A novel method to reduce egg laying in companion avian species using a hen model

Reproductive-related diseases in female avian species are a common problem in zoological companion animal medicine. Of particular concern is a potentially serious condition called egg-binding where eggs are retained within female reproductive tract. In chronic cases, treatment involves preventing egg production with surgical removal of the ovary or administration of hormones such as leuprolide acetate, or deslorelin acetate. These approaches are problematic, as surgical gonadectomies in birds are difficult, if not impossible, and hormonal injections and implants are expensive, variably effective, and short-acting; therefore, an effective nonsurgical method of suppressing egg production is needed. We are developing a nonsurgical approach to reduce gonadal activity and germ cell production using an antiMullerian hormone receptor 2 antibody (AMHR2)-guided lipid nanocomplex carrying a cytotoxin (saporin) to induce apoptosis in gonadal support cells exhibiting AMH2 receptor. This method disrupted gonadal architecture and germ cell development in rats and pigs. We hypothesized that this unique technology would reduce hens egg production. Rhode Island Red laying hens (n = 12) formed control group (n = 6, 0.5 ml sterile intravenous saline) and treatment group ([n = 6], administered 0.5 ml of sterile intravenous saline containing 100 nmol of nanocomplex). Hens were housed separately, weighed twice weekly and photographed once a week. General health and number of eggs laid were evaluated daily starting 13 days prior to treatment until 28 days after treatment. Blood was collected prior to treatment and at end of study for concentrations of estradiol, progesterone and androstenedione. Hens were euthanized via intravenous pentobarbital and left ovary was collected, measured, weighed, and formalinfixed for H&E histology. There were no differences between groups in general health, body weight, ovarian weight, or blood hormone concentrations. Histologically, all ovaries had evidence of follicular activity. Most obvious effect was cessation of egg laying in all treated hens starting 3 days postinjection and lasting at least 16 days in 4 of 6 treated hens. All injected hens eventually resumed laying eggs.

Administration of nanocomplex resulted in short-term cessation of egg laying in all treated hens without impacting overall health of these birds supported the hypothesis. Further studies are needed to determine if a different dose and/or route of administration could increase the length of this cessation, or even lead to a permanent loss of egg production.

Keywords: Gonadal suppression, fertility, avian egg laying, egg-binding, nanocomplex

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.