The tetracyclines (TTC) and sulfonamides are among the most common residues found in bulk raw milk samples. Detection of drug residues in bulk milk (BM) tankers demonstrates that the product is not suitable for human consumption. Discarding BM with residue-contaminated milk is a waste of a valuable commodity, and a repurposing for consumption at calf ranches is a way to recapture some value. However, if calves consuming milk with drug residues are slaughtered for veal, their meat could contain drug residues. The objective of this review is to provide a residue avoidance strategy for TTC and sulfonamide residues in veal. To determine the pharmacokinetic properties of each drug a structured review of the literature was performed and the study inclusion criteria were that the publication used dairy breed calves, with body weight <330 kg or <6 months of age. The most pertinent parameters were determined to be plasma, tissue elimination half-lives, and systemic bioavailability. The results of this review were integrated with milk and tissue testing levels of quantification and tissue tolerances to formulate a recommended withdrawal interval for calves ingesting this milk. The suggested withdrawal interval of 20 days will ensure that no veal calves will test positive for residues from being fed this milk.

The effects of titanium dioxide coatings of bovine hides on light absorption and transdermal transfer of light-derived heat were investigated. Four hair-on rug hides from Holstein cattle were purchased. Twelve samples about 20 cm on a side were cut from each hide; nine from the black-colored areas, and three from the white areas. Samples were randomized and assigned to four coating treatments: (1) white hide with no coating (White), (2) black hide with no coating (Black), (3) black hide with 50% coating (Mid), and (4) black hide with 100% coating (High). Coatings were applied to the black hide samples using a hand sprayer. Lux measurements were taken using a modified lux meter at three light intensities generated with a broad spectrum, cold halogen light source. Reflectance over a wavelength range of 380 to 900 nm was measured using a spectroradiometer. The transdermal transfer of heat derived from absorbed light was measured by applying a broad spectrum, cold halogen light source to the stratum corneum (coated) side of the sample and recording the temperature of the dermis-side using a thermal camera for 10 min at 30-s intervals. At the high light level, the White, Black, Mid, and High coating treatments had different (P < 0.001) lux values of 64,945, 1741, 15,978, and 40,730 lx, respectively. In the visible wavelength range (400 to 750 nm), Black hides reflected 10 to 15% of the light energy, hides with the Mid coating treatment reflected 35 to 40%, and hides with the High coating treatment reflected 70 to 80% of the light energy. The natural White hide samples reflected 60 to 80% of the light energy. The average maximum temperatures at the dermis-side of the hides due to transferred heat were 34.5, 70.1, 55.0, and 31.7, for the White, Black, Mid, and High treatments, respectively. Reflective coatings containing titanium dioxide on cattle hides were effective in reducing light energy absorption and reduced light-derived heat transfer from the skin surface to deeper skin layers.

Currently flunixin is one of the leading violative drug residue found in veal calves. Although it is approved for use in adult cattle, there is not a specific approval for use in calves that are to be processed for veal. However the drug is often used in an extralabel manner as supportive therapy associated with calf diarrhea or pneumonia. Unfortunately pharmacokinetic data regarding the use of flunixin in young calves is not available. Therefore the primary objective of this study was to examine the pharmacokinetics and tissue elimination of flunixin following administration to veal calves.

Chlortetracycline (CTC) contributes extensively to profitable cattle production as an antimicrobial and growth promoting agent. The NAHMS 1999 Feedlot study reports 51.9% of all feedlots administer CTC as a health or production management tool. However, information regarding the pharmacokinetics and bioavailability of CTC is scarce in the literature. Pharmacokinetic studies were performed using oral and intravenous preparations of CTC to reveal the pharmacokinetic parameters of this drug in cattle.

Safety of food originated from animals is an emerging global health problem, and ensuring food safety is a challenge for the producers and governments who deal with protecting the food supply chain from contamination with hazardous microbes, chemicals and/or drugs. In the United States (US), the Food Animal Residue Avoidance Databank (FARAD) program is a unique consortium of scientific experts who help maintain a proper balance among animal health, food safety, and regulatory policies. Veterinarians must often use drugs in an extra-label manner to treat food animals due to limited availability of Food and Drug Administration (FDA) approved drugs. Extra-label drug use (ELDU) is allowable under the Animal Medicinal Drug Use Clarification Act (AMDUCA). Following ELDU, and before products derived from the treated animal can be sold and marketed, an extended withdrawal time (EWDT) needs to be established, based on appropriate scientific data. The objective of this paper is to discuss the scientific basis for determination of EWDT of drugs used in food animals using kinetic modeling approach.