Make Plans Now to Cool Dry Cows This Summer
The evidence keeps mounting. Cooling dry cows pays you back. Not only does it improve the cows' milk production and reproductive performance in their next lactation, but it also makes a huge difference in the growth and performance of their calves well into adulthood.
New research confirms that late gestation heat stress in dairy cows results in decreased dry matter intake, decreased milk production, smaller calves, decreased reproductive performance, and it changes animal behavior.
"The success of the transition period – the last three weeks of gestation through the first three weeks of lactation – effectively determines the profitability of the cows during lactation," says James Drackley, professor of dairy nutrition at the University of Illinois. Environmental limitations, such as heat stress, and nutritional management during this critical time can impede the cows' ability to reach their maximum milk production.
And when you add in the on-going research from the University of Florida on the effect of late-gestation heat stress on calves and their subsequent performance; it makes a strong case for cooling dry cows. (For more on the Florida research, please see "Cooling Dry Cows Yields More Productive Heifers," in this newsletter.)
This latest research on the effects of late-gestation heat stress was conducted at the Farm Animal Research and Teaching Unit of the Isfahan University of Technology in Iran in conjunction with the University of Illinois. During the 21-day treatment period, direct cooling of animals with fans and sprinklers was used for heat abatement. Cows were housed in sand-bedded stalls.
Researchers compared the behavioral changes of prepartum cows from heat stress during the last three weeks of gestation to herdmates that were cooled with fans and sprinklers from 7 a.m. to 5 p.m. The heat-stressed cows spent less total time eating, less time ruminating, and less time lying down.
Even though heat-stressed cows spent less total time eating and ruminating, they ate more meals per day, and had more rumination bouts per day. Those rumination bouts were just shorter in length than the cooled cows' rumination bouts.
When the time cows spent eating, ruminating and chewing was evaluated based on time per pound of dry matter intake, we found that the results for heat-stressed and cooled cows were similar. "In other words, the cows chewed the same amount for every pound they consumed, but they spent less time eating so they had lower dry matter intake," explains Drackley. "And, because cooled cows ate more and spent less time standing, they spent more time ruminating.
We concluded that prepartum dairy cows adapt to heat stress through slightly increasing the number of meals per day but reducing the duration of those meals." The chart below details the results which were measured at 10 days before expected calving date:
|Eating Time (Min/Day)||147.4||166.2|
|Rumination Time (Min/Day)||243.2||282.5|
|Standing time (Min/Day)||474.0||390.4|
|Bout Length, Minutes/Meals||19.4||25.5|
|Total Chewing Time (Min/Day)||390.6||448.7|
|Drinking Time (Min/Day)||8.1||7.6|
Cooled cows produce more milk
Despite that behavioral adaption, heat-stress during late gestation still takes a toll on the subsequent lactation. Cooled cows produced, on average, 9 pounds more milk per day than heat-stressed cows. Milk production, when adjusted for components, was also greater for cooled cows. And during the 180-days postpartum studied; cooled cows had a greater feed efficiency. The chart below details these findings:
|Milk Production (lbs/day)|
|3.5% Fat Corrected Milk||82.67||93.03|
|3.5% Fat and Protein Corrected Milk||83.55||94.14|
|Postpartum DMI (lbs/day)||40.12||41.89|
|Fat Corrected Milk/Dry Matter Intake||2.06||2.22|
|Prepartum DMI (lbs/day)||30.20||34.17|
Heat stress during the last three weeks of gestation decreased actual dry matter intake by almost 4 lbs/day. That's a lot of lost intake; especially during the transition period when you know that every bite counts to help cows make a successful transition.
Heat stress also decreased dry matter intake as a percentage of body weight before calving. But after calving, dry matter intake did not differ between the two groups.
On the reproduction side, the biggest difference between heat-stressed and cooled cows was the number of services per conception. Cows cooled during the last three weeks of gestation required an average of 1.9 services per conception. Cows that were heat stressed before calving required 2.2 services per conception.
As shown in other studies, heat stress also resulted in calves that were almost 6 pounds smaller than those born to cooled cows. In addition, the cooled cows produced better quality colostrum, although the amount of colostrum was not significantly different.
Get started today
When it comes to helping cows make a good transition the little details matter. Using a negative DCAD diet, testing urine pH, testing for elevated ketones, monitoring rumination time, actively cooling your dry cows to minimize heat stress; all of these things deliver small improvements in cow health and performance. Apply the insights that recent research has given us to make each cow's transition a successful one.