Fly Control

Posted by Dr. Travis White on June 26 2009 08:58

With summer fast approaching it is time to think about fly management and control for our cattle operations. "Horn" and "face" flies are more numerous on pastured and range cattle than on feedlot animals. This occurs because horn fly eggs are deposited in fresh cow manure and develop there. The manure patties in feedlots are much more likely to be stepped on, broken up and the fly cycle disrupted. "Horn" flies stay on the cattle continuously and suck blood, which causes irritation as well as loss of nutrients while "face" flies tend to be more of an annoyance and a vector for disease such as pink eye.

The number of "horn" and "face" flies per animal varies with the time of year, location, and weather patterns. In South Dakota, their numbers gradually increase through late spring, hold steady during the mid-summer months, and then decrease rapidly with frost in the fall. The economic threshold is generally considered to be 100 to 200 flies per animal. If left untreated, horn fly numbers may reach several hundred per animal by late July or early August. At this level, cattle will usually bunch, fail to graze properly and expend considerable energy in tail switching, head throwing and stamping in an attempt to dislodge flies.

High numbers (over 200) of flies may reduce weaning weights, because of reduced cow milk production, yearling weights and cow body condition scores. The degree of loss is associated with quantity and quality of forage available and climate. Hot, dry weather and horn fly stresses seem to be synergistic in Nebraska studies. Weaning weight losses ranged from an average of 22 pounds per calf on a hot, dry year to three pounds on a cool, wet year with an average reduction of 11 pounds per calf over a 10-year study period. Nebraska and Canadian studies indicated that at population levels of less than 200 horn flies per animal, neither weaning nor yearling weights were affected. In addition to losses from "fighting" away flies is the loss incurred due to increased transmission of diseases such as pink eye is significant.

So you need to ask yourself: Are the fly numbers on my cattle high enough to be worth controlling? Is the program and products I am using, working effectively? Spend a little time on several occasions this summer and observe their fly-fighting behavior. Also, ride or walk through the cattle and estimate how many horn flies are present on 15 head and then average up the numbers. You will find that you can soon have some actual information on which to base management decisions.

There are several methods of fly control that can be considered for cattle that are on pasture:

1. Insecticide Ear Tags

   (It is recommended when tags are used that the following guidelines be observed to help prevent a rapid buildup of resistance in the fly population to the product used)

   • Don't apply the tags until the horn fly numbers reach 100 to 200 per head.
   • Follow manufacturer's directions on one or two per animal and whether to also put in calves ears.
   • Rotate the insecticide used in the tag each year; pyrethroid one year and organophosphate the next, etc.
   • Remove the tags in late summer when insecticide content has greatly decreased.

2. Spray or pour-on insecticide

   • Gives a rapid effect against "horn" and "face" flies, but may not last as long. It appears that fly numbers can be kept low if cattle are poured in late June or early July rather than in May when cattle rarely need fly control at that time.
   • Also provides internal parasite control which may result in better feed conversion and average daily gain.

3. Backrubbers

   • Work well in pastures and the animals will "treat" themselves.
   • Backrubbers do require some time and effort to load with insecticide and maintain them.
   • Portable backrubbers can be moved from one pasture to another but bulls are really rough on them and may tip them over.

4. "Feed Through" Insecticides

   • Breaks the fly life cycle
   • Provides long term fly control
   • Safe and effective
   • For best results begin feeding just before the start of fly season

Regardless of which method you choose to control flies on your operation it is important to remember that effective control can only be accomplished if all cattle are treated. Treating only certain classes of cattle will only result in other cattle being overburdened by flies.

Important points to keep in mind: flies can cause a significant economic loss, if present in sufficient numbers on cattle. You can monitor your herd, relatively easily. Several methods of control are available if you decide it would be economically worthwhile. Treat all cattle.

"IMPLANTING" Performance into Your Calf Crop

Many management practices have been developed over the years that significantly help performance and productivity in beef cattle. Of the various practices adopted by many operations one of the most effective, if not THE most effective is the use of growth implants in suckling calves, young growing cattle and finishing steers and heifers destined for slaughter.

Implants are small pellets or devices that are placed under the skin at the back of the ear. Each pellet contains a growth stimulant that is slowly released in to the blood circulation and is subsequently carried to the tissues. We'll discuss more of how implants actually work in a moment.

In a review by Griffin and Mader (1997) they discussed that growth promoting implants have been used extensively in beef production for over 30 years and over this time significant changes in implants and implanting strategies have occurred. Before 1987, available implants were estrogenic agents which metabolically enhanced nutrient use to enhance growth. These products improved feed efficiency 5-10 percent and daily gains from 5-15 percent. In 1987, the androgenic (tissue building) agent, trenbolone acetate, was approved for use in growth promoting implants. This compound had an additive effect with existing estrogenic implants. The androgenic implant enhanced muscle growth and added an additional two to three percent to the feed efficiency and three to five percent to the daily gains.

Today, implants have become almost designer products with varied doses and combinations of estrogenic and/or androgenic agents. While implants tend to be most effective in feed yards, implanting strategies have been effectively applied to other beef production situations. A review by McCollum (1998) showed that implanting of suckling calves and stocker cattle offers one of the highest cost to benefit ratios of any management practice.

Remember there are no substitutes for good management and there are no "silver bullets" out there. Cattle must have adequate nutrition before implants can positively influence feed efficiency and gain. The greatest response to implants tends to be observed in older cattle, near peak periods of lean tissue deposition. Typically these would be yearling cattle consuming high levels of high energy feed but a significant effect is also seen in suckling and grass cattle.

When growth promoting implants are first placed in the animal, there is a rapid release of hormone from the implant. The level of growth promotant being released from the implant will begin to fall after a few days but will remain above an effective growth stimulating level for a varying length of time depending on the design of the implant and the quality of technique used when administering the implant placement. The length of time an implant releases growth promotant at or above the effective level varies from approximately 75 days to an estimated 200 days.

Reimplanting, which is the administration of an additional implant, is usually scheduled to coincide with the declining level of circulating implant growth promotant, but always above the effective level. The optimum reimplant time is referred to as the reimplant window. For maximum benefit, it is important to maintain the level of implant growth promotant above threshold throughout the ownership of the stocker or feeder animal. Therefore, the highest rates of gain can be expected during the first part of the effective period.

The estrogenic implants approved for use in suckling calves have been shown to improve weaning weights three to five percent. Similar performance improvements can be seen in pastured stocker cattle when the base gain is above 1.5 pounds per day.

Previously implanted cattle are of concern to cattle buyers who take advantage of compensatory gain potential of cattle. Producers should receive a premium equivalent to the loss of production to consider not implanting suckling calves or stocker cattle.

In feeder cattle, estrogenic growth promoting implants improve feed efficiency and gain 5-15 percent. Implants which include TBA can provide an additional three to five percent improvement in feed efficiency and daily gain. A properly designed reimplant program can sustain implant associated improved performance beyond the payout that would be expected for a single implant.