Four feedlot experiments with 774 cattle have been completed during 1969 to 1970 evaluating two forms of tylosin activity (50, 75 and 100 mg per head per day continuously of tylosin phosphate or tylosin urea adduct) in high concentrate rations. Continuous administration of these three levels of antibiotic activity from either form of tylosin (1) reduced the incidence of liver abscesses, (2) increased average daily gain, and (3) improved feed conversion of feedlot cattle. Mathematically combining data from all levels of both forms of tylosin demonstrated an 81.8% reduction (24.1% control vs. 4.2% treated)in incidence of liver abscesses (P < .01), a 5.9% increase (2.23 lb. [1.01 kg] control vs. 2.36 lb. [1.07 kg] treated) in average daily gain (P < .05) and a 3.1% improvement (7.65 control vs. 7.41 treated) in feed conversion (P < .10). Control cattle with normal livers gained 17.0 lb. (7.7 kg) more weight during the feeding period than control cattle with abscessed livers.

No abstract

A series of trials were conducted to identify the factors causing loss of estradiol-17 beta (E2-beta) silicone rubber implants from the ears of cattle and to evaluate methods of reducing this loss. Surface application of cattle feces to the ears before implanting resulted in an increase in loss of implants compared with the loss from dry, clean ears (30.6 vs 8.6%; P less than .05). Washing ears with a povidone-iodine antiseptic solution before implanting or treating implant sites with an antibiotic after implanting reduced (P less than .05) implant loss when ears were coated with the fecal slurry. Coating silicone rubber implants with .5 to 2 mg of oxytetracycline hydrochloride (OTC) reduced (P less than .0001) implant loss from 39.8 to 13.8% when ears were coated with fecal slurry. When silicone rubber implants with a 1.5-mg coating of OTC were implanted in cattle before submerging in a dipping vat, implant loss was reduced from 6.2 to 2.7%. In studies designed to evaluate mechanical factors affecting implant loss, implants that were placed in the middle of the ear in tight skin moved .79 cm toward the insertion site during a 14-d period after administration compared with 2.82 cm when placed in the base of the ear. When placed in the middle of the ear in tight skin, only 2 of 399 (.5%) implants were lost from steers submerged in a dipping vat immediately following implantation compared with 42 of 394 (10.7%) when placed in the base of the ear (P less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)