Effect of tulathromycin on abomasal emptying rate in healthy lactating goats

- Concentrate mixture of corn (75%), barley (15%), and molasses (10%) was fed ad libitum.
- Milk production was not measured on daily basis.
- The investigation of tulathromycin prokinetic effect in goat started before it weak prokinetic results on cattle was obtained.
- Thus, handling of respiratory tract infection in goats using tulathromycin not only can achieve a full course therapy by single IM injection, but also, can reduce anorexia, abolished daily weight gain and thus economic loss. Moreover it can be used for hypomotility disorder, as consequences to its acceleration effect on abomasal emptying rate.

Tulathromycin is a long-acting semi-synthetic macrolide antibiotic that is synthesized from erythromycin. Macrolides have pharmacodynamic properties beyond their antimicrobial effects, including anti-inflammatory and immunomodulatory properties that are perceived to be clinically beneficial. An additional pharmacodynamic property of macrolides is a prokinetic effect, which is marked in adult cattle and calves administered erythromycin and less prominent in calves administered spiramycin, tilmicosin, and tylosin. Based on structural similarities to erythromycin, the hypothesis was that parenteral administration of tulathromycin would increase abomasal emptying rate in healthy adult goats. Accordingly, five adult lactating goats (30-36 months of age) received each of the following 3 treatments: IM injection of 2 mL of 0.9% NaCl (control); IM injection of tulathromycin (2.5 mg/kg body weight); IV injection of tulathromycin (2.5 mg/kg body weight). Abomasal emptying rate was assessed by acetaminophen absorption, which was injected into the abomasum through a surgically placed abomasal cannula at 50 mg/kg BW, 15 min after each treatment. Jugular venous blood samples were obtained periodically after injection and plasma acetaminophen concentrations determined using a colorimetric nitration assay. The maximum observed plasma acetaminophen concentration (Actual Cmax) and time of actual Cmax (Actual Tmax) were determined, and pharmacokinetic modeling was used to calculate model Cmax and model Tmax and abomasal emptying half-time (T50). Results showed that tulathromycin (IM and IV) increased abomasal emptying rate, as indicated by a shorter time to actual Tmax and model Tmax, and shorter T50, than control. The clinical relevance of these findings remains to be determined.