"The horse collar eventually spread to Europe c. 920 AD, and became universal by the 12th century.[21] The Scandinavians were among the first to utilize a horse collar that did not constrain the breathing passages of the horses.[22] Prior to this development, oxen still remained the primary choice of animal for farm labor, as all the previous harnesses and collars could only be worn by them without physical penalty."
Not disputing horse collar. Point made in a history of horsemanship (an in turn ploughman trades) was that the trade of ploughmen in england moved away from oxen more to horses as the result of a change in plough design.
This excerpt may have been the design change that was referenced.
"There was little attempt to change the design of the plough until the mid 1600's with the Dutch being among the first in improving its shape. This change in shape was soon discovered in Northern England and Scotland with Joseph Foljambe from Rotherham building and patented a plough having what was described as, the perfect implement then in use."
Discredit? Sorry, not intended. Just confused, since horses had been in use for ploughing for centuries. Unaware of any sea change in technique.
And in America of course we credit John Deere for reinventing the moldboard plow in the early 1800's. Sadly we weren't taught of any English innovations in school.