If a tree falls in the woods and there’s no one around, does it make a sound?
For centuries, philosophers have challenged our minds with such questions. If we define sound as a human experience, the answer would be an unambiguous “NO.” If we define sound as a physical phenomenon, the answer would be “YES.”
A silent heat is defined as “the lack of behavioral estrus symptoms although the genital organs undergo normal cyclical changes.” (ResearchGate) Similar to the “If a tree falls in the woods…” question, the physical phenomenon exists but the human experience (of heat detection) is absent.
Could the reason for this shortfall in heat detection be attributed to increased herd sizes of recent decades?
In the past 25 years, average dairy herd size more than doubled and the midpoint herd size has increased to 900 from 101 in 1992, according to the USDA. It is only logical that having more cows to heat detect makes the task considerably more difficult. Many heats are missed due to the sheer number of cows that are observed.
Healthy, well-fed and comfortable cows cycle. Cows with health issues or cows that are in negative energy balance do not. When an individual cow’s behavior is measured 24/7 by an animal monitoring system, the producer will know if and when every cow in the herd (10 cows to 5,000+ cows) is cycling. Even small changes in her behavior will be picked up and flagged. If she is not changing her behavior, additional information (such as the number of health events and her milk production levels) can provide insight into why she is not cycling.
Activity graph of cow giving 157 lbs at 80 DIM. Each red bar shows change from baseline activity in a two-hour increment. Tan area indicates the “in heat” threshold.
Activity graph of cow giving 90 lbs at 82 DIM. Each red bar shows change from baseline activity in a two-hour increment. Tan area indicates the “in heat” threshold.
Being aware of cow behavior and performance with accurate and non-opinion based data proves that there are no silent heats. Cows either cycle or they don’t, there’s no in between.