Antibiotics mastitis therapy: drug residue in lambs

Meat coming from suckling lambs (max 12 Kg BW) is a typical Sardinian taste dish, normally consumed during the
religious linked feasts. The aim of this work is to evaluate drug residues in suckling lambs meat as consequence of
antibiotics mastitis therapy in their mothers during lactation.
The study was performed on twelve Sardinian ewes, that had lambed within two days of one another, with suckling
lambs from a single flok of 150 animals. Milk bacteriological screening showed that 10 ewes out of 12 were positive
and Coagulase-Negative Staphylococci were identified. The ten positive sheep were divided into two groups A and
B, and each of them were given two successive intramuscularconsecutive intramuscolar injection of 6 ml of oxytetracycline
OTC (Terralon 20% LA, Virbac) within 72 hours; the two negative sheep were used as control (C group).
With the two ewes Group two trials were conducted: to the A treatment started 17 days after delivery, while group
of 6 ewes, drug administration was given when lambs were 17 days old, to the B has been treated 28 days after
delivery. During the experimental period milk was sampled twice a week; 5 milk samples/ewe for group A and 2
samples/ewe for group B were collected. Lambslambs were regularly slaughtered at about 35 days old and muscle
tissue has been collected.sampled. All samples were immediately frozen until analysis. Oxytetracycline milk
residues were measured by High Performance Liquid Chromatography with diode array detector while, for OTC
tissue levels, LC/MS-MS technique was used. OTC concentration in milk, as observed in our own previous study,
decreasedranged from 3,500 to 0,050 μ g/ml over three weeks. OTC residues were detected in both groups of lambs
at levels below Maximum Residue Limit (MRL 0.100 μg/g). In order to avoid any drug residue in food chain, and an
increase of drug resistance, national legislation should pay attention to avoid use of antibiotics in ewes feeding
lambs that will be slaughtered.