Research and IPM

Access industry mite treatment, egg production, and feed consumption records (5 years) to determine possible economic benefits due to mite control.

A five-month study on the UCR campus supports results from the commercial operation. Feed conversion declined, and egg weights were 0.5 to 1.0 g less than in hens with few or no mites. This trend also reversed in a switchback design. Northern fowl mites impact production. This effect may not be seen unless one considers feed consumption and egg weights, as well as hen day production. The studies will be repeated under controlled conditions at least one more time.

Commercial treatments are more effective if early infestations are treated, underscoring the need for mite monitoring. Mites spread from focal infestations that begin in sporadic locations throughout previously infested houses. Egg collection belts enhance the speed and efficiency of mite spread within a row.

We now have followed four hen flocks (four houses per flock with 25,000-30,000 hens per house) for most of the first lay cycle. Fifty marked sentinel hens per house are sampled weekly for mites and twice per month those hens are also weighed. Mite infestations and weights are compared periodically with hens from the general flock to ensure the sentinel birds are representative. Weights of 100 eggs per house are also determined twice per month.

All flocks have arrived (ca. 20 weeks of age) parasite-free. The first mites generally have been detected by about 25 weeks of age. Parasites spread from focal infestations more rapidly along rows of cages, particularly when egg collection belts are used. Treatments with tetrachlorvinphos-dichlorvos (RaVap) thus far have been much more effective at eliminating light infestations than heavy ones, emphasizing the potential advantages of sampling and early treatment. Data analysis is pending regarding mite effects on production and hen and egg weight.

We are now working on two ranches. Beginning at 22-24 weeks of age, we have monitored 50 marked hens in each of four houses (identical in design and management) per farm. Parasites are assessed weekly. Hens and 100 eggs per house are weighed bimonthly. We have sampled randomly selected hens from each house, to compare with our marked hens and confirmed our hens represented the flock in parasite numbers and weights.

Hens arrived parasite-free, but the two sites differed. The first parasites were detected at 25-27 weeks of age. Parasites spread in the flocks from focal introductions, which occurred very rapidly for mites at site 1. By 4-6 weeks from first detection, mites were abundant on hens (> 80% infestation in two of four houses). When hens were 33 and 35 weeks of age, two houses were sprayed with RaVap, maintaining mite populations at a low level (<30% infestation). This created a large difference in mites. Two houses with high mite numbers peaked in week 35, followed by a natural reduction. Houses which were low initially are now experiencing severe mite buildup, and we are watching the egg data. Preliminary data suggest reductions in egg production and feed consumption due to mites.

Site 2 had both mites and biting lice, Menacanthus stramineus. Lice reproduce less than half as quickly as mites, but mites appear to be eliminated by lice when they co-occur on a hen. The slower buildup at site 2 delayed the treatment. One spray has been applied to date, but a second treatment has been delayed by cold weather.