Sakkarbaug Zoo is one of Junagadh's older institutions, founded in the nineteenth century and closely associated with Asiatic lion conservation. That connection matters here: Gir's wild lions are the regional wildlife headline, and the zoo has played a role in captive breeding and public awareness.
A zoo is not a substitute for seeing Gir responsibly, but Sakkarbaug can be worthwhile if you are travelling with children or have a specific interest in Gujarat's wildlife story. Combine it with Junagadh's forts, mausoleums, and Girnar foothills rather than making it the whole day.