The study was carried out in the Fentalle district (Figure 1) located in the eastern Shewa zone, Oromia National Regional State, Ethiopia. The district is found in the Great Rift Valley, 193 km from Addis Ababa, and borders the Arsi Zone, Boset District, Amhara, and Afar National Regional States. The geographic coordinates of the areas are 8°45′ to 9°10′ N latitude and 39°48′to 40°00′ E longitude. The predominant vegetation consists of shrublands and grasslands, which account for approximately 51.3% and 37.3% of the total area, respectively (OPADC, 2021; Yohannes, 2011). The area is distinguished by significant water features such as the Awash River, Kesem, and Lake Basaka. Pastoralism plays an important role in the local economy, which is mainly based on livestock and small-scale mixed farming. However, the district faces challenges such as scarcity of water, disease and pests, and scarcity of pasture (Abdinoor, 2014; UNDP, 2020). Basaka Lake is a shallow saline lake, which has no natural exits and has grown significantly since the 1960s because of factors such as groundwater discharge, hot spring inflow, and excess irrigation water entering the lake through subsurface flows. It has a catchment area of approximately 500 km² and receives about 0.28 billion m³ of rain each year. The lake’s surface area has grown from 3 km² in the 1960s to about 48.5 km² in 2010 (Dinka, 2012; Dinka et al., 2015; Eleni, 2009). Lake Basaka serves as a source of drinking water for cattle, particularly during the dry seasons.

The basic climatic characteristics of the study area (1999–2020) are summarized in Figure 2. Precipitation displayed a weakly bimodal distribution, with a mean annual accumulation of 543 mm, predominantly occurring during July and August. Air temperatures remain elevated throughout the year, with monthly highs reaching 36.1°C (April–May) and rarely descending below 20°C, except during October-December (Gashaw et al., 2023).

Relative humidity (RH) varies seasonally, climaxing during the rainy season (July–September) and declining in dry periods. During February 2019, a study month characterized by extreme aridity, maximum and minimum temperatures were 32.5°C and 21.0°C, respectively, yielding a daily mean of 26.75°C. Mean RH was 36%. These conditions elevated thermal load and evaporative water loss in livestock, exacerbating physiological stress from combined heat and water scarcity (Aboul-Naga et al., 2021; Egbe-Nwiyi T et al., 2000).

The temperature-humidity index (THI) was calculated using the modified small ruminant-specific equation (Marai et al., 2007): THI = AT − 0.31 − 0.31 × RH × AT − 14.4 where AT is the air temperature in degrees Celsius (°C), and RH is the relative humidity expressed as a fraction. Substituting February’s values (AT = 26.75°C; RH = 0.36) into the equation yielded a THI of 24.3°C. This value means severe heat stress according to established livestock thresholds, possibly increasing observed physiological and biochemical responses in animals consuming saline water under pastoral management systems.

A comparative cross-sectional study was conducted to investigate the physiological effects of chronic consumption of saline water from Lake Basaka on small ruminants managed under a traditional pastoral production system in Fentalle District, East Shewa Zone, Ethiopia (Figure 3). This district was purposefully selected due to its proximity to Lake Basaka, a prominent source of naturally saline water. A multistage sampling strategy was employed. Initially, 50 households were selected using systematic random sampling, based on criteria including ownership of both species, depending on either Lake Basaka or Awash River as the sole water source, and the presence of clinically healthy adult female animals. A total of 260 adult female indigenous small ruminants (130 sheep and 130 goats) were selected. Of these, 65 sheep and 65 goats consumed saline water from Lake Basaka, while the remaining 65 sheep and 65 goats consumed freshwater from the Awash River. Only non-pregnant, non-lactating females with one parity were included to control for physiological variation and better represent the demographic structure of pastoral herds, while males were excluded due to seasonal migration (Jemberu et al., 2022; Solomon et al., 2010). Animals with known health disorders, recent medical treatment, or old age were excluded. All study animals were managed under traditional extensive grazing systems, traveling 1–4 km daily in search of forage and water, and primarily grazing on natural pasture dominated by Chrysopogon plumulosus, followed by different species of Sporobolus, and in the dry seasons supplemented with very few agro-industrial by-products from the Metehara Sugar Factory. Baseline physiological parameters (body temperature, heart rate, and respiratory rate) and hematological indices were recorded to establish reference values. A one-month pre-sampling monitoring period was conducted to ensure exclusive use of the elected water sources and validate exposure classification. Informed consent was obtained from all pastoralists following FAO ethical guidelines for livestock research in indigenous communities (FAO, 2024).

All statistical analyses were conducted using SAS software (version 9.4; SAS Institute Inc., Cary, NC, USA). Data are presented as least-squares means with their corresponding standard errors of the mean (SEM). The probability value of *p* <0.05 was considered statistically significant. Post hoc comparisons were adjusted using the Tukey-Kramer method to control for multiple testing. The experimental design included two fixed factors: water type (Basaka water consumers vs. non-consumers) and species (sheep vs. goats). Due to the longitudinal nature of physiological measurements, separate statistical models were applied for repeated and single-time-point outcomes.

The physicochemical parameters of animal drinking water sources revealed significant differences between the Basaka lake water and the freshwater, highlighting potential implications for animal health and productivity (Table 2). The pH of Lake Basaka water was significantly higher (p < 0.05) than that of freshwater across all sampling periods, with mean values of 9.52 ± 0.05, compared to 7.65 ± 0.05 for freshwater. In agreement with earlier studies that reported average pH values of 8.55 (Melese and Debella, 2023), 9.30 (Tenagashaw and Tamirat, 2022), and 9.16 (Yirga et al., 2019). These values exceed the recommended range of 6.5–8.5 for livestock drinking water. Alkaline, poor-quality water with a pH greater than 9 has negative impacts on digestion, water and feed intake, and altered feed conversion efficiency (Cervantes et al., 2024; Higgins et al., 2000). Prolonged exposure can also result in metabolic alkalosis, B vitamin deficiencies, and symptoms similar to moderate acidosis (Cardoso et al., 2021; Mcgregor, 2004). The high pH observed in Basaka lake water, particularly during the dry season, highlights the need to monitor and mitigate pH imbalances to protect the wellbeing of livestock, especially young and growing animals.

The electrical conductivity (EC) of Lake Basaka water was significantly higher (p < 0.05) than that of freshwater throughout the measurement period, with mean values of 3,992.53 ± 37.28 μS/cm, compared to 641.53 ± 19.20 μS/cm for freshwater. Elevated EC reflects increased levels of dissolved ionic solutes, which serve as a substitute for salinity. Previous studies have reported EC values for Basaka lake water that range from 1,407 to 3,321 μS/cm (Umer et al., 2020) and up to 2.72 mS/cm (Melese and Debella, 2023), and 2,978 μs/cm (Tenagashaw and Tamirat, 2022). Water with an EC below 5,800 μS/cm is considered safe for most livestock species (ANZG, 2023; DPIRD, 2024; Emon, 2018; NSW, 2014). However, prolonged exposure to higher levels of EC, particularly during the dry season, can adversely affect livestock productivity. The elevated EC values observed in Lake Basaka are likely attributable to runoff, pollutants, and natural evaporation processes that concentrate dissolved salts in the lake. These findings underline the importance of addressing salinity concerns to mitigate the impact on livestock health and productivity.

Total dissolved solids (TDS) concentrations further support the increased salinity of Lake Basaka compared to freshwater sources. In this study, mean TDS levels were 2,728.00 ± 25.06 mg/L, significantly higher than freshwater at 430.33 ± 16.33 mg/L. Although these concentrations remain below the maximum tolerable limits established for most livestock species, typically between 3,000 mg/L (Emon, 2018; Meehan et al., 2021) and 4,000–5,000 mg/L (DPIRD, 2024; NSW, 2014), which indicates moderate salinity stress with potential impacts under unfavorable exposure. These results align with previous reports of TDS in Lake Basaka, ranging from 2,304.5 mg/L in the dry season to 840.3 mg/L in the wet season (Umer et al., 2019), demonstrating seasonal variability. Elevated TDS reduces water palatability, which can decrease water intake and impair livestock productivity. This issue is exacerbated in semi-arid regions where limited freshwater availability increases reliance on saline sources. The persistent salinity is primarily driven by the area’s hydrogeological and climatic factors, including high evaporation, low freshwater input, and solute accumulation, posing long-term risks to livestock health and agricultural sustainability.

The chemical composition of Lake Basaka water also reflects elevated levels of some key minerals, including sodium, potassium, chloride, carbonate, and bicarbonate, compared to freshwater. Sodium concentrations reached 1,180.69 mg/L, far exceeding the recommended limit of 300 mg/L for livestock drinking water (Davis, 2016; Higgins et al., 2000). Similarly, potassium and chloride levels were significantly higher than tolerable thresholds. Chloride levels exceeding 300 mg/L impart a salty taste and have the potential to reduce water intake (Davis, 2016; Higgins et al., 2000). Excess chloride intake has also been linked to changes in rumen function and reduced milk production. The combined impact of these high concentrations of minerals poses considerable challenges for livestock in the study area. Long-term consumption of mineral-rich saline water is particularly challenging for animals in dry and semi-dry areas, where the quality and quantity of feed are already a stress for livestock (Cardoso et al., 2021; Hussein et al., 2022; Mcgregor, 2004). Short-term exposure to water above the recommended limits may not immediately affect growth or reproduction; however, long-term consumption can lead to chronic health problems and reduced productivity (Cervantes et al., 2024). These findings emphasise the need for regular water quality monitoring and the implementation of mitigation strategies to ensure sustainable livestock management (Çapar et al., 2020) in areas dependent on natural saline water sources.

The physiological responses of sheep and goats to different water sources and diurnal variations are presented in Table 3. The finding revealed that, animals drinking saline Lake Basaka water showed significantly higher rectal temperature (RT: 39.3°C ± 0.04°C vs. 39.1°C ± 0.04°C) and pulse rate (PR: 85.1 ± 0.39 vs. 83.2 ± 0.39 beats/min) compared to those on freshwater (p < 0.05), while respiration rate (RR) remained unaffected. Diurnal changes were marked, with afternoon values significantly higher than morning for RT, RR, and PR (p < 0.05). The higher RT may result from increased heat production during mineral excretion via urine (Thiet et al., 2022), greater energy use for mineral absorption and excretion (Mdletshe et al., 2017; Tsukahara et al., 2016), or the impacts of increasing Temperature-Humidity Index (THI) during daytime in this study. A significant species × water interaction (p < 0.05) showed that sheep had the highest physiological responses on saline water (RT: 39.4°C ± 0.04°C; PR: 85.4 ± 0.39 beats/min), while goats revealed lower values (RT: 38.9°C ± 0.04°C; PR: 82.9 ± 0.39 beats/min). Although the values in this study were significantly different, they remained within the normal range for the species (Li et al., 2021; Reece and Prater, 2015). Sheep’s higher water intake may be due to their evaporative cooling mechanisms, as they pant more frequently than goats. Another reason sheep require more water for thermoregulation is their longer fleece, which increases endogenous heat production (AL-Ramamneh, 2023). The absence of an influence on RR in the current study, along with values within the normal range, indicates that these breeds of sheep and goats, which are ideal for tropical conditions, were tolerant to drinking saline water, and their thermoregulation was not significantly compromised (Adeniji et al., 2020). Previous studies by Yirga et al. (2024) found no significant effects of water salinity on respiratory rate (RR), rectal temperature (RT), and pulse rate (PR) in Blackhead Ogaden sheep and Somali goats. This underscores the variability in physiological responses to saline water among different animal breeds. These findings are consistent with previous studies (Abera et al., 2024; Nguyen et al., 2024; Rahardja et al., 2011; Yirga et al., 2024), all of which contributed to a growing body of evidence regarding the physiological adaptations of these animals in response to varying saline water and availability.

The different physiological responses can be attributed to a variety of factors, including species differences, age, adaptability to water stress, and the nutritional status of grazing animals (Mane et al., 2022; Mdletshe et al., 2017; Nguyen et al., 2024). Increased levels of rectal temperature (RT), respiratory rate (RR), and pulse rate (PR) in grazing sheep and goats can be associated with environmental factors such as high ambient temperatures and physical stress from grazing and movement. Increased physiological parameters do not necessarily indicate heat stress, as effective thermoregulation can help maintain homeostasis. For example, Gupta et al. (2013) found that goats exposed to high temperatures for 6 hours showed an increase in rectal temperature from 38.97°C to 39.35°C and in respiratory rate from 43.66 to 77.33 breaths per minute. Similarly, Sejian et al. (2017) reported significant increases in these parameters in sheep during a 14 km daily grazing routine under walking stress. Since water quality affected the physiological parameters in the present study, implementing measures to decrease water-related stress, such as improving the drinking water quality and monitoring grazing patterns, could increase livestock productivity and welfare.

The hematology profiles of sheep and goats that consumed different water sources were evaluated, and the results are presented in Table 4. Sheep and goats consuming saline Lake Basaka (LB) water exhibited significantly higher (P < 0.05) hemoglobin (Hb: 13.74 vs. 9.48 g/dL) and red blood cell counts (RBC: 11.51 vs. 9.28 ×10⁶/mL) compared to freshwater (FW). A significant species effect was observed for RBC count (P < 0.05), with sheep (11.13 × 10⁶/μL) recorded as higher than goats (9.65 × 10⁶/μL), suggesting that sheep may have a healthier erythropoietic response to osmotic stress. The elevated values of Hb and RBC in animals consuming Lake Basaka water could be explained by the higher levels of salt in the drinking water, which is likely to induce hemoconcentration. This phenomenon may occur due to dehydration or fluid loss associated with the osmotic effects of high sodium chloride (NaCl) content in the water, particularly under arid conditions (Egbe-Nwiyi T et al., 2000; Hussein et al., 2022). Moreover, the erythrocyte indices, mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC), also showed significant differences between water types, with higher values observed in sheep and goat consuming Lake Basaka water (MCH: 12.26 vs. 9.08 pg; MCHC: 37.39 vs. 26.72 g/dL) compared to those in freshwater (FW). Increased MCH and MCHC values are revealing of a compensatory hematological response to the osmotic imbalance and potential chronic dehydration caused by high salt intake, which leads to hemoconcentration and an increase in red blood cell density and hemoglobin content, suggesting an adaptive response to hyperosmolar and hypovolemic conditions (Antunović et al., 2022; Barsila et al., 2020). However, other hematological parameters, including packed cell volume (PCV), white blood cell count (WBC), and mean corpuscular volume (MCV), showed insignificant variations between water sources or species. A related study was reported by Abera et al. (2024), and Yirga et al. (2024) observed that Blackhead Ogaden sheep and Somali goats exposed to different total dissolved solids (TDS) levels have varied hematological parameters under controlled experimental conditions. These compare and contrasting results in with a previous study, indicating that species, breed, exposure time, and water composition significantly influence hematological parameters of animals exposed to saline water. Despite these variations, all measured haematological parameters remained within their respective normal ranges between species and water sources (Fanta et al., 2024; Mane et al., 2022; Tschuor et al., 2008). This indicates that sheep and goats can adapt to saline water without immediate negative effects. However, the long-term health impacts of saline water intake require further study to understand the mechanisms involved and guide effective livestock management. This research is essential for maintaining the health and productivity of small ruminants in areas reliant on saline water for drinking.

To improve the understanding and management of saline water impacts on livestock, continuous studies will be required to determine effects on productive and reproductive performance, growth, and carcass quality across different livestock species, breeds, sexes, age groups, and physiological states, under different seasonal and environmental conditions. Genomic and molecular investigations will identify genes associated with salinity tolerance could inform targeted breeding programs to enhance adaptive resilience. Furthermore, comprehensive water quality analyses from all available drinking sources across seasons should be prioritized to establish baseline data and guide sustainable water resource management strategies.