Cow-calf producers are well aware that no two calving seasons are the same. In some years, the percentage of cows delivering viable calves is quite high. In other years, there seem to be a greater number of cows who, for various reasons, lose their calves soon after birth.
For producers faced with cows who lose calves at or shortly after birth, a common thought is to direct the mothering and milking ability of that cow towards another calf. In some cases, a calf is available within the herd for this purpose (a twin or calf whose mother is not milking, etc.). In other cases, producers are tempted to source a calf from another operation or a sale barn to graft on to the calf-less mother.
Many health problems can result from the practice of bringing in a calf from an outside source, the least of which may be limited to the new calf itself. Infectious agents that are not native to the operation have the potential to spread through the herd and affect calves already on the ground as well as those yet to be born. A good case report documenting this phenomenon is available in the 2003 SDSU Beef Report (http://www.sdstate.edu/ars/species/beef/beef-reports/upload/2003-02-A-retrospective-case-study-implicating-foster-calves-in-a-calf-diarrhea-epidemic.pdf).
There are several reasons why foster calves from outside sources present risks to an operation. Different cattle operations have different sets of native organism present in their animals. Viruses, bacteria, and protozoa that may be part of the normal environment of one operation may prove highly pathogenic to another operation, in which the animals have no prior experience or immunity.
In addition, calves from outside sources usually undergo varying degrees of stress. The stress of being born, transported, auctioned, and grafted all contribute to the level of stress the calf experiences. Stress has the effect of dampening the immune system, so that any potential pathogens the calf has in his system has a great chance to multiply within the digestive tract. Often these calves have questionable colostrum consumption early in life, contributing to the growth and shedding of potential pathogens to herdmates.
A common, and the best, recommendation regarding foster calves is to avoid them. If it’s decided that this must occur, a producer should first consult with their veterinarian about the proper way to bring the calf into the herd. The following guidelines should be discussed: