Postnatal insulin secretion and sensitivity after manipulation of fetal growth by embryo transfer in the horse.

The research article explores the impact of prenatal growth manipulation on the insulin secretion and sensitivity in new-born horses. Specifically, it utilizes embryo transfer among different horse breeds to investigate the connection between varying birth weights and insulin-related factors.

Research Methods

• The researchers used an embryo transfer process between small pony and large Thoroughbred mares. This method produced four different groups of foals, each with separate birth weights. The groups include pony to pony (n=7), pony to Thoroughbred (n=7), Thoroughbred to Thoroughbred (n=8), and Thoroughbred to pony (n=8).
• On the second day after birth, each foal was given a dose of glucose (0.5 g/kg) intravenously. Over the next two hours, blood samples were collected to determine the plasma glucose and insulin concentrations.
• On the third day, the foals’ insulin sensitivity was tested by administering insulin (0.75 U/kg i.v.) and monitoring the reduction in plasma glucose levels.

Findings

• The study found no significant differences in insulin secretion, insulin sensitivity, or glucose tolerance between control and growth-retarded Thoroughbred foals. This indicates that reduced growth rate in the womb does not significantly alter these insulin characteristics.
• Contrastingly, pony foals that were oversized due to being delivered by Thoroughbred mares had higher baseline insulin levels and more significant beta cell responses to glucose. This suggests that it is overgrowth, not growth retardation, in the womb that affects insulin secretion and beta cell response.
• The relationship between plasma glucose and insulin was also more steep in overgrown pony foals than in the other groups, further supporting the influence of prenatal overgrowth on postnatal insulin secretion in horses.

The research concludes that variations in intrauterine growth rate have a specific impact on postnatal insulin secretion in horses. This understanding could have significant implications for managing equine health, particularly for those horses artificially bred through embryo transfer techniques.