The Malabari is a prolific indigenous breed of goats in South India, traditionally reared for meat and milk production. Its adaptability and high reproductive potential make it a valuable genetic resource, with 50 per cent twinning, 25 per cent triplets and 5 per cent quadruplets (Verma et al., 2009). Optimal foetal development in this breed, as in other small ruminants, is critically dependent on placental growth and function, which precedes and governs the pace of foetal growth. The placenta serves as the primary interface for the exchange of nutrient, gas and waste between the dam and the developing foetus. In goats and sheep, which possess an epitheliochorial-cotyledonary placenta, the number and surface area of cotyledons play a decisive role in regulating maternal-foetal nutrient transfer. Placental traits such as weight, cotyledon number and surface area have been associated with foetal growth parameters, particularly birth weight and postnatal viability. A strong positive correlation between placental and foetal weights has been reported in sheep, goat and humans, indicating the significance of placental mass as a predictor of neonatal outcome (Wallace et al., 2000; Jiang et al., 2017). However, in multiple pregnancies, the increased litter size often results in reduced individual birth weights due to competition for uterine space and limited placental efficiency. Lower cotyledon density in such cases may reflect a higher proportion of less functional cotyledons per gram of placental weight, compromising nutrient delivery (Konyali et al., 2007). Furthermore, placental insufficiency has been implicated in impaired foetal brain development, reduced neuronal connectivity and delayed neuromotor reflexes postpartum (Dwyer et al., 2005). Understanding the mechanisms underlying foetal growth in goats requires a detailed evaluation of placental morphology and efficiency in relation to litter size. Accordingly, the present study aimed to investigate how differences in placental structure and function associated with singleton and multiple pregnancies affect kid birth weight in Malabari goats.

The study was conducted during the period from 2022 to 2025 at the University Goat and Sheep Farm, Mannuthy, under Kerala Veterinary and Animal Sciences University, in 50 healthy pregnant Malabari does rear under a semi-intensive management system with standardized feeding and management practices. The animals were classified into two groups based on litter size, Group I (singleton pregnancies, n=25) and Group II (multiple pregnancies, n=25). Both primiparous and pluriparous does were included, with parity ranging from 1 to 5, body condition scores between 2.5 and 3.5 and body weight between 27 and 35 kg. Placenta were collected immediately after parturition, evaluated for placental weight, number and dimensions of cotyledons (length, width, depth) (Fig 1), total and average cotyledon surface area, cotyledon density, cotyledon efficiency and placental efficiency. Birth weight of kid was measured immediately after birth using a calibrated digital weighing scale. The data were statistically analysed using SPSS software and differences between groups were evaluated using an independent t-test.


 
Placental characteristics in Malabari goats
 
Placental weight (PW)
 
Immediately after parturition, the placenta from does under the experimental study in each group were collected and weighed. The fresh weight of each placenta was recorded using a precise digital scale and recorded in grams.
 
Placental efficiency (PE)
 
Placental efficiency (PE) is defined as the ratio of kid’s birth weight to the placental weight, serving as an indicator of the functional capacity of the placenta (Konyali et al., 2007). The male foetus, female foetus and total PE were calculated.
 
Cotyledon number (CN) and size
 
Immediately after kidding, the total number of cotyledons were counted and recorded. Thirty cotyledons of similar size were selected from each placenta and their length (CL), width (CWi) and depth (CDe) were measured (cm) using a digital vernier calliper.
 
Cotyledon density (CD)
 
Cotyledon density (CD) referred to the number of cotyledons per gram of placenta (Ocak and Onder, 2011).
 
Total cotyledon surface area (TCSA) and average cotyledon surface area (ACSA)
 
The total cotyledon surface area (TCSA) was calculated using the formula (Ocak et al., 2015; Ocak et al., 2016).
 

TCSA = [CWi (cotyledon width) + CL (cotyledon length)/4]² × π × TCN (total cotyledon number)

 
The average cotyledon surface area (ACSA) was derived by dividing the TCSA by the total number of cotyledons (cm²).
 
Cotyledon efficiency (CE)
 
Cotyledon efficiency (CE) was calculated as the ratio of the birth weight of kids (g) to the total cotyledon surface area (TCSA), using the formula (Konyali et al., 2007).
 

CE = Birth weight of kids (g)/TCSA 

The birth weight of kids and the data obtained on placental characteristics were compared between singleton and multiple pregnancies (Table 1).


 
Birth weight of kids (g)
 
In Malabari goats, the mean birth weight of kids was influenced by the litter size as indicated by significantly higher mean birth weight of singleton kids (2251.60±86.89 g) than multiple pregnancies (1974.40±82.34 g) (p<0.05). The birth weight might decline with increasing litter size and decreasing gestation length in small ruminants (Leymaster, 2004; Otal et al., 2010; Mellado et al., 2011; Vinayak, 2017). The present observation aligns with the previous study in Malabari breeds, where the birth weight of kid was significantly higher in singleton pregnancies (2.16±0.08 kg) compared to multiple pregnancies (1.78±0.12 kg; p<0.05) [12]. This marked difference underscores the impact of intrauterine environment on foetal development. In singleton pregnancies, lower physiological stress supports consistent ossification during early gestation (Vinayak, 2017). However, as gestation progresses and the need for soft tissue and muscle development increases, multiple pregnancies face limitations in uterine space and nutrient supply, imposing greater stress on the developing foetuses. This intensified stress likely leads to inter-foetal competition, restricted growth and subsequent reduction and variation in birth weights among offsprings from multiple pregnancies.
 
Placental weight (PW)
 
In Malabari goats, the mean placental weight between singleton (254.28±10.64 g) and multiple pregnancies (285.48±18.93 g) did not differ significantly. Despite indistinguishable variations, singleton pregnancies demonstrated greater placental efficiency per foetus, indicating more effective nutrient transfer relative to foetal demand. These observations were contrary to the previous findings (Ocak et al., 2015) in Damascus goats, where the placental weights were significantly higher in twin pregnancies (803.40±59.19 g) compared to singletons (525.54±19.65 g). Interestingly, they found that mixed-sex twin litters exhibited particularly efficient placental function, suggesting that placental adaptation may vary based on litter composition and foetal sex.
       
Placental development is heavily influenced by maternal factors such as parity, litter size and breed. It has been established that parity enhances reproductive performance by improving the ovulation rate, uterine capacity and the vascular supply to the placenta (Fahumy, 1990). Primiparous does typically exhibited reduced prolificacy and smaller placentas due to incomplete reproductive development. In contrast, older and heavier dams tend to had a more developed reproductive system and a well-established metabolic and hormonal balance, which supported improved placental growth and function (Perry et al., 1991; Tummaruk et al., 2007).
       
In saanen goats, the average placental weight was 432.76±48.61 g, with birth type significantly influencing placental weight, although parity and offspring sex did not have a significant effect. The study also observed a range in placental weights from 310.00±125.44 g to 592.12±39.79 g, later being the highest in triplet pregnancies. These findings supported the concept that placental mass increases with litter size, potentially as a compensatory mechanism to meet the greater metabolic demands of multiple foetuses, however, the efficiency of each placenta may decrease when shared among more foetuses. Histological studies have suggested that placental vascularization and surface area, rather than weight alone, are critical for efficient nutrient exchange, particularly in older goats where enhanced vascular systems facilitated more effective foetal support (Perry et al., 1991).
 
Placental efficiency (PE)
 
In Malabari goats, the total PE was significantly higher in singleton pregnancies (9.05±0.35) (p<0.05), the male foetus PE was notably elevated in multiples (p<0.05), whereas female foetus PE, though higher in multiples, was not significantly different. In damascus goats, the PE in singletons was 9.11±0.25 and in multiple pregnancies was1 0.77±0.75 (Ocak et al., 2015), suggesting breed-specific variability.
       
Placental efficiency, a key factor in uterine capacity, varied significantly among conceptuses and was therefore considered as an individual trait (Wilson and Ford, 2000). The placental efficiency tends to increase with parity in cattle and sheep, suggesting improved uterine function over successive pregnancies (Dwyer et al., 2005; Echternkamp, 1993) and might also be influenced by both genetic and environmental factors, with maternal age, parity and reproductive maturity playing key roles. Yet, the point at which increasing parity begins to negatively affect PE remains unclear (Ocak et al., 2013) and no clear association has been reported between placental weight and efficiency across parities in goats and sheep (Konyali et al., 2007).
       
While singleton pregnancies typically show higher overall placental efficiency, the sex of the foetus and the type of litter can strongly affect individual results.  This aligns with the present findings, showing greater PE in male foetuses from multiple pregnancies, while singletons in Turkish Hair goats exhibited increased cotyledon number and diameter (Ozyurek and Turkyilmaz, 2020).
 
Cotyledon number (CN) and size
 
In Malabari goats, singleton pregnancies exhibited a significantly higher CN (76.92±1.94) compared to multiple pregnancies (67.12±1.91). However, CL and CWi were significantly greater in multiple pregnancies (p<0.01) and CDe was higher in singletons. Supporting this finding, the multiparous Scottish Blackface and Suffolk ewes exhibited increased cotyledon number and size but reduced depth and placental efficiency, indicating structural compensation for larger litters (Dwyer et al., 2005). In Saanen goats, cotyledon length, width and depth were influenced by birth type (p<0.01), while parity and sex had no significant effect (Kandemir et al., 2021). In Turkish hair goats, higher cotyledon number in singleton, while larger cotyledon dimensions in multiple births were observed (Ozyurek, 2019). The study also reported strong correlations between cotyledon surface area and both length (r=0.985) and width (r=0.969) (p<0.01). 
       
In the present study, cotyledon depth (CDe) was higher in singleton pregnancies. A cotyledon depth implies more extensive vascular branching and tissue thickness, which can enhance nutrient absorption, transport and thus improved placental efficiency in singletons. These structural variations were consistent with the findings from other breeds (Saanen and Turkish Hair goats) and align with known biological principles, that the placenta adapts structurally based on litter size, parity and foetal demand, aiming to optimize the intrauterine environment. However, despite structural adaptations such as increased cotyledon size or placental mass in multiple pregnancies, the shared intrauterine environment may still constrain nutrient availability, often leading to reduced individual birth weights, as observed across breeds including Saanen and Turkish Hair goats (Kandemir et al., 2021; Ozyurek, 2019).
 
Cotyledon density (CD)
 
 In Malabari goats, CD was significantly higher in singleton pregnancies (0.31±0.01) than in multiple pregnancies (0.24 ±0.01), with the difference being statistically significant (P<0.01). A higher cotyledon density in singleton pregnancies indicates a more compact placental structure. Singleton pregnancies consistently exhibited higher CD, which aligns with the previous findings in small ruminants (Ozyurek and Turkyilmaz, 2020; Alkass et al., 2013; Ocak et al., 2014). In Morkaraman sheep, significant effect of birth type on birth weight, CN, CD and PW had been reported, highlighting similar trends across the species [24]. In mixed-breed goats, CD declined from 0.17±0.01 in first-parity does to 0.12±0.01 in fifth parity, indicating that CD decrease as parity advanced  and supporting these findings with those of Saanen goats (Sen and Onder, 2016) and Morkaraman sheep (Ozyurek and Turkyilmaz, 2020).
       
Placental efficiency in goats is mainly influenced by cotyledon surface area rather than the count or weight of cotyledons (Ocak et al., 2015). Increasing litter size or maternal parity leads to reduced cotyledon density and number due to intrauterine competition and age-related decline in uterine capacity, ultimately diminishing efficiency and neonatal outcomes.
 
Total cotyledon surface area (TCSA) and average cotyledon surface area (ACSA)
 
In Malabari goats, the TCSA did not differ significantly between singleton pregnancies and multiple pregnancies, yet ACSA showed a statistically significant increase in multiple pregnancies (5.81±0.02 cm²) than singleton (4.93 ±0.01 cm²) (P<0.05) indicating compensatory cotyledon enlargement in response to higher foetal nutrient demands. This aligns with observations in Turkish Hair goats, where ACSA (7.58±0.13 cm²) exhibited very strong positive correlation with cotyledon length (r=0.985; p<0.01) and width (r=0.969; p<0.01), while showing significant negative correlations with the number of small cotyledons (r=-0.553; p<0.01) and cotyledon density (r=-0.779; p<0.01). Moreover, ACSA was found to be the lowest (7.33±0.99) in sheep having a parity of two and the highest (8.61±1.5) and a parity of four in Morkaraman breed (Ozyurek and Turkyilmaz, 2020). These observations collectively support the concept that cotyledon enlargement favouring increase in average surface area is the primary adaptive placental response in multiple pregnancies than cotyledon numbers or density. In the present study in Malabari goats, foetal cotyledon enlargement at each placentome likely increases maternal to foetal exchange surface area, thereby enhancing oxygen and nutrient transfer to support foetal growth and viability under the elevated uterine demands of multiple pregnancies.
 
Cotyledon efficiency (CE)
 
Cotyledon efficiency (CE) in singleton and multiple pregnancies was 6.005±0.28 and 5.16±0.25, respectively with CE being significantly higher in singletons (P<0.05) indicating greater nutrient transfer efficiency per cotyledon in singleton gestations. It was shown that CE was a reliable marker of placental adequacy, as there was a strong positive correlation between CE and placental efficiency (r=0.75 overall; for twins r=0.829) in goats (Ocak et al., 2015). Contrary to our findings, a higher CE of 11.91±0.91 was reported in twin-bearing Morkaraman sheep and with parity significantly influencing placental characteristics, including PW, CN, CE and ACSA (P<0.05) (Ozyurek and Turkyilmaz, 2020).
       
In multiple pregnancies, ACSA could serve as more reliable supportive factor of uterine capacity than CE or placental efficiency, due to the division of resources among multiple foetuses. In multiple gestations, although each cotyledon may grow larger to support shared foetal demands, the efficiency per cotyledon naturally declines due to resource competition. Consequently, cotyledon enlargement becomes a critical adaptive response to maintain overall nutrient exchanges.

The study revealed significant differences in placental traits between singleton and multiple pregnancies in Malabari goats. Singleton pregnancies exhibited higher birth weight of kids, placental efficiency, cotyledon depth, cotyledon density and cotyledon efficiency, indicating more effective nutrient transfer per foetus. In contrast, multiple pregnancies showed increased cotyledon size and average surface area as a compensatory response to higher foetal demand for multiple foetuses. These findings hold practical significance for managing reproductive performance in prolific breeds like the Malabari, as understanding placental adaptations can guide breeding and nutritional strategies to enhance foetal growth, improve neonatal outcomes and reduce perinatal losses, particularly in multiple pregnancies.

The present study was supported by the facilities and infrastructure provided by the University Goat and Sheep Farm, Mannuthy and the Department of Veterinary Gynaecology and Obstetrics, College of Veterinary and Animal Sciences, Kerala Veterinary and Animal Sciences University. The authors gratefully acknowledge the assistance rendered by the farm staff and laboratory personnel during the course of the study.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided and do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Informed consent/ethical approval
 
All experimental animal procedures were conducted in accordance with the guidelines of the Institutional Animal Ethics Committee. The animal care and handling techniques used in the study were approved by the University Animal Ethics Committee.

The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, interpretation of data, decision to publish or preparation of the manuscript.