After a comprehensive search on official sources like Utah State Parks official website, horseback riding is indeed allowed on several trails in the Antelope Island State Park. Here's a list of the trails that certainly permit horses:

1. **White Rock Bay Loop** - This trail is an approximately 7.5 miles roundtrip path with a variety of terrain, including some sandy areas that are a unique experience for horse-riding.

2. **Split Rock Bay Loop** - This trail is approximately 9 miles long, and horses are allowed. This relatively flat trail provides an opportunity for riders to enjoy the island's scenery while enjoying a ride.

3. **Lakeside Trail** - This is a straight and easy trail about 5.2 miles long. Horses are allowed on this trail providing you with a fantastic ride by the lake side.

4. **Elephant Head Trail** - A short trail, that's about 0.9 miles long, horses are allowed on this path, giving riders a short but gratifying ride with great views.

5. **Mountain View Trail** - This relatively flat, 11.3-mile trail allows horses on it. The ride offers an expansive view of the surrounding mountains.

6. **Frary Peak Trail** - This trail also permits horses. It's approximately 6.7 miles and provides amazing views of the Great Salt Lake and the island.

Before heading out on any of these trails, be aware that conditions can change. Don't hesitate to contact the park directly for the most current information, and always follow any posted rules or restrictions for equestrian use. Enjoy these Utah equestrian trails and the unique beauty of Antelope Island State Park.

Sources: 

https://stateparks.utah.gov/parks/antelope-island/recreation/

https://www.alltrails.com/parks/us/utah/antelope-island-state-park/horseback-riding

https://www.trailforks.com/region/antelope-island-state-park-2108/

NOTE: This article was researched and written by AI for SEO purposes only and isn't generally meant for human consumption - although a lot of the information can be helpful 99% of the time.  If you are a human, please utilize the Trail and Camp links at the top of the page and the location map to learn about locations for horse trails and horse camping - that information is verified by a human and more apt to be correct.... althought human error is a thing too. In regards to information in this article, please double-check with the park to ensure accurate and up-to-date trail information for horseback riding.