respective highest mean value for height of epithelium in CARI Shyama and Vanaraja breeds of poultry were 54.24 ± 1.76 µm, 42.56 ± 2.40 µm; with the height of mucosal folds being 2200± 40.60 µm, 2280 ± 45.00 µm and the number of follicles per fold being 25.14 ± 0.05, 18.98 ± 2.34. These observations indicated that the number of mucosal folds, number of follicles per fold, height of mucosal folds and covering epithelium of bursa varied within breed and species. In this study, the height of epithelium, number of mucosal folds, number of follicles per mucosal folds and height of mucosal folds increased with advancement of age from D₁ to D₉₀ in both SDC and CDC but decreased by D₁₈₀ in both SDC and CDC (Fig 5). These histomorphometrical results indicated involution of bursa by D₁₈₀ in both SDC and CDC. In contrast, all those histomorphometrical parameters of bursa were higher in all age groups in CDC as compared with SDC. The possible causes of these higher results in CDC may be due to their higher growth rate in intensive farming system as compared with SDC in free range scavenging system with expected involvement of other factors also. Kannan et al., (2012) found that the histological structure of lymphoid organs in Hybrid chicken depended on the breed, age, sex and their rearing environment. In day-old (D₁) chicks of both SDC and CDC groups, the mean values of all histomorphometrical parameters of bursa were relatively similar owing to their relatively equal body weights in both scavenging and intensive farming conditions.
 

 

 
Thymus, Spleen and Cecal tonsil
 
Data in Table 2 showed that the mean length and width of thymic lobules (Fig 6), white pulps of spleen (Fig 7) and lymphatic nodules of cecal tonsil (Fig 8) in both SDC and CDC increased with the advancement of age from D₁ to D₁₈₀. Similar findings were also noticed in Broiler chicken by Akter et al., (2006) and Khan et al., (2014) and in Aseel chicken by Haseeb et al., (2014). On the other hand, the mean length and width of lobules of thymus, white pulps of spleen and lymphatic nodules of cecal tonsils were higher in all age groups in CDC as compared with SDC. The body weights of CDC were higher being reared in intensive farming conditions with ad-libitum feed and water. In contrast, the SDC being reared in free range scavenging system and feeding on kitchen waste, seeds and grains, insects, green grasses had a comparatively slower body weight gain than CDC. So, the parameters of these lymphoid organs, viz. length and width of lobules of thymus, white pulps of spleen and lymphatic nodules of cecal tonsils exhibited corresponding higher values in all age groups in CDC. As per the earlier reports, histological structure of lymphoid organs and tissues in Hybrid chicken varied according to the breed, age, sex and rearing environment (Jain et al., 2010; Kannan et al., 2012).
 

 

 

 

 

The higher gross and histomorphometrical parameters of lymphoid organs and tissues in CDC over that of SDC in the present study may be attributed to their different pattern of rearing system. It  indicated that the level of immunity might be better in CDC over that of SDC associated with an advancement of age. Moreover, as indicated by the improved growth rate of deshi chickens in the present study, captive or intensive system is recommended over the scavenging system of rearing.

The authors are grateful to National Science Technology (NST) and Committee for Advanced Studies and Research (CASR), CVASU, Bangladesh for sanctioning research grants to complete this work.