Fly control is critically important on all livestock farms. Flies negatively impact dairy calves in two primary ways:
- Spread disease such as E. Coli and Salmonella
- Reduce animal comfort, resulting in increased stress and reduced efficiency of growth
The key with any fly management strategy is to start early in the season before fly populations become a problem. A simple but useful way to monitor the fly population on your farm is to place at least 10 3-by-5-inch index cards throughout your operation. Take corrective action if more than 10 fly spots (black dots) occur on any one card during a 24-hour period. It is important to develop an integrated pest management plan to maximize fly control on your operation.
Maintain sanitized environment
The first step is maintaining sanitation within the calf’s environment. Flies reproduce in undisturbed, damp organic matter. Minimize the amount of wet bedding, wasted hay, and manure near calves and heifers. Remove and dispose of wasted feed daily. Consider alternative bedding. Some calf growers will switch to sand bedding during the summer. Sand is inorganic and does not support the growth of flies.
Work toward building your whole program around source reduction through prevention and debris management. Scout for maggots to see where flies originate and then target debris management tactics accordingly.
Soiled bedding under confined calves and heifers is likely to be the principal source of house flies and stable flies. Organic debris left over from winter is a big hazard and should be dispersed by May 1 (and probably earlier the farther south you are).
Spilled hay, TMR, and silage, if wet, will be fly sources too. Organic debris older than two weeks in summer will have been around long enough to produce new adult flies. So, if scrape-and-haul is an option, do it every-other week and replace with fresh bedding. Haul to spread or to active compost, not just cold stack. Flies will easily disperse a half mile, so simply stacking soiled bedding in a corner of the property will not be adequate. Eliminate weeds and tall, unwanted vegetation around facilities to reduce attractiveness to flies.
Insect growth regulators
Next, consider feeding an insect growth regulator. An insect growth regulator (IGR) is a feed additive that can be added to milk or milk replacer (either during milk replacer manufacturing or as an add-pack). It may also be added in calf starter grain. An IGR should be added to the feed several weeks before the start of fly-season so that manure in calf housing contains IGR if and when flies begin reproducing.