Improving fiber production through nutrition

CEW-MR-1-Improving fiberby Tamara Scully

Producing wool doesn’t start with shearing the sheep; it begins well before birth. Two primary factors which affect wool quality are genetics and nutrition. Dr. Nancy Irlbeck, of the University of Colorado — a sheep farmer herself — discussed the importance of nutrition in fiber development, offering producers tools to use to grow quality fleece.

“I’m not going to tell you what feeds to use. I’m going to give you why we need to feed what we do,” Irlbeck said.

Good fiber

Good fiber is that with a low micron count, and a high fleece weight. Studies determining the impacts which environment have on wool production have focused on fine wool breeds, mostly Merinos, but apply to all wool breeds. The hair breeds are “a little bit different than the wool breeds,” she said.

Using fiber microscopy, researchers can see the impact that nutrition and environment have on fiber  Fiber is composed of the root, the shaft and the tip. When sheep are not fed properly, changes in the fiber are seen. Sheep with inadequate diets develop very thin fibers, with an increase in fractures and breaks. Overfed sheep produce coarse wool.

Fiber doesn’t only show the effects of poor feeding. It can also reflect other environmental stressors, particularly with fine wool. Sheep exposed to severe storms, illness or injury will show fiber breaks. The best Merino wool is raised on confinement farms, where the ewes are kept clean and fed properly, but also kept in a controlled environment where stressors are minimized.

“Fine wools take the greatest management, the greatest husbandry,” Irlbeck said

Producing wool

Wool quality is determined by genetics, and by environmental factors. Breeding for quality wool production has its limits, as genetic selection for one trait carries increased risk of negative factors, Irlbeck said. In sheep, selection for fine fiber has led to small animals and low fleece weight.

But genetics is only the beginning. Whatever genetic potential an animal has is impacted by its environment. While external environmental stessors can break the fibers, the animal’s nutritional intake has the most impact. Age and gender are also a factor. As the animal ages, its wool quality decreases. Wethers tend to produce a coarser wool.

“The wool is a part of the animal’s skin,” Irlbeck said. “The maximum number of follicles that a lamb can form is determined genetically. You can’t change that other than breeding your animals through your different lines and different rams that you are using.”

But the actual number of follicles which do form is greatly influenced by nutrition. Nutritional needs vary depending on life stage. Meeting the increased nutritional demands of certain stages is the key to increasing secondary follicle production, and increasing wool quality.

Primary follicle development is not susceptible to nutritional concerns. Secondary follicle development, however, is highly dependent on nutrition. Secondary follicles add weight and density to the wool. These are the fine fibers. The quantity of secondary follicles which develops is determined during the third trimester. At this time, the lamb is putting increased demands on the ewe, and the amount of rumen capacity available to her is rapidly decreasing. Adequate nutrition at the right time is needed to promote this crucial secondary follicle development, allowing producers to readily influence the quality of the wool.

Critical nutrition

Adequately feeding sheep throughout their live stages, beginning in utero, maximizes fiber quality. Lambs born to dams who didn’t eat properly during gestation will show increases in fiber diameter — a negative trait, as fine wool is prized — and a decrease in fleece weight.

“If you are feeding the animals according to the physiological status, and feed the most nutrients in that third trimester, not before, you will have the greatest amount of secondary follicles produced.”
The progeny of poorly fed dams will show large decreases in secondary follicle growth. Likewise, if multiples are being carried, the “fetus are competing for the same amount of nutrients,” Irlbeck said, and the amount of secondary follicle development will be impacted.

If a ewe loses one-half of a body conditioning score during gestation, the clean fleece weight from the lamb will be decreased. Likewise, the micron count of the fiber will increase, making a coarser wool. In the case of multiple births, Irlbeck recommends separating out those carrying more than one fetus, as well as young mothers, and providing “a higher plane of nutrition,” which these animals will require to maintain body conditioning score. Other critical nutritional stages demanding high-quality feed to meet increased demands for energy include: pre-weaning; lactation; and post-weaning.

The animals don’t only need grain during these critical life stages. They need high-quality forage. With multiple births, “even with high quality forage and a bit of grain, they often get very, very thin,” Irlbeck said. “They tend to lamb a little bit earlier, just because they don’t have the capacity to consume enough feed.”

Forage and supplement

“For maximum genetic expression, one would need to supply extra feed,” to pastured sheep, Irlbeck said. “On pasture, sheep don’t realize their maximum genetic potential for wool production,” if the only source for nutrients is grazing. Irlbeck recommends that hay be tested for its nutritional content.
While grain does not have to be fed to pastured sheep at all life stages, the critical stages demand additional feed if the goal is to produce the best wool. Without adding additional feed to pasture forage at critical times, “you won’t get to their genetic potential” for wool quality.

Whole shelled corn is an economical grain supplement. Sheep chew very well, she said, and fine grains cause acidosis concerns. Corn stalks provide enough feed to eat so the animals don’t feel hungry. The stalks keep them from overfeeding, while their nutritional needs are met by the alfalfa.

“I never feed grains to my lambs after 100 days,” Irlbeck said, explaining that once the earlier growth stage is past, the energy demands decrease. “I only feed to meet their nutritional needs. I only feed the alfalfa enough to meet their needs per feeding. The rest of the time they get corn stalks.”

Selecting for fleece

Lambs’ wool has a tell-tale sharp tip, indicating that it has never previously been sheared. It is very fine, and valued by spinners, Irlbeck said.

Keeping records is the best way to select for wool quality, Irlbeck advised. When selecting for wool, culling animals if the fiber length and crimp isn’t satisfactory at 150 days is appropriate. Keeping records of fleece weight, indicating the sheep which are producing heavy fleece, is another way to assist with genetic selection.

Making shearing decisions depending on factors which affect the wool quality is smart. Irlbeck shears in winter in her winter-lambing flock. If not, the mothers are apt to lay down in the snow to cool down while giving birth, and the lambs will be lost to the cold. Another reason for winter shearing is that cold conditions will cause stress breaks in the fibers.

“Genetics… you can only do so much,” Irlbeck said. “Feed according to physiologic status, but be cognizant of how you are feeding and the impact on potential wool production.”

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