At the second annual Heat Stress Road Show held earlier this year, Dr. Robert Collier, a professor at University of Arizona, offered a few pieces of advice for dairy producers looking to minimize the negative impacts of hot summer days.

Besides animal health, heat stress impacts many other aspects in cows. Collier’s research shows that when parturition is in late summer months, milk yield and protein levels plummet compared to winter months where it is the highest.

Additionally, the cooler months show increased birth weight in Holstein calves. Lower production, decreased protein and lighter calving weight for a herd in late summer months are harsh effects from heat stress that will impact the dairy.

Collier explained that as global temperatures steadily rise over the next century, heat stress prevention is even more important than it was in the past.

“As milk yield increases with continued genetics, nutrition and management, improvement in the sensitivity of high-producing animals to heat stress increases,” he stated. The combination of today’s efficient and high-producing cows with the warming world give the animals an increased metabolic challenge.

Collier offered a few suggestions for minimizing the costly consequences of heat stress:

Avoid unintentional overcrowding
Overcrowding can be a motivation for heat stress. Though a pen has plenty of room for the number of cows in it, cows can still become overcrowded. As the sun shines on the barn, half of the space will be in the sun, leaving the cows standing crowded in the shaded side. Applying shade cloth on the sides of the barn can greatly alleviate this issue.

Keep it cool in the stalls
Using conductive cooling through direct skin contact is one additional way that heat stress can be minimized. Collier was involved in an experiment where heat exchanger panels in the stall beds were used to determine whether sand or dry manure is best in reducing heat stress.

Over two periods of 40 days, it was tested in hot, dry, thermo neutral, and hot and humid conditions. The sand and dry manure bedding were tested with and without activated heat exchangers. Collier noted that sand bedding – with or without heat exchangers – was a more effective cooler than dry manure; thus, sand can be part of a heat abatement plan.

Give her a haircut
When cows are dealing with heat stress, sweating is one way to expel heat. Increasing the amount of perspiration is another way to help with dairies’ heat abatement programs. Collier noted a trial that compared perspiration rates between cows that were clipped versus those not. The shaved cows had higher perspiration than non-shaved, which means that clipping a herd in the early summer months could help in dealing with heat stress.

Collier also shared an experiment that looked at the relationship between hair color (blacker Holsteins versus whiter Holsteins) and rate of sweating. Results showed that the Holsteins that were more black in coloration were able to sweat in higher amounts than their mostly white herdmates.

Adjust feeding times for better consumption
Moving feed times to the cooler part of the day will keep the cows’ nutritional needs met as well as reduce heat stress by letting them lay in the hot hours. TMRs can be created to help them during these times. However, altering feeding times can also be a nutritional benefit to the herd.

“Try breathing 120 BPM (breaths per minute) while eating a bowl of Cheerios,” Collier explained.“It will not work. Those Cheerios will end up all over you.”

The same is for cows. If cows are fed during the hottest part of the day, they will be challenged to consume adequate amounts of feed while breathing heavily. PD

Rylin Lindahl is a freelance writer and a student at California Polytechnic State University in San Luis Obispo, California.