For the purpose of Trich CONSULT, a controlled breeding season means that the bulls have access to the cow herd for 4 months or less and are housed separately from the cows for the remainder of the year. 

A controlled breeding season is important for the control of Trich because infected cows often lose their pregnancy and begin to cycle again before they clear the infection.  Bulls that are exposed to these cows can become infected with Trich.  This is a serious issue as bulls are chronic carriers of the disease and can spread the disease to any cows that they breed for the remainder of their life. 

A controlled breeding season also makes it easier to determine if you have been successful in removing Trich from your herd through evaluation of pregnancy rates.

Alexander et. al, Aus Vet J, 1953. BonDurant et. al., Infect Immun, 1993. Clark et. al., Aus Vet J, 1983. Mancebo et. al., Vet Parasit.  1995.  Mardones et. al., Vet Parasit, 2008. Parsonson et. al., J Com Pathol. 1976.  Rae et. al. JAVMA. 1989.  Rae et. al., Theriogeneology. 2004.  Skirrow et. al., Am J of Vet Res. 1990.   Skirrow et. al., JAVMA, 1987.  Szonyi et. al., Vet Parasit, 2012.