i 



jumped 3.2 pounds per cow for the period following treatment, whereas production in untreated herds fell 

 off 1.7 pounds per cow for the same period. In general, butterfat production went down as the number of 

 tabanids per cow went up. 



Especially noteworthy were the records of seven cows in continuous lactation throughout the ex- 

 periment. These cows were subjected to a heavy outbreak of two species of small tabanids that appeared 

 in May and lasted through June, when the large tabanids became abundant. Attack by the tabanids was 

 quickly followed by a drop in butterfat production. However, during the first period following treatment, an 

 increase of more than 20 per cent occurred. In the two periods before treatment on June 29, the seven 

 cows averaged 45 and 41 pounds of butterfat per cow; in the two periods following treatment, they averaged 

 52 and 49 pounds per cow. 



HORSE FLY CONTROL ON BEEF CATTLE 



Practical control of horse flies on range beef cattle was first obtained in the summer of 1950 

 through use of an automatic microspray applicator designed and constructed by the senior author. The 

 unit consisted of two small hydraulic pumps, noz^es, copper connecting pipe, gallon can of spray concen- 

 trate, homemade chute, treadle, connecting rod, and wind shield. When a beef animal, in passing through 

 the chute on the way to water or salt, stepped on the treadle mounted in the floor of the chute, the connect- 

 ing rod operated the two small pumps mounted above the chute and sprayed a minute amount of concentrate 

 on the animal. The concentrate spray used was Pyrenone T-143 , which containetl 1.0 per cent pyrethrins 

 and 10.0 per cent piperonyl butoxide. 



Throughout the period horse flies were abundant, the apparatus was used in pasture no. 1 of experi- 

 ment no. 10 at the Dixon Springs Experiment Station of the University of Illinois. In this experiment, 10 

 comparable beef animals were pastured for a designated time in each of six adjoining 10 -acre improved 

 legume and grass pastures. A high degree of tabanid control was obtained on the animals in pasture no. 1. 



GAINS FROM HORSE FLY CONTROL ON BEEF CATTL€ 



In the 38 days for which records were kept, the 10 beef cattle in pasture no. 1 gained 20 to 30 

 pounds per animal more than those in the other pastures. These weight gains were striking but, because 

 of the shortness of the test period, they should not be considered conclusive. 



In all but one of pastures 2 through 6, fly counts and weight gains were roughly proportional to the 

 nearness of these pastures to pasture 1. Evidently, many horse flies from the other pastures wandered 

 into pasture 1, where they came in contact with the insecticide on the sprayed animals. 



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