Larger animals can go longer without food or water without ill effects. Studies indicate that only after 24 hr of road transportation does a lack of water and physical fatigue become detrimental to cattle welfare (Knowles et al., 1997; Tarrant and Grandin, 2000). Cattle are typically fasted for 6 to 12 hr before transportation (Lapworth, 2004), and this state must be considered when assessing the physical condition of cattle during transportation. The primary reason for fasting is to limit manure accumulation in the trailer and thus prevent slipping and falling.
Horses can also experience dehydration after 24 hr of transportation (Friend, 2000; Friend et al., 1998; Stull and Rodiek, 2000). Friend et al. (1998) found that horses transported for long distances during hot weather drank less water (20.9 L) than horses penned under similar conditions (38.2 L). In a later study, Friend (2000) found that respiration, heart rate, blood sodium, osmolality, and chloride were significantly higher in nonwatered horses after 30 hours of transportation in hot conditions (indicating dehydration), than in horses that had received water during similar transport. However, offering of water to horses transported under cool conditions appeared to result in no added benefit to their well-being. Stull and Rodiek (2000) assessed the condition of show horses transported in a commercial van during the summer. They, too, concluded that after 24 hr of transportation, horses begin to show changes in physiological markers of hydration. In general, it appears that horses in good physical condition can be safely transported in hot weather for at least 24 hr, when provided with water.
Estimating the amounts of food and water that should be placed in the enclosure during transportation is relatively simple. Initially, the caloric and water requirements of the species must be determined. That information can be found in the Nutrient Requirements of Domestic Animals series, a group of reports from the National Academies that cover farm animals, laboratory species, wildlife, and companion animals. When the minimal requirements have been determined, several other factors must be considered, including (Wallace, 1976):
Expected duration of the journey;
Initial weight and life stage of the animal (for example, caloric and water requirements vary with age);
Special requirements of the species or strain of animal (for example, some transgenic animals may have altered nutritional or caloric requirements); and
Expected environmental conditions (for example, animals may consume more water in low-humidity environments).