Focusing on your pre-weaned calves, here are some basics to follow for improved calf health and growth during hot weather.
First, it’s important to recognize that your calves tolerate slightly higher daytime temperatures than your cows, with stress beginning when the temperature is over 80o F (26oC).
Encourage Food Intake
Calves born in hot summer months have lower average daily gains versus those born in other seasons (Bateman & Hill, Progressive Dairyman, 2012). Reduced average daily gain means a delay in time to puberty, longer interval to first calving and ultimately delayed return on investment. One way to encourage intake, gain and rumen development in your calves is by making fresh starter feed available. Starter intake is also directly related to water intake.
“Like people, your calves’ appetites are reduced during periods of heat stress.”
Drink Plenty of Water
Fresh, clean and abundant water helps to cool calves and is crucial during periods of heat stress, especially for calves with scours. During ideal temperatures calves that are 1-2 months old consume 0.5 - 2.0 gallons of water per day. That amount increases exponentially with heat and humidity and can reach up to 6 gallons per day in young calves.
Rinsing water buckets daily and frequent refills are also advisable. If your calves habitually spill their water, then wire or cable tie bucket handles to holders.
Supplement as Needed
Like scours, heat stress can lead to dehydration. Pay close attention to each calf’s attitude and ability to suckle. Oral electrolyte solutions, like NuLife® Oral Electrolytes, can help replenish fluids. The amount to use depends on the level of dehydration and the ambient temperature. For example, a 100-pound calf that only has a weak suckle may be 5% dehydrated. At normal outdoor temperatures, this calf would require 2.5 quarts of electrolyte solution per day. However, if the outdoor temperature is over 100oF (38oC), the amount should be doubled to 5 quarts per day in addition to normal feedings of milk or replacer (Bentley, Iowa State University Extension).
Provide Air Movement
Air movement promotes cooling; in fact, calves in a curtain sidewall barn showed a 23% increase in average daily gain when cooled with fans (Hill et al, Journal of Dairy Science, 2011).
Air movement also helps your calves by reducing the bacterial load and reducing noxious gases like ammonia in the air.
Recommendations for airflow are over six times higher in hot summer weather than in winter. Your local extension specialist or veterinarian may be able to help you determine if airflow in your calf facility is adequate for summer heat.
For calf hutches, a simple way to improve air flow is to raise the rear of the hutch (can be supported with a cement block). For maximum airflow in hutches place them 4 feet apart with 10 feet between rows.
Block out Direct Sun
No matter the type of housing, your calf needs to be able to get out of direct sunlight. A shade cloth above hutches can reduce the temperature inside the hutch by 3-4 degrees, and therefore reduce body temperature. Calves housed in barns need the ability to move out of sunlight coming through sidewalls or windows. Calves in group housing will “bunch” to move away from direct sunlight or flies, thereby limiting their individual air flow.
Keep Bedding Dry & Combat Flies
Expending energy to swat flies adds to the detriment of heat stress, so use fly control products. Also, fly eggs need moisture to hatch; therefore, use of dry inorganic bedding helps limit flies in the calf rearing area. Having four or more inches of gravel below the bedded surface of hutches or pens helps to drain the fluids away too.
“Expending energy to swat at flies adds to the detriment of heat stress.”
Keep the area under feed and water buckets clean and dry to reduce hatching of maggots. Finally, trimming weeds around calf housing improves ventilation and reduces moisture in the soil.
In summary, you can reduce heat stress in calves to improve their health and your farm’s profitability by following these simple steps in summer months:
› Provide fresh starter daily
› Offer large amounts of clean water
› Provide electrolyte therapy to dehydrated calves as needed
› Produce adequate air flow
› Furnish shade
› Supply dry bedding
› Undertake fly control measures
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