Comparative hematological responses of indigenous and crossbred cattle to seasonal environmental stress

Introduction

Hematological indicators serve as essential markers for evaluating physiological adaptability, health status, and heat tolerance in livestock. In tropical climates, cattle are routinely exposed to high temperature-humidity index (THI), predisposing them to heat stress, oxidative load, and altered blood physiology. Indigenous breeds such as Gir, Sahiwal, Tharparkar, Rathi, and Red Sindhi are known for robust heat tolerance, adaptive evolution, and improved hematological resilience. Crossbred cattle, although productive, often show reduced physiological tolerance to heat stress due to exotic inheritance. This study aims to compare hematological responsiveness between indigenous and crossbred cattle across three seasons: summer, rainy and winter.

Materials and Methods

Animals

The study included indigenous cattle (Gir, Sahiwal, Tharparkar, Rathi and Red Sindhi) and crossbred cattle maintained under uniform management.

Seasonal categorization

Data were recorded in three seasons: Summer (High THI), Rainy (Moderate THI), and Winter (Low THI).

Hematological parameters

RBC, WBC, HGB, HCT, and MCV were analyzed using standard Hematology analyzers.

Statistical analysis

Factorial ANOVA with breed and season as fixed factors was employed. SEm, SEd, CD (5%), and CV% values provided in tables were used for interpretation. Indigenous breeds recorded significantly higher RBC values across seasons compared to crossbred cattle. In summer, Gir showed the highest count (7.85), while crossbred cattle showed the lowest (7.59). Rainy and winter values followed a similar trend, with indigenous breeds maintaining better erythrocyte status. Seasonal differences were significant (CD 5% = 0.03), with rainy season showing the highest RBC levels, followed by winter and summer. WBC count increased from summer to winter in all breeds. Indigenous breeds had slightly higher WBC concentrations in summer and rainy seasons, while crossbreds showed a marginal rise in winter. Seasonal effect was significant (CD 5% = 0.17), indicating improved immune response during cooler periods. HGB concentration followed a breed pattern similar to RBC. Gir and Sahiwal recorded the highest values, while crossbred cattle exhibited lower HGB across all seasons. Rainy season had significantly higher HGB levels (12.31 g/dL in indigenous vs. 11.61 g/dL in crossbreds), highlighting favourable environmental conditions during this period. Indigenous breeds showed significantly higher HCT values than crossbred cattle. Gir demonstrated the highest HCT in all seasons (35.6-39.5%), whereas crossbred cattle remained lower (33.45-37.29%). Seasonal variation was significant (CD 5%=1.64), with winter showing the highest values. MCV differed from the other parameters, with crossbred cattle showing substantially higher MCV (54.05 fL in summer) than indigenous cattle (range 43.6-44.4 fL). This indicates larger erythrocyte volume in crossbreds but does not necessarily reflect improved oxygen-carrying efficiency. Seasonal changes were also significant (CD 5% = 0.34).

Results

Red Blood Corpuscles (RBC)

White Blood Corpuscles (WBC)

Hemoglobin (HGB)

Hematocrit (HCT)

Mean Corpuscular Volume (MCV)

Discussion

The present study revealed a significant (p<0.05) seasonal and breed-wise variation in RBC count, with lower values during summer, higher values during the rainy season, and intermediate values during winter across all breeds. Clement Ebenezer Henry et al. (2025) [10] reported reduced RBC counts during hot periods in crossbred Jersey cattle, which agrees with the lower summer RBC values observed in the present study, particularly in crossbred cattle. Velayudhan et al. (2022) [18] demonstrated that increasing THI alters hematological parameters, supporting the higher RBC counts observed during the rainy season under relatively lower thermal stress. Habiba et al. (2025) [8] observed a decline in RBC count under heat stress conditions, corroborating the reduced summer RBC values noted in the present investigation. Choi et al. (2016) [4] also reported lower RBC counts during hot seasons and higher values during cooler periods in Holstein cattle, a trend consistent with the seasonal pattern observed in the present study. The comparatively higher RBC counts in indigenous breeds such as Gir and Sahiwal indicate superior adaptability to thermal stress compared to crossbred cattle. The superiority of indigenous cattle in hematological resilience observed in this study aligns with well-established reports on their genetic adaptation to heat and environmental stress. Their higher RBC, HGB, and HCT values indicate better erythropoietic activity, oxygen transport, and thermotolerance. This agrees with the findings of Nardone et al. (2006) [13] , who highlighted the enhanced physiological competency of native cattle breeds in tropical environments. Seasonal variations showed clear trends: summer stress reduced RBC, HGB, and HCT, whereas rainy and winter seasons improved these values due to decreased heat load and enhanced feed intake. This is consistent with Bernabucci et al. (2014) [3] , who documented significant heat-induced hematological suppression in cattle exposed to high THI. The elevated MCV values of crossbred cattle suggest larger erythrocytes, potentially a compensatory mechanism for oxygen deficiency. However, the lower RBC and HGB levels indicate that their overall oxygen-carrying capacity remains inferior to indigenous breeds, particularly in summer. Armstrong (1994) [1] and Hansen (2004) [9] likewise reported weaker thermoregulatory competence in crossbred and exotic cattle under heat stress. Seasonal and breed-wise variation in hematological parameters, with indigenous cattle maintaining higher RBC, HGB, and HCT values than crossbred cattle across seasons. Summer heat stress significantly reduced these parameters, likely due to hemodilution, oxidative stress, and suppressed erythropoiesis, while rainy and winter seasons showed recovery under lower thermal load. Similar heat-induced declines in erythrocytic indices have been reported by Rhoads et al. (2018) [15] and Collier et al. (2019) [5] . The superior hematological stability observed in indigenous breeds supports their better genetic adaptability and thermotolerance, as also reported by Kumar et al. (2021) [11] and Das et al. (2023) [6] . Enhanced physiological resilience of indigenous cattle under tropical stress conditions has been widely documented by Sejian et al. (2019) [16] and Sejian and Bhatta (2021) [17] . White blood corpuscle counts increased from summer to winter, indicating improved immune competence during cooler periods, while heat stress was associated with immunosuppression during summer. This agrees with the findings of Lacetera (2019) [12] and El-Tarabany et al. (2020) [7] . Crossbred cattle showed significantly higher MCV, particularly during summer, suggesting macrocytic erythrocytes as a compensatory response to reduced RBC count; however, this did not improve oxygen-carrying capacity, as reflected by lower HGB and HCT values. Similar alterations in erythrocyte morphology under heat stress have been reported by Banerjee et al. (2022) [2] . Collectively, the results reinforce that indigenous cattle possess inherent hematological and physiological mechanisms that confer superior adaptability to tropical climates, while crossbreds remain more vulnerable to seasonal stress.

Conclusion

The comparative analysis reveals that indigenous cattle consistently outperform crossbred cattle in key hematological parameters across all seasons, indicating superior physiological stability and adaptation to tropical climatic stress. Seasonal shifts strongly influenced Hematology, with rainy and winter seasons offering favourable conditions and summer imposing significant thermal burden. Crossbred cattle showed reduced erythropoietic efficiency and greater heat sensitivity, as reflected in their lower RBC, HGB, and HCT levels. These findings underscore the inherent climatic resilience of indigenous breeds and support their prioritization in breeding, conservation, and sustainable livestock programs across tropical regions

Conflict of Interest Not available

Financial Support

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