Evaluation of Selected Antibiotic Residue Screening Tests for Milk from Individual Goats

Abstract

Because somatic cell counts (SCC) of caprine milk are higher than SCC of bovine milk, the performance of antibiotic residue tests for screening bovine milk was investigated for caprine milk. Eighty-five does that were free of antibiotic usage for at least 30 d and that were free of clinical mastitis were sampled at three milkings during a 37-d period. At each sampling, foremilk was collected for bacteriological analysis, and composite bucket milk samples were collected for antibiotic testing and SCC. Day of lactation, parity, 305-d mature equivalent milk yield, and SCC averaged 221 d (57 to 577 d), 2.3 lactations (one to nine lactations), 1160 kg (623 to 1750 kg), and 2.2 x 10(6)/ml (0.3 to 30.7 x 10(6)/ml), respectively. The mean Dairy Herd Improvement Association test day milk yield for the month of sample collection was 3 kg (1.4 to 6.4 kg). Intramammary infections were present in 54% of the goats and in 36% of the udder halves. Assays included positive (5 and 10 ppb of penicillin-G and 50 ppb of ceftiofur) and negative controls that had been prepared in caprine milk and controls supplied by the manufacturers. One false-negative outcome and one false-positive outcome were recorded. For one sampling day, a positive linear relationship existed between SCC and the results of one test, and a quadratic relationship existed between SCC and the results of another test. The antibiotic residue screening tests for milk from individual goats adequately identified milk that was free of antibiotic. These tests are therefore recommended for use with caprine milk.

Detection limits of four antimicrobial residue screening tests for β-lactams in goat's milk

“…In contrast, the LacTeck B-L failed to detect tolerance levels of several antimicrobials, including penicillin G, in goat's milk. Given the devastating consequences of false positives (Cullor, 1992), in a previous study we assessed 9 different ARST commonly used in the United States for cow's milk on individual goat's milk samples (Contreras et al, 1997). These tests covered a variety of analytical principles for assaying β-lactam and ceftiofur residues and we were able to conclude that they were capable of adequately identifying goat's milk that was free of antimicrobial residues.…”

Extralabel drug use in small ruminants

“…The composition of the casein and whey protein fractions of caprine milk differs from that of bovine milk, and caprine milk has a higher proportion of free fatty acids and smaller fat globules than bovine milk. 105 Additionally, milk is secreted by an apocrine process in goats and a merocrine process in cows; consequently, milk of healthy goats has a higher somatic cell count than the milk of healthy cows. 106 All of those factors can affect the pharmacokinetics of drugs following IMM infusion.…”

Milk hygiene in small ruminants: A review

“…calidolactis. Different studies on the sensitivity of microbial tests have been developed in the last two decades by different authors using sheep and goat milk (Contreras et al, 1997;Molina et al, 2003;Sierra et al, 2009a,b;Comunian et al, 2010;Beltrán et al, 2013) and important efforts have been carried out in recent years by manufacturers to improve the performance and sensitivity of microbial tests (IDF, 2010). As a whole, microbial inhibitor tests using Geobacillus stearotermophilus var.…”