Joe Sheehy: 93% of cows should show heat in 40 days

Check records regularly and give particular attention to animals within 18 to 21 days of previous heat or service. The strategic use of tail paint colours or other aids will help simplify heat detection. Good observation of cows early in the morning, at mid day and late evening is essential.
Stock bulls can become intermittently infertile in the breeding season, especially if they get lame or suffer any illness. So check bull fertility at the beginning of the season, and keep a close eye on him during the season, check if cows are repeating.