Stressed livestock costs producers millions of dollars each year and research has proved that healthy, happier cattle are often those which have the fewest food safety problems.
Dairy heifers, for instance, can produce profound changes to their offspring's physiology and behaviour if subjected to stressful conditions during pregnancy, while stressed dairy calves are more susceptible to Salmonella and other infections.
For commercial reasons, mothers are often separated from their calves at birth so they are able to produce milk for a longer period.
"Transporting farm animals is one of the most stressful practices for dairy calves," commented Susan Eicher, the ARS animal immunologist responsible for developing the feed supplement.
This practice has not sat favourably with animal rights campaigners, however, who claim that the practice is unethical and that calves would naturally suckle for a period of six to twelve months.
Eicher and her colleagues discovered that calves were particularly vulnerable to stress at the age of four days, after taking calves on six to eight hour weekly trips as part of the study.
Furthermore, tests to measure stress-induced weakened immunity showed that these animals had a much lower immune response and ability to fight pathogens than prior to, or after, the age of four days.
In response, Eicher has developed a milk formula supplement for calves, which contains beta-glucan from yeast cell walls and vitamin C among other ingredients, designed to artificially lower stress levels.
Holstein dairy calves (favoured by the dairy industry because of their ability to produce high milk yields) when fed the supplement soon after birth, were found to be more active, had higher levels of immunoglobulin (an indicator of a good immune system) and also lower levels of a liver protein (a common stress indicator).
In a similar investigation, involving both confined and grazing herds, Eicher found that acquainting young, pregnant heifers with milking parlours and practices before their first births helps lower stress levels when they are milked after their calves are first weaned.
"There was lowered stress - as measured by increased milk production, less nervous weight shifting in milking stalls, and a quicker return to normal levels of heptaglobin, a protein that cleans up hemoglobin after tissue damage or other stresses - in the cows in both experiments. But the benefits were clearer in the confined herd," she commented.