in fig1 a mass of microencapsulated dye particles 10 are shown as embedded in coating 11 of a substance or paint which dries or sets and holds the microcapsules in place . the paint or coating substance is selected to be durable , to resist dissolving or spreading when wet , as in a rainstorm , and to be sufficiently flexible to resist breaking and sloughing off under pressure such as that of a mounting animal . the materials and the methods for effecting the microencapsulation of various substances are well known in the prior art . for example , the microencapsulated dye particles may be prepared in accordance with the teaching of u . s . pat . no . 2 , 800 , 457 issued to barrett k . green and lowell schleicher , which relates to a method of making them by coacervation . by way of example , and not by way of limitation , one paint - like substance effective for the detection of heat in cows was prepared as follows : a solution was prepared by dissolving 15 grams of gum arabic ( sigma , st . louis , mo .) and 15 grams of type iii ( sigma ) 225 bloom stength calf - skin gelatin in 750 grams of water at 75 ° c . this solution was contained in a one - liter resin - kettle , stirred at 800 to 1300 rpm , and maintained at a temperature of 75 ° c . the stirring was effected by an axial - flow plastic impeller at the bottom of a vertical shaft driven by an electric motor . to this solution was added 75 grams of a one - to - one mixture of automate yellow 8 dye ( morton chemical division of morton norwich products , inc ., chicago , ill .) and mineral oil ( heavy , sigma ). then about 33 milliliters of 10 % aqueous solution of acetic acid was added which brought the ph of the mixture to about 3 . 5 . then the stirring rate was reduced to about 400 rpm , and the stirred mixture was allowed to cool slowly to room temperature . the coacervation of the encapsulated dye particles was effected during this stage of the process . the mixture was then cooled further to about 10 ° c . with an ice bath . 75 milliliters of a solution of glutaraldehyde ( 25 % by weight , aldrich , milwaukee , wis .) was then added to the stirred mixture , and the ph of the mixture was then adjusted to about 9 by addition of a 50 % solution of sodium hydroxide in water . an additional 75 milliliters of 25 % glutaraldehyde was then added . after about 15 minutes the reaction mixture was diluted with water and poured onto a set of sieves . the microcapsules were washed with water on the sieves , and oversized and undersized material was removed . excess water was allowed to drain from microcapsules of the desired size in range of about 50 to 150 microns in diameter . the resulting wet microcapsule paste amounted to about one quart in volume , and when mixed with the acrylic paint base in approximately a one - to - one ratio produced about two quarts of heat - detector paint . the acrylic paint base which was used was speedball titanium white acrylic latex paint ( hunt manufacturing co ., statesville , n . c .). the paint base was selected to have the property of retaining the color of the dye for a sufficiently long period , say , at least twenty - four days , and further , it was flexible or rubbery when dried . a single blow against the flexible dried paint would break few , if any , of the microcapsules , while rubbing under substantial pressure would break most , if not all , of the microcapsules in the pressure area . the size range of the mocrocapsules and the wall thickness were selected to provide such strength characteristics and the material may thus be designed for specific use requirements . for the purpose of inhibiting the growth of bacteria a suitable antimicrobial preservative is thimerosal , sold under the name &# 34 ; merthiolate &# 34 ; by the eastman company of rochester , n . y . - this preservative is a mercury compound sodium - ethyl - mercuri - thiosalicylate ( c 9 h 9 h g nao 2 s ). thimerosal was found to be compatible with the coating substance formulation of this invention and with the animals &# 39 ; skin when used in a concentration of 0 . 05 percent by weight . referring now to fig2 when the estrus - detecting material is to be used , a layer of the material is applied as a patch to each cow in the herd , the patch being located on the rump near the tailhead , as indicated at 12 ; a second patch 13 may be applied along the back forward of the rump and spaced several inches from the patch 12 . if the cow is mounted and does not reject the mount , heavy pressure and usually some rubbing is applied at the patch 12 and numerous microcapsules are broken and the dye escapes and colors the patch . this provides a positive indication that the cow has been mounted and is in estrus . the patch 13 is out of the pressure area and remains uncolored so that it provides a clear contrast with the vivid color of the patch 12 . thus the use of the two patches provides a proofing system to aid in the quick inspection of the herd . fig3 shows the patch 12 after its change of color , indicated by shading , and also shows the patch 13 as unchanged in color . the color of the dye is selected to provide a contrast with the color of the base or background paint . a dye of bright or brilliant color is preferable ; the colors red , blue and yellow are effective in providing the desired contrast . the yellow dye in the above example is brilliant in color and highly satisfactory for the purposes of this invention . a light color is preferred for the base and white has been found preferable for most applicaions . the size of the microcapsules and the thickness of the walls are selected to provide the strength required to avoid breaking of the capsules unless they are subjected to a substantial pressure . the paint or coating material is preferably selected to remain flexible after it has dried and a tough rubbery characteristic has been found to be advantageous . the hardness of the capsule walls may be increased by using a cross - linking agent , and in the above example the glutaraldehyde is a cross - linking agent used for this purpose . the use of such cross - linking agents in a process for making minute capsules is described in u . s . pat . no . 3 , 190 , 837 issued to carl byrnko and joseph a . scarpelli . the selection of the materials and the sizes and strength of the particles makes it possible to design a coasting substance which will effectively perform the function of remaining in place after application and will last for a long period and at least for more than twenty - four days . the ability of the coating substance to resist temperature and moisture changes assures its effectiveness during inclement weather . the use of a brilliant colored dye in the capsules assures quicker detection of color changes of the patches on cows which have been mounted by another animal . this provides a reliable and positive method for detecting which cows in a herd are in estrus . paint material prepared in accordance with the above example was tested by application to each of the cows in one herd of fourteen cows . the rump of each cow adjacent the tailhead was painted with a patch of the material and a second patch or strip was painted on several of the cows along the back several inches forward of the first patch and beyond the mounting pressure zone . the cows were observed and checked at itervals of 12 to 24 hours . the covering substance or paint remained in place and unbroken on all cows in the herd and the appearance of color of the patch on the rump provided an accurate identification of those cows which had come into heat and had been mounted during the period between the test observations . when a cow having a second patch had been mounted as indicated by the color of the patch of coating material or paint on the rump the second patch which had not been subjected to the mounting pressure did not change color and the vivid contrasting color difference served as an easy and positive confirmation or proof of the color change of the first patch . the microcapsules are not of uniform shape or size , and the dimensions indicated as being diameters are , in effect , the average maximum dimensions of the capsules . each capsule contains one or more oil droplets each droplet ladened with dye . the terms &# 34 ; paint &# 34 ; and &# 34 ; paint - like &# 34 ; as used herein have reference to a spreadable substance or coating material which has the characteristics identified herein . it is not required that it be a paint as such ; for example , it need not be a coating material intended for conventional painting use . the words &# 34 ; coating material &# 34 ; as used herein mean either the spreadable substance alone or the spreadable substance on an adhesive backing which backing attaches to the animal . the dye may be a liquid , fluidized finely divided solid particles , or other compatible fluid substance which upon release produces a visible indication on the coating material . while the invention has been described in connection with a specific embodiment , various modifications and other applications will occur to those skilled in the art , and it is intended , by the appended claims , to cover all modifications which fall within the spirit and scope of the invention .
a substance for facilitating the detection of estrus applied to the tailhead and rump of a cow as a patch comprises a mass of microencapsulated dye mixed in a suitable paint . the paint dries as a durable layer the color of which will change when substantial pressure is applied for a predetermined time . should the cow be mounted by another animal for say five seconds or more a large portion of the microcapsules will break and release the dye which colors the patch . the cows with colored patches can then be found by periodic inspection and removed from the herd for insemination .