Why does the amount of cream on top of the yogurt change seasonally?
The reason for the lower amount of cream currently on our yogurt is simple:
- We operate/manage a semi-seasonal grass fed herd of cross-breed cows.
- Our yogurt is made from milk straight from our bulk tank that is less than 48 hours old. It is not separated and "standardized" to a flat 3.25% like industry yogurt that is called whole milk yogurt (A rare thing BTW).
The meaning of the above two points = Our yogurt is a mirror of the average butterfat level in our milk. The majority of our cows calve in March and April with the last ones calving by August. This means the cows peak in milk production in the Spring (when grass growth is at its peak which allows us to produce more milk on a very high percentage grass diet) and go through the normal butterfat percentage curves together. It is normal for our cows to produce slightly lower levels of butterfat during and immediately following peak milk for each lactation. Combine that norm with the normal grass growth slump and hot weather we experience each summer in late June though August causes our average butterfat levels to be at their lowest.
Our dairy herd's average butterfat is usually at it lowest of about 3.9% in June and at the highest of 5 - 5.5% in December or January. You can expect to see a correlation between the thickness of the cream top and what time of year it is. Note that the US average butterfat level from most conventional holstein herds is in the 3.25 - 3.5% range. Due to our crossbred Jersey/Friesian/Ayrshire genetics and being grass-based our average is much higher at about 4.5%.