May, 1997 ^. Volume 20, Number 4

Fly management on a hog farm is largely a matter of good sanitation. Flies are attracted to manure and other decomposing organic matter, and are not a serious problem where waste is handled properly. Modern hog facilities are designed to dispose of the manure and urine generated by a large number of animals kept in confinement. The proper maintenance and operation of these waste handling systems reduces the accumulation of material suitable for fly breeding.

The important phrase to remember in this discussion is, "...suitable for fly breeding". The odors commonly associated with any type of animal facility (e.g., confinement buildings, corrals, kennels, stockyards, etc.) attract a wide variety of fly species. These can properly be thought of as the background population of flies attracted to potential breeding sites. This "potential" is always present with animal production, but it's wrong to assume that the surrounding area will be overrun with flies simply because a hog farm or other animal facility is nearby. A little understanding of what makes suitable fly breeding habitat, fly movement and fly behavior will help the hog farm manager minimize the likelihood of raising more than hogs at his or her facility.

Filth flies (mainly house flies and related species) have specific requirements for successful reproduction. There must be suitable material (manure or carrion in this case) for them to lay eggs, and for the maggots that hatch from these eggs to feed. There must also be suitable sites for the fly maggots to pupate and complete their development to adult flies. On both counts, the design and operation of swine waste handling systems do not provide opportunity for successful fly reproduction. Manure and other wastes are flushed regularly into a holding lagoon where they are unavailable for fly breeding. Even were house fly maggots able to survive in the lagoon, there are no adequately dry locations for successful pupation. Admittedly, there is a small amount of fly breeding that occurs on a hog farm, but it is minimal. In general, there is less suitable fly breeding habitat available in a properly managed hog building than there is in a horse barn half its size.

What about fly movement? Do flies typically move from the hog farm to other locations? The simple answer is no. Movement is limited. There have been a number of studies over the years looking at the question of house fly dispersal in urban and agricultural settings. To summarize, fly numbers drop off dramatically at distances greater than 50 to 100 meters from breeding sites (e.g., dumpsters, poultry houses and cattle lots). When dispersal does occur, the tendency is toward other potential breeding sites. The consensus among researchers is that house flies will disperse no more than a mile under normal conditions. The perception of long distance dispersal from hog and poultry houses probably has more to do with relative fly density in a given area, weather events and nearby breeding sites that may go unnoticed (crop debris, dumps, kennels, small loafing pens and barns, poorly maintained compost piles, etc.). It=s important to point out, however, that the limited dispersal of filth flies is not an excuse to neglect fly management.

Now, let's talk about pesticide use. From time to time, insecticides may be needed to reduce fly numbers no matter how well a farm is managed. One of the biggest mistakes made with chemical fly control is the way in which surface applied insecticides are used. There are two things that usually go wrong: 1)Putting spray where it's not effective; and, 2)using the least effective formulation. The best that can happen in either case is that the treatment won't control flies. Application of the "right" kind of surface spray to the "right" target can reduce labor, save money and minimize the risks to the environment.

Let's start with the second point. Most of us don't think much about the kind of formulation used when it comes to applying sprays to a surface for fly control. It does make a difference though. Making the correct choice is pretty straight forward. It all depends on how porous the treated surface might be. Where surfaces are porous (unpainted cement block and wood for example), a wettable powder formulation is generally the best choice. Once dry, wettable powders leave a more uniform residue on these rough, porous surfaces. Emulsifiable concentrates, on the other hand, are absorbed into porous materials and may not be as well distributed over the surface of porous building materials. Emulsifiable concentrates are equally effective on less porous surfaces such as painted blocks, metal and vinyl. Even though wettable powders are as effective in this case, they may be less desirable because they are harder to mix and require constant agitation.

There's one other point to be made about formulations and the type of surface treated. Remember that no matter which formulation is used, rough, porous surfaces will need significantly more spray for thorough coverage than smooth, impervious surfaces. For example, cyfluthrin formulations used for fly control call for 1 gallon of spray (water) for each thousand square feet of painted plywood surface. Compare that with the recommendation of 2.7 gallons for a thousand square feet of unpainted plywood. Where painted cement block is to be treated, cyfluthrin labels still call for 3.2 gallons of spray per thousand square feet. Treatment of unpainted cement block calls for 36 gallons of spray for each thousand square feet!

Finally, fly sprays need to be targeted where they'll do the most good. All too often I see surface sprays for fly control applied to every available surface in swine buildings. This practice is wasteful and can be dangerous to non-target organisms. A more selective approach to the application of fly sprays significantly reduces risk and saves both labor and insecticide.

House flies tend to migrate upward at night. A large percentage will spend the evening resting on rafters and other overhead surfaces. That's where to direct surface sprays. Alternatively, treatment under eaves and on the southern or eastern exposures of exterior walls will often yield good results. Southern and east-facing walls are particularly good treatment areas when evening temperatures are cool. Large numbers of flies gravitate to these exposures to warm up in the morning. It's simply not necessary to spray the entire building from top to bottom, inside and out. It pays to observe where flies tend to congregate in any building. Those are generally the only sites one needs to treat.

Mike Stringham
Dept. of Entomology, NCSU

Adding gilts into the breeding herd is a major task in sow herd management. The magnitude of this task is highlighted by the large replacement rate that all sow herds experience. In PIGTALES REVIEW 1996, the average annual replacement percent for all US herds that were recorded in PIGTALES in 1995 was 52.6 percent. This included 367 farms with 251,095 sows. The annual replacement rate in the top ten percent of those herds, based on pigs weaned per sow per year, was 44.3 percent.

Critical to the success of adding in the necessary herd replacements is accurate estrus detection in the gilts. A recent report from Nebraska indicates that, of the several variables suggested to influence heat detection, the actual method of detection may be the most significant.

In the 1997 NEBRASKA SWINE REPORT, researchers Dr. Dwane Zimmerman and Denny Aherin reported on their study that compared accuracy and rapidity of heat detection in gilts heat checked with fence line exposure in each of three treatments. These treatments were with gilts housed in either stalls or in pens and given fence line boar exposure or with gilts housed in pens and relocated to the boar room for fence line exposure.

Twenty-four gilts, each of which had cycled two or more times, were randomly assigned to one of the three treatments. The stalls were 18 inches wide with vertical bars on 4 inch spacings on the front gates. The gilts in pens had four to the group in 6 foot by 9 foot pens that had front gates with vertical bars on 4 inch spacings. The gilts in the third group were in pens similar to those in the other pen treatment but were relocated to the boar room for fence line heat detection. After all the gilts completed one heat detection observation, they were rerandomized across treatments and again heat checked with the same procedures. All gilts were housed in the same room and not exposed to boars except during the actual heat checking process. Two boars were used on alternate days for 10 minutes of fence line exposure daily.

All but one gilt had two estrus periods during this experiment. One other gilt had a 33 day estrus cycle and the experiment was concluded before her second heat period.

The completed observations are outlined in Table 1. Detection of both first and last day of heat with in-place fence line boar exposure was essentially the same in gilts housed in pens and stalls (stalls, 67% vs. Pens, 68%), but heat detection rate in gilts relocated to the boar room was higher (81%, P < .05). All gilts, regardless of how they were housed (stalls or pens) or were they were heat checked (in-place or relocated), responded during mid-estrus.

Gilts relocated for boar exposure responded more quickly to heat checking than those left in-place (1.7 min vs. 2.3 min, P < .05). Also, gilts in pens tended to respond more quickly than those in stalls (2.0 vs. 2.5 min, P < .10) when both were heat checked in-place. No difference was detected in the duration of estrus among the treatment groups. Overall, the average length of estrus was 52.1 hours.

The researchers concluded from this study that relocating gilts from their home environment to another environment for boar exposure gives a higher rate of heat detection and a more rapid estrus response than obtained in gilts heat checked in-place. Also, gilts not responding to fence line exposure should be given physical boar exposure. Additionally, method of housing gilts, ie. pens or stalls, is of much less importance than the method of exposing them to the boar. In summary, they stated that the key to achieving accurate and rapid heat detection is to provide gilts with novel stimuli, including physical contact, from a high libido boar(s) at a site other than the gilt's residence.

Charles Stanislaw

If water is recycled from the treatment lagoon, salt buildup in pumps and pipes is a common problem. Avoid sharp turns in the supply pipe because they add to pressure drop and create turbulence conducive to salt precipitation. Regular addition of dilution water to the lagoon and removal of salts by irrigation will reduce problems. In most areas of the U.S., add a volume of dilution water which is equal to the volume of waste added. Use fresh water, lot runoff, roof runoff or other sources of dilution water.

Dilute acetic or hydrochloric (muriatic) acids can be used to dissolve salt deposits. Muriatic acid can be bought in paint and hardware stores and is usually available at 20% solution. Plastic pipe can be dosed with undilute 20% muriatic acid solution by filling the piping system with this acid, letting it stand overnight and then flushing the acid solution through the system. If possible, field spread this acidic high salt material at a very low rate, rather than back to the lagoon. If the flush system has metallic parts such as pump housing or metal valves, the acid should be diluted (1 part acid to 12 parts water) to prevent damage to the metal. CAUTION: DO NOT ADD WATER TO CONCENTRATED ACID! WHEN MAKING THE DILUTION-ALWAYS ADD THE CONCENTRATED ACID TO WATER. Use care and wear protective equipment because mixing acid can be very dangerous!

The following recommendations can reduce the rate of salt buildup on a recycling system:

• Ground the electric pump-housing to prevent an electrostatic charge from building up on the metallic parts of the pumping system. Even if the pump is grounded through the electrical system, ground the pump by attaching a cable to the pump-housing and to a ground rod driven into damp soil.
• The pump suction line must be large enough to prevent cavitation (excess turbulence, resulting in a sharp pressure drop and increased salt deposition). A rule of thumb is that the suction line should be one standard size larger than the discharge of the pump. Locate the pump below or as close to the lagoon water level as possible to minimize the suction lift.
• If the pump does not run continuously, modify the system so the pipes can drain between use.
• The pipe from the lagoon to the gutter should have a minimum diameter of 1-1/2 in. The problems are not as great in large lines as they are in smaller ones.
• Consider oversizing the supply pump and piping system, operating it on a timer and allowing the system to drain when not in use. While more expensive to purchase, contact time between the pump and pipes and the lagoon water can be greatly minimized in this manner.

PIH-63
"Recirculation Systems
for Manure Removal"

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Last modified August 1, 2000