The effects of high saline water on physiological responses, nutrient digestibility and milk yield in lactating crossbred goats

Nguyen Thiet¹, Nguyen Trong Ngu², Nguyen Thi Hong Nhan² and Sumpun Thammacharoen³

¹ College of Rural Development, Can Tho University, Can Tho City, Vietnam
nthiet@ctu.edu.vn
² College of Agriculture, Can Tho University, Can Tho City, Vietnam
³ Faculty of Veterinary Science, Chulalongkorn University, HenriDunang street, Bangkok 10330, Thailand

Abstract

This experiment aimed to evaluate the effects of high saline water on physiological responses, nutrient digestibility and milk yield in lactating crossbred goats. Ten crossbred dairy goats were selected and divided into two groups, five animals each. Animals received either control (fresh water, DSW0.0) or high saline water (1.5% diluted seawater, DSW1.5). The results showed that rectal temperature (RT) and respiration rate (RR) from DSW1.5 were higher than those from DSW0.0 at 13:00 and 15:00 h. Dry matter intake, milk yield and body weight did not differ between groups. Dairy goats in DSW1.5 were lower water intake and urine volume, whereas plasma ADH concentration increased. Therefore, water balance was lower from DSW1.5 over 24 h. The results from present study indicated that dairy goats drank with 1.5% saline water which decreased thermoregulation’s capacity via higher RT and RR.

Key words: dairy goat, diluted seawater, production, thermoregulation, water balance

Introduction

Goat production in the Mekong delta is an important source of income for costal provinces and protein for human diets in Vietnam. However, the sector is faced with environmental challenges due to climate change while the demand for animal products is growing. One of the main challenges is the lack available freshwater during the dry season, lower water quality due to saline intrusion. Therefore, animals exposed to saline water or heat stress can get ill or even die. Runa et al. (2019) found that Boer goats rejected saline water at 1.25 to 1.5% NaCl and were more sensitive to the ingestion of salt from drinking water after prolonged exposure to saline water. Nguyen et al. (2022a) reported that growing Boer crossbred goats drank with 1.5% saline water increased water intake (WI) and decreased dry matter intake (DMI), nutrient digestibility and followed by decreasing weight gain. In addition, Bach Thao goats can be tolerant with saline water up to 1.0% without effects on thermoregulation via unchanging rectal temperature and respiration rate compared to fresh water group (Nguyen et al., 2022b), whereas Nassar and Mousa (1981) found that goats could accept 1.5% NaCl in drinking water. The animal’s ability to tolerate various degrees of salt loads in drinking water may be related to kidney function (Potter, 1963). Similarly, Abou Hussien et al. (1994) found that sheep and goats drinking saline water controlled their salt load by excreting more urine and increasing the filtration rate, while camels drank less saline water to decrease salt stress. Although goat may tolerant to saline water up to 1.5 % due to renal adjustment, physiological condition, breeds or climate conditions as reported by previous studies, but there is little information about the effects of high saline water on physiological responses, nutrient digestibility and milk yield in lactating crossbred goats. Therefore, the objectives of the present study were to evaluate the effects of high saline water on physiological responses, nutrient digestibility and milk yield in lactating crossbred goats.

Materials and methods

Experimental design and animal care

The experiment was conducted on 10 crossbred dairy goats (Saanen x Bach Thao goats), at 120 days in milking. Each animal was in a healthy state and was not suffering from dangerous infectious diseases. All animals were kept in individual metabolic cages in 1.2 x 0.7 m shaped pens with plastic floors, hanging together with feeders and drinking troughs for adaptation period (10 days). This period all goats ate the same experimental diets and drank fresh water. After that, the experiment was arranged completely randomized with two groups, a control group of goats drinking fresh water (DSW0.0) and a treatment group of goats drinking saline water with a concentration of 1.5% (DSW1.5), with 5 replicates. The study used concentrated seawater (9%) mixed with fresh water to achieve water with a salt concentration of 1.5% (DSW1.5), according to the formula C₁V₁ = C₂V ₂ (where C₁ is the concentration of the starting solution; V₁ is the volume of the starting solution; C₂ is the concentration of the final solution an V₂ is the volume of the final solution), and the salinity was then checked by a refractometer (Master S28M, Atago, Japan). For the concentrated seawater, we bought from the aquaculture farm and then delivery to experimental site. The chemical composition from water samples were presented in the companion paper (Nguyen et al., 2022a). This experiment lasted for 3 weeks, with 7 days for the pretreatment period (from the 1^st – 7^th day) and 14 days (from the 8^th - 21^st day) for the treatment period. All goats were offered the same ration, with 0.5 kg concentrate and 0.5 kg total mix ration (commercial TMR) for the morning feeding and natural grass ad libitum for afternoon feeding. This ration was formulated according to the farm’s protocol. The chemical compositions of the ration are presented in Table 1. The animal received the same ration, twice daily at 08:00 and 14:00 h and had free access to water.

The ambient temperature and humidity were recorded at 07:00 hour, 09:00, 11:00, 13:00, 15:00, 17:00 and 19:00 h. The temperature and humidity index (THI) was calculated as recommendation from Thammacharoen et al. (2020). The environmental conditions from the current study were presented in Table 2.

Data collection and measurement

Feed offered and grass refusals (10%) were recorded daily in the morning starting from day 1^st to 21 ^st from the experiment. Feed and refusal samples were collected daily from day 1^st to 21^st and were divided into two parts: one half was immediately dried in the oven at 105 °C until its weight remained constant to determine dry matter, and the remaining samples were kept frozen at -20 °C until chemical analysis. At the end of the experiment, all feed samples were thawed and mixed thoroughly, and subsamples were dried at 65 °C approximately 12 hours for nitrogen and ash analysis according to AOAC (1990), neutral detergent fiber (NDF) and acid detergent fiber (ADF) using the procedure developed by Van Soest et al. (1991).

Water intake (WI) was measured daily from the beginning to the end of the experiment. The measurement of water intake was performed by subtracting the weight of water offered from the weight of water refused. Goats were milked by hand milking twice daily at 06:00 and 14:00 h, recorded daily throughout the experiment. All of the goats were weighed before the morning feeding at the beginning and the end of experiment.

Rectal temperature (RT) and respiration rate (RR) were determined one per week and measurements were collected at two-hour intervals during the day time (from 09:00 h to 19:00 h). RT was determined by a digital clinical thermometer(digital clinical thermometer C202, Terumo, Tokyo, Japan). RR was measured by counting the movement of the flank within one minute.

On day 21^st, blood samples from the jugular vein were collected at 07:00 h before the morning feeding and were then placed in a lithium heparin tube, kept on crushed ice and centrifuged at 3,000 rpm for 10 minutes. The plasma samples were stored at -20 °C until analysis. Total urine and feces were recorded from day 15^th to 21^st (Week – 3). The water balance from third week of this experiment was calculated using the difference between water input (ingested water, feed water) and water output (milk, urinary excretion, feces) throughout the experiment, without taking account of the water in metabolism. Plasma ADH was determined using an enzyme-linked immunosorbent assay kit specific for goat hormone (MBS262591, MyBioSource, San Diego, CA, USA).

Statistical analysis

All data from present experiment were analysed using an unpaired T-test. Significance was declared at p < 0.05.

Results and discussion

The lactating dairy goats in this study stayed at high ambient temperature from 30 to 32 ⁰C from 11:00 h to 17:00 h with THI from 81.26 to 82.74, whereas animals stayed at low ambient temperature and THI during early morning and evening (Table 2). This experimental condition indicated that animals were exposed to modest heat stress conditions from 11:00 to 17:00 h and there was an absence of heat stress conditions during early morning and evening (Silanikove and Koluman 2015). Heat stress in dairy animals changes physiological responses such as increasing RR and RT as reported in previous studies (Chaiyabutr et al. 2000; Hamzaoui et al. 2013). The current study showed that dairy goats in both groups increased RT and RR in relation to increments in ambient temperature and THI throughout the day (Table 3). However, the animal’s responses were not similar between groups. Animals in the high saline water group demonstrated a higher RT than those in the control group at 13:00 h and 15:00 h. Similarly, animals from high saline water group increased RR throughout the day, even when there was an absence of heat stress. Previous studies suggested that higher water balance would not only provide a reservoir of soluble metabolites for milk synthesis but would be useful in slowing down the elevation in body temperature during high ambient temperature in dairy cows (Chaiyabutr et al. 2000) and in dairy goats (Nguyen et al. 2018). This would be confirmed by the current experiment when lower water balance from DSW1.5 increased RT and RR than those from DSW0.0. Moreover, higher RT from high saline intake may be due to greater heat production use for mineral urinary excretion as suggested by Arieli et al. (1989). Previous study suggested that RT was increased by saline water (Eltayeb, 2006). In contrast, some studies found that saline water from 0.55% to 1.1% did not effect on RT of goats (Mdletshe et al., 2017) or RR from Boer goats (Runa et al., 2019). The present results suggest that dairy goats drank with high saline water under tropical conditions may be more sensitive than those consumed fresh water due to higher RT and RR.

There were not effects of high saline water on DMI, milk yield and body weight from this study (Table 4; p>0.05). Previous studies found that DMI from saline water did not differ in growing goats Tsukahara et al. (2016), sheep (Moura et al., 2016). Similarly, Paiva et al. (2017) found that dairy goats drank with 0.83% TDS, nutrient intake and milk yield was the same with control group. But some studies have reported that DMI is negatively affected by increasing levels in saline water (Mdletshe et al., 2017; Nguyen et al., 2022a). The decrease in DMI that animals drank with high saline water was decreased by nutrient digestibility (Mdletshe et al., 2017; Nguyen et al., 2022a). However, the present study showed that DMI and nutrient digestibility did not differ between groups (Table 4 and 5; p>0.05). The different responses from the present and previous studies may be different in physiological condition or breeds.

Daily WI from high saline water was lower than from fresh water (Table 4; p<0.01). Eltayeb (2006) found that water intake was greater at low levels of salinity, but when the saline level increased up to 2%, the water consumption decreased. These results indicate that at low levels of saline, animals consume more water, but when given high salinity water, animals decrease water intake to avoid salt stress from saline water (Simon, 2006). But some studies found that WI increased as the salinity levels increased (Mohammed, 2008; Nguyen et al., 2022a) and also increased electrolytes excretion via renal route (Nguyen et al., 2022a). This study dairy goats have decreased WI from high saline groups, followed by lower urine volume compared to control group.

Water balance from DSW1.5 was lower than from DSW0.0, whereas plasma ADH concentration from SW1.5 was greater than those control group (Table 6, p<0.05). The effects of water balance from this study may have mediated the effects of high salinity levels on urinary volume in relation to plasma ADH level. Theoretically, high saline water may relate to the increase in Na⁺ or K+ intake followed by increasing plasma concentrations of Na⁺ and K⁺. This causes an increase of osmotic pressure of plasma. These conditions would stimulate the thirst center in the brain and increased water intake by the animal (Blair-West et al., 1992) and followed by increasing blood volume, reducing ADH secretion and renal water reabsorption. Consequently, urinary excretion would increase. However, the present results indicated that lactating crossbred goats consumed with high saline levels decreased WI and urine volume compared to fresh water group and followed by water balance from DSW1.5 decreased. As a result, plasma ADH concentration from SW1.5 was greater than other treatments from present experiment. The result in water balance from DSW1.5 agreed with Assad and Elsherif (2002) for ewes. In contrast, previous studies showed that saline water was not effect on water balance in Morada Nova sheep (Araújo et al., 2019), feedlot lambs (Albuquerque et al., 2020) and dairy goats (Paiva et al. 2017).

Conclusion

• The results from current study indicated that lactating crossbred goats response to high saline water by decreasing water intake e to minimize the salt stress.
  
  
• DMI, milk yield and body weight was not affected by high saline water from the current study.
  
  
• Water balance decreased and plasma ADH concentration increased from high saline water group.
  
  
• These leaded to decrease the thermoregulation’ capacity via higher RT and RR from high saline group.

Acknowledgments

This research is funded by the Ministry of Education and Training, Vietnam under grant number B2020-TCT-08.

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