Researchers talk cattle stress in dairy production

HERSHEY, Pa. — At Penn State’s Dairy Nutrition Workshop on November 5 and 6, a number of researchers addressed stress in dairy cattle.
Throughout the production cycle dairy cattle can experience environmental, managerial and nutritional stressors. These can inhibit productivity and well-being due to neuroendrocrine disruption and immunosuppression.
Physiological stress can result from nutrient restriction or deficiencies, glandular disorders and other endocrine disruptors.
Fear can trigger psychological stress. Social mixing, exposure to atypical environments, loud or unusual noises, and restraint can produce stress.
Physical stress can be due to injury, hunger, thirst, fatigue and disease.
Thermal stress caused by heat or cold is often difficult to prevent, and that stress engenders significant economic burdens on the dairy cattle industry.
The consequences of heat stress include increased respiratory rates and decreased feed and water intake. In summer high ambient temperatures, relative humidity, solar radiation and low wind speed affect the cattle, which cope by attempting to reduce their core body temperature through less dry matter intake. During lactation, declines in milk production can approach 25 percent depending on the severity and duration of heat stress. Negative impacts continue. When dry cows are exposed to heat stress, they produce less than cooled dry cows in the next lactation.
Udder health is affected. Moreover, heat stress retards immune function. Plus, heat stress also affects the immune status of the developing fetus. Calves are born four to five days earlier. Poorer immune status compromises later health as well.
Shading, sprinkling, misting and fogging along with feed restriction can improve overall productivity. Shade fans over feed stalls and soakers over the feed lines provide important cooling.
Early snowstorms and severe cold events also take a toll on dairy cattle. Using environmental and nutritional strategies during cold stress periods can be economically feasible management.
Studies reveal several social factors that cause stress as well.
Dairy cows exhibit stress when deprived of social conduct. When isolated from their group, they vocalize, pace, and have higher heart rates. Social isolation is particularly pronounced with removing the calf from a cow. The longer the dam and calf remain together, the greater the stress response when separated.
Moving between social groups when transported and with pen management creates social instability and requires cattle to re-establish social status. Regrouping has been shown to take several days for the social disturbance to return to normal.
Overcrowding in feeding or lying space can trigger aggression such as head-butting in competing for resources.
Because the transition period—three weeks before calving and three weeks after birth—has a high risk of diseases, much research has focused on that period.
In addition, more recent research is assessing the cumulative impacts of multiple stressors.
Management for social stress reduction includes practices as keeping densities low and limiting pen moves before and after calving.
Livestock producers have recently been under considerable pressure from consumer groups and policy makers to restrict or eliminate antimicrobials in livestock production. Researchers note that enhancing how to use nutritional supplements for stress reduction will provide viable non-antimicrobial alternative strategies for managers. Vitamin and mineral supplements, lipid, protein, and amino acid forms and concentrations within livestock diets are being evaluated to assess their impact on stress and immune systems.
The papers on dairy stress and its management are available in the proceedings of the Dairy Nutrition Workshop. They are online at https://scholarsphere.psu.edu/collections/wm326.268b. Individual files can be downloaded or all of the files in one large zip file.