Milk Protein Drops-Causes and Solutions

Milk protein varies with genetic potential, breed and stage of lactation.  Milk protein starts high after calving, reduces in early lactation (dilution effect of increased yield) and increases thereafter.  Cow nutrition influences protein as follows:
• If total energy intake is reduced at any stage during lactation milk protein drops, see Cows’ energy cycle below.  A major drop in protein % and/or low milk protein (below 3%) can be an early warning sign that cows are underfed (particularly if combined with reduced milk yield) and corrective action should be taken to avoid subsequent fertility issues as well as correcting milk protein %. 
• Cows’ energy cycle

• Additional dietary protein intake has little effect on milk protein concentration.  The diet needs to be very low in dietary protein quality and quantity to see a reduction in milk protein. 

The graph below shows the protein % in a spring calving herd under the Teagasc Moorepark system.  The blue line represents a well fed herd.  The red lines represent two protein drops that can commonly occur on commercial farms:

Lactation Protein variation under the Teagasc Moorepark system
1. Cause
Reduced dry matter intake (DMI) due to overestimation of grass supply and poor grazing conditions (typically in early March).
Solution
Maintain concentrate feeding levels to match grass supply or increase concentrate to compensate for poor grazing conditions.
2. Cause

Grazing grass covers that are too strong resulting in low digestibility, low energy grass (typical in June-July).
Solution
Ensure milking cows always graze high quality grass where possible.  Employ good grass management techniques to achieve this.

2013 Warning
In many cases silages are of poor quality (low energy) this spring.  Ensure to compensate by matching feeding levels to herd energy needs and forage quality to avoid low milk protein and a large energy gap (fertility impact).  High starch levels in the concentrates fed will also aid milk protein production.

Be careful not to overestimate grass intakes