Rumen bypass and biodistribution of l-carnitine from dual-layered coated pellets in cows, in vitro and in vivo

A ruman bypass delivery system was investigated to improve the delivery efficiency of l-carnitine in biological samples of cows. Highly water-soluble l-carnitine used for dietary supplement in ruminants was chosen. l-Carnitine-loaded compact pellets were prepared by extrusion method and then coated with various coating materials such as ethylcellulose (EC), Eudragit E100 (E100), Eudragit RS100 (RS100), stearyl alcohol and glyceryl monostearate, for single-layered coated pellets (SCP). Two types of dual-layered coated pellets (DCP) were also designed as DCP-A (inner E100/outer EC) or DCP-B (inner EC/outer E100). Preparation of compact pellet and methods of polymeric coatings are the most important strategies for modulated release and rumen bypass efficiency based on chewing behaviors and physiology of veterinary species. DCPs were more efficient in retarding l-carnitine release in rumen fluid (pH 6.8) than the SCP but DCP-B gave much faster release in abomasums fluid (pH 1.2). Both DCP-A and DCP-B showed high in vivo rumen bypass efficiency in cows compared with the nonprotected preparation and most of l-carnitine was readily absorbed. DCP-B was also efficient for delivering l-carnitine in biological samples of cows, mainly in muscle but no statistical differences were observed among the tested preparations after the multiple oral feeding to cows for 3 months. Interestingly, DCP-B produced higher l-carnitine levels in milk in a dose-dependent manner. However, delivery efficiency of l-carnitine preparations in biological samples of cows would rather be more dependent on feeding schedules.