Application of Biotechnology and Husbandry Practices for the Conservation, Characterization and Enhancement of Production Potential of Available Goat Genetic Resource in Bangladesh

Abstract

A goat is a small ruminant found across the globe. However, each and every type of goat has some unique characteristics and is popular for specific reasons in a specific area. The Black Bengal goat is the only recognized goat breed in Bangladesh and is famous for its high fertility, prolificacy, superior skin and meat quality, early sexual maturity, disease resistance and short kidding interval. In this chapter, we focused on available goat genetic resources in Bangladesh, breed characteristics, morphometric characterization, husbandry practices, feed and nutrition used for goat production, productive and reproductive performances under subsistence farming system, disease and health management, biotechnological approach for conservation like estrus synchronization, semen quality analysis, cryopreservation of semen, Artificial insemination, in vitro embryo production of embryos and multiple ovulation and embryo transfer. Moreover, the contribution of goat production in poverty alleviation and women empowerment in Bangladesh was also highlighted. Thereafter, constraints on goat production and future recommendations for sustainable goat production in Bangladesh were given.

1. Introduction

Goats are economically very important and promising animal genetic resources in developing countries, especially in Asia and Africa [1]. Goats are preferred for rearing especially in small holding farming systems due to its unique ability to adapt and maintain them in harsh environments [2]. They are also known as the “poor man’s cow” for their significant contribution to the poor man’s economy [3]. Archeological evidence indicates that the goat was one of the first animals to be domesticated by humans around 10,000 years ago at the dawn of the Neolithic period in the Fertile Crescent [4, 5]. The tropical and subtropical climate in association with topography provides a unique habitat for goats [6]. There are about 300 breeds and varieties of goats domesticated in the Indian subcontinent [2]. Like other domestic goat breeds in South Asia, the Bengal goat is believed to be derived from the wild bezoar of Pasang (Capra aegagrus) with infiltrated blood from markhor (Capra falconeri) [7].

Black Bengal, the only recognized goat breed of Bangladesh, is known for its excellence in reproductive capabilities and production of quality meat [8]. It is one of the most compliant, all-around adjusted, early maturing, prolific, productive, and tropical disease—resistant goat types of the world [9]. Goat meat is more expensive as compared to other livestock and poultry meats [8]. They also contributed to the GDP of Bangladesh by producing quality meat and elegant leather that earns a lot of foreign currency; income generation and poverty alleviation, creating employment opportunities in rural areas as well as cash income for empowering the poor and destitute women [10]. For rearing goats, a minimum investment of money is required, even without specific arrangement of housing, grazing on barren and road-side grassland and least homemade supplied feed (rice gruel, boiled rice, skins of vegetables etc.) in the Indian subcontinent. In addition, goats are fed on the leaves of jackfruits, which are available in most of the rearing areas in Bangladesh [11]. Since goats (Capra hircus) can utilize fibrous plant materials to produce meat, which offers a reliable source of animal protein in developing countries, their abundance may have led to an increasing preference for goat meat in developed countries [12, 13].

2. Methodology

Bangladesh is a hot humid country which lies between 88°01′ to 92°41′ east longitude and 20°34′ to 26°38′ north latitude. Average temperatures in winter raged from 11°C (Min.) to 29°C (Max.) whereas average summer temperatures are 21°C (Min.) and 34°C (Max.). Annual rainfall ranges from 1194 to 3454 mm. The highest humidity is 80–100% in August–September and the lowest is 36% (February–March) [14].

Goat keepers usually reared the goats under a semi-intensive management system in traditional houses. Bucks and does were kept separated tethered by rope and allowed to graze in roadside grass and available pasture land near the farmer’s house. Vegetable kitchen wastes, leftovers from family meals and tree leaves were also fed to the goats. Traditionally concentrate feeds @ 200 g/day were fed only to pregnant and lactating does [15]. Availability of drinking water was ensured all the time.

Measurements of the morphometric characteristics were taken according to [15]. Body weights at birth, 3, 6, 9 and 12 months of age were measured using the weighing balance based on different factors (sex of kid, type of birth, parity of dam, season of the year). The year was divided into three seasons namely winter (November–February), summer (March–June) and rainy (July–October) [16].

Among the reproductive parameters, age at first heat, age at first kidding, service per conception, gestation length, litter size, post-partum heat period and kidding interval were measured according to [1].

Semen collection was done with an artificial vagina (AV) maintaining an optimum temperature of about 41–43°C. Each ejaculate was evaluated for sperm motility, concentration, viability and morphology immediately [17]. After evaluation, semen aliquots were diluted by Triladyl, Andromed and Tris-based diluter separately to obtain a final concentration of 100 million spermatozoa per dose and then filled manually into 0.50-ml straws. One part of the evaluated extended semen was used for AI as fresh semen and another part was used for cryopreservation in liquid nitrogen using the standard protocol [18, 19]. The motility, morphology, viability and membrane integrity of fresh diluted and fresh-thawed semen were evaluated critically. Artificial insemination was done 24 hours [20] after the visible sign of natural or synchronized estrus. It is noteworthy to mention that successful synchronization of estrus was performed by using intramuscular injection of either progesterone or synthetic PGF2α analogue (Dinoprost®) in Black Bengal does [21, 22]. Does were closely monitored for up to 48 hours to record the signs of synchronized estrus behavior. Fertility after AI was calculated as the percentage of inseminated females actually kidding [18]. On the other hand, for multiple ovulation and embryo transfer (MOET), Black Bengal goats (BBGs) were synchronized with Gabbrostim® (Alfaprostol, VETEM, Italy @ 2-mg equivalent to 1 ml/goat), superovulation with PMSG (Folligon®, Intervet International B.V, Holland @ 900 IU, 800 IU and 700 IU, respectively) and test the efficacy of the dose. A surgical procedure was used to flush the embryos [23].

For In vitro production of embryos, goat ovaries were collected from a local slaughterhouse, processed and COCs were collected in three techniques (puncture, slicing and aspiration) and each graded into four grades as described [24]. Normal COCs (A and B grade) were transferred into the maturation medium and kept in a CO₂ incubator at 38.5°C with 5% carbon dioxide for 22 hours. About 15–20 matured oocytes were transferred to each of the sperm drops (sperm concentration 12.5 × 106 per ml) and incubated for 5 hours. Thereafter, the fertilized oocytes were transferred to another culture drop (600 μl) of TCM-199 with 5% FCS and kept in CO₂ incubator. The development was checked in every 48 hrs and the culture was continued up to 6–7 days [25].

In statistical analyses of the data, analysis of variance (ANOVA) was performed using a completely randomized design (CRD) [26] by the Statistical Analysis System (SAS, 1998) package program. Significant differences between the mean values were separated by Duncan’s Multiple Range Test (DMRT) [27].

3. Results and discussion

3.1 Available goat genetic resources

BBG is the most well-known perceived goat breed speaking to over 90% of the all-out goats of the nation [28]. Although various types of goats are available in Bangladesh, BBGs are the most popular and dominantly (almost 90%) distributed throughout the country. Jamunapari goats concentrated in the northern and northeastern parts, Beetal, Sirohi and their crosses in the western part of Bangladesh [29, 30].

3.2 Breed characteristics

BBG is a dwarf goat breed and known to be famous for its high adaptability, fertility, prolificacy, delicious meat and superior skin [12, 31]. BBG is also reputed for its early sexual maturity, better resistance against common diseases, low kidding interval. In spite of having the above qualities, they are inferior in some economic traits such as birth weight, growth rates, milk yield, and kid survivability [9].

3.3 Morphometric characterization of Black Bengal Goat

Morphometric measurement is conducted for the characterization of the breeds of animals as well as the assessment of carcass quantity. Morphometric characterization contributes to the improvement of animal genetic resources in the context of country-level implementation [32]. Morphometric measurement of adult BBG is shown in Table 1.

Traits	Measurements
Body weight	14.05 ± 0.14 to 15.37 ± 0.23 kg [15]; 16.56 ± 0.57 kg [33]
Body length	47.83 ± 0.75 cm [33]; 46.50 ± 0.77 cm [34]
Height at wither	48.50 ± 0.42 cm [35]; 47.92 ± 0.76 cm [33]
Heart girth	59.08 ± 0.87 cm [33]; 55.70 ± 0.20 cm [34]
Ear length	14.21 ± 0.09 to 15.02 ± 0.16 cm [15]; 12.69 ± 0.27 cm [33]
Ear breadth	6.02 ± 0.04 to 6.20 ± 0.04 cm [15]; 5.70 ± 0.20 cm [34]
Head length	16.67 ± 0.26 cm [33]; 15.10 ± 0.56 cm [34]
Head breath	10.51 ± 0.06 to 11.56 ± 0.07 cm [15]; 12.33 ± 0.34 cm at 12 month [33]
Tail length	10.25 ± 0.31 cm [33]; 9.80 ± 0.20 cm [34]
Scrotal circumference	19.72 ± 0.33 cm [33]; 19.60 ± 0.24 cm [34]
Testicular length	9.80 ± 0.37 cm [34]

Table 1.

Morphometric measurement of Black Bengal Goats in Bangladesh.

3.4 Husbandry practices

Due to the hardy nature; resistance to diseases and better adaptability BBGs can reproduce and thereby thrive well under various types of climatic conditions [23]. The poor farmers mainly keep goats in a semi-intensive production system without any supplementation [6]. The majority of landless farmers opted to construct their farm sheds using natural materials such as bamboo, wood or occasionally coconut and straw for the roof. Some of the sheds were constructed of mud and earth. Some farmers put their goats under their beds in the same rooms where they slept [3].

The production system of BBGs in Bangladesh is generally characterized by poor feeding, housing, breeding and health management and consequently low return from sale.

3.4.1 Feed and nutrition used for goat production

Goats are excellent in utilizing tree leaves if provided properly. In terms of the availability of grazing land to the ruminant livestock, the stocking rate is high and supplementation of cereal grain and by-products is a costly proposition to goats for achieving higher productivity [36]. Availability of forages is not constant throughout the year and varies with season particularly, during the cropping seasons when more land is bought under cultivation.

Green grass does not fulfill the appetite and nutrient requirements as a sole feed [37]. Most of the farmers (82%) supplied concentrate feed with the green grass for their goats while very few farmers supplied green grass alone to their goats [38]. Some goat farmers gathered various feed items (wheat bran, broken rice, rice polish, oil cake, and so on) and blended a balanced diet on their farm premises [3]. Most of the farmers used concentrate feed once in a day with green grass and supplied water. Major sources of drinking water for goats were tube well and most of the farmers grazed their goats [39]. The majority of farmers preferred roadside grazing (86.7%) due to enough natural grass around their garden whereas only 8.3% cultivated high-yielding fodder on their own land [3] for feeding the goats. Farmers supplied 2.63 ± 0.05 kg/day of green grass, 60.00 ± 5.86 g/day concentrate and 0.62 ± 0.03 kg/day of tree leaves per animal during the lactation stage [38]. Concentrate supplementation is undoubtedly important to meet up the nutrient requirements, and to get the best result it can be supplemented up to 30% of the required DM. Under the stall feeding system, a concentrate supplementation with 15.60% CP is recommended for improving the growth performance of BBGs in Bangladesh [37].

3.4.2 Disease and health management

Hot and humid conditions in Bangladesh favor various diseases [40, 41]. The disease impairs the productivity of animals and incurs huge veterinary costs. The productivity of densely populated goats is poor due to the incidence of disease [42]. The common causes for goat morbidity and mortality in rural areas were: (a) viral diseases such as PPR, contagious ecthyma, goat pox and viral pneumonia; (b) bacterial diseases like brucellosis, tetanus, enterotoxaemia, mastitis and metritis; (c) fungal diseases such as ringworm infection and (d) rickettsial infections like conjunctivitis [43].

Among these infectious diseases, Peste des petitis ruminants (PPR) has become an important disease due to its effect on direct economic losses. PPR is an acute and extremely infectious viral disease that severely affects goats. The common symptoms were high fever, mucopurulent nasal and ocular discharge, pneumonia, necrosis, erosive stomatitis, ulceration of mucous membranes and inflammation of GI tract resulting in severe diarrhea. Age categories of goats, sex, breed and seasonal influence were found to be significantly associated (p < 0.01) with the prevalence of PPR. The susceptibility of BBGs to PPR was higher than other breeds [44].

Among the seasons of the year, the occurrence of various infectious diseases was higher in the rainy season (36.43%) followed by the winter season (34.94%) and summer season (28.62%). In respect of sex, the female goat was found to be more susceptible (64.22%) than the male (35.77%) [45].

The highest incidence of gastro-intestinal infection was diarrhea (31.1%) and the second highest incidence was pneumonia (27.4%). Several other diseases like lameness (9.0%), mange (6.2%), contagious ecthyma (4.4%), malnutrition (3.2%), fever (2.7%), conjunctivitis (2.6%), bloat (2.1%), abortion (1.7%), mastitis (1.7%), tympany (1.5%), abscess (1.1%), actinomycosis (1.1%), poisoning (0.8%), retained placenta (0.6%) and urolithiasis (0.4%) [46]. Large flock size was more infected to parasitic infestation (both by ecto- and endoparasites) than the smaller ones and this is due to direct contact, overcrowding and unhygienic condition of the goat farm. Usually, goats are maintained on the muddy floor in rural areas. Goats maintained on the muddy floor were infected more with parasitic infestation than the slatted floor and this may be explained as due to low level of hygiene and favored reinfestation [46]. Goats often suffer from a wide variety of surgical affections; e.g., gid disease, wound, urolithiasis, lymphadenitis, subcutaneous cyst, fracture, myiasis, bloat and so on and all these are curable if surgical intervention is performed at an appropriate time [47, 48].

Kid mortality was found 15.0 ± 0.50% in semi-intensive conditions and 10.07 ± 0.32% in extensive conditions [49] and the average kid mortality rate was 12.88% at farmers’ houses [50]. Kid’s mortality was due to infectious disease (63%), predators (10%), mechanical (4%) and congenital (1%). Among the infectious diseases, kid’s mortality was recorded as 30, 27, 23, 17 and 2% by diarrhea, pneumonia, bloat, enterotoxaemia and ecthyma, respectively [51]. Overall adult mortality was 12.69% [51]. Better housing, management, routine vaccination and timely deworming can reduce mortality as well as ensure better health management and higher productivity.

3.5 Productive performance

Adult body weight is an important economic factor that influences the growth and production pattern of any goat enterprise and has more influence mainly on the growth behavior of kids [52]. Average daily gain (g/d) was 43.29 ± 1.82 at birth to 3 months, 39.50 ± 1.91 at 3–6 months, 26.48 ± 1.99 at 6–9 months and 23.04 ± 1.30 at 9–12 months in the semi-intensive system of rearing in rural areas [53]. On the other hand, in the fully intensive management system body weight gain were 66.34 ± 1.69, 41.54 ± 2.02, 49.97 ± 3.10 and 39.28 ± 4.35 g/d, respectively. Average daily milk yield, lactation length and total milk per lactation were 287.7 ml/d, 61.5 days and 19129.40 ml, respectively [54]. Body weight differed in respect of sex, type of birth, parity and season of birth which is illustrated in Table 2.

Factors	Body wt. (kg)
	Birth	3-month	6-month	9-month	12-month
Sex of kid
Male	1.3 ± 0.10 [16]; 1.16 ± 0.07 [55]	5.20 ± 0.6 [16]; 5.70 ± 0.21 [55]	8. 90 ± 0.8 [16]; 8.65 ± 0.11 [55]	13.20 ± 0.60 [16]; 11.55 ± 0.33 [55]	17.9 ± 0.70 [16]
Female	1.2 ± 0.1 [16]; 1.07 ± 0.07 [55]	4.50 ± 0.6 [15]; 5.01 ± 0.17 [55]	8.10 ± 0.8 [16]; 7.40 ± 0.21 [55]	10.10 ± 0.5 [16]; 9.93 ± 0.30 [55]	12.10 ± 0.5 [16]
Type of birth
Single	1.40 ± 0.1 [16]; 1.11 ± 0.01 [55]	5.50 ± 0.5 [16]; 5.48 ± 0.19 [55]	8.60 ± 0.5 [16]; 8.58 ± 0.13 [55]	12.70 ± 0.7 [16]; 11.66 ± 0.31 [55]	16.50 ± 0.5 [16]
Twin	1.30 ± 0.1 [16]; 1.09 ± 0.01 [55]	5.3 ± 0.4 [16]; 5.23 ± 0.16 [55]	7.70 ± 0.4 [16]; 7.76 ± 0.16 [55]	11.10 ± 0.1 [16]; 11.56 ± 0.28 [55]	13.30 ± 0.70 [16]
Triplets	1.10 ± 0.1 [16]; 0.86 ± 0.01 [55]	4.6 ± 1.5 [16]; 4.78 ± 0.11 [55]	7.60 ± 1.1 [16]; 5.57 ± 0.16 [55]	9.90 ± 1.3 [16]; 10.72 ± 0.24 [55]	12.1 ± 1.30 [16]
Parity of dam
First	1.10 ± 0.1 [16]; 1.03 ± 0.10 [55]	4.40 ± 0.5 [16]; 4.70 ± 0.11 [55]	7.70 ± 0.7 [16]; 7.76 ± 0.16 [55]	11.50 ± 0.6 [16]; 11.06 ± 0.23 [55]	14.80 ± 1.5 [16]
Second	1.10 ± 0.10 [16]; 1.17 ± 0.17 [55]	5.60 ± 0.60 [16]; 5.62 ± 0.18 [55]	8.50 ± 0.90 [16]; 8.51 ± 0.13 [55]	11.20 ± 1.20 [16]; 11.01 ± 0.22 [55]	13.60 ± 1.0 [16]
Third	1.30 ± 0.10 [16]; 1.24 ± 0.10 [55]	5.70 ± 0.7 [16]; 5.70 ± 0.17 [55]	8.10 ± 1.0 [16]; 8.33 ± 0.13 [55]	10.60 ± 1.30 [16]; 10.63 ± 0.18 [55]	12.10 ± 1.50 [16]
Fourth	1.50 ± 0.10000 [16]	6.90 ± 0.2 [16]	8.50 ± 0.2 [16]	10.8 ± 1.8 [16]	12.62 ± 1.93 [16]
Season of birth
Winter	1.30 ± 0.10 [16]	5.44 ± 0.62 [16]	8.50 ± 0.7 [16]	12.70 ± 0.6 [16]	15.49 ± 0.70 [16]
Summer	1.30 ± 0.1 [16]	5.32 ± 0.63 [16]	8.10 ± 0.8 [16]	10.10 ± 0.5 [16]	12.3 ± 0.60 [16]
Rainy	1.22 ± 0.06 [16]	3.64 ± 0.94 [16]	5.70 ± 1.24 [16]	9.69 ± 0.32 [16]	14.49 ± 0.31 [16]

Table 2.

Body weight at different ages of Black Bengal goat in respect of sex, type of birth, parity, and season of birth.

3.6 Reproductive performance

Reproductive efficiency is always considered to be the most vital factor ensuring the increase in productivity to a certain environmental condition [56]. One of the most favorable attributes of the BBG is its year-round breeding, high rate of reproduction and prolificacy. It reaches puberty earlier by 6 months and gives birth 2–3 kids at a time. The overall reproductive performance of the BBG is shown in Table 3.

Parameter	Performance
Age at puberty (days)	182.7 ± 7.25 [54]; 209.00 ± 32.25 [56]
Age at first service (days)	187.56 ± 8.33 [54]
Service per conception (No.)	1.46 ± 0.53 [57]; 1.37 ± 0.03 [54]
Age at first kidding (month)	13.85 ± 0.41 [57]; 401.50 ± 32.08 days [56]
Gestation length (days)	146.00 ± 2.15 [57]; 142.45 ± 0.31 [54]
Litter size (No.)	1.92 ± 0.90 [57]; 1.75 ± 0.03 [54]
Kidding interval (days)	177.00 ± 7.44 [57]; 188.01 ± 2.14 [54]
Post partum heat period (days)	33.39 ± 1.82 [54]; 47.50 ± 0.87 days [1]

Table 3.

Reproductive performance of Black Bengal Goat.

3.6.1 Seminal attributes of Black Bengal buck

Male fertility is an important issue in caprine reproduction. As a result, determining male fertility before breeding is critical for breeding success. The most efficient parameter for selecting breeding buck is the semen quality. The evaluation of sperm motility and morphology is an essential parameter in the examination of sperm quality and the establishment of a correlation between semen quality and fertility [58]. Fertilizing capacity of semen has always been regarded as one of the key factors in running an AI program [59]. Semen quality and attributes were influenced by body weight, body condition score, age, scrotal circumference, testicular circumference, breed, management, climatic, nutrition, technique for semen assortment and level of sexual incitement [60, 61, 62, 63]. Like rams, buck ejaculates are small in volume with a high concentration of spermatozoa [64]. The characteristics of Black Bengal buck semen are shown in Table 4. Sperm motility accounts for around 10–15% of the total variation in male fertility measured by the non-return rate (NRR) [70].

Parameters	Mean ± SE
Ejaculate volume (ml)	0.58 ± 0.17 to 1.04 ± 1.1 [65]; 0.37 ± 0.02 to 0.53 ± 0.03 [66]; 0.46 ± 0.08 to 0.71 ± 0.06 [67]
Concentration (10^9/ml)	2.11 ± 0.09 to 2.69 ± 0.08 [66]; 2.4 to 2.7 [67]
Fresh semen motility (%)	80.83 ± 3.5 [68]; 75.00 ± 5.3 [69]; 72.65 ± 0.56 [59]
Live spermatozoa (%)	87.58 ± 0.96 to 92.95 ± 0.74 [65]; 86.16 ± 1.54 to 89.22 ± 0.79 [67]
Normal spermatozoa (%)	91.39 ± 0.24% [59]; 87.17 ± 2.40 to 91.85 ± 1.38% [65]; 90.44 ± 0.27 to 91.41 ± 0.32 [67]
Head abnormalities (%)	2.50 ± 1.70 [68]; 1.40 ± 1.30 [69]
Mid piece abnormalities (%)	6.90 ± 2.50 [68]
Tail abnormalities (%)	7.10 ± 2.60 [68]

Table 4.

Characteristics of Black Bengal Goat semen.

3.7 Application of biotechnological tools

3.7.1 Estrus synchronization

Estrus synchronization is an essential element for the improvement of reproductive efficiencies through implementing fixed-time artificial insemination (AI), MOET, laparoscopic ovum pick up (LOPU), etc. As the duration of the estrous cycle and estrus period is variable, therefore, estrus synchronization is an important tool to increase reproductive efficiency [71]. Approaches toward synchronizing estrus are done by the manipulation of either the luteal or the follicular phase of the estrous cycle. Strategies can be employed to extend the luteal phase by supplying exogenous progesterone analogs in conjunction with or without gonadotropins or to shorten this phase by prematurely regressing existing corpora luteal through using prostaglandin (PGF2α) or by the combination of both techniques. Exogenous hormones are used to modify the physiological chain of events involved in the sexual cycle, while the non-hormonal methods of oestrus synchronization involve the use of light control or exposure to a male [72].

Worldwide, progestogen or progesterone treatment in the form of vaginal devices (Sponges/CIDR) or ear implants is usually used. In Bangladesh, two synchronization methods for goats have been evaluated under research conditions and concluded that 12.5 and 15.0 mg progesterone could be used as an effective way for estrus synchronization in Black Bengal does [21]. Another report showed that synchronization of estrus with dinoprost®, a synthetic analog of 1 ml/does PGF2α may be suitable for estrus synchronization of BBG [22]. Besides these, synchronization of BBG was also done successfully with Alfaprostol (Gabbrostim®, VETEM, Italy) and luprostiol (Prosolvin®, Intervet International, Netherlands) at the dose rate of 2 and 7.5 mg, equivalent to 1 ml/goat, respectively [73].

3.7.2 Cryopreservation of semen

Cryopreservation is the method that preserves structurally intact living cells at very low temperatures and during this process, all metabolic activities are minimized due to the freezing and the low temperature of storage [74, 75]. This technique is important for the breed conservation process. Furthermore, this technology can contribute to the extension of artificial insemination, which is a landmark technology in the modern livestock industry [76]. The success of semen preservation is markedly dependent on the semen quality and the major parameters include sperm morphology, sperm concentration and sperm motility [77].

A standardized freezing procedure for goat sperm includes semen samples collection, assessment of semen samples, semen extension and packaging into plastic straws, cooling and freezing of semen. But, several limiting factors such as: semen concentration, storage temperature (optimum freezing and thawing rates), the composition of extension media and cryoprotectants used during the freezing process are responsible for the low quality of goat cryopreserved semen. For cryopreservation of goat semen, different extenders and freezing procedures have been used [78, 79, 80, 81]. It was revealed that motility of the frozen semen differed according to the kinds of diluter (Triladyl: before dilution 81.7 ± 1.05% and post thawed 42.50 ± 1.71%, Andromed 83.3 ± 0.589% and 34.67 ± 1.67% and Tris diluter 80.1 ± 0.825% and 28.71 ± 1.55%, respectively) [82]. A comparative study on fresh and frozen–thawed semen quality revealed that sperm motility ranged from 70.83 ± 1.54 to 74.23 ± 1.59% vs. 44.17 ± 2.39 to 52.31 ± 1.08% in fresh and frozen–thawed semen of BBG. On the other hand, sperm abnormalities were found 8.82 ± 0.24 to 9.71 ± 0.52% in fresh and 11.18 ± 0.42 to 16.55 ± 0.09% in frozen–thawed semen, respectively [18]. In case of membrane integrity, a significant difference was also observed between fresh and frozen–thawed semen. An experiment result showed that the mean membrane integrity of fresh semen was 71.9% which declined to 62% after dilution which further reduced to 58.4% in case of post-thawed semen of BBG [19]. Semen cryopreservation exhibited detrimental effects on post-thaw semen motility, plasma membrane, acrosomal status and DNA integrity which ultimately affect the fertility outcome [83].

3.7.3 Artificial insemination

Artificial insemination (AI) is the most commonly applied means of assisted reproduction in domestic species. AI remained the main vehicle that offers a relatively simple and easy method for the dissemination of valuable genes rapidly to improve production traits. Furthermore, it avoids dissemination of various infectious and venereal diseases. The efficiency of AI is counterbalanced by two limitations resulting from the less number of breeding males used, which decreased the genetic variation, genetic defects or uncontrolled (or unknown) diseases could spread, and the inbreeding coefficient might be increased that affecting maternal traits [84].

For the implementation of AI, the collection of semen from male goats requires a teaser and an artificial vagina and it is a fully established technique [85]. Three methods of semen preservation (fresh, refrigerated and frozen) and three techniques of insemination (vaginal, cervical and intrauterine) are used worldwide in goats [85, 86, 87]. The use of two different forms like fresh and frozen–thawed semen influenced the fertility rate of goats. When artificial insemination was performed with fresh semen, the kidding rate was found higher than AI with Frozen–thawed semen [18]. The overall kidding rate of BBG achieved with fresh semen was 59.8%, using frozen–thawed semen it was found 43.9% [18]. On the other hand, when the conception rate was compared between the two kinds of frozen semen (diluted with Egg YC and Tris) it was revealed that the kind of semen had no significant effect (p > 0.05) on conception rate [88]. Similarly, the pregnancy rate did not differ when AI was done with the semen processed with different concentrations of egg yolk [89]. On the other hand, on the basis of the liquid preservation periods at 4°C, a kidding percentage was 69% (53 of 77), 68% (17 of 25) and 56% (14 of 25) after insemination with day 1, day 2 and day 3 semen, respectively [90].

It is a bitter truth that though AI has gained widespread acceptance in the cattle industries of most developed countries, it has not yet received such acceptance in the goat industries of Bangladesh [91]. With the exception of one region (Mymensingh), where 12% of farmers relied on artificial insemination in goats whereas almost all farmers (100%) of the country had to rely on natural mating to serve their does [92].

3.7.4 Multiple ovulation and embryo transfer (MOET)

In cross-breeding program, male germplasm through artificial insemination program has made tremendous progress in domestic species whereas MOET is considered as an effective means of increasing the contribution of superior females to breeding programs and it is also an essential procedure of embryo biotechnology [93]. MOET protocols have resulted in significant improvements in domestic animals over the last two decades; however, unlike cattle, goat MOET is underdeveloped, as collection and transfer of embryos via surgical procedures have limited advantages in small ruminants like a goat. In larger domesticated animals such as the cow and horse, manipulation of the genital tract per rectum facilitates the collection and transfer of embryos through the cervical canal and into the uterine horn ipsilateral to the ovulating ovary, whereas, the application of successful MOET in small ruminants has been constrained by the tightly folded form of the cervix, the variable ovarian response to various super ovulatory treatments, and the need for labor to handle animals, especially during large-scale production [94, 95].

MOET aims to fertilize multiple oocytes in a shorter time to produce a large number of viable embryos, that are transferred into the recipient animal which leads to a higher birth rate [96, 97]. The basis of this technology is to synchronize estrus, hormonal stimulation and AI of donors, thereafter collect the viable embryos and transfer them in the recipient animal by surgical procedure [98, 99]. Focusing on its beneficial effects, a series of works in goat MOET has been done around the world. But very few published work has been reported on multiple ovulation and embryo transfer in BBG in Bangladesh where they determine the responses of BBG following synchronization with Gabbrostim® (Alfaprostol, VETEM, Italy @ 2-mg equivalent to 1 ml/goat), superovulation with PMSG (Folligon®, Intervet International B.V, Holland at the dose rate of 900, 800 and 700 IU, respectively) and embryo collection with the surgical procedure was used to flush the embryos. The results of the experiment found that better super ovulatory response with 900 IU (13.6 ± 3.6) PMSG and the recovered embryos were 100% fertile [89]. However, MOET has not yet become a widespread tool for genetic improvement for a variety of reasons including its costs, technical demands and variable and unpredictable efficiency [100].

3.7.5 In vitro embryo production (IVP)

IVP is a very promising technique that offers an alternative to superovulation as an excellent source of low-cost embryos for transfer and manipulation purposes. It is a multistep methodology comprising the following procedures: [1] retrieval of oocytes from the ovary [2] in vitro maturation (IVM) of oocytes, [3] in vitro fertilization (IVF) with capacitated sperm and [4] in vitro culture (IVC) of zygotes to the blastocyst stage after that this could be directly transferred to the recipient animal or preserved in liquid nitrogen for long term use [101]. Moreover, IVEP from slaughterhouse oocytes represents the most convenient and cheapest source to develop basic research on oocyte maturation and cell cycle regulation, gametes recognition and fusion and regulation of early embryo development.

In Bangladesh, IVP technology in goats is new and very few research work done regarding goat IVEP including evaluation and grading of ovaries, oocyte retrieval, grading of oocytes IVM and IVF are lacking in BBGs in Bangladesh. Qualitative and quantitative assessment of ovaries from BBGs was conducted in view of IVP [102]. The average number of good quality oocytes recovered from ovaries without corpora lutea was more as compared to the ovaries with corpora lutea (CL). The number of follicles measuring 2–6 mm in diameter was found to be higher in ovaries without CL than in ovaries with functional and regressed CL [103]. Besides this, quality cumulus oocyte complexes (COCs) with a homogenous evenly granulated cytoplasm possessing multi-layers of compact cumulus cells are also important criteria for the production of goat embryos in IVP [25].

Results of investigation on the effect of collection techniques on COCs recovery indicated that aspiration of 2–6 mm diameter follicles is the most effective technique for oocyte recovery among the three techniques (puncture, slicing and aspiration) from slaughterhouse goat ovaries, however, there was no significant (p > 0.05) effect of COCs collection techniques on IVM and fertilization in goats [104]. Whereas other reports [105] suggested that the slashing technique is more suitable for harvesting a greater number and superior quality of COCs. The efficiency of fertilization and post-fertilization development is influenced markedly by IVM conditions [106]. Goat follicular fluid is one of the alternatives of macromolecules that can be used as supplementation in the maturation media because it is easy to get and also cheap [107]. Moreover, it is reported that goat follicular factor (gFF) has a positive effect on in vitro production of embryos in BBGs, and a 10% level of gFF is recommended based on the improvements observed and the associated economic benefits [108].

Besides this, it has been reported that supplementation of a protein source named bovine serum albumin (BSA) in basic medium improves maturation, fertilization, blastocyst formation and hatching rates in vitro embryo to the presence of a relatively high molecular weight protein which contributes to the maturation of oocytes [109, 110, 111, 112]. Bovine serum albumin at 5% level has been recommended as a supplement for the maturation and fertilization of goat oocytes in the TCM-199 medium [113]. The efficiency of in vitro fertilization and subsequent development of goat embryos using fresh and frozen semen for IVF was examined and found that both fresh and frozen semen can be used for IVF and subsequent development of goat embryos [114].

3.8 Contribution of goat production in poverty alleviation and women’s empowerment

Goats are highly valued for their diverse production profiles and important contributions, including their meat, milk and industrial raw materials including skin, fiber and dung. Goats play a significant role in enhancing household nutrition as well as producing employment, income and capital storage [115, 116]. The raising of goats by struggling women and poor farmers requires little financial commitment in Bangladeshi culture, according to [117] and goats are now highly regarded in Bangladesh because of their role in reducing rural poverty. Bangladesh Government has also given special emphasis and adopted a national program on BBGs for poor farmers to reduce poverty for the achievement of Millennium Development Goals (MDGs) since 2003 [118]. Bangladesh Livestock Research Institute (BLRI) developed a technology package namely “Goat rearing model for landless and small farmers”, which showed that one female goat keeper could earn an annual additional income of about BDT 1455. Besides these, they also recommended that it would possible to earn around BDT 7000–12,000 per year (from the second year) from goat farms starting with five does [119]. Findings from the project “National program on poverty reduction through goat production” showed that goat rearing improved livelihood dramatically; food purchasing capacity increased from 20 to 28% per annum and uplifted the farmer’s social status. Moreover, health facilities, festivals and educational status acceptance were increased by 28, 26 and 19%, respectively by goat rearing [119].

Women’s empowerment, particularly at the individual level, aids in creating a foundation for social change and is a crucial prerequisite for the eradication of global poverty and the protection of human rights [120]. Compared to women in other nations, Bangladeshi women are less advantaged economically and socially. In Bangladesh, women make up roughly 50% of the population and 80% of them live in rural areas. Previously in Bangladesh, rural women were restricted to homestead production and post-harvest operations; but nowadays they are involved in a variety of agricultural sub-sectors such as livestock, poultry and fishing in addition to caring for children and preparing and serving meals for the family. Employment opportunities in these subsectors are growing now. Goat rearing in Bangladesh enhanced employment for men, employment for women, social dignity, and social acceptance at rates of 35, 24, 58, 26 and 23%, respectively [121]. Moreover, one recent study conducted on entrepreneurship development among women through community-based goat rearing in char areas of Bangladesh (Figure 1a, b) found that community-based goat rearing helped to develop entrepreneurship among women and 70% of women in char areas opined that their overall livelihoods have been improved. The majority of the women entrepreneurs (71.61%) received benefits from BDT 10,000 to more than BDT 20,000 which facilitated them to help their husbands during a crisis moment, can give money to their children for education, buy personal commodities [122].

Figure 1.

(a, b): Entrepreneurship development among women through goat rearing (Photo credit: Prof. Dr. Auvijit Saha Apu).

4. Constraints

One of the main livestock species ensuring Bangladeshi farmers’ stability of livelihood is the goat. Goats are crucial as “mobile” food assets in emergency situations [123]. During religious festivals and ceremonial gatherings, goats are frequently used as a “sacrificial” animals. The Sustainable Development Goals can be achieved in large part through goat farming. However, goat farmers face a number of challenges in Bangladesh include a lack of education, inadequate veterinary services, a lack of feed, and a lack of fodders [124]. Another problem is the prevalence of PPR and skin disease in BBGs because the farmers have little or no knowledge about the causes of these diseases [121]. Aside from these, there are some other major constraints that affect sustainable and commercial goat farming in Bangladesh, such as farmers’ lack of knowledge on improved production management of goat rearing and proper feed preparation, a lack of low-cost complete feed, an acute shortage of good quality Black Bengal breeding bucks or AI facilities so that a large number of heated does remain unserved. In Bangladesh, unfortunately, the number of breeding bucks is decreasing day by day because the majority of goat farmers castrate almost all of the male calves at a young age for social and economic reasons [125]. Additionally, the use of the same buck from generation to generation has increased the likelihood of inbreeding, which lowers reproductive performance and facilitates the spread of infectious and venereal diseases [126]. Moreover, the lack of linkage between the wholesale market and farmers also affects the profitability in case of commercial farming.

5. Conclusion

Black Bengal goat (BBG) is the heritage and pride of Bangladesh. It is a dwarf breed found almost in all villages in Bangladesh. The higher demand of meat and skin in the local as well as foreign markets, focused goat enterprise as extremely important to the vulnerable group of people in the existing socio-economic conditions of the country. Due to several reasons, this breed is haphazardly crossed with an exotic breed and loses its purity. Therefore, the application of biotechnologies and modern husbandry practices should be implemented for the conservation, characterization and enhancement of the production potential of BBGs in Bangladesh.

Acknowledgments

The authors gratefully acknowledge the contribution of Professor Dr. Syed Sakhawat Husain, Bangladesh Agricultural University, Bangladesh for his enormous support and time-to-time advice to improve the manuscript.

Conflict of interest

The authors declare no conflict of interest.