Overcoming tender wool problem in sheep
18 July 2007
Dr B Scott
Research projects are under way in Australia focused on tender wool and how the problem can be overcome in sheep flocks
Tender wool could be avoided by genetically changing the nutritional makeup of the feed available to sheep, coupled with genetic engineering of key nutritional pathways in the animal itself. In Australia, CSIRO researchers have found the lack of amino acid cysteine is the major factor causing tender wool. Dietary cysteine is broken down rapidly and recycled by microbes present in the sheep’s stomach and these provide the only source of cysteine for the animal. Research is now under way to provide sheep with the ability to make their own cysteine to improve wool growth.
A recent article in “FARMING AHEAD” published in Perth, OVERCOMING TENDER WOOL, brings to light some very interesting questions.
The article suggests that a lack of the amino acid cysteine is a major factor causing the inability of the sheep to produce quality wool.
If the feed available to sheep can influence the character of the wool, why don’t we spend some effort to provide the proper diet? Analysis of the amino acid cysteine reveals a little different structure than many of the amino acids.
Cysteine contains the element sulfur. There are 20 amino acids that we know today that are specified by the genetic code. These twenty amino acids are much like the alphabet in constructing words. The 20 amino acids have been assigned a letter and these 20 letters make up the alphabet scientists use to plot the DNA code. By knowing the placement of each of these code letters we can now actually read the genetic code much the same way as we can read this letter. This knowledge can make a tremendous breakthrough in the skills of management. If we recognise what Pro-Ag of Australia consultants have been saying in their explanation of nutrition, that diets must match the requirements of the animal in order to obtain optimum production. The article in “FARMING AHEAD” points out that we must improve diets to improve production.
When it is described in scientific journals and the structure of the amino acid is written in schematic form like the chemist’s use it looks like this:
Name Symbols Schematic structure.
NH2
Cysteine Cys HOOC – OH – CH2 - SH
We know that the amino group needs to be present in order to make an amino acid. Notice the placement of the NH2 in the diagram. Then notice the element sulfur almost at the last position on the right. It is represented by the symbol S. The inclusion of the S is the reason this specific amino acid is empowered to contribute instruction to the genetic code.
Cysteine and methionine are the only two amino acids in the critical 20 that contain sulfur. Scientists have known for at least 50 years that these two amino acids were essential amino acids. Students of nutrition were made to study the list of essential amino acids.
Why is sulfur so critical in the diet?
The body uses relatively few Anions in the chemistry of the manufacture of flesh and blood. When we study the major elements, phosphorus or P is one of the five major elements.
When we study the trace elements, sulfur or S is also an anion and the bulk of the rest of the elements are cations. The anions have a positive charge and are often the key element in the structure of the rest of the compound.
The soil is the plant’s stomach. The only way to know if there is sulfur in the soil is to do a soil analysis.
Soil analysis has been one of the key portions of the Pro-Ag consultation service. Since the pressure in some communities has made the reliance on high analysis chemical fertilizers low in sulfur, we have many soils that are low in sulfur. Also many areas of farm land do not receive adequate sulfur even when they are fertilised.
Another factor in the metabolism of sulfur
Photosynthesis is the process that occurs in the leaf of a plant that allows the plant to manufacture food. The plant must take up nitrogen from the soil in order to have it present in the leaf. Much of the nitrogen comes into the plant as a compound we call nitrates.NO3 .
Now look back at the structure of the amino group in the diagram of cysteine. The amino group requires nitrogen to be associated with two H or hydrogen atoms instead of three O or oxygen atoms. The conversion of nitrate to amino is done in the plant and requires two factors. Sunshine and water. The water supplies the hydrogen. H2O. The plant’s metabolism releases oxygen. Then energy required for the conversion of nitrate to amino is also a part of the process.
Plants high in nitrate are incapable of including sulfur in the final product. High nitrate portions of the diet encourage microbes to require the sulfur present in the diet so the animal is deprived of cysteine.
The bottom line
Until the diet is properly balanced, we cannot expect animals to perform up to their genetic potential. It is quite foolish to attempt to change the animal’s genetic makeup when we aren’t feeding them the correct diet to enable them to perform with their current genetic capability.
Australian breeders have developed strains of the merino breed through selective breeding to produce the finest wool ever made by any sheep in the world. Now I would hope those same farmers would learn how to best develop the correct diet for those sheep.