Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Thomas M. Gilmore


Mastitis is the one major disease affecting dairy cows; considerable direct and indirect economic losses can be attributed to mastitis (6). Treatment of mastitis with antibiotic preparations will alleviate most disease symptoms. Problems may arise when cows treated with antibiotics have their milk used for commercial milk processes before antibiotics are clear. They are: 1) some people are allergic to penicillin, and 2) cultured dairy products may not grow because of inhibition. The Food, Drug, and Cosmetic Act established that milk and milk products containing antibiotics are considered adulterated. Due to recent innovations in antibiotics testing The National Conference on Interstate Milk Shipment (NCIMS) has just recently voted to amend the 1978 Pasteurized Milk Ordinance (77). The amendment provides for a bottom detection limit of 0.01 ppm of penicillin residues in fluid milk products. Testing which is done by the Bacillus stearothermophilus disc assay having a zone less than 16 mm is acceptable. The reason for the change is below 0.01 ppm penicillin no inhibition of cultured dairy products occurs. It is nearly impossible to manufacture cultured dairy products with milk containing greater than 0.01 ppm antibiotic (16, 20, 30, 31). Penicillin inhibits Streptococcus thermophilus at 0.01 to 0.004 IU per ml, and Lactobacillus bulgaricus at 0.10 to 0.02 IU per ml (76). The detection of antibiotics residues in milk can be done by direct methods such as microbiological assays. The Food and Drug Administration (FDA) recognizes the Sarcina lutea cylinder plate method for assaying for penicillin quantitatively. A sensitivity of 0.01 ppm is possible. The method is-tedious and time consuming. Many other qualitative methods have been developed which are quicker; however, this has led to increased antibiotic sensitivities which has led to more milk being labeled adulterated. This is part of the reason for the change proposed by the NCIMS. Another method for detecting antibiotics is by the use of indirect methods, namely, the addition of marker dyes to antibiotic preparations used for mastitis treatment. The best effective formulations have dye and antibiotics being depleted from milk at the same time. The advantage of using dyes is dairymen would notice milk which is contaminated because of the visible color change and proceed to discard the milk. Testing methods for dye detection are possible at the level 0.125 mg of FD&C Blue No. 1 or 2 per liter of milk which is the visual endpoint. Tested preparations are therefore safe to use when the dye is no longer visible following a 24 h interval. The biggest problem associated with dye marking is correlating the dye excretion to that of the antibiotic in unknown or new preparations so clearance times coincide. The objectives of this research were: 1) to determine excretion endpoints of eight dye-antibiotic dry cow intramammary infusion products, 2) to determine if the 250 mg level of FD&C Blue No. 1 (CI 42090) was irritating to dry cow udders, 3) to ascertain results when dry cows are treated just prior to calving, 4) to determine excretion endpoints of two dye-antibiotic intramammary infusions used in lactating animals, 5) to determine the most effective dye level of FD&C Blue No. 1 to use when treating only one quarter, and 6) to determine if FD&C Blue No. 1 was irritating to healthy lactating udder tissue.

Library of Congress Subject Headings

Dyes and dyeing
Milk contamination
Antibiotic residues.


Includes bibliographical references (pages 76-82)



Number of Pages



South Dakota State University


In Copyright - Non-Commercial Use Permitted

Included in

Dairy Science Commons