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Over the last several years, there has been a lot of research conducted on understanding heat stress in dairy cows and the modification of facilities and changes in nutrition to help alleviate it.
Most of the information presented on this subject has focused on lactating cows and rightly so, as heat stress has an immediate and lasting negative impact on milk production. However,
recent research from Israel shows that cooling dry cows can have a significant effect on their subsequent lactation performance and profitability.
The study was conducted under moderate temperatures, averaging in the low to mid 80s, but relatively humid conditions. Evaporative cooling was used to cool cows during the entire dry period (55 to 60 days).
The study showed that cooled cows ate an average of 2.5 lb. more dry matter per day during both the far-off and close-up dry periods but drank 5 gal. to 8 gal. less water per day than noncooled cows.
Calf birth weight was about 5 lb. heavier and the number of metabolic problems was reduced in cooled cows compared to noncooled cows. At calving, cooled cows produced more colostrum (1 qt. to 2 qt.), with higher immunoglobulin content, than noncooled cows.
Milk production was 3.5 lb. (4% fat) per day greater for cooled cows over the first 90 days of lactation. An earlier study from Israel showed a similar production response to cooling, as did a 2006 California study (3 lb./day for the first 60 days in milk).
What's important about the Israel study is that the cows were only in a high Mild Stress to low Distressed condition based on heat stress charts. The temperature-humidity index was 75 to 80—far below the levels encountered in many parts of the U.S. during the summer months.
Thus, cooling of dry cows this summer appears to be a profitable strategy to minimize milk loss.
heat stress in dry cows:
- Results from all three studies show that sprinklers along with fans and shade are important for most effectively abating heat. Producers should cool cows for the entire dry period, but as a minimum, for the month prior to calving.
- Ample quantities of cool, clean water are needed for cows to dissipate heat. The Israel study showed that noncooled cows drink 40% to 50% more water than cooled cows as a means of relieving heat load. Make sure adequate water space per cow (3") is available and at least two water locations in a pen. A few heat-stressed cows can dominate a waterer and block access by other cows.
- Watch feed intake closely. A Wisconsin study indicated that dry matter intake decreases in dry cows about 3.5% for each 5¢ª degree rise in temperature above 75¢ª.
- The best time to feed cows is in the evening. The effect of body heat produced during feed digestion during the evening and nighttime will have the lowest additive effect on environmentally induced heat stress. Also, feeds will remain fresher in the bunk longer during nighttime. A smaller feeding of fresh feeds in early morning before the heat of the day starts is also a good idea.
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