Oestrus during pregnancy in the cow

Area of Science:

• Veterinary Science
• Animal Reproduction
• Behavioral Biology

Background:

• Estrus, or heat, is a critical period for reproduction in cattle, characterized by specific behaviors indicating readiness for mating.
• While estrus is typically associated with non-pregnant states, observations of estrus-like behavior in pregnant cattle have been reported but not fully characterized.

Purpose of the Study:

• To investigate and describe the occurrence, characteristics, and physiological correlates of estrus-like behavior in pregnant cows.
• To differentiate estrus-like behavior in pregnant cows from true estrus in non-pregnant animals.

Main Methods:

• Observational study across beef suckler and dairy herds, recording instances of estrus-like behavior in pregnant cows.
• Behavioral observations included standing to be mounted, interaction with other cows, and response to bulls.
• Physiological assessments included examination of genital tract changes, cervical mucus, ovulation, and hormonal profiles.

Main Results:

• Forty-three instances of estrus-like behavior were observed in 35 pregnant cows across multiple herds and stages of pregnancy.
• Behavioral signs were similar to true estrus but occurred more frequently between 121-240 days of gestation and had a shorter duration.
• No ovulation, metoestrous bleeding, or typical hormonal changes associated with estrus were detected in pregnant cows exhibiting this behavior.

Conclusions:

• Pregnant cows can display estrus-like behaviors that are behaviorally indistinguishable from true estrus but lack the underlying physiological events of ovulation and hormonal surges.
• This phenomenon occurs throughout pregnancy, with a higher incidence in mid-gestation, and pregnant cows showing these behaviors have better body condition scores.
• Further research is needed to understand the triggers and implications of estrus-like behavior in pregnant cattle.