Dr. Naomi Botheras, Animal Welfare Program Specialist, The Ohio State University
Traditionally, most dairy cattle lived on one farm from birth to death. However, transportation of young animals has now become a routine management practice on many dairy farms. Heifer calves are frequently moved off the farm to separate rearing facilities within the first week of life, and then perhaps moved again during the first year, before returning to the farm prior to calving. Furthermore, most bull calves are also transported off the farm very early in life, typically either to a grower facility to be raised for veal or dairy-beef production. Research suggests that handling and transport can be a severe stress for animals, and the welfare of calves may be at particular risk during transport. The welfare of calves during handling and transport has been comprehensively reviewed by Trunkfield and Broom (1990), and several other reviews of cattle transport are also available (Tarrant, 1990; Hemsworth et al., 1995; Grandin, 1997; Knowles, 1999; Eicher, 2001).
Transportation can be subdivided into several elements: handling, loading and unloading, mixing of unfamiliar animals, confinement and space limitations, unfamiliar environment, feed and water deprivation, fluctuating and/or extreme temperatures, and motion of the vehicle during transit. The ability of the animal to cope with these elements of transport varies with age, and importantly, the immune status of the animal influences the animals' coping response.
Loading and Unloading
Two of the greatest difficulties with handling and transporting very young calves are that they are often unable to walk without assistance, and they also fail to display following behavior, thus preventing them from being effectively herded. Consequently, these young weak animals are often difficult to handle and herd, and in many cases, forced movement results in the calves being mishandled and roughly treated when trying to move them on the farm and load and unload them from transport vehicles. Use of an electric prod or biting dogs to force calves to move, and throwing or dragging calves on or off trucks, all represent totally unacceptable ways of managing young calves. Loading and unloading of calves appear to be the most stressful stages of transport, as indicated by rises in the blood concentration of the stress hormone cortisol during this transport event (Trunkfield and Broom, 1990; Eicher, 2001). Calves find it difficult to navigate ramps and inclines, and calves often fail to remain upright during unloading from trucks, particularly if the unloading ramp is steep. The welfare of calves falling or sliding down a ramp is compromised, and in many situations, bruising may also occur, with welfare and economic consequences. In one study of 7,500 transported calves, an average of 80% of calves failed to remain upright during unloading from decks with a ramp incline of 18.8° (Bremner et al., 1992), and in another study of 16,400 transported calves, 50% of the calves had bruised stifles (McCausland et al., 1977).
Mortality and Shipping Fever
Transportation of calves has been shown to increase mortality rates of calves (Hemsworth et al., 1995; Knowles, 1995). However, few calves usually die during transport, but succumb to a secondary infection within the following 4 weeks. Neonatal animals are usually immuno-suppressed, and this makes it more difficult for the animal to cope with the additional stress of transport. A strong negative correlation exists between age at transport and mortality rate, such that mortality rates are reduced as calf age at transport increases. While death is an extreme consequence of transport, the welfare of a significant number of other calves is also likely to be compromised when mortality rates are high. Transport or shipping fever, also known as bovine respiratory disease, is generally considered to be caused by stress-induced changes in the immune system during transport, which increases susceptibility to viral and bacterial infections. Hence, transport may increase the rates of illness and disease. Furthermore, preliminary evidence suggests that calves are particularly vulnerable to transport stress at 4 days of age. Calves shipped at 4 days of age show a much lower immune response and ability to fight pathogens than calves transported before and after that age, suggesting that transporting calves at 4 days of age should be avoided.
During transport, calves may lose weight. It appears that this weight loss results from food and water deprivation, and defecation and urinary losses, which can lead to acute dehydration and hypoglycemia (Trunkfield and Broom, 1990). Calves that are subject to long journeys are increasingly susceptible to acute dehydration and chronic hypoglycemia, and transportation is often associated with problems of scouring, which in turn may also lead to dehydration. Electrolytes given orally during or after transport, or subcutaneously after transport, have both been found to be beneficial, particularly in the young calf. The major effects are reduced dehydration, earlier return to interest in eating and improved growth rates, immune stimulation, and reduction of losses in both liveweight and carcass weights (Knowles, 1999; Eicher, 2001).
Physical and Environmental Effects
Neonatal calves prefer to lie down during transport, so sufficient space needs to be provided to allow animals to do this. A suitable bedding material, such as straw, also needs to be provided so the animals are comfortable, warm, and dry. Calves have little natural tolerance of the cold, so protection from wind chill and rain during transport in cold weather is very important. However, adequate ventilation must still be maintained to ensure suitable air quality. Care must also be taken when handling and transporting calves in hot weather, and particularly, if it is also humid. It may be necessary to reduce stocking density in such conditions, and extra patience when moving animals to prevent overexertion is important. The length of the journey, and thus the length of feed and water deprivation also need to be considered. It is suggested in the Australian Model Code of Practice for the Welfare of Animals: Land Transport of Cattle (2002) that all calves must be fed as close as possible to, and at least within 6 hours of, the time of transportation, and calves must not be deprived of appropriate liquid feed or water for more than 10 hours in total, including the mustering and holding period prior to transport, the actual transport, and the time after unloading. The Canadian Recommended Code of Practice for the Care and Handling of Farm Animals: Transportation (2001) recommends that calves be provided with suitable feed and water at least every 12 hours. The metabolic (feeding) needs of the young calf have been linked to critical body temperature, so the need to maintain the critical temperature of the neonate is apparent. Colostrum also increases a calf's tolerance to cold temperatures.
Transport has various effects on the calf, and the evidence suggests that many are adverse. The extent to which calves are able to cope with transport, and the extent of their suffering, are questions which must be answered if good welfare of calves in transit is to be ensured. Due to the difficulties in handling and transporting very young calves, and the associated welfare (and economic) risks, it has been suggested that calves should not be transported until they have dry, withered navel cords, and that they must be fit and strong enough to be transported, i.e., calves must be bright and alert, robust, and able to rise and walk without assistance (UK Welfare of Animals (Transport) Order, 1997; Canadian Recommended Code of Practice for the Care and Handling of Farm Animals: Transportation, 2001; Australian Model Code of Practice for the Welfare of Animals: Land Transport of Cattle, 2002). The importance of all calves (heifers and bulls) receiving an adequate quantity of high-quality colostrum as soon as possible after birth, preferably within one hour, also cannot be emphasized enough. Providing an adequate volume of high-quality colostrum is critical to calf health and is the single most important factor to prevent illness of young calves. Studies have indicated that as few as 20% of calves entering veal production units in the United States have acquired adequate transfer of Immunoglobulin G from colostrum (Wilson et al., 1994).