Cold, snow, wind, and more – winter in the northern climates brings extra challenges for dairies and their animals.
“We think a lot about heat stress, but cold stress also is a factor on many dairies,” stated Dr. Heather Dann, President of the W.H. Miner Institute, Chazy, N.Y. on a recent episode of The Dairy Nutrition Blackbelt podcast.
Fortunately, lactating cows produce a lot of heat. Dr. Bill Weiss, Professor Emeritus at Ohio State University, said on a recent episode of the Dairy Podcast Show, that a cow producing 100 pounds of milk per day will generate 40 mcal of excess heat per day. How much is 40 mcal in relatable terms? About the same amount of heat energy as 1.5 gallons of gasoline.
“In the summer, that’s a problem, because that excess heat must be dissipated,” said Weiss. “But in cold conditions, it can help keep cows warm.” In fact, he said the lower critical temperature – at which their body needs to make adjustments to maintain core body temperature – may be as low as -20°F in good shelter.
But while the rumen may act as a terrific furnace for lactating cows, that’s not the case for dry cows and young stock. Weiss said their lower critical temperature is more likely in the neighborhood of 10-20°F. Accommodations that should be made for them include:
- Housing and shelter – Preweaned calves need deeper bedding and the ability to nest to stay warm. Older heifers and dry cows, too, can endure winter conditions more successfully with better shelter. “There’s a lot of cost to poor facilities,” declared Weiss. And even though lactating cows in free stalls are less susceptible to cold, Dann noted the importance of maintaining and utilizing curtained sidewalls to better shelter cows in harsh conditions and protect the function of equipment like waterers.
- Body condition monitoring – Fat is an excellent insulator, and Weiss cautioned against heifers and dry cows losing condition through the winter. “We know losing body condition in the dry period definitely puts cows at risk for metabolic problems,” he said. “For heifers and dry cows, you might have to improve forage quality and reduce fiber a little bit to get the energy they need to stay warm. But as soon as it turns warm, we’ve got to lower energy intake to keep body condition steady.
- Increased nutrients – Lactating cows often naturally consume more dry matter in cold conditions. Dann said calf nutrition needs can be accommodated by increasing feeding frequency or adjusting the type and/or quantity of milk replacer. For dry cows, Weiss advised their energy requirements will typically increase by 10-20%, requiring a bump of 1-2 mcal net energy/head/day. “The source of the nutrients, as long as it’s digestible, doesn’t matter that much,” he stated. “You’re not going to make those dry cows fatter or produce a bigger calf. It’s just going into metabolic cycles to produce heat.”
Additionally, Dann cautioned that one of the dangers of extremely cold weather is frozen silage. If big chunks find their way to the lactating ration, sorting and TMR inconsistency can result. She advised defacing silo faces 6 inches or more at feed-out to prevent frozen chunks, and managing plastic covers on silo faces to prevent snow melt that creates frozen patches.
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