Kinetics of lithium as a lithium chloride dose suitable for conditioned taste aversion in lactating goats and dry sheep

Lithium chloride (LiCl) is widely used for inducing conditioned taste aversion (CTA) so that livestock will reduce or avoid ingestion of toxic plants and graze groundcover mingled with valuable crops. However, pharmacokinetic studies of LiCl at effective CTA doses are lacking. With this aim, 6 Murciano-Grandina dairy does during late lactation and 6 dry Manchega dairy ewes were orally dosed with 200 and 225 mg LiCl/kg BW, respectively. Does were placed in metabolism cages whereas ewes were group fed in pens. Lithium was measured over 168 (does) and 192 h (ewes) at predefined intervals in plasma, urine, feces, and milk using flame atomic absorption spectroscopy. Plasma Li concentrations reached a maximum at 4 h in does (13.4 +/- 1.35 mg Li/L) and 12 h in ewes (17.7 +/- 0.8 mg Li/L). The cal-culated plasma half-lives were 40.3 +/- 3.8 and 30.9 +/- 2.1 h for does and ewes, respectively. In goats, all Li administered was recovered at 96 h (92 +/- 4% in urine, 6.5 +/- 1.3% in feces, and 2.8 +/- 0.4% in milk); however, the estimated clearance time in feces was 11 and 9 d for does and ewes, respectively. Additionally, maximum Li excretion in doe milk was 15.6 +/- 0.5 mg/L, which was approximately half of the calculated effective dose for a 5-kg BW sucking kid. In conclusion, Li kinetics in goats and sheep were similar to cattle and elimination took longer than in monogastric species. The low concentration of Li in feces, urine, and milk, as well as the complete elimination of Li from the body after 1.5 wk allows us to conclude that LiCl is safe and suitable for inducing CTA in ruminants.