# Administration of Human Chorionic Gonadotropin Combined with Phenylbutazone at the Time of Embryo Transfer Synergistically Improves Pregnancy Rates in Dromedary Camels

## TL;DR

Combining hCG and Phenylbutazone at embryo transfer improves pregnancy success in dromedary camels more effectively than other methods.

## Contribution

A new, cost-effective luteal support protocol using hCG and Phenylbutazone is introduced for camel embryo transfer.

## Key findings

- The hCG + Phenylbutazone group had the highest pregnancy rates at day 60 post-transfer.
- This combination outperformed eCG in pregnancy maintenance and reduced embryonic loss.
- The protocol is more practical and cost-effective than eCG-based methods.

## Abstract

Pregnancy rates after embryo transfer in dromedary camels vary widely due to biological and management-related factors, with inadequate luteal function being a key limiting factor. This study provides practical evidence that optimizing luteal support at embryo transfer can improve pregnancy outcomes. Recipient camels were allocated to four groups: a control group receiving no luteal support; Phenylbutazone alone; a combination of human chorionic gonadotropin (hCG) and Phenylbutazone; and stimulation with equine chorionic gonadotropin (eCG). The combined administration of hCG and Phenylbutazone at embryo transfer yielded the highest pregnancy rates at day 60 post-transfer, compared with the control and other treatment groups. From a practical perspective, this protocol offers a feasible and cost-effective alternative to eCG-based stimulation, which requires repeated handling, multiple injections and higher costs and is known to have several drawbacks in camelid reproduction. The improved outcomes are likely due to the synergistic anti-luteolytic effect of Phenylbutazone and the luteotrophic action of hCG, resulting in enhanced and sustained luteal function. Additionally, hCG may improve endometrial receptivity, further supporting embryo survival. Overall, these findings offer a practical, field-applicable strategy to enhance the efficiency and success of camel embryo transfer programs, particularly under large-scale production conditions.

Effective luteal support is crucial for successful pregnancy following embryo transfer in dromedary camels, highlighting the importance of maintaining adequate luteal function. This study compared three luteal support protocols for pregnancy rates after embryo transfer (ET) in dromedary camels. Recipients with a single ovarian follicle (14~16 mm) were assigned into: (1) untreated control, (2) Phenylbutazone (PBZ) at 3.7 mg/kg IV prior to ET, or (3) human chorionic gonadotropin (hCG) 2000 IU plus 3.7 mg/kg IV PBZ prior to ET. Recipients that showed ovarian inactivity were treated with an injection of 1800 IU of equine chorionic gonadotropin (eCG) after progesterone (P4) priming. Pregnancy was assessed on days 10 (P4 assay) and 60 (transrectal ultrasonography) post-ET. Pregnancy rates on day 10 were higher in the hCG + PBZ (73.3%) and eCG (68.0%) groups than in the PBZ (44.0%) and control (35.0%) groups (p < 0.05). By day 60, the hCG + PBZ group exhibited the highest pregnancy maintenance rate (81.8%) and the lowest embryonic loss rate (18.2%), compared with eCG (53.0%; 47.0%), PBZ (54.5%; 45.5%), and control (57.1%; 42.9%) groups, respectively (p < 0.05). However, there was no significant difference among the eCG, PBZ, and control groups in embryonic loss rates. In conclusion, hCG synergizes with PBZ to enhance corpus luteum function, uterine receptivity, and pregnancy maintenance more effectively than PBZ or eCG.