GnRH boost for piglets?
INJECTING outdoor sows with gonadotrophin-releasing hormone (GnRH) may improve piglet viability during pregnancy, shown by increased numbers of piglets born alive.
But the original aim of the trial, reported in Vet Record (Dec 2), undertaken by Andy Peters and his colleagues at the Royal Vet College, Herts, was to see if a synthetic GnRH – buserelin – would improve farrowing rate and litter size.
Improvements in management over recent decades have led to reductions in the farrowing interval and pre-weaning mortality, but average litter sizes have not changed since the early 1900s, according to Prof Peters.
A total of 1231 mixed parity sows from five outdoor units in East Anglia were tested. Sows received an intramuscular injection of buserelin, either within 24 hours of insemination or on day 11 or 12 after service.
Neither treatment was shown to alter fertility, apart from on one unit, but it did increase piglet viability on all units, especially in sows up to second parity. These young sows produced an extra 0.4 live piglets a litter when treated after service and one live piglet a litter when treated at 11 or 12 days post-service.
GnRH treatment may have resulted in an improvement in the quality or viability of embryos and subsequent foetuses, either by improving synchrony between service and ovulation or by increasing progesterone production, says Prof Peters. *