The largest single production cost in
any livestock operation is feed. Due to the unique nature of the
sheep’s gastrointestinal tract, forages can comprise the majority
of a ewe’s diet. Sheep diets must be designed to support optimal
production, while also being economical. Nutritionally sound diets
will avert nutrition-related disorders, thus promoting health and
productivity. Nutrient requirements are influenced by:
Age
Stage of production
Forage quality and quantity
Production system (range versus
confinement)
Environmental/climatic conditions
Management
Body condition
Nutrient needs include water, energy,
protein, minerals, and vitamins. Sheep nutrient requirements can
be obtained from Nutrient Requirements of Sheep published by The
National Academy of Sciences.
Water: The need for water is
basic. An unlimited, fresh water supply is needed for sheep in all
stages of production. Limitations to water intake may limit feed
intake, hampering production, and contribute to the occurrence of
urinary calculi in male sheep.
Energy: Insufficient energy
limits ewe performance more than any other nutrient. The
predominate energy source for ewe diets is forage. The use of
highly digestible fiber sources in complete sheep feed enables
healthier rumen function. A lack of protein can result in ewes not
efficiently utilizing energy in forage. For feedlot lambs, grain
sources are used to supply most of the energy needs. Energy
content of finishing diets can be boosted with the addition of
2-3% fat. Using more than 3% fat may reduce feed intake, decrease
gain, and cause “off-color” carcass.
Protein: The need for
supplemental protein depends on production stage and quality of
available forages. Protein supplementation of sheep on medium to
low-quality pasture/range can increase rumen microbe activity,
thereby increasing forage intake, digestion, and performance.
Sheep can utilize non-protein nitrogen (NPN), such as urea and
biuret. Limit NPN to 1% of the total ration or not more than 1/3%
of the total ration nitrogen. Non-nitrogen protein sources should
not be used in rations for young lambs and in creep rations.
Young, growing lambs and high producing ewes require higher levels
of amino acids. Sheep, like other ruminants, derive amino acids
from feed protein that bypasses the rumen and from microbial
protein produced in the rumen. Most amino acids are derived from
microbial protein; however, microbial protein may not supply all
amino acids needs for high producing ewes and young lambs. Rumen
by-pass protein sources may be beneficial for improved performance
of young lambs and high producing ewes.
Minerals: The relationship of
minerals to each other must be taken into account when formulating
supplemental sheep mineral products. The amount of one mineral may
influence the amount of another mineral needed in the diet. Lack
of a mineral creates a deficiency, while too much may cause
toxicity. Sheep are especially sensitive to copper. While they
need some copper in the diet, the spread between requirement and
toxicity is very narrow. Zinc, especially complexed zinc, has been
associated with enhanced hoof health and immune response. The
inclusion of ammonium chloride in high-grain rations has been
shown to lessen the likelihood of urinary calculi.
Vitamins: Sheep require
dietary sources of the fat-soluble vitamins A, D, and E. Young
lambs also require vitamin K and B-vitamins until the rumen
becomes functional. Depending on grazing/harvest conditions,
forage may be low in vitamin A, creating a need for
supplementation. Niacin, a B-vitamin, is beneficial for increasing
gain and feed efficiency in rations containing higher energy and
protein. Another B-vitamin, thiamin may help prevent
polioencephalomalacia in feedlot lambs.
