Design and development of a biological implant for long term intravaginal retention in cattle.

ABSTRACT

OBJECTIVE: Design, develop and trial an intravaginal device able to remain within the bovine vagina for up to 6 months, accommodating various technologies, while not adversely affecting the cow, or pregnancy. METHODS: Device scoping required minimal interference with vaginal drainage, no constant pressure on any single point of the vaginal mucosa and minimal footprint on the vaginal floor. A polycarbonate prototype was developed consisting of a central cargo space to house sensors and battery, with a separate retention module. Mathematical modelling informed the required length and flexibility of the arms on the retention module to reduce pressure necrosis and inflammation within the vagina. The prototype was initially trialled, with a loaded cargo pod, for 4 weeks in five non-pregnant cows. Cows were monitored for signs of systemic infection and inflammation by collecting blood samples for haematology and acute phase inflammatory proteins. Cows were also assessed for general demeanour, signs of discomfort and positioning of the device. Later, the device was inserted into 20 early pregnant cows, with 20 contemporary, untreated controls. Cows were monitored, as in the initial trial, every 4 weeks for the next 5 to 6 months until calving. RESULTS: In Trial 1, there was 100% retention with no adverse effects. In Trial 2, device retention was 75% until calving with no adverse effects on cow health or pregnancy. CONCLUSIONS: We describe the longest successful deployment of an intravaginal device in pregnant and non-pregnant cattle, with long-term retention, no adverse effects and 28 cm3 of cargo space.