Research by Penn State University has been investigating the influence of seasons on the production levels of dairy cows. The caveat placed on the research is that most  of the data was derived from conventional farms, and there is potentially a difference in the reaction from grazing herds. There is a natural change in milk yield, milk fat percentage and yield, and milk protein percentage that follows a cosine curve throughout the year. Milk yields peak around March, while component percentages (milk fat and protein) peak in late December/early January, with milk fat and protein yields falling in between these two dates. There are regional differences where the amplitude of the change (difference in height of the curves) varies. In the Northern part of the United States, there is an increase in amplitude on the components, whereas there is a larger amplitude of milk yield in the Southern part.

Before you start to say “Of course, there is a drop off because of the summer,” the exciting part of this data is that the pattern is visible even when accounting for the influence of heat stress/temperature fluctuations. The scientific hypothesis is that the patterns seen are evolved traits that could be influenced by several factors, such as photoperiod or seasonal hormonal changes.

What does this mean for dairies?
The most significant implication from these patterns is on the managerial side of dairy farms. Benchmarking is a tool that can help see where improvements have been made or where there needs to be an improvement. However, if there is an unexplainable difference between seasons for production, potentially, the benchmarks should be changed to fit the season. Looking on the nutrition side, there may be less potential in a cow during a particular season, which allows for a different ration throughout the year. In theory, cows calving in during the fall could maximize their potential on the cosine curve. Maybe the fall is where most first lactation cows should be calved in, to try and optimize their lifetime milk by maximizing their first lactation’s yield.

While this research is exciting and puts a new spin on evaluating dairy management practices, there is still much research to be conducted. Right now, there is a limitation on using this new knowledge; however, there is potential for groundbreaking changes in how dairy farms in the future are operated.