Packaged rodenticidal bait

Abstract

A packaged rodenticidal bait comprises a soft bait composition enrobed in a perforated thermoplastic film, wherein the soft bait composition comprises a blend of at least one edible fat, at least one particulate food component and at least one rodenticidally-active substance. Preferably, the thermoplastic film comprises one or more polyolefins. The perforated film used in the manufacture of the packaged bait according to the invention does not absorb fat, unlike conventionally-used paper sachets. The packaged bait composition of the invention is palatable to rodents such that rodents may take a lethal dose of a rodenticide from the bait in a single sitting.

Claims

1. A packaged rodenticidal bait comprising a non-particulate soft bait composition enrobed in a perforated thermoplastic film, wherein the soft bait composition comprises a blend of at least one edible fat, at least one particulate food component and at least one rodenticidally-active substance.

2. The packaged rodenticidal bait of claim 1, wherein the perforated thermoplastic film comprises one or more polyolefins.

3. The packaged rodenticidal bait of claim 2, wherein the perforated thermoplastic film comprises a polyolefin selected from polyethylene, polypropylene and copolymers of ethylene and propylene.

4. The packaged rodenticidal bait of claim 1, wherein the thermoplastic film is a monolayer film.

5. The packaged rodenticidal bait claim 1, wherein the thermoplastic film is a multi-layer film.

6. The packaged rodenticidal bait of claim 1, wherein the thermoplastic film is a shrink film.

7. The packaged rodenticidal bait of claim 1, wherein the perforated thermoplastic film contains from 100 to 300 perforations per square decimeter.

8. The packaged rodenticidal bait of claim 7, wherein the perforated thermoplastic film contains from 150 to 250 perforations per square decimeter.

9. The packaged rodenticidal bait of claim 1, wherein the thermoplastic film has a thickness of from 15 to 25 μm.

10. The packaged rodenticidal bait of claim 9, wherein the thermoplastic film has a thickness of from 18 to 20 μm.

11. The packaged rodenticidal bait of claim 1, wherein the soft bait composition contains a fat which is not completely liquid at a temperature of 35° C.

12. The packaged rodenticidal bait of claim 1, wherein the fat is an animal fat, a vegetable fat or a mixture thereof.

13. The packaged rodenticidal bait of claim 12, wherein the fat is refined palm oil.

14. The packaged rodenticidal bait of claim 1, wherein the soft bait composition contains at least one particulate food component which is a vegetable flour selected from cereal flour and non-cereal flour.

15. The packaged rodenticidal bait of claim 14, wherein the vegetable flour is selected from the group consisting of oat flour, wheat flour, rice flour, maize flour, potato flour, peanut flour and soy flour and combinations thereof.

16. The packaged rodenticidal bait of claim 1, wherein the soft bait composition contains one or more whole grains or seeds, ground grains or seeds, cut or comminuted grains or seeds and combinations thereof.

17. The packaged rodenticidal bait of claim 16, wherein the soft bait composition contains one or more of pinhead oatmeal, cut wheat, corn grits, canary seed, poppy seed, sesame seed and sunflower seed.

18. The packaged rodenticidal bait of claim 1, wherein the rodenticidally-active substance is selected from the group consisting of difenacoum, brodifacoum, flocoumafen, bromodiolone, difethialone, warfarin, coumatetralyl, chlorophacinone, diphacinone, coumachlor, coumafuryl, pindone, ergocalciferol, cholecalciferol, norbormide, alphachloralose, strychnine, sodium monofluoroacetate and sodium cyanide.

19. A method of manufacturing the packaged rodenticidal bait of claim 1, comprising the steps of: (i) providing a soft bait composition on a sheet of perforated thermoplastic film; (ii) folding the sheet of perforated thermoplastic film such that an upper portion of the film overlies a lower portion of the film and the soft bait composition is located between the upper portion and the lower portion of the folded sheet of film; and (iii) heat-sealing together the upper portion of the film with the lower portion of the film where the upper portion contacts the lower portion so as to enrobe the soft bait composition in the film.

Description

EXAMPLE

(1) 1. A five-layer coextruded polyolefin shrink film, pre-perforated at a perforation density of 200 per square decimeter, was used to manufacture a packaged rodenticidal bait according to the present invention.

(2) A soft bait composition having the formulation shown in the Table below was prepared according to conventional methods.

(3) TABLE-US-00001 TABLE Ingredient Amount (g) Cholecalciferol 0.075 denatonium benzoate 0.001 oils and fats 14.5 sugar 10.0 inerts and colourant 1.0 vegetable flour and edible seeds/grains balance to 100 g

(4) 100 g of the soft bait composition was placed on a 6 cm×14 cm sheet of the pre-perforated polyolefin film. The film was folded, lengthwise, over the bait composition with the three free edges of each of top and bottom portions of the film superimposed. The superimposed top and bottom portions of the film were heat-sealed together to make a packaged bait wherein the bait composition is enrobed in the polyolefin film.

(5) 2. Packaged baits, according to the invention, prepared in accordance with the above-described procedure were used in a field trial as described below. For comparison, conventional paper sachets containing the soft bait composition having the formulation shown in the above Table were prepared and used in the field trial.

(6) In accordance with standard procedure, suitable trial sites, each having an identified infestation of mice (Mus domesticus) were selected and baiting locations in the mouse runs were identified. Tracking activity for the mice was measured over 4 days prior to each trial (pre-census) and for 4 days post trial (post-census). Non-poisoned bait was used for the pre-trial census and post-trial census periods and the poisoned bait, as described above, was used for the trial period itself which lasted 21 days. Bait take by the mice, over these periods, was regularly measured. In one trial, the bait composition described above and packaged in paper sachets was used. In the other trial, the bait composition described above enrobed in pre-perforated polyolefin film, as described above, was used.

(7) For the trial using the paper sacheted bait composition, tracking scores indicated that no reduction in mouse population had occurred and bait take was low. It was calculated from the tracking scores and the bait take measurement that 0% control was achieved over the trial period using the bait composition packaged in paper sachets.

(8) For the trial using the bait composition enrobed in the polyolefin film, tracking scores dropped sharply over the 21 day trial period. Over the same period, take dropped from over 300 g (in the pre-trial census period) to about 15 g on day 21. It was calculated from the tracking scores and the census take measurements that 92% control had been achieved over the trial period using the bait composition enrobed in the polyolefin film.

(9) The results of these trials indicate that the mice in the field trials found the paper sacheted composition to be unattractive whereas the polyolefin film-enrobed composition was highly palatable to the mice.

(10) 3. Polyolefin film-enrobed bait composition prepared as described in 1. above and conventional paper sachets containing the soft bait composition having the formulation shown in the above table, as described in 2. above, were heat-treated for 24 hours in an oven at a temperature of 54° C. Following this heat treatment, the polyolefin film-enrobed bait composition and the paper sachets were allowed to cool to ambient temperature and each was used as test bait in the following test procedure.
Test Procedure

(11) The test bait and an alternative control (containing no active substance) were offered to each of five male Wistar Rats. The alternative control used in the test was LabDiet (Registered Trade Mark) EURodent Diet 22% 5LFS from PMI Nutrition International. The ingredient composition of this diet is:

(12) TABLE-US-00002 cereal products (corn, wheat, wheat middlings) 58.2% vegetable proteins (dehulled soybean meal, 37.2% dehydrated alfafa, dried beet pulp, dried brewers yeast) energy sources (soybean oil) 1.75% supplementation (vitamins, major minerals, 2.85% trace minerals, amino acids)

(13) The total test bait and control diet for all five animals were summed and the palatability ratio for each test bait was calculated as follows:

(14) $\begin{array}{c}\mathrm{Palatability}\mathrm{Ratio}\\ \left(\mathrm{group}\mathrm{of}\mathrm{five}\mathrm{animals}\right)\end{array}=\frac{\mathrm{Total}\mathrm{test}\mathrm{bait}\mathrm{take}\left(g\right)}{\mathrm{Total}\mathrm{control}\mathrm{diet}\mathrm{take}\left(g\right)}$

(15) Thus, a palatability ratio of >1.0 indicates that the test bait was more palatable to the rats than the control diet whereas a palatability ratio of 1.0 indicates that the test bait and the control diet were equally palatable.

(16) The palatability ratio obtained for the heat-treated, packaged bait of the invention was 4.51. Compared to this, the palatability ratio obtained for the heat-treated paper sachet containing the bait formulation shown in the table was 3.51. The result of the test can be explained by the fact that the conventional paper sachets absorb fat which is released from the bait formulation during the heat treatment and that the fat absorbed into the paper sachet reduces palatability of the packaged bait. Although the difference between these palatability ratios is not a significant one, the results indicate a trend which is expected to be mirrored in the field.