Goats are the primitive discoveries of mankind in ancient times as ready and easy source of meat for humans. The present worldwide distribution of goats shows that the majority of milch type or meat type goats are primarily located in the sub-tropical and tropical areas of Asian and African countries. There are about one-fifty well described breeds of goats available around the globe; which are dairy, meat and fibre types or their various combinations (Jain et al., 2023). Again, the sheep (Ovis aries) represents a crucial livestock species that significantly bolsters the agricultural economy, particularly supporting the livelihoods of a vast demographic comprising landless labourers as well as marginal and small-scale farmers. Among India’s economically disadvantaged communities, the rearing of sheep is exceptionally prevalent and is frequently regarded as a “mortgage lifter” for impoverished agriculturalists (Poonia et al., 2012).
       
In herbivores, the tongue functions as the most important prehensile organ for grasping food items (Meier et al., 2016). It is capable of both strong and precise movements, as in prehension, lapping, grooming and manipulation of food within the mouth on the one hand and speech articulation on the other, while in other animals, the tongue assists in the heat loss by panting, such as the dog (Dyce et al., 2010).
       
The goat is a browser, while the sheep has a grazing behaviour. Earlier reports in small ruminants have primarily focused on gross biometry (Chudasama et al., 2018), lingual papillae distribution, or species-specific histology without detailed age-wise quantitative comparisons. Considering this, the present study has been planned to elucidate the probable anatomical differences in regard to the micrometry of the tongue (major prehensile organ of the small ruminants) of crossbred sheep and non-descript goats at various ages of Jammu region of state of Jammu and Kashmir.

The present study was conducted from January, 2025 to December, 2025 in the Division of Veterinary Anatomy, Faculty of Veterinary Science and Animal Husbandry, SKUAST-J, R.S. Pura, Jammu (India). In this study, thirty-six (36) heads of freshly slaughtered apparently healthy crossbred sheep and non-descript goats were collected from the slaughter houses located in and around Jammu city and immediately brought to the laboratory of Division of Veterinary Anatomy, Faculty of Veterinary Science and Animal Husbandry, SKUAST-J, R.S. Pura, Jammu (India). The sample size was determined based on availability of healthy animals representing defined age categories and species. Equal representation of animals in each subgroup was maintained to minimize sampling bias. Tongue samples were collected from apparently healthy crossbred sheep and non-descript goats immediately after slaughter. Animals selected for the study showed no visible lesions, deformities or pathological abnormalities of the oral cavity and tongue during postmortem examination. Complete individual nutritional and management histories were not available due to slaughterhouse-based sampling, only animals with normal body condition and apparent good health status were included in the investigation to minimize nutritional or systemic bias. The tongues of crossbred sheep and non-descript goats were divided into three age groups (young: below 1 year; Adult: 2-3 years and Senile: 4 years and above) as per the dentition (Solaiman, 2010). Six (6) samples from each age group of sheep and goats were used for this study. After recording the gross parameters, the tongues were preserved in 10% neutral buffered formalin solution (Luna, 1968). The tissue pieces from the tip, body, torus linguae and root were processed for paraffin block preparation by alcohol-benzene schedule (Luna, 1968). Identical anatomical landmarks in all the specimens were used to minimize regional variation. Tissue sections of 5 mm were obtained from these blocks on clean glass slides with the help of rotary microtome. The sections were then subjected to routine histological studies and micrometrical measurements with Haematoxylin and Eosin stain along with various histochemical methods as detailed in Table 1. Micrometry was done and the selected fields were photographed by using a microscope and image analyser (Magnus MX2iLED). The micrometrical observation included:
1. Thickness (µ) of surface keratin layer:
a) At the tip.
b) At the body.
c) At the torus linguae.
d) At the root.
2. Thickness (µ) of epithelium:
a) At the tip.
b) At the body.
c) At the torus linguae.
d) At the root.
3. Number and type of papillae per field (on the tip, body and root per field) were recorded for each species of animals.


       
The data recorded in the study was expressed as mean±SE (Standard error of mean) and was subjected to Standard Statistical Analysis (Snedecor and Cochran, 1994).

Gross morphology
 
In crossbred sheep, the tongue was pointed at the apex and exhibited a distinct median longitudinal groove on the dorsal surface, whereas in non-descript goats the tip of the tongue was spatula-shaped with an indistinct median longitudinal groove. In both crossbred sheep and non-descript goats, the tongue was studded with five different types of lingual papillae, namely, filiform, fungiform, conical, lenticular and circumvallate papillae, which varied in distribution across the tongue similar to the observation reported earlier by Sethi et al. (2026). In both crossbred sheep and non-descript goats, the filiform papillae were the most abundant and were pointed, thread-like and directed caudally. Fungiform papillae were mushroom-shaped and increased in size antero-posteriorly in the tongue as previously observed in adult rams (Murad et al., 2010). Lenticular papillae were arranged in two parallel rows on the torus linguae in goats but irregularly distributed in sheep. In both crossbred sheep and non-descript goats, the conical papillae were found on the torus linguae, lateral to lenticular papillae and orientated caudally. the circumvallate papillae were located on the torus linguae, spherical in shape and encircled by a deep moat which was surrounded by a slightly higher mucosal ring. They were arranged in two rows as also reported in goats (Deore et al., 2002).
 
Keratin thickness
 
Age related and region-specific variations in keratin thickness of tongue of crossbred sheep were observed in the present study (Table 1). The surface keratin layer consistently increased in thickness with advancing age across all tongue regions with the senile group exhibiting the greatest keratinization. Significant differences (P<0.01) were especially evident between adult and senile animals, whereas variations between young and adult sheep were non-significant. This progressive keratinization with age may reflect adaptive responses to prolonged mechanical wear and dietary factors at the torus linguae and apex, both dorsal and ventral surfaces showed the same trend of increasing keratin thickness with age; however, in some location’s differences between adult and senile animals were not statistically significant, suggesting that keratin deposition may spike after adulthood in certain regions. However, no relevant literature on related species of animals was available to compare with the present findings.
       
On the other hand, in non-descript goats, the keratinization pattern differed from that seen in crossbred sheep (Table 2). While the root and body showed progressive thickening of the keratin layer with age-with the senile group consistently exhibiting the highest values- the torus linguae displayed maximum keratin thickness in adults, followed by a slight decline in the senile animals as also observed by Shao et al., (2010) in yak and cattle. At the apex, the ventral surface showed the thickest keratin layer in senile goats, whereas the dorsal surface was thickest in adults. These results indicated a region-dependent remodelling of keratin deposition in goats, possibly reflecting species-specific feeding behaviours and mechanical stress profiles. Statistically, differences were often highly significant (P<0.01) across age groups, particularly at the ventral apex.


       
In this study, while the micrometrical measurements in regard to keratin thickness was compared in between crossbred sheep and non-descript goat, marked differences in the micrometrical values of the lingual surface keratin layers between crossbred sheep and non-descript goats, as well as among various regions of the tongue and age groups was noticed (Table 3). The keratin layer varied with species, age and region of the tongue. In all the age groups, non-descript goats generally exhibited a thicker keratin layer than crossbred sheep at most locations. In senile animals, the keratin layer was greatest in the root region in both species, while goats continued to exhibit relatively greater keratin thickness at most sites, except at the ventral aspect of the apex, where both species showed comparable values. Statistical analysis indicated that these differences between species were highly significant (P<0.01) at several locations, particularly in the root, torus linguae and apex dorsal, both for young and adult animals, suggesting strong site-specific and age-influenced variation. In young animals, the greater keratin thickness in goats at most locations suggests their early adaptive specialization, possibly linked to harder, more abrasive dietary habits or innate species differences in oral mucosal structure for their well-known browsing feeding habit. This finding agrees with observations that keratinized epithelium in ruminants like Iraqi goats was typically robust and well-developed on the tongue surface (Jabur and Atyia, 2023). Such findings were also reported by Shao et al., (2010) in the yak. 


       
Adults and senile goats consistently showed thicker keratin layers than crossbred sheep, underlining a probable species resilience and structural adaptation of the oral mucosa with aging. The thickening at specific sites, especially the torus linguae and dorsal apex, may reflect sustained mechanical challenge and wear in goats, which are known for their diverse grazing habits and tough foraging behaviours. Again, highly significant variations observed in this study among specific locations suggest functional differences in epithelial adaptation and keratinization, with the apex dorsal and root of the tongue undergoing greater cornification likely to protect against physical damage during food manipulation. The pattern and progression of keratin thickness with age also point to age-related changes in mucosal regeneration and keratin dynamics, where goats may maintain a protective barrier longer into senility compared to sheep. These results aligned with existing literature reporting strong keratinization and histological adaptation in the tongues of ram, reinforcing the significance of both genetic and environmental factors in the development of oral mucosal structures (Al-bazii et al., 2021).
 
Thickness of lingual epithelium
 
In this study, the thickness of the lingual epithelium in crossbred sheep did not follow a uniform age-related increase (Table 1). Across all age groups, epithelial thickness increased from the root toward the apex, with the ventral apex presenting the maximum epithelial height. Interestingly, the adult group showed the thickest epithelium at most levels except the torus linguae, indicating a potential remodelling or epithelial thinning in senile animals. The epithelial thickness peaked in adult in sheep. Statistical analysis confirmed highly significant (P<0.01) differences between adult and senile sheep at nearly all levels, suggesting age-associated epithelial regression after maturity.
       
However, this study revealed marked regional and age-dependent differences in epithelial thickness in non-descript goats, reflecting functional and adaptive changes linked to aging (Table 2). At the root of the tongue, a progressive increase in epithelial thickness was recorded from the young to the senile group. Comparable epithelial thickness had also been recorded in adult Awassi rams and Billy-goat (Kadhim, 2016). This gradual thickening was statistically highly significant (P<0.01) among all age groups, suggesting enhanced keratinization and epithelial proliferation with advancing age, possibly as an adaptive response to prolonged mechanical and masticatory stress. In contrast, at the torus linguae, the epithelium showed a declining trend in thickness with age. The thickest surface keratin layer was observed in the young goats and the variation was highly significant (P<0.01) between the young and adult groups but non-significant between adult and senile groups. This thinning may indicate a reduction in functional demand or epithelial turnover in older animals. A similar pattern was also evident in the body of the tongue, where mean epithelial thickness decreased with advancing age. The variation between adult and senile groups was statistically highly significant (P<0.01), reflecting substantial atrophic changes and reduced keratinization with age as also reported in herbivores (Meier et al., 2016), while no significant difference was observed between young and adult animals.
       
While comparing the micrometrical measurements in regard to epithelial thickness in between crossbred sheep and non-descript goat in their various age groups and different regions of the tongue (Table 3), it was observed that in young animals, crossbred sheep exhibited significantly thicker epithelium than goats at the root, torus linguae and apex ventral, likely reflecting early developmental, genetic, or dietary factors that may require more robust epithelial protection in sheep during initial growth and adaptation to feeding (Can et al., 2016).  Again, in adults, crossbred sheep continued to show significantly greater epithelial thickness across almost all regions of the tongue, except the root, suggesting that as both species matured, sheep maintained or further developed a relatively thicker epithelial layer. This variation may underline species-specific adaptation, where sheep possibly encounter tougher or more abrasive forage, necessitating sustained epithelial development for mucosal protection. In senile animals, this pattern persisted, with sheep consistently showing greater epithelial thickness than goats at most locations and highly significant differences remained. However, the sharp thinning observed in aging goats, particularly at the body and some apex regions, might be correlated with accelerated mucosal atrophy or reduced epithelial renewal, possibly due to age-related decline in metabolic and cellular activity.  In the present study it was observed that, crossbred sheep of Jammu region generally sustain a thicker lingual epithelium than non-descript goats, especially as they age, indicating differences in mucosal resilience, possibly stemming from dietary habits or genetic predisposition. However, paucity of available literature restricted us to compare our findings with age related findings in similar species of animals. In this study, it was also seen that, both the species experience changes in epithelial thickness with age, but the extent and patterns of these changes, particularly the preservation of epithelial thickness in sheep, suggest better maintenance of oral mucosal health into senility compared to goats. These findings provide a valuable reference for normal histological variation in ruminant tongues and underscore the interplay between age, species and functional adaptation in oral epithelial biology.
 
Number of different papillae at various regions of the tongue
 
In the present study, the density, or number per field, of various lingual papillae was compared between crossbred sheep and non-descript goats across three age groups (young, adult and senile) and different tongue regions (root, torus linguae, body and apex) (Table 4,5). The data revealed a complex, papilla- and region-specific pattern of density distribution, with a general tendency for the non-descript goat to exhibit a higher density of most papillae, particularly the filiform and fungiform.





Filiform, fungiform and lenticular papillae
 
In the present study, the lenticular papillae at the torus linguae were denser in the non-descript goat in the young and senile groups, but slightly denser in the crossbred sheep in adult group. A consistent and notable sequence emerged for the fungiform and filiform papillae in most regions of the tongue. The number of fungiform papillae at the torus linguae and apex was consistently higher in the non-descript goat across all three undertaken age groups. The filiform papillae also manifested a strong trend towards higher density in the goat in the body (all ages) and the apex (all ages). Even at the torus linguae, where the young sheep had a slightly higher filiform density, the density was significantly (P<0.05) higher in the adult and senile goat. The only exception for fungiform papillae density was at the body, where the sheep had a more number in young and adult undertaken age groups before trend reversed in senile animals. Similar micrometrical values in related animals in available literature are very scant to compare to our present findings, however, Unsal et al., (2004) reported that the mean density of fungiform papillae (papillae number per cm²) in young males, young females, old males and old females were 13.26±0.20, 16.13±0.40, 9.24±0.10 and 11.87±0.60, respectively in Akkaraman sheep.
       
Again, it was observed that the non-descript goats mostly exhibited a higher density (number per field) of the mechanically and gustatorily important filiform and fungiform papillae across the body, apex and torus linguae, particularly in adult and senile stages. This greater number of papillae per unit area suggests a potentially finer-grained textural structure on the goat’s tongue. The crossbred sheep tended to show a greater density of conical papillae at the root and vallate papillae in younger animals at the torus linguae, as also reported in, Japanese black bear and the mountain goat (Inatomi and Kobayashi, 1999; Emura et al., 2001), silver fox (Jackowiak et al., 2017), Cape hyrax (Yoshimura et al., 2008) and in the giant panda (Pastor et al., 2011). This might be related to specific roles in bolus manipulation and deglutition in these regions. The increasing density of filiform papillae in the goat with age, especially at the apex and body, contrasts with the pattern for conical papillae at the root, suggesting that species-specific feeding adaptations result in differential development or maintenance of papillae across the life stages.
 
Conical and vallate papillae
 
In this study, it was observed that, at the root of the tongue, the density of conical papillae per field was initially equal in young animals but became greater in the sheep in both adult and senile groups. Conversely, the vallate papillae at the torus linguae were more numerous in the sheep in the young and adult groups, but this trend reversed in senile animals, where the goat showed a higher density. The density of conical papillae at the torus linguae showed an alternating pattern, being greater in the young sheep, adult goat and again the senile sheep. However, no relevant literature on related species of animals was available to compare with our present findings.
 
Ethics
 
Tongue samples were collected from apparently healthy animals immediately after slaughter from local abattoirs of the Jammu region, which require no IAEC approval. No experimental procedures were conducted on live animals.

The findings demonstrated distinct age and species-related variations in the keratinized epithelial layer of the tongue in crossbred sheep and non-descript goats. In young animals, crossbred sheep generally exhibited a thicker keratin layer, whereas adult goats showed greater keratinization across most tongue regions. In contrast, epithelial thickness remained consistently greater in crossbred sheep across all age groups. These differences, particularly the highly significant regional variations, indicate species and age-related adaptations of the lingual epithelium.

The present study was supported by S.K. University of Agricultural Sciences and Technology, Jammu (JandK).
 
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, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Informed consent
 
This study used animal specimens collected from dead animals from the slaughter houses, which does not require approval from the Institutional 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, decision to publish, or preparation of the manuscript.