Introduction
Calves undergo significant physiological and psychological stress during weaning, transportation and adjustment to the feedlot environment (Loerch and Fluharty, 1999). These stresses are responsible for poor calf performance, morbidity, and mortality resulting in an estimated annual cost to the U.S. beef industry of $500 million (NASS, 1996).
Newly weaned calves undergo a period of depressed feed intake during the first two weeks following feedlot arrival (Cole and Hutcheson, 1988; Fluharty et al., 1994b). This depression in feed intake occurs at the same time that the calves need to mount an immune response to pathogens and vaccines given at the time of arrival. Recent research has shown that the reduction in dry matter intake (DMI) normally associated with newly arrived feedlot calves is not due to a reduction in the digestive capability of the ruminal microbial population (Cole, 1991; Fluharty et al., 1994a; Fluharty et al., 1996). Opportunities to modify stress-associated behavior as a mechanism to improve DMI of newly received calves has not been thoroughly explored. Prior to weaning, calves are reared in a hierarchical society, with the brood cow as the dominant figure. When newly weaned calves are grouped together in a feedlot, they are placed in an environment where the feed and water sources are foreign, and the social hierarchy is destroyed. In much of the United States, there is an abundant supply of cows in the fall that have not re-bred and are destined for market. These cows may be ideal trainer animals for newly weaned feedlot calves, because they could possibly show the calves how to eat from a feed bunk and drink from a waterer. Furthermore, due to their thin condition, efficiency of gain may be excellent for these animals when given a feedlot receiving diet (Cranwell et al., 1996; Schnell et al., 1997). The objective of these trials was to determine the effects of trainer animals on performance, health, and eating behavior of newly arrived feedlot calves.