Under the capable management of William Sinclair Brooks, the Brooknill herd, established in 1927, became recognized as one of the outstanding Guernsey herds in Canada. The first sire used in this herd, Bonnie Brae Trojan, imported from the United States, started Bill Brooks on the road to success. This bull gained national recognition as the result of winning a record number of championships at major Canadian shows. His record, however, was later broken by Brooknill Double Romulus and Brooknill D.R. Defender, two bulls bred at Brooknill that exerted a beneficial influence on the breed wherever they or their offspring were used.

As evidence of his success as a cattle breeder, and having met the requirements for type and production, Bill Brooks was awarded a Master Breeders’ certificate in 1948, one of only two issued by the Canadian Guernsey Breeders Association previous to 1972.

In addition to his accomplishment as a breeder, Bill Brooks utilized his talents in the field of breed promotion. While serving as president of the Canadian Guernsey Breeders’ Association, he pressed for the formation of a national-type committee, and served as its first chairman.

In his capacity as director of the Ontario Guernsey Breeders’ Association, he advocated the hiring of a full-time secretary, who would be responsible for promoting the Guernsey breed and the sale of Guernsey milk.

Aside from his Guernsey activities, Bill Brooks served as chairman of the Canadian National Livestock Records Board in 1958; and as a director of the Royal Agricultural Winter Fair.