Effects of level of brackish water on feed intake, digestion, heat energy, and blood constituents of growing Boer and Spanish goat wethers1

Twenty Boer (6.1 mo old and 21.3 kg) and 20 Spanish (6.6 mo old and 19.7 kg) goat wethers were used to determine effects of brackish water on feed intake, digestion, heat energy, and blood constituents. Brackish water had 6,900 mg/L total dissolved salts, 1,885 mg/L Na, 75 mg/L Mg, 1,854 mg/L chloride, 2,478 mg/L sulfate, and 9 mg/L boron. Water treatments were 100% tap water (control), 100% of a brackish water source (100-BR), 33% control and 67% brackish water (67-BR), and 67% control and 33% brackish water (33-BR). Water and a moderate-quality grass hay (8.5% CP and 68% NDF) were offered free choice. The experiment consisted of 14 d of adaptation, 5 d for metabolizability measures, and 2 d for determining gas exchange and heat energy. There were no interactions ( > 0.05) between breed and water treatment. Water intake (931, 942, 949, and 886 g/d [SE 59.1] for the control, 33-BR, 67-BR, and 100-BR, respectively) and DM intake (525, 556, 571, and 527 g/d [SE 31.0] for the control, 33-BR, 67-BR, and 100-BR, respectively) were similar among treatments ( = 0.876 and = 0.667, respectively). Urinary water was greater for brackish water treatments than for the control ( = 0.003; 211, 317, 319, and 285 g/d [SE 25.6] for the control, 33-BR, 67-BR, and 100-BR, respectively) and fecal water content was similar among treatments ( = 0.530; 247, 251, 276, and 257 g/d [SE 19.0] for the control, 33-BR, 67-BR, and 100-BR, respectively), implying less water loss by other means such as evaporation when brackish water was consumed. Total tract OM digestibility was lower ( = 0.049) for treatments with brackish water than for treatments without brackish water (64.2, 61.5, 58.6, and 59.3% [SE 1.86] for the control, 33-BR, 67-BR, and 100-BR, respectively), although ME intake was similar among treatments ( = 0.940; 4.61, 4.57, 4.60, and 4.31 MJ/d [SE 0.394] for the control, 33-BR, 67-BR, and 100-BR, respectively). Daily heat energy in kilojoules per kilogram BW was less with brackish water than without brackish water ( = 0.001; 474, 436, 446, and 445 kJ/kg BW [SE 7.7] for the control, 33-BR, 67-BR, and 100-BR, respectively), although values in megajoules were similar among treatments ( = 0.588; 4.36, 4.12, 4.22, and 4.18 MJ [SE 0.124] for the control, 33-BR, 67-BR, and 100-BR, respectively). Body weight of wethers consuming brackish water decreased less than that of wethers consuming the control water ( = 0.006; -37, -14, -7, and -16 g [SE 7.2] for the control, 33-BR, 67-BR, and 100-BR, respectively), but recovered energy was similar among treatments ( = 0.923; 0.25, 0.45, 0.38, and 0.13 MJ/d [SE 0.356] for the control, 33-BR, 67-BR, and 100-BR, respectively). In conclusion, brackish water inclusion in drinking water had a number of effects, but it does not appear that consumption of this source would adversely impact performance of growing meat goats.