66 Effects of level of protein supplementation on intake of wheat straw and drinking water varying in salinity by Boer and Spanish goats

Abstract The effect of level of supplemental protein on intake of wheat straw by yearling meat goats drinking saline water was determined. Eighteen Boer and 18 Spanish wethers (initial BW 37.5±0.97 and 34.0±0.41 kg, respectively) consumed straw ad libitum supplemented with soybean meal DM at 0.14 or 0.28% BW (LP and HP, respectively) during 2 4-wk phases. Phase-1 water treatments were fresh water [FW; 233 ppm total dissolved salts (TDS)] and FW with 10,000 and 15,000 ppm TDS added via NaCl (MS and HS, respectively). The added TDS level for HS was 20,000 ppm in phase 2. In the preceding 8 wk, MS- and HS-wethers consumed water with 5,000 and 10,000 ppm TDS, respectively. There were no interactions between supplement and water treatments in water or DMI in the last 2 wk of phases. In phase 1, water intake varied among water treatments (1,075, 1,080, and 1,362 g/d; SEM=74.9) but was not influenced by supplement treatment (1,150 and 1,195 g/d; SEM=61.1), and DMI was similar for both water (603, 598, and 640 g/d for FW, MS, and HS, respectively; SEM=30.0) and supplement treatments (627 and 600 g/d for LP and HP, respectively; SEM=24.5). In phase 2, there was a breed×water treatment interaction (P = 0.039) in water intake (1,038, 1,178, and 1,907 for Boer and 744, 1,029, and 1,340 g/d for Spanish consuming FW, MS, and HS, respectively; SEM=77.7). However, straw intake was not influenced by water (717, 736, and 759 g/d for FW, MS, and HS, respectively; SEM=36.4) or supplement treatment (732 and 743 g/d for LP and HP, respectively; SEM=29.7). In conclusion, with relatively high levels of TDS in drinking water achieved by NaCl addition, a high level of supplemental protein did not enhance intake of wheat straw. However, future research should address other types of saline water.