The congenital abnormalities are much more frequent in domestic ruminants and have been reported to be about 2% to 3.5% of all births (Muirhead et al. 2014). Among those, anomalies involved in the limbs and musculoskeletal systems (particularly the axial and appendicular skeleton) of newborns are common in bovine species (Kim et al. 2001; Alam et al. 2007; Abdel-Hakiem and Elrashidy 2017). These defects are usually responsible for economic losses to the food-animal farms due to the reduced market values (Neupane 2018), incapability of production and performance, stunted growth, etc., of the affected animals. For these reasons, congenitally defective animals are often euthanized/culled or slaughtered after a short-term fattening (Morath-Huss et al. 2019). In contrast, genetically exceptional animals having the extra growth of limb(s), head, horn, eye, or other organs are supposed to be the worship materials for wish fulfillment by some tribal and regional people (Green 2021); however, science suggests these as superstitions.
Polymelia being an inheritable defect with the additional limb(s) in animals, especially in cattle, has been found in various crossbred and exotic groups and is not a fatal defect. In addition, among the indigenous species; only the Korean indigenous cattle have been reported with this defect (Kim et al. 2001; Yun et al. 2015). In this study, an indigenous Bangladeshi female bovine calf was found to have a special type of polymelia called pygomelia showing a non-functional and smaller fifth limb, and to the best of our knowledge, this is the first observation of such a case in the native bovine species in Bangladesh.
Occasionally polymelia is combined with other skeletal disorders, such as the absence of certain bone(s), or underdeveloped/maldeveloped bones or bony fragments (Murondoti and Busayi 2001; Shojaei et al. 2007; Montalvo et al. 2014), and/or with different genetic disorders (Ajadi and Olaniyi 2018; Daneze and Brasil 2018; Liu et al. 2019). In addition, the affected animals may have simultaneous incidences of ectopic lungs, ectopia cordis, atresia ani, and rectovaginal fistula (Yun et al. 2015; Ali and Ibrahim 2018). In the present study, the pygomelia in the calf was associated with another skeletal defect involved in the caudal spine and sacrum, which had affected the tail to become somewhat contracted and short in length.
As a certain type of polymelia, this case (pygomelia) represented the extra growth of an entire but shorter hind limb in the perineal region between the normal hindlimbs of the calf, being correlated with the findings of other researchers (Mistry et al. 2010; Ajadi and Olaniyi 2018; Singh and Vikram et al. 2022). Apart from pygomelia, there are frequent reports of other types of polymelia. Notomelia is the attachment of the additional limb(s) to the region of the embryonic notochord that helps to develop the axial skeleton and intervertebral disk(s); cephalomelia represents an attachment of the limb(s) to the head between the horn/horn-buds or caudally to the skull, and thoracomelia means this type of limb attachment to one or both lateral/medial side(s) of the thorax (Sinowatz 2010; Muirhead et al. 2014). In the case of symmetrical or asymmetrical conjoined twins mediated polymelia in cattle, the additional growth of six or eight limbs is found, whereas only one or two supernumerary limb(s) can be observed in heterotopic polymelia (Yun et al. 2015). These defects are often due to some sex-linked recessive traits (Mistry et al. 2010) and are usually diversified with animal species, breed, geographical distribution, and other environmental factors (Muirhead et al. 2014).
The pygomelia mentioned in this case might be the consequence of the presence of certain recessive genes either from the dam or sire ancestors, or due to some embryonic and teratogenic factors during the maternal period from exogenous or endogenous origins. Previously, genetic analysis for polymelia in Angus cattle showed evidence of a developmental duplication (inherited mutation) in the novel NHLRC2 gene responsible for this defect, which was found to correlate with those of Holstein calves experimented to determine the genetic loci of polymelia (Neupane et al. 2017). Although our present study did not focus on the genetic characterization of pygomelia in that native Bangladeshi calf, this might be the further interest of this study. Determination of the genetic basis of pygomelia in indigenous Bangladeshi cattle would be helpful for selective breeding purposes by identifying the carriers to avoid these hereditary disorders.
During the clinical examination, the diagonal rotation of the accessory limb including selective extension, flexion, abduction, and adduction was carried out to manually estimate the degree of its attachment, root of articulation and stump, and internal tissue involvements to the perineum near the caudal extremity of the bony pelvis. This study did not involve any radiographic examination for pygomelia diagnosis due to the very early age (only 2-day-old) of the calf. In fact, the younger animals are much more sensitive to the radiation of X-rays, and this might cause harmful effects on the immature as well as growing cells of the neonates’ bodies. However, ultrasonography or safe CT scanning can be performed in this context, although we did not use these in our study. Hematobiochemical examinations were not performed as the animal was found apparently normal with preferable clinical parameters.
Electrosurgery was performed to reduce the hemorrhage and to ensure minimum tissue damage in a least invasive way, and the exchangeable cutting and coagulation effects using the mentioned electric energy are consistent with other studies (Alkatout et al. 2012; Watts 2018; Thakare et al. 2022). As far as we know, this type of electrosurgical intervention for pygomelia correction has not yet been reported.
During the surgery, blunt and transverse dissection aided to detect thoroughly the attachment of the limb to the perineal region that revealed an association with thin cartilages, fibrous tissues, and muscles free from any involvement to the joints or bones of the pelvis, sacrum, and caudal part of the vertebral column. However, we did not perform any anatomical dissection, imaging, or laboratory examinations of the severed limb due to the unwillingness of the owner.
This case revealed an abnormality in the skeletal development of the caudal vertebrae and part of the sacrum presenting an S-shaped bending of the tail having a notable rigidity and squat appearance. This might be attributed to some anomalies during the early embryonic development within the mesodermal derivatives. Although the aforementioned ectopic limb was surgically excised, this curled tail was kept untreated at the time of the study because there might be further chances to decide the fate of the tail based on the body stance, locomotory balance, and musculoskeletal developments with age. Reconstructive surgery or docking or leaving it intact for the rest of its life would be the possible option(s) accordingly.
It might be expected that there would be no long-term major complications or obstacles regarding the reproductive behavior and performance of the calf after maturity as there was no deeper involvement of the excised aberrant limb to the bony pelvis and pelvic outlet (birth canal) or caudal vertebra(e) or other visceral genital organs. In addition, as there was no neuromuscular dysfunction in the pelvic and perineal regions following surgery; the act of parturition in the future might not be affected as well. Besides these, from a negative perspective, there might be the chances of difficulties in matting and thereafter dystocia if there are considerable defects further seen in the pelvic canal unpredictably including the internal and external genitalia due to congenital or other abnormalities. Moreover, the contracted tail might be a definite concern if it carries the same defect and rigidity with a larger size after growth and development. Because the tail should be lifted to expose the external genitalia, i.e., the vulva and vagina during natural matting or artificial insemination, and again during parturition. That time, docking of the tail can be considered to overcome this trouble.
The presurgical administrations of atropine sulfate and xylazine HCl for premedication and sedation, and 2% lidocaine HCl for caudal epidural anesthesia and ring block for the perineal surgery are in agreement with those protocols of different research (Ismail 2016; Munif et al. 2022a). The used suture materials and suture patterns, in this case, are consistent with other reports from various experiments (Ali and Ibrahim 2018; Ryu et al. 2018; Munif et al. 2022b).
Postoperatively, there might be the chances of infections, inflammation, and myiasis. To prevent these coincidences and also to facilitate early healing and recovery, the animal was treated with supportive medications along with maintaining proper hygiene of the animal shed. Besides these, fluid therapies were provided during the presurgical and postsurgical periods to check dehydration and balance fluid, electrolytes, and energy to prevent perioperative incidences such as hypovolemia and shock. Vitamin supplementations were given to promote the growth and development of the animal.