Perhaps you should try some spelling variations:
"improving primary performance measures." » "improving preliminary performance measures.", "improving animal performance measures.", "improving optimal performance measures."
"improving thermal performance metrics." » "improving external performance metrics.", "improving animal performance metrics.", "improving erm performance metrics."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving primary performance measures.") or ("improving thermal performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving primary performance measures.") OR ("improving thermal performance metrics."))*.
• Removing quotes may allow a broader search: (( improving primary performance measures. ) or ( improving thermal performance metrics. ))*.