Dairy Cows On Pasture

The role of pasture in dairy management systems is lessening with the trend towards more intensive operations and increased production. The high moisture content of pasture makes it difficult for milking cows to consume the large amounts of feed necessary to support the high levels of production expected.

Many dairy producers do, however, effectively utilize pasture as part of their feeding program. Advantages of pasture include improved health and reproduction due to exercise, more efficient use of areas not suited to crop production and reduced feed costs. Concentrate feeding can be reduced when cows are on good quality pasture but pasture cannot substitute for all the concentrate in a ration. It has been estimated that without any grain, good cows on excellent pasture can produce about 50 lbs milk/day. Higher levels of milk production will require supplementation with additional grain, protein and/or forage.

Some of the disadvantages associated with pasture are increased maintenance requirement due to grazing activity (estimated to be equal to 4 lbs of milk energy), increased heat and fly problems, wasted feed due to trampling and lack of uniform feed quality. Changes in quality and difficulties in estimating pasture intake make ration programming more difficult.

Consider the following when pasturing your cows:

    1. Ensure pasture is young, actively growing and in good supply. Begin grazing when tall-growing, cool-
        season grasses and legumes are 8-10 inches tall and short-growing, cool-season grasses and legumes
        are 4-6 inches tall. At these heights, pasture quality is high, forage is easy to eat, and recovery after
        the last graze has been sufficient. Rotational grazing and strip grazing help ensure maximum
        productivity of cows and pastures. Dairy researchers suggest offering cows fresh pasture every 12 to
      24 hours to improve intake.

     2. Make a gradual change to heavy pasture over 1 - 3 weeks by limiting grazing time initially and gradually
        reducing intake of stored forage.

     3. Lower grain levels slowly (4 lbs/week) to prevent sudden drops in production.

     4. Feed grain at levels indicated by pasture analysis and ration formulation.

     5. Help to maintain a stable rumen pH of 5.8 to 6.2 by limiting concentrate intake to 5 lbs per feeding,
        feeding at least 5 lbs of baled hay or 10 lbs of silage DM with half the particles over one inch in length,
        feeding stored forage (long particles) prior to grain and pasture and including buffers in the ration.

     6. Degradable and soluble protein levels in an accompanying TMR or grain mix can often be dropped
        because of their high content in lush pasture.

     7. Pasture intake can be estimated from the NDF value. Wisconsin researchers suggest that cows can
        eat 1.2% of their body weight as NDF. NewZealand researchers report a normal grazing time of 6 to
        8 hours per day with a consumption of 4 lbs of pasture dry matter for each hour of active grazing.

     8. Remove cows from pasture at least two hours prior to milking if off- flavours are a problem.

     9. If a TMR is fed with pasture, reduce TMR feeding to maintain a 5% refusal.

   10. As intake of a TMR and grain mix is reduced, remember to increase levels of minerals and vitamins
        accordingly.

   11. Provide shade and ample quantities of good water.

Dr. Mike Hutjens of the University of Illinois suggests three approaches to pasture systems.

Approach 1.	Feed grain at 2 to 4 lbs per day (New Zealand system) or at 10% of the total ration dry matter. Milk yield could be 30 to 50 lbs per cow per day.
Approach 2.	Supplement 2 to 5 lbs of forage dry matter (silage or hay) and feed one pound of grain for each 5 lbs of milk or at 30% of ration dry matter. Potential milk yield could be 40 to 60 lbs per cow per day.
Approach 3.	Feed 50% of the dry matter from pasture and 50% from a PMR (partial mixed ration). Milk yield could be 60 to 80 lbs per cow per day.

Prepared by:
Karen Dupchak, M.Sc., Farm Production Extension - Animal Nutritionist
Livestock Knowledge Centre - Manitoba Agriculture, Food and Rural Initiatives
Nutrition Update (Volume 17 No.1)