Effect on Acceptability and Fecundity to Pigeons of Coating SC 12937 Bait with Zein or Ethocel

Pigeons (Columba livia) fed 0.1 percent SC 12937-treated corn coated with Zein or Ethocel over a 10-day period ate only about one-half that eaten by birds fed untreated corn. Dosage was approximately 0.16 gm SC 12937 per bird. When offered a choice between treated corn coated with Zein and corn that had not been treated or coated, the average daily intake per pair was only 2.3 gm of the treated Zein-coated corn but 44.S gm of the control corn. The maximum weight loss in the pigeons, due to bait refusal, during the lSday treatment period was 28 percent. Results of blood analyses and fecundity data support the findings of other researchers that SC 12937 is a debilitatig agent rather than a chemosterilant. Transaminase and buffy layer values of treated birds increased during treatment and remained high for most of the 160-day experiment period. Depressed fertility occurred for 3 months in the Zein group and S months in the Ethocel group, while fertility of pigeons with a choice of food was normal. Mean clutch size was not depressed in any group, but number of one-egg clutches increased during the first 4 months in the Zein group. Four treated birds died during the experiment; at autopsy, internal anatomical abnormalities were found in the majority of Zein and Ethocel group birds. Neither Zein nor Ethocel coating increased acceptability of SC 12937-treated corn by pigeons, and pigeons with no choice of food other than SC 12937-treated corn become physically debilitated, thereby reducing reproductivity. Elder ( 1964:556) suggested a hypocholesterolemic compound 22, 25 diazachloestanol dihydrochloride (SC 12937, G. D. Searle and Company, Chicago)3 may be useful as an oral contraceptive agent for nuisance birds. Research on chickens by Nichols et al. (l962) is in agreement with Elder ( 1964 ) and Wofford and Elder (1967) working with pigeons, that reproductivity of these birds is reduced after oral consumption of SC 12937. Experimentation by Powell ( 1966 ), Becker ( 1966 ) and Lofts et al. (1968) suggested that SC 12937 ingested at the level recommended by Elder is toxic to pigeons and quail ( Coturnix coturnix ) . 1 This is a contribution of the Massachusetts Cooperative Wildlife Research Unit ( supported by the U. S. Bureau of Sport Fisheries and Wildlife, The Massachusetts Division of Fisheries and Game, the University of Massachusetts, and the Wildlife Management Institute ) and the Massachusetts Agricultural Experiment Station. 2Present address: Department of Poultry Science, University of Wisconsin, Madison. 3 Trade names referred to in this publication do not imply endorsement of commercial products. 776 This paper reports a study conducted to determine the acceptability of Zein-(prolamine, alcohol-soluble protein in corn gluten) and Ethocel-(ethyl cellulose) coated SC 12937 bait as compared with untreated bait. A second objective of this study was to determine the effect of SC 12937 on fecundity of pigeons for 5 months after treatment. Previous work on birds svith SC 12937 (Powell 1966, Becker 1966, and research in our laboratory) suggested that the depressed reproduction may have been due to general debilitation. Therefore, several indicators of general health were recorded in this study. MATERIALS AND METHODS The experimental design is sunlmarized in Table 1. All 80 pigeons, from feral flocks in central Massachusetts, were laparotomized to determine sex before being paired at random. Except when on treated food, pigeons had commercial pigeon pellets and water ad libitum during the study. This content downloaded from 207.46. 13.33 on Wed, 23 Nov 2016 04:32:26 UTC All use subject to http://about.jstor. org/terms Table 1. Experimental design for testing acceptability by pigeons of corn treated with O.l-percent SC 12937 and coated with either Zein or Ethocel. GROUP NUNIBER OF PAIRS TREATSIENA COATING CHOICE Zein 10 0.1% SC 12937 Zein no (0.16 gm)a Ethocel 10 0.1% SC 12937 Ethocel no (0.16 gm) Choice 10 0.1% SC 12937 Zein yes (0.01 gm) Control 10 None none no a Actual dosage as derived from total treated food eaten by end of treatment period. EFFECT OF COATINGS ON BAIT ACCEPTABILITY TO PIGEONS * Sturtevant and Wentworth 777 Treatment was applied for a lO-day period. All birds were weighed before treatment, 10 and 20 days post treatment, and again at autopsy, 160 days after treatment began. Uneaten food (yellow corn during the test period) of both treated and control birds was weighed daily during the 10 days of treatment and also for 10 days after treatment. Post-treatment food was commercial pigeon pellets. In the Choice group ( Table 1 ) both Zein-coated SC 12937-treated and control feed were weighed. The following fecundity data were recorded after treatment: 1. Number of days after treatment when pair laid first egg. 2. Number of days between successive clutches for a period of 160 days. 3. Incubation behavior for each pair after clutch completion during the 160 days. 4. Fertility and hatchability for 160 days; after S days of natural incubation, the eggs were placed in a mechanical incubator. A record of erythrocyte sedimentation rate (described by Seiverd 1964), packed cell volume (hematocrit), buffy layer (according to the Wintrobe macrohematocrit method ), and plasma transaminase ( SigmaFrankel 505 procedure, Signla Technical Bulletin No. 505) was obtained at 0, 10, 20, 40, 80, and 160 days post treatment. All birds were killed at the end of the study and weights were recorded of the liver and spleen, the oviduct, ovary, and two largest follicles of females as well as testes of males. The time share CDC 3600 computing system at the University of Massachusetts aided in making applicable statistical comparisons. Body and organ weights were analyzed by variance and t-test analyses; if a significant difference occurred in body weights, co-variance analysis was used to adjust mean organ weights. Fecundity data were analyzed by Chi-square, and blood analyses were by variance tests. We are grateful to M. R. Woulfe of the G. D. Searle Company, Chicago, for supp]ying Ethocel and Zein-coated SC 12937treated corn. G. Balsley assisted with technical work during the study.