In the video all the lambs (the ones without collars) are rams 

Born late March/early April. Papered parents. 
St Croix are the most disease resistant, and parasite tolerant of all the sheep breeds. Conscientious St Croix Sheep breeders do not worm their sheep. They HOPE for worms to reveal the individual culls so they can eliminate them from the breeding program and strengthen the breed.  St Croix thrive on 100% forage and work hard at it.  
 

St Croix Sheep are smaller and grow slower so the same ground can support a larger number of them.  They thrive without any chemical inputs. Without the grain there is no hoof trimming, they are hair sheep so no shearing, and no tail docking.  Small farms and homesteads are also discovering them for these advantages. They are good mothers with lots of milk so triplets do not require bottle feeding.  St Croix Sheep take a lot of the work and headache out of having sheep.

In a study by the University of Utah, St Croix Sheep came out number one in the best tasting most pleasurable meat of all the breeds tested.  

These reasons are why many breeders of many various breeds use St Croix genetics to improve their line of sheep.
 

Use a pure bred St Croix ram as a pure and natural wormer for your lamb crop. You won't have to pollute your soil or your meat with so much chemical wormer. 
 

All this wormer everywhere is building stronger worms, bigger drug companies, and weaker livestock. You know it's true.