NDSU Extension - Williams County


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Spruce Popular Home Landscape Tree - Protein Analysis of Forage

Published February 1, 2015
Spruce Popular Home Landscape Tree - Protein Analysis of Forage

Colorado Blue Spruce


Spruce Popular Home Landscape Tree

Two years ago I tried to make it a practice each week to write about a tree, pros and cons, which might be useful in this area.  All of these writings were about deciduous trees but nothing on deciduous shrubs or coniferous evergreen shrubs or trees.  Because of this and questions coming to our office I want to resume this type of discussion starting with the evergreen trees.

The first will be the Colorado (blue) spruce.  This one is a favorite for a lot of people because of its beautiful pyramidal shape and dense branches which are mostly horizontal to the ground.  This tree can grow upwards of 35 to 65 feet which is mostly dependent on water availability and soil conditions.  As a rule of thumb, a healthy blue spruce will grow about one foot per year while the horizontal branches grow approximately six inches per year.  It is possible the crown width can be upwards of 15 to 25 feet.  When spacing these trees, I often find they are planted to close to one another, thus not able to express their natural beauty.  Blue spruce has a shallow root system thus not able to access moisture which is not available deeper into the root system.  This shallow root system and dense foliage makes the tree more susceptible to up-rooting due to strong winds.

Like all other trees, blue spruce has environmental problems other than the need for moisture beyond what mother-nature usually provides in this region.

For diseases, my observations indicate cytospora canker is the most common problem.  Rhizosphaera needle cast is more common in regions of the state where high summer humidities are common.

In this area of the state insects are more problematic than diseases.  These include spider mites, aphids, pine needle scale and the yellow-headed spruce sawfly.  The latter can severely stress the spruce to the point of “death” within just a few weeks.

Next time I will discuss why I think ponderosa pine is my choice over the spruce.

Protein Analysis of Forage

Occasionally I receive questions relating to forage quality.  Cattlemen generally look to protein as the first nutrient to analyze because they feel there is a positive correlation between protein and energy levels of the forage.  Also, protein is usually the most limited nutrient in our beef cattle rations.  So, understanding what protein analysis tells about the quantity and quality of the forage is important.

When a laboratory uses wet chemistry, crude protein most likely will be measured by the standard Kjeldahl procedure. This measures total nitrogen, which then is multiplied by 6.25 to arrive at the crude

protein value for the forage.  The 6.25 figure is used because most forages have about 16 percent nitrogen in the protein (100 divided by 16 = 6.25).  The crude protein value includes true protein and nonprotein nitrogen compounds. True-plant protein is roughly 70 percent of the protein in fresh forages, 60 percent of the total in hay forage and lower than 60 percent in fermented forages.  Ruminant animals are able to utilize a portion of both types of protein.  Many laboratories report a digestible protein value.  This is a calculated number, such as 70 percent of the crude protein or crude protein minus 4.4. It is an estimate of protein digestibility only and has limited value in formulating rations.

Excessive heating in hay and silage can reduce the amount of protein available.  However, crude protein analysis gives no indication that excessive heating may have rendered a portion of the protein unavailable.  However, laboratories can test for the amount of “bound” protein which is unavailable.

-Warren Froelich

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