By Rick Lundquist
The immediate future is dim for making any money in the dairy industry, but that doesn't preclude dairy producers from doing their best to provide for their animals. It was nearly 90 degrees last week in South Florida and over 100 degrees in Arizona.
Cows were starting to show the early effects of heat stress already. Considering the dismal price of milk, the inevitable milk loss due to heat stress is not a scenario we look forward to. On top of this, heat stress can also take a toll on rumen health, reproduction and foot health.
Now is the time to plan your summer rations and nutritional management for heat stress. Here are some items for your checklist:
- Ration energy. Because of reduced dry matter consumption and hence, reduced energy intake, the natural response is to increase energy density of the ration. This usually means increasing the proportion of grain in the ration. However, heat stressed cows are already prone to acidosis because of other metabolic factors, so higher grain levels may add to this risk. Feeding high quality forages is a better solution. Rumen inert fat or tallow is also a safer strategy for increasing energy density without risking acidosis. Cows require glucose for milk production, so increasing the rumen production of glucose precursors, mainly propionate, will help maintain milk production. Feeding Rumensin is a safe, economical way to maximize propionate production and maintain rumen pH.
- Ration protein. Don't overfeed protein to heat stressed cows. Besides being expensive, digesting excess protein generates more metabolic heat.
- Water. This is the cheapest and most important factor for maintaining milk production and health during heat stress. Make sure plenty of water is available and troughs are clean and accessible.
- DCAD, minerals and vitamins. Maintain a positive dietary cation-anion difference (DCAD) of 20 to 30 meq/100 grams dry matter for lactating cows. Dietary potassium should be increased to 1.4%–1.6% of dry matter during the summer. This should come from high potassium forages and potassium carbonate (not potassium chloride). Magnesium and sodium should also be increased. Keep salt available free choice. Rumen protected niacin may reduce body temperature during moderate heat stress.
In addition to these nutritional strategies, feeding times should be adjusted to the cooler parts of the day and lockup times for treatments should be minimized.
Anyone in the dairy industry is in for a long hot summer this year. I think a boost in milk price would alleviate much of the "heat.”
Reference: Baumgard and Rhoads. The Effects of Heat Stress on Nutritional and Management Decisions. 2009 Western Dairy Management Conference Proceedings.
--Rick Lundquist is an independent nutrition and management consultant based in Duluth, Minn. You can contact him at firstname.lastname@example.org.
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