Early weaned calves come to the feedlot with some baggage. Their light weight makes them an odd duck from the standpoint of facilities and feeding management. But the primary concern is immune function.
If calves come in having previously had access to some supplemental feed source, beyond what the cow and pasture may have provided, and they are carrying acceptable condition, immune function is normally not of any greater concern than normal-aged calves. In fact, if calves haven’t been stressed nutritionally, 90-120 day old calves often have better health status than normal-aged calves. And given the light weight of the calves, they should have tremendous feed efficiency.
However, if the calves have been nutritionally stressed, waiting for a rain, their immune function is likely stretched pretty thin. If weather during weaning, transport, and upon arrival are not extreme (hot, dusty, etc.), the disease risk is manageable. However, health challenges in calves received during hot, dusty conditions can be at least as severe as those encountered during a cold, rainy fall. Previous nutritional state is likely key to the outcome.
Upon arrival, treat early weaned calves like other extremely high-risk calves. Prior to processing, give them a period of time to rest, bed down, and find hay and water. One rule of thumb is 1 hour of rest for every hour on the truck. However, if calves are local and won’t require a great deal of time to process, they may be processed either immediately off the truck or after a short rest. Have the receiving pen bedded with light colored material, such as corn stalks or wheat straw. The surface temperature of these materials is much lower than dirt or manure pack during the heat of the day, and either on a hot day or following a rain this area will be a welcome area for tired calves.
After they’ve rested, process the calves as you would other high-risk calves. But during the summer months, avoid processing after about 9 or 10 a.m., depending on the temperature forecast. The heat accumulated during handling, standing, mingling, and processing, will add to the heat accumulated during the heat of the day, adding to stressful conditions, and reducing the animals’ ability to fight disease. Cloudy days are less critical than sunny, and humidity always makes the rising temperature more challenging.
After processing, make sure the animals have access to abundant, fresh, clean water. Have you checked the water tanks in your receiving pens lately? Scum and algae probably don’t make the water tank appealing and a few minutes may improve your outcomes.