Q & A About Sugar and Dairy Feeding

 

What does sugar do in a dairy ration?

 

Sugar is a carbohydrate source that is more rapidly fermented in the rumen than any other compound. This can allow better utilization of the proteins by supplying an additional carbohydrate source. The rumen microbes need various protein and carbohydrate sources to achieve optimal rumen function. Sugar will complement the other carbohydrate sources that are being fed.

 

What is the amount of sugar that is recommended for today’s dairy rations?

 

Research has shown that feeding 4-7% total sugar on a dry matter basis can have a positive effect on milk production. There also have been studies that show a negative effect from having more than 7% total sugar in the ration.

 

Here are the results of a recent university study in which molasses replaced high moisture corn on a dry matter basis:

 

% Added Molasses

0

4

8

12

Fat Corrected Milk lbs/day

91.3

92.6

95.7

87.1

Dry Matter Intake lbs/day

55.3

56.9

57.8

57.3

Assayed TMR % Sugar

2.6

4.2

5.6

7.2

 

In this case, increasing the sugar level in the TMR by 3% was beneficial, but a greater increase appeared to depress milk production.

 

Why should we limit sugar above a certain level?

 

Sugar is ready for rumen microbes to make use of immediately.  That helps support microbial protein synthesis.  More sugar than they can use for that purpose may be converted to fermentation acids rapidly enough to depress rumen pH, leading to decreased fiber digestion and acidosis.

 

How much sugar is in a typical dairy ration?

 

There are variations from farm to farm and from year to year.  TMR ranges are typically from 1-6% total sugar on a dry matter basis.  Last year most dairy rations were close to the 2-4% range. This would suggest adding 2-3% sugar to most dairy rations. Here are some typical lab assay ranges for sugar content on common feedstuffs:

 

 

Sugar % Range

 

Sugar % Range

Corn Grain

0.8 – 4.0

Alfalfa Hay

2.8 – 11.1

Soybean meal

10.4 – 11.8

Haylage

2.2 – 5.1

Corn Silage

0.7 – 8.4

Whole Cottonseed

1.5 – 2.2

 

What causes variation in sugar content of feeds?

 

Sugar content is affected by maturity and by time of day at harvest, and by storage loss. 

To get higher sugar, harvest early in maturity stage, but late in the day.  As plants mature, their sugar content declines, so harvesting at an early stage of maturity will result in higher sugar content than harvesting later.  Sugar content will be higher in hay and haylage cut late in the day because that gives photosynthesis more daylight hours to produce sugars. 

 

Sugar cannot be gained during preservation and storage – it can only be lost.  If forage is too wet or too dry when cut for silage, the ensiling process will be prolonged and the sugar will be consumed in fermentation.  One study showed that in a typical corn silage,  sugar content was reduced from 11.9% in the fresh cut corn plant to 3.5% in the preserved silage.

 

If hay is cut too wet or rained on, the sugar content will  decrease due to prolonged respiration while in the field, and to leaching.

 

Are there other benefits from adding sugar to a ration?

 

 Sugar improves palatability.  Liquid ingredients and blends also improve mix integrity and reduce sorting by cows.  One study recently showed that liquid supplements reduced or eliminated sorting as measured by the Penn State screen evaluation method.

 

How can I tell if I should add sugar to my TMR?

 

A lab test is the most certain way to help decide.  Several laboratories offer accurate wet-chemistry sugar analyses.  Westway representatives can help you find laboratories to do the assays.

 

However, without doing an assay, here are indications that sugar may be beneficial:

 

 

Why is sugar an issue now?  Hasn’t it always had the same benefits?

 

It’s the cows.  Sugar has always stimulated rumen microbial fermentation.  However, in the past, a cow could maintain expected production levels without maximizing rumen fermentation efficiency.  The amazing milk production of today’s (and tomorrow’s) cows requires that the rumen produce at full capacity.  That’s why we are concerned with rumen degradable protein, escape protein, NSC, fiber solubility, and so many more ingredient characteristics that weren’t an issue years ago.  Sugar is part of the picture today’s cows require us to look at.