An apparatus to determine the rate of release of chemotherapeutics from vehicles was developed. It consists of a semi-permeable chamber within a larger glass chamber. The semi-permeable chamber has direct contact with milk within the glass chamber. Preliminary evaluation for rapidity of release of chemotherapeutics by vehicles, in decreasing amount of antibiotic released, showed them to be water, sesame oil, sweet cream butter, peanut oil with aluminum monostearate, lanolin and petrolatum.
Summary Five penicillin preparations (G crystalline penicillin of potassium, sodium, benzathine, procaine and diethylaminoethylester hydriodide – DAEEH –) were administered to lactating cows at three, six and nine million unit dosages. The penicillins were in aqueous, peanut oil, sesame oil, and peanut oil with two percent aluminum monostearate (PAM) vehicles. DAEEH penicillin appeared in the milk at the highest concentration and benzathine penicillin was detectable in the milk for the longest period of all penicillins investigated. It would appear the DAEEH penicillin would be the penicillin of choice for mastitis medication in that high levels were obtained soon following administration and that this penicillin was adulterating milk for 48 hr only following administration. Aqueous and peanut oil vehicles provided the highest concentration of penicillin for the longest post-administration period. There was extensive variation in milk concentration of penicillin between cows and for the same cow upon repeat administrations. The concentration and duration of penicillactia following various dosage levels was comparable with the dosages given. Repeat administrations within 24 hr of the initial administration resulted in higher penicillin levels and extended the period of penicillactia. No definite relationship was demonstrated between milk production or stages of lactation and penicillin concentration in milk.
The results of 26 farm visits and several hundred Whiteside tests on bulk herd milk indicate that there is a relationship between the Whiteside reaction of bulk herd milk and the incidence of mastitis in the herd. Mastitis was detected by use of the strip cup on milk from each quarter of the udder.