Effects of frequency of treatment with recombinant equine somatotropin on selected biological responses in geldings.

The research investigates the different effects of daily, every-other-day, and multiple times daily administration of recombinant equine somatotropin (eST) on hormone and nutrient response in gelding horses. It concludes that optimal eST treatment regimens depend on the targeted response and must be determined alongside experimental empirical data.

Research Methodology

• The research paper frames around two separate experiments with gelding horses, examining the responses to different eST treatment frequencies.
• The first experiment involved ten geldings, with half receiving daily and half receiving every-other-day injections of eST for a duration of 30 days. The researchers then monitored plasma levels of glucose, insulin, non-esterified fatty acid (NEFA), and plasma urea nitrogen (PUN) in both groups, along with the concentration of insulin-like growth factor-I (IGF-I) and endogenous somatotropin (ST).
• The second experiment involved 16 geldings, divided into four groups. The first group served as the control and received saline injections. The other three groups were administered different eST doses in varying frequencies. The researchers then focused on changes in plasma IGF-I, insulin, and PUN concentrations.

Findings from Experiment 1

• Both groups, receiving daily and every-other-day eST injections, experienced an increase in plasma glucose, insulin, and NEFA concentrations, and a decrease in PUN levels.
• IGF-I levels also increased in both groups, with a noted higher concentration after day 2 in geldings treated daily.
• The daily treatment inhibited the ST response more than the every-other-day treatment.

Findings from Experiment 2

• All groups that received eST injections, regardless of the frequency, showed increased plasma IGF-I and insulin levels. The increase in these concentrations was proportional to the injection frequency.
• However, the decrease in PUN concentrations was equal in all groups, irrespective of the eST injection frequency.

Conclusion

• The results indicate that the efficacy of eST treatment regimens, be it daily or every-other-day, depends upon the specific response being measured.
• For IGF-I concentration measurements, the every-other-day regimen wasn’t ideal. Injections more frequent than once daily were more effective for achieving higher IGF-I and insulin concentrations, but not for PUN concentrations.
• The authors concluded that for establishing an optimal eST injection regimen for any new application, the biological responses cannot be inferred from previous data alone and need to be determined through empirical trials.