Author: Michael Ferrari, PhD
VP, Applied Technology & Research

For some time, we have known about the positive relationship between La Nina-like conditions and milk production for US herds.  During an El Nino, conditions for much of the US may tend to be warmer and wetter, and as dairy cows exhibit sensitivity to heat stress and/or muddy fields, these conditions correlate with decreased milk production, particularly during the key months (Mar-Jul) in the annual cycle.  As the opposite La Nina pattern has been developing for the last several months, cooler temperatures have been present across much of California (the largest producing state), limiting heat stress and contributing to an active grazing season, both of which are good for milk yields.  As Weather Trends has been advising to our clients, this particular La Nina is actually shaping up to be a pretty strong event, and as a result, we have been expecting better US production numbers to follow.  Note that this does not take into account decreased herd size, so the emphasis is on milk yield per cow.

To test this idea, we looked at the relationship between the Southern Oscillation Index (SOI), which is an ENSO guide, and US milk production over the last decade.  Specifically, we highlighted periods where there has been a stronger trend towards positive-phase SOI in recent months relative to the 6 month moving average; the assumption being a stronger relative acceleration towards positive phase supports better milk production weather.  Using a simple decision-tree scheme, the time series was split by grouping all months where the more recent period showed stronger positive SOI characteristics (as defined by a quantitative index).  Of this reduced group of months, we then looked at monthly normalized US milk year–over-year (y/y) production to see if stronger numbers may have been related to the index.  We found that using a sample size (n)  of 60 months, y/y milk yields increased in 52 of these months (87%), verifying that a positive correlation exists. 

 

We do not suggest that the SOI, or any other weather parameter is the primary factor in assessing potential milk production.  Many other components go into strong yields, including herd management, feed quality, and of course, economics.  But this simple analysis does demonstrate that weather can be a key driver in the amount of milk that is flowing from producers to consumers, and it bears watching as a signal for forward pricing, and assessment of global stocks.  Also, this is just one example – we have developed many more sophisticated means at quantitatively and qualitatively assessing the weather/yield relationships across a wide variety of sectors within commercial agriculture.

Please contact Weather Trends if you would like to learn more about our work being done in this area.