EFFECTS OF SALINITY OF DRINKING WATER ON PERFORMANCE OF SMALL RUMINANTS

Abstract

The general objectives of the study were to provide information necessary for the development of appropriate management strategies to ensure improved quality of drinking water for livestock and to determine the extent to which consuming saline water affects performance and health of sheep and goats. Specific objectives were to analyze the quality of water from rift valley lakes of Ethiopia for livestock drinking and to determine the effects of salinity of drinking water on performance and health of sheep and goats of different ages and breeds. Water sample was taken from inlets, sites influenced by human activity and livestock drinking sites of Lakes Awassa, Beseka, Chamo, Langano and Shala to evaluate quality based on physicochemical and microbiological properties. There was variation in water quality among the lakes (P<0.01) but it was similar among sampling sites (P>0.05). Comparison of the measured quality parameters with guideline values, i.e. maximum tolerable levels in drinking water of livestock, shows that the levels of iron and few toxic elements in water of all the lakes, and alkalinity, total dissolved solids (TDS), sodium, potassium, chloride and bicarbonate ions in water of Lake Shala were beyond the limits. Thus, the studied lakes, except Lake Shala, can be considered suitable drinking water sources for livestock. Effects of salinity of drinking water on performance of sheep and goats were determined in two experiments. The first one evaluated effect on feed intake, digestion, heat energy, ruminal fluid characteristics, and blood constituent levels in growing Boer goat wethers (GRO-G) and mature Boer (MAT-G) and Katahdin sheep wethers (MAT-S) using fresh water (0-BRW), 50% fresh water and 50% brackish water (50-BRW), 100% brackish water (100-BRW), 100-BRW plus 3450 mg/l NaCl (Low-SLW), and 100-BRW plus 6900 mg/l NaCl (Mod-SLW). The second experiment evaluated effect on water intake and loss, feed intake and digestion, body weight (BW), thermoregulation traits, and blood constituent levels in growing Blackhead Ogaden sheep (GRO-S), mature Blackhead Ogaden sheep (MAT-S), growing Somali goat (GRO-G) and mature Somali goat (MAT-G) using fresh water (FRW), and low (Low-SLW), moderate (Mod-SLW) and high (High-SLW) levels of salinity (i.e., NaCl addition at levels of 10, 13.5 and 17 g TDS/l, respectively). xv The experiment on Boer goat and Katahdin sheep revealed intakes of organic matter (OM) and nitrogen (N) for MAT-G (P=0.049 and 0.036 with quadratic effects), and metabolizable energy (ME) for goats (P=0.025 with linear effect for GRO-G and MAT-G, respectively) decreased with increasing water salinity. Digestion of dry matter (DM), OM and N for GRO-G decreased (P=0.006, 0.004 and 0.024), and total water intake for MAT-G increased (P=0.004) with linear effects due to increasing water salinity. Drinking and total water intake, urine excretion and total water loss increased (P≤0.004) while nutrient digestibility decreased linearly (P<0.001) with increasing water salinity in the experiment on Blackhead Ogaden sheep and Somali goat. Digestibility of N at High-SLW (P=0.017) and water balance at Low-SLW (P=0.040) were greater for mature than growing Blackhead Ogaden sheep and Somali goat. Levels of blood packed cell volume (PCV) and hemoglobin (HB) at FRW (P=0.059 and 0.070, respectively) tended to be greater but aspartate aminotransferase (AST) (P=0.036) at Mod-SLW was lower for Blackhead Ogaden sheep than Somali goats in the same level. The results from the first animal experiment indicate that higher salinity levels of drinking water more adversely affected digestion of growing goats compared with mature small ruminants. While the observed similarities in feed intake, BW, thermoregulation or blood parameters, and increased water consumptions in the second experiment suggest considerable tolerance of the animals to relatively high levels of salinity in drinking water. Greater water balance and N digestion for mature than growing animals could be an indication of better tolerance of mature than young animals to salinity of drinking water; while lower levels of hematological profiles and increased level of AST for goats than sheep might indicate better tolerance of sheep than goats to salinity of drinking water. In conclusion, increasing salinity levels up to 13.6 g TDS/l in drinking water had effects on intake and digestion of Boer goat and Katahdin sheep that differed among animal types. But, increased salinity of drinking water by NaCl addition up to 17 g TDS/l, level above the salinity of Lake Shala water, had no observable adverse effect on feed intake, BW, or health status of Blackhead Ogaden sheep and Somali goats.