Drinking behaviour of llamas (<em>Lama glama</em>) and horses (<em>Equus caballus</em>) in response to saline drinking water

Abstract

Saline drinking water can play an important role in the nutrition of domestic animals, either through the salinization of natural drinking water sources or the intentional application as part of rehydration therapy after exercises in horses. Whereas sodium (Na) constitutes an essential nutrient for several body functions in animals, excessive Na intake could affect feed and water consumption, and even cause death. Therefore, animals possess various strategies to prevent an excessive ingestion of Na and avoid detrimental effects on their health. However, there is still lack of knowledge on the sensitivity of llamas (Lama glama) and horses (Equus caballus) to varying NaCl concentrations in their drinking water. Using the example of two different digestive strategies, such as foregut fermenters (llamas) and hindgut fermenters (horses), the extent to which differences exist in their salt sensitivity in drinking water was investigated. <br /> As a holistic approach, animal behaviour was examined in choice experiments, where the animals (n = 12 llamas, and n = 6 horses) could choose between different salt concentrations. The aims were to provide more insight into drinking behaviour of both species and to determine their behavioural adaptation strategies in discriminating and selecting different concentrations of saline water in choice tests. For both species, the same experimental design was applied which consisted of three phases: (1) a control for 1 week with only fresh water provided in two buckets, (2) a pairwise preference test for 3 weeks offering in two buckets the choice between fresh water and a saline solution with stepwise increasing NaCl concentration (0.25, 0.5, 0.75, 1.0, 1.25 or 1.5%), and (3) a free-choice test for 3 weeks with six simultaneously provided buckets containing 0, 0.25, 0.5, 0.75, 1.0, or 1.25% NaCl, respectively. The body weight, body condition score and intake of water, feed and Na were recorded. Extensive 24-h video recordings were used to evaluate the duration and frequency of drinking behaviour. <br /> The results demonstrated that both species possess a remarkable capacity to differentiate between saline water concentrations in two different experimental setups and to adjust their Na intake in self-selection. The typical reaction with higher Na intake was to avoid very high Na concentrations or to increase the total water intake. Both species had an outstanding interest in low-concentrated saline water without compromising their health or performance. The detailed analyses of llamas’ drinking behaviour revealed their capacity for behavioural adaptation when more choice options were offered by changing their drinking pattern with increased frequency of drinking and testing, while maintaining their diurnal rhythm of water intake.