Impact of Northern Fowl Mite on Broiler Breeder Flocks in North Carolina 1 J.J. ARENDS, S. H. ROBERTSON, and C. S. PAYNE Department of Entomology, North Carolina State University, Raleigh, North Carolina 27695-7613 (Received for publication January 6, 1984) ABSTRACT The impact of a northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini and Fanzago), infestation on broiler breeder layers in the field was evaluated by comparing flocks in two adjacent houses (ca. 5, birds each). The NFM-free birds produced 3,158.7 dozen more eggs than NFM-infested birds, which was equal to 7.7 eggs per hen housed more than infested birds over the life of the flock. Feed efficiency was affected; feed costs for NFM-infested birds ranged from $.1 to $.6/dozen higher than the feed costs for NFM-free birds. (Key words: northern fowl mite, broiler breeders, egg production, feed efficiency) INTRODUCTION The northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini and Fanzago), is a hemotophagous ectoparasite of poultry and considered to be the most important ectoparasite of poultry in the United States (DeVaney, 1978). There is, however, some disagreement as to the specific impact that NFM has on poultry. Decreased egg production from mite infested birds has been reported by DeVaney (1978, 1979) and Matthyssee et al. (1974), whereas Loomis et al. (197) found no difference in egg production. Birds with severe mite infestations have been shown to exhibit anemia (Matthyssee et al, 1974), decreased seminal fluid (Deloach and DeVaney, 1981), and weight loss (DeVaney et al., 1977). In addition, northern fowl mites are an irritation to egg handlers and people working near infested flocks. All previous investigations evaluating the impact of NFM have been conducted with caged layer birds, and the impact of NFM on broiler breeder layers has not been examined. The production practices used with broiler breeder layers are much different from caged birds. In broiler hatching egg production, roosters and hens are unrestrained in a house, are on limited feed, and social interactions that are stressful may influence the impact of a NFM-infestation on broiler breeder layers. 1 Paper No. 996 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7613. The use of trade names in this publication does not imply endorsement of the products named or criticism of similar ones not mentioned. 1984 Poultry Science 63:1457-1461 In North Carolina, the Agricultural Extension Service has instituted a poultry integrated pest management program that utilizes ectoparasite monitoring and cultural, biological, and chemical controls to manage pest populations in an attempt to maintain pests below economic injury levels. Our field investigation was conducted to elucidate the impact of NFM on broiler breeder layers and to define an economic threshold and economic injury level for NFM on breeder flocks. MATERIALS AND METHODS One flock of 9,8 Peterson males and Arbor Acres pullets were randomly allocated at 22 weeks of age to two adjacent side slat broiler breeder layer houses, 4,9/house with a male to female ratio of 1:1. The birds were maintained using standard production procedures for broiler breeder layers with automatic waterers, chain feeders, and manual egg collection. The birds were brought into production at 28 weeks of age and were taken out of production at 68 weeks of age. Mortality, feed consumption, and egg production were recorded on a daily basis from each house throughout the life of the flock. All management decisions concerning lighting, amount of feed increases and decreases, etc. were made by the flock serviceman. The poultry operation was a participant in the North Carolina State University Integrated Pest Management (IPM) program, and as such, the birds and facilities were monitored for pests and ectoparasites on a twice monthly schedule. Ectoparasite monitoring was done by entering the house, randomly selecting hens and roosters {ca. 2 each 1457
1458 ARENDS ET AL. TABLE 1. Numerical rating equivalents of number of northern fowl mites (NFM) per bird Rating No. NFM/bird 1-1 11-1 11-1, 1,1-1, 1,1 + house) and examining them for the presence or absence of NFM. Each bird was rated using the rating scheme of DeVaney (1981) (Table 1). An average mite rating for each house was obtained by averaging bird scores in each house each week. An arbitrary economic threshold of 11 to 1, NFM per feather part (Score 3) was used in the IPM program. This threshold was based, in part, on accepted levels of mites on birds by poultry flock servicemen. Treatment of birds was not recommended until the average score of all birds monitored exceeded a score of 3. The data for all measurements from the flock were analyzed by an analysis of variance test using the general linear model procedure of Statistical Analysis System (Helwig and Council, 1979). RESULTS AND DISCUSSION The production curves of the two flocks (Fig. 1) were identical until Week 41, when some differences were observed. The NFM were first observed at Week 43 in House 1. At this time, efforts by the producer were taken to avoid transfer of mites into House 2 by always completing all work in House 2 for each day prior to entering House 1. Care was taken to inspect flats prior to taking them into the house, and NFM were kept out of House 2 during the investigation by following these procedures. At Week 46, the average NFM score was 1 + in House 1. The NFM populations continued to increase in House 1 and by Week 48, 7% of the birds monitored were given a NFM score of 3. It was at this time that treatment for NFM was recommended. The flock was treated at Weeks 54 and 56 with Rabon as recommended by the manufactures. Little NFM control was observed following the initial spraying due to poor application technique. Corrections were made in spraying technique and greater than 95% control was observed following the second spraying. Percent production between the two houses was equal throughout the months of January and February (Weeks 33 to 4). Following the initial infestation of NFM (Week 43), House 1 (NFM-infested) production began to decline below that of House 2 (NFM-free) (Fig. 1). Production in House 1 fell below 7% at Week 45, whereas production in House 2 did not fall below 7% until Week 52; the NFM free-house had 7 additional weeks of production at>7%. Production from the NFM-infested birds continued to be significantly below that of the NFM-free birds until Week 61 (Fig. 1). Successful treatment at Week 56 was responsible for the plateauing of production (Fig. 1) at that time. There was no significant increase in production following successful treatment but rather a leveling of the production until it equaled that of the NFM-free house (Fig. 1). Another indication of the impact of NFM on r 3 3 2 J&6 3 3 6 8 LEGEND: % 4 A 4 4 4 2 4 & & A 2 X 6 WEEKS OF AGE HOUSE 1 - NFM score i> 2 = ffm score 1+ 3 = NFM score 3 4 - Treatment 4 Vfl_BAi 4 a' "* FIG. 1. Effects of northern fowl mites (NFM) on broiler-breeder layer production when hens were naturally infested with NFM (House 1) or no NFM were present (House 2).
RESEARCH NOTE 1459 the birds was illustrated by production in House 1, which was erratic when compared to that of House 2. The erratic and depressed production from House 1 was an indication of the stress on the birds from the NFM infestation and was similar to that reported by De- Vaney (1978). For comparison of production on an individual house basis, the eggs per hen housed/ month (EHH) were computed (Table 2). There was no significant difference between the numbers of EHH for Months 1 and 2. Beginning with Month 3, the onset of the NFM infestation, and continuing until Month 7, House 2 had significantly more (P<.5) EHH than the NFM-infested house 1. These differences ranged from.67 to 2.1 EHH with the total average EHH for House 1 = 15.3 EHH and House 2 = 157.73 EHH. House 2 (NFM-free) had 7.7 EHH more for the total life of the flock. In total egg production, 3158.7 doz more eggs were produced from the NFM-free House 2. The direct costs incurred by the producer from the decreased production of 3148.7 doz eggs from the NFM-infested house would have been $661.22, using a.21/doz contract price. Actual value of the eggs to the integrator can be computed using $1.4/doz for a total cost of the NFM infestation in House 1 of $3,274.65. If the birds had been treated at the initial discovery of the infestation, treatment costs would have ranged from $9.2 to $25 for insecticide plus labor to apply treatment, for a total cost of $5 to $1 for two treatments at a 1- to 14-day interval. The impact of NFM should be measured not only in decreased egg production but also in total bird or flock performance. Feed costs account for 65% of the costs associated with production, and as such, if feed intake and utilization are affected by an ectoparasite infestation, the monetary loss could be substantial. In many cases, when production is observed to be below expected levels, the first corrective measure is to increase the amount of feed per day to bring the flock back into its "expected" production. Although this increase can often allow the birds to compensate for stress and produce at the expected level, it adds cost to the total cost of production and results in poorer reproductive function due to increased body weight (McDaniel et al., 1981). Feed increases were administered in House 1 in an attempt to equalize production with House 2. The impact of the NFM, however, was great enough that these feed increases did not totally remove production differences and in fact they greatly increased costs (Table 3). During Months 1 and 2 (Table 3), there were no differences in kg feed/doz eggs; however, from Month 3 to 8, differences in kg feed/doz eggs ranged from $.1 to $.6/doz. In this case, birds affected by NFM produced less eggs and were fed more feed than the NFM-free birds, thereby increasing production costs. DeVaney et al. (1977) reported decreased volume of seminal fluid from NFM infested birds as well as decreased body weights of the infested birds. Hatchability records were not available; however, DeVaney (1978) reported TABLE 2. Comparison of eggs per hen housed (EHH) per month of NFM infested broiler breeder layers and NFM-free broiler breeder layers Month Age in weeks first of month House l 1 House 2 Difference H2-H1 1 2 3 4 5 6 7 8 Total EHH 33 37 41 45 49 54 58 62 2.2 21.18 22.71 19.94 19.24 17.2 14.2 15.72 15.3 19.61 21.76 23.38* 21.68* 21.34* 18.62* 15.24* 16.1 157.73.67 1.74 2.1 1.6 1.4 7.7 1 Infested with NFM. Means for EHH/month significantly different (P<.5).
146 ARENDS ET AL. TABLE 3. Comparison of kilograms feed per dozen eggs of broiler breeder layers infested with northern fowl mites (NFM) and NFM-free broiler breeder layers Month House l 1 House 2 Difference Hl--H2 Feed cost 2 differential/ doz 1 Infested with NFM. 3.22 2.61 2.63 2.83 2.94 3.12 3.2 3.27 2 Feed at $18/97.18 kg. (kg feed/doz eggs) 3.17 2.64 2.56 2.6 2.63 2.87 3. 3.1 that certain roosters with heavy NFM infestations would not produce semen and hens with NFM did not lay during the peak NFM infestation. This aspect could not be evaluated in this flock because hatchability records were not available on a house basis. The data from our investigation indicate that there was a substantial economic loss from an infestation of NFM in broiler breeder layers at low to moderate levels, Score 1 in this investigation. Treatment was recommended at a NFM level that was too high to avert economic loss from the NFM infestation but at a level lower than that used by many producers to determine when treatment is needed. Data from studies (unpublished) indicate that once established, NFM numbers continue to increase and can be spread to other uninfested farms via egg flats and cases. Control of the NFM when at low numbers is required to stop transmission to uninfested farms and to avert economic losses from this pest. By using an integrated approach, such as North Carolina Extension Service's poultry IPM program, proper monitoring for NFM is done at regular intervals, enabling early detection of NFM infestations and the use of cultural and chemical controls to control the NFM. Cultural controls such as isolation of egg flats and cases from an infested farm, all service personnel using clean coveralls and boots at each farm, etc. can be used in conjunction with properly applied chemical treatments to control ectoparasites..4 -.3.7.23.31.25.2.17.1.4.6.5.4.3 Data from this investigation and unpublished data suggest that an economic threshold for NFM in broiler breeder layers would be a single infested bird. Treatment of the flock at this time would be recommended to avert subsequent mite population increases on the flock and transmission of NFM to other farms, causing losses in these flocks as well as greater treatment costs to control NFM in more than one flock. REFERENCES DeLoach, J. R., and J. A. DeVaney, 1981. Northern fowl mite, Ornitbonyssus sylviarum (Acari macronyssidae), ingests large quantities of blood from White Leghorn hens. J. Med. Entomol. 18:374-377. DeVaney, J. A., 1978. Effects of the northern fowl mite, Ornitbonyssus sylviarum (Canestrini and Fanzago), on fertility and hatchability of eggs from artificially inseminated White Leghorn hens. Poultry Sci. 57:1189-1191. DeVaney, J. A., 1979. The effects of the northern fowl mite, Ornitbonyssus sylviarum, on egg production and body weight of caged White Leghorn hens. Poultry Sci. 58:191-194. DeVaney, J. A., 1981. Effects of the northern fowl mite, Ornitbonyssus sylviarum (Canestrini and Fanzago), on egg quality of White Leghorn hens. Poultry Sci. 6:22-222. DeVaney, J. A., M. H. Elissalde, E. G. Steel, B. F. Hogan, and H. D. Peterson, 1977. Effect of the northern fowl mite, Ornitbonyssus sylviarum (Canestrini and Fanzago) on White Leghorn roosters. Poultry Sci. 56:1585-159. Helwig, J. T., and K. A. Council, ed., 1979. SAS User's Guide. SAS Inst., Inc., Raleigh, NC. Loomis, E. C, E. L. Bramhall, J. A. Allen, R. A. Ernst,
RESEARCH NOTE 1461 and L. L. Dunning, 197. Effects of the northern fowl mite on White Leghorn chickens. J. Econ. Entomol. 63:1885-1889. Matthyssee, J. G., C. J. Jones, and A. Purngsiri, 1974. Development of northern fowl mite populations on chickens, effects on the host, and immunology. Search Agric. 4(9). McDaniel, G. R., J. Brake, and R. D. Bushong, 1981. Factors affecting broiler breeder performance. 1. Relationship of daily feed intake level to reproductive performance of pullets. Poultry Sci. 6:37-312.