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INTRODUCTION
Duck rearing is an integral part of poultry production in Bangladesh and is considered as the second important poultry species used for egg and meat purposes. Duck population of Bangladesh is estimated to be 57.75 million (DLS, 2019). This is the 5th largest duck population in the world (FAOSTAT, 2019) whereas 90% of them are non-descript indigenous type scattered throughout the country (Hoque and Sultana, 2003). Ducks are very efficient to convert waste resources like insects, weeds, aquatic plants, snails, nuts, bulbs, roots, succulent leaves, grasses and fallen seeds into meat and eggs. Duck meat is popular irrespective of religion, caste and community in Bangladesh. However, the country’s growing demand has been fulfilled partially with the available indigenous and exotic egg type ducks due to absence of suitable meat type duck breed. Farmers also prefer indigenous ducks under traditional husbandry practices owing to higher adaptability to scavenging conditions, better foraging ability and appear to be more resistant to diseases (Pervin et al. 2013; Morduzzaman et al. 2015). Notably, agroecological zones have potential influence on duck demography and concentration. Large-scale flock ranging from around one hundred to thousand is found particularly in the north-eastern wetlands and coastal regions of Bangladesh (Khanum et al., 2005). Apart from this, duck rearing system throughout the country is mostly semi-scavenging with a small number of individuals.
Nageswari (N) is an egg type indigenous duck breed of Bangladesh having black or penciled black plumage color except white in breast region. Under intensive management condition, the average annual egg production was 204.23±14.19 and the 9th week live weight was only 1076.11±16.34 g (Bhuiyan et al., 2017). However, this breed is well adapted to agro-climatic condition and existing management system of Bangladesh (Morduzzaman et al. 2015). On the other hand, Pekin (P) is an exotic meat type duck breed that has been introduced recently in Bangladesh and are being reared commercially by some farmers under intensive management condition. In confinement with adequate nutrients, it grows rapidly up to 2.5-3.0 kg at market age of 8 to 10 weeks and lays an average of 200 eggs per year (Microlivestock, 1991). However, they are not good scavengers and production is largely affected in semi-scavenging condition with poor quality and fluctuating feed supply. Therefore, their adaptability under semi-scavenging condition of Bangladesh is a big challenge for a profitable duck farming. Under the circumstances stated above, reciprocal crossing between Pekin and Nageswari will create opportunity to utilize hybrid vigor in the descendants for increasing meat production potentials without compromising egg production. The better performed crossbreds would be expected more adaptable under semi-scavenging production system of Bangladesh as of their 50% native inheritance.
Crossbreeding is a potential tool for improving growth and production potentials through exploitation of heterosis. Previous studies on intra and inter-generic crossbreeding have been reported to improve productivity, meat quality and reproductive traits (Padhi, 2010; Brun et al., 2012; Matitaputty et al., 2015). Reciprocal crossing is generally used to perform to identify suitable combination for commercial exploitation of production traits. Pekin and Muscovy ducks had significant additive effects on growth performance, meat quality and plumage color parameters (Matitaputty et al., 2015). However, crossbreeding effects on productivity using indigenous Nageswari duck is lacking in the literature. Therefore, the objectives were to investigate the morphological features, growth performance and meat production potentials of reciprocally produced Pekin-Nageswari F1 crossbred ducks under intensive management condition.
MATERIALS AND METHODS
This study was conducted as per guidelines of the Animal Care and Use Committee of Bangladesh Agricultural University (IACUC) and approval was taken from the University Ethical Committee (No.: BAURES/2020 ESRC/AH/03). Pekin and Nageswari breeding flocks were grouped into four different pens in order to get pure Pekin and Nageswari day old ducklings as well as their reciprocal crossbreds. In total, 400 fertile eggs were collected after 2 weeks of group formation and was incubated at Regional Duck Breeding Farm, Mymensingh. The male and female ratio was 1:6 in each breeding flock. A total of 301-day old ducklings were hatched out (hatchability 75.25% based on total eggs). The flocks were maintained up to 20th week of age on perch in a shed at Bangladesh Agricultural University Artificial Insemination Center. Commercial compound starter feed (Quality Feed Ltd., Bangladesh) was provided two times a day during the first four weeks of age while hand mixed compound feed was provided twice daily as per requirement of the dual type duck throughout the growing and pre-laying period. The nutrient contents of the supplied rations are given in Table 1. The shed was cleaned regularly and birds had unrestricted access to drinking water. Ducks were vaccinated against duck plague, avian influenza and duck cholera and vaccination schedule is presented in Table 2. Strict bio-security measures and hygienic control were maintained to ensure healthy environment of duck during the experimental period. Rigorous selection was performed twice at the age of 10th and 16th week based on their growth performance and phenotypic features.
Pekin and Nageswari possess their typical breed characteristics regarding plumage color, morphological features and morphometric measurements. Hence, our aim was to investigate the inheritance of plumage color and pattern, morphological features and morphometric measurements in crossbreds. Six different morphometric traits were investigated in this study such as shank length, neck length, body length, wing length, bill length and shank circumference.
Weekly live weight was recorded from day old to 12th week of age and then fortnightly live weights were recorded up to 20th week of age. To make homogeneity of data, live weight was always taken in the morning before supplying feed and water. Based on the recorded information, several production efficiency indicators like growth rate (g/bird), feed conversion efficiency were estimated.
A total of 16 ducks (8 males and 8 females) were selected randomly and were slaughtered at 12th week of age (marketing age) having 4 individuals (2 males and 2 females) from each genotype. The slaughtered birds were allowed to bleed thoroughly and were subsequently dressed, eviscerated and dissected as per description of Ferdaus et al. (2015). The investigated traits were average live weight (g), neck weight with skin (g), carcass weight without giblet (g), dressing (%), heart weight (g), liver weight (g), gizzard weight (g), back half weight (g), drumstick with thigh weight (g), drumstick weight (g), thigh weight (g), wings weight (g), back weight (g), breast meat weight (g) and keel bone length (cm).
Data on growth, meat production, morphology and morphometric traits were screened and compiled in excel spread sheet. All sorts of descriptive statistics such as mean, standard error, frequency, percentage and ANOVA were performed using SAS software for windows (SAS ver. 9.1.3). Sex of the birds were fitted as fixed effect in the analysis. Mean separation procedures were computed using Duncan’s Multiple Range Test (DMRT).
RESULTS
The morphological features and their distributions are presented in Table 3. Pekin and Nageswari ducks possessed their typical breed characteristics. Here, our main focus on the inheritance of plumage color and pattern, and morphological features in P♂ × N♀ and N♂ × P♀ crossbreds. Typically, the black color was predominant over white color for all considered traits. However, there are considerable differences have been observed regarding plumage color and pattern between these two crossbreds. In particular, the head color was equally distributed as white spotted black (50%) and only black (50%) in P♂ × N♀ genotype while it was almost black (91.17%) in N♂ × P♀ crossbred. Breast color of P♂ × N♀ genotype was mostly white in color (93.33%) that extended up to belly but N♂ × P♀ possessed black with white spotted breast (91.17%). Wing color of two crossbreds was distinct, the P♂ × N♀ genotype had white primary and secondary feathers (80%) while complete black wing except few white primary feathers was observed (94.12%) in N♂ × P♀ crossbreds. The bill, shank and web color of P♂ × N♀ genotype was found dominantly yellowish or yellowish black. On the contrary, N♂ × P♀ crossbred genotype had mostly black and black with yellowish tint for the aforementioned traits.
Table 4 represents morphometric features of Pekin, Nageswari and their reciprocal crossbred ducks. The morphometric traits like neck length, shank circumference and body length had highly significant differences among the 4 genotypes (P<0.01). There were insignificant differences (P>0.05) observed among the four genotypes for wing length and shank length trait. However, bill length was highly significant among the four genotypes (P<0.01) in female while it was non- significant in males. The highest body length was found in exotic Pekin ducks and the lowest was in Nageswari ducks while the two crossbreds placed in intermediate position with insignificant differences.
Growth performances of Pure Nageswari, Pekin and their reciprocal crossbreds under intensive management up to 12th week of age are presented in Table 5. Growth performances were highly significant among the genotypes (P<0.001). As expected, pekin ducks had the highest growth performance throughout the experimental period while Nageswari attained the lowest live weight among the 4 genotypes during the stipulated time. The average live weights of Pekin, Nageswari and two other crossbreds (P♂ × N♀ and N♂ × P♀) at day old and 12th week of age were 46.06±0.64 and 2038.35±29.74; 37.93±0.60 and 1542.44±33.61; 46.52±0.85 and 1851.85±28.59 and 42.18±0.48 and 1691.08±27.80 g, respectively. It is notable to mention that the P♂ × N♀ crossbred occupied 2nd position next to Pekin for growth performance. At marketing age (12th week), Pekin and P♂ × N♀ F1 crossbred gained about 500 g and 250 g more live weights, respectively, than pure Indigenous Nageswari duck of Bangladesh. In addition, the mortality rate was found only 3.98% up to 12th week of age (data not shown).
In total, 15 different meat yield parameters were investigated in this study and are presented in the Table 6. All of the considered traits varied significantly among the 4 genotypes except the traits’ liver and gizzard weight. The average eviscerated hot carcass weight of Pekin (1082.75±43.20 g) and two other crossbreds (1033.75±60.68 and 1031.25±48.85 g, respectively) had highly significant differences with Nageswari ducks (774.50±38.98 g). Accordingly, the dressing % was non-significant among the three genotypes (Pekin, P♂ × N♀ and N♂ × P♀) but differed significantly with Nageswari duck.
In addition, the significantly contributed meat yield traits like back half weight, drumstick with thigh weight, drumstick weight, thigh weight, wing weight and breast meat weight had insignificant differences among the Pekin, P♂ × N♀ and N♂ × P♀ genotypes. The drumstick with thigh weight was found 272.00±10.86, 252.75±13.37, 252.75±21.39 and 195.75±10.18 g in N♂ × P♀, Pekin, P♂ × N♀ and Nageswari ducks, respectively. However, breast meat yield, wing weight and hot carcass weight without giblet was found higher in Pekin duck.
DISCUSSION
Crossbreeding experiment have been performed across the world utilizing different duck populations for harnessing the heterosis effect in crossbreds. But those type of experiments are scare particularly in Bangladesh that limits to compare our results with previous literature. To our knowledge, this study is the first report involving P, N and their reciprocal crossbreds under intensive management condition of Bangladesh. The appearance of P × N F1 crossbreds was almost similar with N ducks with some variations in the web, shank, wing and breast regions. This is might be due to influence of dominant E locus as black color dominant over white color in mammals and birds. Our result is similar with the findings of Lin et al. (2014) who reported Putian black colored duck exhibited full expression of extended black (E gene) over white and multicolored egg type Chinese duck breeds. E locus is controlled by at least 11 different multiple alleles those involve in the plumage colors and patterns of domestic fowl (Crawford, 1990) that corroborates the present findings. In addition, the c.52 G>A and c.376 G>A substitutions of MC1R gene associated with extended black variants (E allele) in domestic duck (Yu et al., 2012) and the reconstructed haplotype (AAGC) of this gene showed association with the plumage color of Nageswari duck that possessed an extended black phenotype (Sultana et al., 2017). All of the previous studies reported that the black phenotype in domestic ducks is caused by a gain‐of‐function mutation in the extended black (E) locus which harbored by the MC1R gene.
All of the morphometric traits of this study varied significantly among the genotypes except shank and wing length in both males and females. Similar to our findings, Henrik et al. (2018) reported that reciprocal crosses increased the morphometric measurements in Indonesian local duck populations. They found that body weight, chest circumference, body length and neck length were highly significant (P<0.01) among Indonesian Tegal, Megalang and their crossbred ducks. Kokoszyński et al. (2019) found significant differences in all body measurement traits like neck length, trunk length, chest circumference, keel length, thickness of breast muscles, drumstick length and shank length among three lines of Pekin ducks at 49th day of age and is consistent to the present findings. According to Yakubu et al. (2011), the morphometric traits like body weight, neck length, foot length and thigh circumference differed significantly between two Muscovy populations and supports this study. Padhi and Sahoo (2012) found significant differences (P<0.05) for shank and keel length among Indigenous, Khaki Campbell, White Pekin and their crossbreds. They observed positive heterosis (%) estimates for these two parameters. Altogether, earlier studies showed that diallel and reciprocal crossing had positive effects on morphometric traits in different duck breeds.
Similar to the findings of this study, Heo et al. (2015) reported that weekly live weight of two commercial Korean native ducks and their reciprocal crossbreds differed significantly (P<0.05) except 2nd week of age. However, their average live weights were significantly higher as compared to this study at 2, 4, 6, and 8 weeks of age to be 625, 1,617, 2,466, and 2,836 g, respectively. These differences might be attributed with breed or genotype, quantity and quality of supplied feed. The weekly live weight of three Pekin lines differed significantly in both sexes up to 7th week of age except the 2nd week of age. Apart from this, greater paternal influences have been observed in most crossbred ducks during 6th to 8th week of age for growth rate and meat yield characteristics (Górska et al., 2014) and is similar to this study where Pekin male mediated P♂ × N♀ crossbred had better yield than the N♂ × P♀ genotypes. Prasetyo and Susanti (2000) reported that crossbreeds between Alabio and Mojosari duck breeds of Indonesia had potential in improving growth performance and production traits and supports our findings.
Pekin is mainly raised for meat production and the main goal for crossing ducks with this breed is to improve meatiness (Kokoszynski and Bernacki, 2011; Xie et al., 2014). In a crossbreeding study with Pekin, Deshi and Jinding ducks, the breast meat yield was found significantly higher (P<0.05) in (Pekin × Pekin) than that of (Pekin × Deshi) and (Pekin × Jinding) crossbreds (Ansary et al., 2008) and is consistent with the present study. Similar to the present findings, Kokoszyński et al. (2019) found significant effects on preslaughter body weight, carcass weight, breast muscle yield, neck weight, liver weight and gizzard percentage among the three lines of Pekin ducks. Pekin derived crossbred ducks had better growth rate and meat yield characteristics like breast muscle yield, leg muscle yield and muscle yield in carcass at 8 weeks age (Padhi and Sahoo, 2012; Górska et al., 2014) and support the present results. In conclusion, considering growth, morphology and meat yield characteristics, our results suggested the P♂ × N♀ F1 crossbreds could be an alternative genotype for better meat producing duck in Bangladesh. This crossbred genotype possesses 50% native inheritance and therefore, adaptability would be expected higher under hot and humid conditions of Bangladesh compared to exotic Pekin duck.
