Modelling speed and inter-race intervals to assess post-race recovery in racing greyhounds

The recovery of greyhounds post-race has important welfare implications, primarily to avoid over-running and prevent greyhounds with subclinical injuries from racing. Both situations could reasonably be expected to reduce speed, which may be identified by comparing the successive race performances of individual greyhounds. The focus of this analysis was on reportedly sound greyhounds. Thus, the hypothesis was that changes in speed could be linked with the inter-race intervals, and that shorter inter-race intervals would compromise glycogen restoration and therefore affect performance in subsequent races. A dataset contained 206,686 runs made by 12,883 reportedly sound GBGB-licenced greyhounds and was analysed using multilevel (mixed effects) models. Speed was slightly elevated above baseline from two days between races and declined over increasing inter-race periods up to 12 days between races. Inter-race intervals of two or more days had no biologically significant effects and were less than the normal variations in speed. Due to an absence of data for one day between races, this period could not be modelled. The findings are consistent with the fact that glycogen stores are normally restored by two days after fast exercise, and a ruling that greyhounds should not race more frequently than every fourth day is reasonable and would include greyhounds which might take slightly longer to recover. Performance depression after four days' rest might suggest a subclinical injury. Expanded datasets are required to determine the effect of a one-day gap between races.