Wednesday, July 4, 2012

Push Metabolizable Protein in Close-up Cows

We spend so much time fine-tuning transitional management in our quest to achieve optimal performance.  The performance of an athlete, a sprinter, is highly dependent on how they start; if they stubble out of the blocks, they have already lost the race and some may never finish.  The same is true for the cow in relation to the starting point of the lactation period.  We are constantly seeking the perfect dry cow ration, the ration that will solve all of your transition problems.  In this article, we will focus on the importance of protein, particularly metabolizable protein (MP), in the close-up period.

Metabolizable protein (MP) is a better predictor of protein availability for the cow’s use compared to crude protein (CP).  MP passes from the rumen as rumenal undegraded protein (RUP), rumen microbial protein (yes, rumen bugs are an excellent source of protein), and endogenous protein, digested in the abomasum, and absorbed as amino acids in the small intestine.  Therefore, the goal of nutritional program is to maximize rumen microbial protein, in essence, “Feed the Bugs!”  If the rumen microbial protein can not be enhanced further, more RUP, rumen bypass protein, needs to be fed.  

Why is metabolizable protein important for the dry cow?  In all ruminants, the rumen microbes need readily available protein and energy sources in order to survive and grow.  In return, the rumen microbes ferment fiber and rapidly multiply providing more MP.  The cow has important maintenance requirements.  A protein called albumin transports calcium, sodium, potassium, etc  and helps to maintain fluid balance throughout tissues.  Protein is needed for proper liver and immune system function.  Higher protein levels improve sensitivity to insulin as well.  So, it seems reasonable to assume that if MP is low, more metabolic problems ensue.  The growing fetus increases protein demands.  Sixty percent of the calf’s total body weight occurs in the last 2 months of gestation.  The 2001 NRC (National Research Council, Nutrient Requirements of Dairy Cattle) fails to account for the protein demand needed for mammary growth and colostrum production.  Heifers have an additional protein requirement for growth.  Finally, a higher pre-calving protein level is needed so requirements are met in the face of dry matter intake declines.  Individuals with lower dry matter intakes, such as heifers, cows with BCS>3.75, cows with twins, lame cows, etc, need to consume a ration with a higher protein level.

Controlled energy dry cow diets minimize the intake decline pre-calving and are excellent one group dry cow rations.  However, when problems arise we typically find particle length >2” which promotes sorting, low starch, and/or low MP.  Starch is needed to feed rumen microbes, from which the cow derives protein.  Therefore, when starch is limited, more rumen undegradable protein (bypass protein) is needed to maintain adequate MP levels.  Close-up rations higher in Non-Fiber Carbohydrates (NFC) or starch have higher levels of MP as long as the starch and rumen degradable protein fractions are adequate. 

Meeting a dry cow’s metabolizable protein requirement is extremely important.  Meet and exceed a Close-up dry cow requirement of 1200g MP per day.  Due to lower intakes and declining rumenal volume due to the growing calf, a close-up cows require a higher level of rumen undegradable protein in order to meet MP requirements.  If commingling all dry cows in a single group, the close-up ration should address the nutritional needs of the groups with lowest dry matter intakes, i.e. your heifers, fat cows, cows with twins, lame cows, etc. 

Eliminate the stumbling blocks that will prevent your cows from achieving a productive lactation.  Critically analyze your close-up dry cow diets.  Feeding appropriate levels of metabolizable protein to your close-up cows will enhance performance and improve health.   

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