By BOB PADULA
ASI Wool Quality Consultant

(February 1, 2009)  It is well known that wool traits are highly heritable and genetics plays a large role in the quality of the wool produced. Every grower makes a conscious decision regarding wool quality when they turn in the ram for breeding. However, once fertilization takes place, the role of genetics is essentially done and environment and management determines how the animal expresses its genetic potential.
Ironically, when producers devote more attention and management to lamb production and increased lamb survival and growth, wool production benefits by the extra attention and producers are actually doing their wool clip a favor by letting the sheep reach its genetic potential for wool. 

It is well known that nutrition has a large impact on wool production. Wool is the “canary in the coal mine,” and for years, researchers have measured, recorded and evaluated wool as a means to assessing animal nutrition and health status. Biologically, the sheep will divert nutrients away from wool production to other requirements in order to survive, reproduce or provide for their young. This means that wool production will be compromised if animals are not fed and managed properly at the various stages of production during the year. Improper feeding shows up first in wool, but also has detrimental affects on lamb performance during the early part of the lamb’s life.   

The most recent National Research Council Nutrient Requirements for Sheep (2006) provides detailed information on the nutrient requirements for sheep production, including wool. The recommendations indicate that additional nutrient requirements for wool-bearing sheep are not appreciably higher than those of wool-less or hair sheep, and therefore these small amounts of additional nutrients required for wool production are included in the maintenance requirement. The additional nutritional requirements for the various stages of production are related to the increased requirements for the non-wool components.

The basics of wool production have been known for years and can be found in the Wool chapter of the Sheep Production Handbook available from the American Sheep Industry Association. The follicles which produce the wool fibers are broadly categorized into primary follicles and secondary follicles. Primary follicles are usually the largest, and generally arranged in rows in the skin in groups of three, known as a trio group. In the fetus, primary follicles are formed first (by 100 days gestation) and all of the primary follicles are formed and growing fiber by the time the lamb is born.    

The secondary follicles are the most numerous, tend to be smaller follicles and tend to grow finer wool than the primaries. The secondary follicles are formed later on in gestation (day 90 to birth) and by birth nearly all the secondary follicles are developed, but many do not mature (produce fiber) until after birth. Most follicles are producing a fiber by about one month after birth.

When pregnant ewes are not properly fed and managed during late gestation and lactation, wool growth for the ewe is impaired and reduced. However, this improper feeding can also reduce secondary follicle development in the growing fetus(es) and nursing lamb(s). If the follicles do not mature and develop, they can not grow wool fibers and this will be detrimental for wool production the entire life time of the young animal. Therefore, managing and feeding ewes for fetal growth and lactation is critically important for producers from both the lamb and wool side of the equation.

On the other side, over-feeding is not only uneconomical and costly for the flock, it can also be a negative for wool. Over-fed ewes are more prone to ketosis or pregnancy toxemia, birthing problems, lambs that lack vigor and reduced milk production. The end result is lambs that are not as thrifty early on in life during the crucial period of secondary follicle development and maturation. In addition, over-fed ewes will have coarser wool, which is lower in value. Over feeding is economically and biologically damaging. 

Bottom line, growers that focus on lamb production by feeding their sheep properly throughout the year are helping their sheep grow the best wool genetically possible.