SUMMARYIn the near future, ruminants may be forced to consume low-quality water since potable drinking water will become increasingly scarce in some regions of the world. A completely randomized design trial was completed to evaluate the effect of increasing concentrations of total dissolved salts (TDS) (640, 3187, 5740 and 8326 mg TDS/l) in drinking water on the performance, diet digestibility, microbial protein synthesis, nitrogen (N) and water balance using 24 Red Sindhi heifers (200 ± 5 kg) that were fed Buffel (Cenchrus ciliaris) grass hay and concentrate in a ratio of 50 : 50. After a 15-day diet adaptation period, the digestion study was completed over a 5-day period and the performance trial was completed over a 56-day period. Dry matter intake, average daily gain, feed:gain, intake and digestibility of most feed components were unaffected by the concentration of salt in the water. However, intake and digestibility of neutral detergent fibre declined linearly as TDS inclusion rate increased. Further, the inclusion of TDS resulted in a linear increase in the intake of drinking water and total (food plus drinking) water intake. Similarly, TDS inclusion levels resulted in a linear increase in total water excretion, with urine being the major route of water excretion. In contrast, increasing concentrations of TDS caused a linear decrease in creatinine and allantoin excretions. Finally, increasing the inclusion rate of TDS resulted in a linear decrease in N retention and a linear increase in urinary N excretion, which may pose a considerable challenge for farmers with respect to the reduction and management of nutrient losses.

The objective was to evaluate the effects of potential use of brackish water as a source for Sindhi heifers on ingestive behavior and physiological and serum parameters. Twenty-four Sindhi heifers were distributed in a completely randomized design with four treatments and six replications, with levels of total dissolved solids (TDS) of 640, 3200, 5760, and 8320 mg/L. Three 24-hour behavioral tests were performed, which were divided into four observation shifts (00:00 to 06:00; 06:00 to 12:00; 12:00 to 18:00 and 18:00 to 00:00) at the beginning, middle, and end of the experiment. The highest values of black globe temperature humidity index and air temperature were observed at 14:00 h, with values of 92.7 and 34.1 °C, respectively. The different levels of TDS did not promote significant differences (P > 0.05) in the variables feed intake, rumination, idling, feeding efficiency as a function of dry matter and neutral detergent fiber intake, rumination efficiency as a function of dry matter and neutral detergent fiber intake, heart rate, rectal and surface temperature, creatinine, and potassium. Among the assessed shifts, feed and water intake showed higher frequencies in the shifts 2 (06-12 h) and 3 (12-18 h) and rumination showed a higher frequency in the shifts 1 (00-06 h) and 4 (18-00 h). The physiological variables presented higher indices during the warmest hours of the day. A linear behavior was observed for the serum sodium level, presenting a average of 134.4 mmol/L. Water containing up to 8,326 mg/L TDS can be used in the watering of Sindhi heifers in short periods in the season of highest water shortage without affecting the ingestive behavior and physiological and serum parameters of the animal.