Dietary Crude Protein Levels

With first cut silages now in the pit, second cut not far away for many, and then with potential wholecrop and maize harvests to come, it may seem early but its already time to start thinking about diets for the coming winter, especially if you are autumn calving, as I’m already putting together my first transition diet for the coming season.

With protein prices high, and early first cut silage results showing low crude protein levels, now would be the time to review your plans for the coming winter and consider the overall crude protein levels in your diet and what some alternative sources maybe, because as well as the price of supplementation, as an industry we are under environmental pressure to reduce the nitrogen, therefore proteins, used within our systems.

To give you some context, ruminants are incredibly inefficient with their nitrogen use with an average of only 25% of protein fed to cows being converted to milk or meat.  The other 75% is excreted as either urine or feaces!  This is much lower than the monogastric sector who feed lowered crude protein diets and supplement with specific targeted Essential Amino Acids (EAAs) to meet requirements.

The advantage for most of the monogastric sector is they are in closed environments where every detail of their diet is known, and specific needs are required and met.

As a sector we are dealing with constant environmental changes, i.e. weather, and feed changes, i.e. the forages change from day to day.

As an industry we have traditionally blanket fed crude protein in our diets, and if we take a step back in time, we consistently fed diets greater than 20% CP, with maximum yield considered to be between 21% & 23% CP.  We as an industry seemed to be determined to produce as much milk as possible, at any cost.

Some of this increased production was because increased protein levels lead to increased intakes, and therefore increased production, it also made her “work” harder, but it was to the detriment of the cow, her health and her fertility.  Too much protein can affect the blood chemistry of a cow and therefore change the uterine environment, and so affect her ability to conceive.

In more recent years the goal has been for diets to be between 16% & 18% CP, but I still see diets that are 19%+ CP, and when you comment that this is too high, I’ve often had the response “well they know how to make the cow milk!”.  Yes, they might but at what cost.

Work from different studies, including a long-term project from the University or Reading, seem to indicate that is doesn’t matter if your diet’s crude protein level is lower, as long as it is correctly supplemented with the required EAAs. In the monogastric sector they deal with multiple EAAs, but so far in the ruminant sector we are only working with methionine & lysine, but more are coming!

Personally, I currently aim for my outside diets to be around the 16.5% CP, but I can see these edging slightly lower with the correct and balanced use of EAAs, it will all depend on the individual farm requirements.

In the UK, most of the diets are deficient in methionine, but once you remove soya from a diet you are also short of lysine.  The way to combat these deficiencies is to supplement the diets with rumen protected EAAs.

The benefits of using EAAs can include improved milk solids, improved calf health when cows are fed during the transition period, and improved fertility at joining, as well as improved reduction in early embryo loss, so again improving overall fertility.

I’ve been seeing this last winter with a high yielding client where we reduced the soya in the diet, but didn’t eliminate it entirely, and supplemented with methionine & lysine.  We saw fantastic butterfat percentages, hitting 4.3% with no palm derivatives being fed, and reducing the calving block by another month for this coming year.  As a comparison when previously producing this last winter’s level of production, we were struggling to maintain 4.0% butterfat with C16 being fed.

There also appears to be a lower energy requirement when using EAAs, again probably because the animal is not using energy to expel the excess protein.  While this isn’t a great deal it is still a saving, or potentially extra milk over the course of the lactation.

The long-term trial at the University of Reading followed three groups of cows, at different crude protein levels (14%, 16% & 18%), but with no EAA supplementation, for three lactations they found that the cows they fed the lower crude protein diet to had poorer survivability.  The 16% CP diet was formulated to meet all the cow’s protein requirements, but the 14% CP didn’t, and so saw a higher level of cows culled over the course of the study.

The comment from the study was as long as the diet was formulated to meet all the cows’ requirements, and where required supplemented with EAAs, then they saw no reason why they couldn’t work.

It however isn’t something to just happen, you need to work with your nutritionist to make it happen in planned stages, over a period of time.  You can’t drop say from a 18% CP diet to a 15.5% CP diet without correct planning and implementation.

The expected reduction of soya in diets will undoubtedly reduce the protein levels in the majority of diets, and strategies for replacing this is another whole article!

Therefore, I certainly believe that for higher yielding herds the use of EAA supplementation will be the way forward as it will reduce the crude protein requirements of the cow by supplementing her more precisely and have both environmental and economic benefits.

If you would like to review or discuss diets call FAR registered Dairy Nutritionist & CowSignals® Master Andrew Jones on 07717 44288 or email