A Randomized Cross-Over Field Study of Pre-Hydration Strategies in Dogs Tracking in Hot Environments

Abstract

The objective of this study was to evaluate 4 pre-exercise hydration strategies (oral water, chicken-flavored water, chicken-flavored oral electrolyte solution, and subcutaneous electrolyte solution) in working dogs conducting rigorous tracking operations in hot and arid conditions. In a randomized cross-over field study, 7 Border Patrol Search, Trauma, and Rescue (BORSTAR) Unit dogs working/training out of Fort Bliss in El Paso, Texas were randomly assigned to one of 4 different hydration strategy treatments each day for 4 days of study participation. Dogs were provided hydration treatment prior to running 2 separate one-mile tracks and were offered water while tracking. Body weight, blood, and urine were collected at the beginning of the study day and at the completion of each track. Core body temperatures were recorded using internal temperature sensing capsules. The impact of hydration strategy on change in weight, peak temperature, and serum chemical, hematological, and urinary parameters were analyzed using the COIN procedure in R^a. Compared to the other 3 hydration strategies, dogs receiving chicken-flavored water had higher blood creatine kinase values at the end of the second track (p = 0.0361). Otherwise, hydration strategy had minimal effects on blood or urine parameters. Total fluid intake was lower with water only compared to the other three hydration strategies. Dogs developed elevated core body temperatures (median 41°C; 106°F) without signs of heat exhaustion or heat stroke. Alternate hydration strategies increased total fluid intake compared to water alone; however, chicken-flavored water resulted in increased markers of muscle injury suggesting electrolyte-enriched strategies may have an advantage as a hydration strategy. Additionally, electrolyte-enriched fluids before exercise may help these dogs maintain lower peak temperatures.

Keywords: electrolytes; field study; sports medicine; thermoregulation; working dogs.

Figure 1

An illustration of the tracks that were laid for each dog during each of the tracking sessions (Track 1 and Track 2).

Figure 2

A schematic of the study design. Water was restricted at designated times (no H₂O). An initial physical examination (PE), body weight measurement (BW) and blood and urine collection were performed at the start of each day. Dogs were randomly assigned to the treatment groups for each day and in this cross-over design, all dogs participated in each treatment group. Fluid consumption was measured after each dog was given its assigned treatment, after each track during which the handler kept track of the amount of water consumed, and during the rest period. Temperature was monitored continuously during the tracking exercise. Temperature (T), pulse (P), respiration (R), and body weight (BW) were measured and blood and urine were collected after each track. Activity was monitored continuously during each study day.