Essential Nutrient Requirements of Sheep
Of primary importance in sheep nutrition are water, energy, protein, minerals (with salt, calcium, and phosphorus the most critical components), and vitamins (with vitamin A of primary concern).
Energy. Insufficient energy limits performance of sheep probably more than any other nutritional deficiency. An energy deficiency may result from inadequate amounts of feed or from feeds (generally forages) that do not contain enough protein to sufficiently "unlock" the energy in the feedstuff. The major sources of energy for sheep are hay, pasture, silage, and grains. Milo, barley, corn, oats, and wheat also can be used to raise the energy level of the diet when necessary. Energy deficiencies can cause reduced growth rate, loss of weight, reduced fertility, lowered milk production, and reduced wool quantity and quality.
Protein. In sheep rations, the amount of protein is much more important than quality of protein. However, since the sheep is a ruminant, mature sheep use effectively the naturally occurring protein and nonprotein nitrogen (urea) in their diets. Common sources of natural protein supplements include cottonseed, soybean, sunflower, linseed, and peanut meals. These oilseed meals contain from 40 to 50 percent protein and are excellent sources of supplemental protein. High-quality legume hays can contain from 12 to 20 percent protein and provide adequate protein for most classes of sheep when fed as a complete ration. Grains, however, are low in protein. They generally contain only 8 to 11 percent protein. Additional protein is necessary in high-grain, lamb-finishing rations for maximum performance.
Nonprotein nitrogen sources should not be fed to young lambs. Young lambs are not functioning ruminants until they are approximately 2 months old, depending upon how soon they have access to grain and forage. However, mature sheep can be fed low levels of nonprotein nitrogen. In general, supplemental nonprotein nitrogen is beneficial only when adequate energy is available. Urea should never make up more than one-third of the ruminally degradable protein in the diet. Additionally, nonprotein nitrogen sources should not be used when lambs are limit-fed. Urea can be toxic if consumed in large amounts over a short time, especially when the diet lacks ruminally available energy. Furthermore, urea is very unpalatable.
When supplementing range sheep in New Mexico, it is important to consider the quantity of available forage in the pasture. If adequate forage is present, but the standing forage is dry and brown (containing < 5 to 6 percent crude protein), it may be necessary to supplement with a high-protein feed (> 35 percent protein). However, if the amount of available forage is insufficient or if the forage is still somewhat green (> 6 percent protein), a lower-protein supplement should be fed to provide additional energy, if needed. Lactating ewes have the highest protein requirement and may require supplemental protein if the range forage contains less than 10 to 12 percent crude protein.
Water. Water is essential for all livestock. Producers must plan for an adequate supply of clean water when designing any type of sheep enterprise. The quality of the water is also important. Sheep will not consume enough water if it is stagnant or of poor quality.
Ordinarily, sheep consume two to three times as much water as dry matter. Abundant, clean, ice-free water is a must in lamb feedlots. Without water, lambs may eat less. Water running through a low trough or water dripping into the trough can help to start the lambs drinking and eating.
Minerals. Approximately 13 different minerals are essential in sheep nutrition. Most of these requirements are met under normal grazing and feeding habits in New Mexico. Those that are most deficient are salt (sodium chloride) and phosphorus.
Salt is essential for many body functions. When sheep are deprived of salt, they generally consume less feed and water, produce less milk, and grow slowly. Animals that are deprived of adequate salt may try to satisfy their needs by chewing wood, licking dirt, or eating toxic amounts of poisonous plants. Inadequate salt intake may cause decreased feed consumption and decreased efficiency of nutrient use. When adding salt to mixed feed, add 0.3 percent to the complete diet or 1 percent to the concentrate portion. In general, supplemental salt should be provided to range ewes at a level of 8 to 11 g of salt per head per day. Provide loose salt rather than salt blocks. Sheep tend to bite instead of lick salt blocks; as a consequence, their teeth may break or wear down prematurely.
Almost all pastures and hays contain an abundance of calcium, but grains are lower in calcium. When lambs are fed on a high-concentrate diet, calcium supplementation may be necessary.
In New Mexico, pastures and hay are generally low in phosphorus. In grains, however, the amount of phosphorous is moderate to high. Since any efficient sheep operation uses a high percentage of roughage or pasture, it is good insurance to assume that the sheep need phosphorus supplementation. Phosphorus deficiency causes slow growth, reduced appetite, unthrifty appearance, listlessness, abnormal bone development, and poor reproductive performance. It may be beneficial to provide phosphorus supplements year-round for the breeding flock.
When purchasing commercial mineral blocks or loose forms of mineral supplements, look at the calcium-to-phosphorus ratio. The narrower this ratio, the better. However, it is important to make sure that the ratio is not inverted (more phosphorous than calcium). If producers prefer to mix a mineral supplement, mix 50 percent salt with 5 percent cottonseed meal and approximately 45 percent bone meal or dicalcium phosphate. Provide this supplement free choice and year-round in a feed box protected from rain and moisture.
Mature sheep require all the fat-soluble vitamins: A, D, E, and K. They do not require supplemental B vitamins, which are synthesized in the rumen. Normally, the forage and feed supply contain all essential vitamins in adequate amounts, except vitamin A, which is sometimes deficient in dormant forage. However, sheep can store vitamin A for a considerable time. If ewes have been pastured on green forage or have had access to high-quality legume hay, vitamin A is not usually deficient.
In some areas, lambs may develop white muscle disease. This is thought to be caused from a deficiency of vitamin E, selenium, or both. Treatment is most effective with early diagnosis and injection of a vitamin E-selenium material (see page 26).
Creep Feeding. The objective of any farm sheep enterprise should be to develop thrifty, fast-gaining lambs that can be marketed at an early age. Creep feeding may help accomplish this objective.
The most efficient conversion of feed to weight gain occurs during the first 100 to 120 days of a lamb's life. Lambs can easily gain 1 pound per day in their first 70 to 80 days. In well-managed flocks of efficient, fast-gaining breeds, it is common for lambs to reach weights of 110 pounds at 120 days of age.
Young lambs gain 1 pound for every 3 to 4 pounds of feed consumed. By comparison, old-crop feeder lambs require 5 to 6 pounds of feed per pound of gain. There are several potential advantages to using a creep-feeding program:
- Increased weight gains, especially for multiple-birth lambs.
- Highly efficient feed conversion.
- Early marketing.
- Early growth and development of the lamb lessens the stress of early weaning.
When practical, start lambs on creep feed as soon after birth as possible. Ordinarily, lambs do not consume much feed until they are 3 to 4 weeks of age. However, the small amount consumed at earlier ages is critical for establishing rumen function in the lamb. Most studies have shown that if the intake of the creep ration does not average 1/2 pound per day from 20 days of age to weaning, then no increase in lamb performance is realized from creep feeding.
Locate the creep feeders where the lambs will use them. In a drylot, place the feeders in a convenient, dry, well-bedded, protected area. In pasture areas, place the feeders relatively close to water tanks, resting areas, or salt and supplement feeders.
To get lambs started on a creep, make sure the starter ration is palatable. Soybean meal in the starter ration increases palatability and provides additional protein. However, soybean meal is expensive. High-quality alfalfa hay, alfalfa pellets, and oat grain also are very palatable.
The creep ration does not have to be complex. It should provide at least 15 to 16 percent natural protein. A simple creep ration containing 80 percent grain sorghum, 10 percent oats, 10 percent oilseed meal, with alfalfa hay free choice should be adequate. Depending on the cost of grain, corn can be substituted for grain sorghum, and wheat or barley can replace half the grain sorghum. In general, young lambs prefer coarse, rolled grains and pelleted feeds. The cost of preparation can make the ration costly, but rate of gain and feed efficiency are increased by pelleting complete feeds, concentrates, and roughages. Pelleting also allows the producer to include different additives, standardize the grain-roughage ratio, and lessen feed waste. Do not feed dusty, moldy, wet feeds. If practical, give any feed left in the creep feeder daily to the ewes, and provide the lambs with fresh feed every day. Add antibiotics to creep rations according to a veterinarian's recommendations to provide some protection against low-level infections.
Individual management systems differ, but often it is feasible to discontinue feeding the ewes grain after the lambs are approximately 6 weeks old and are eating adequate amounts of the creep feed. It is more efficient to feed the grain directly to the lambs because they will convert the feed to gain more efficiently than the ewes can convert feed to milk to lamb gain.
Some producers wean lambs when they are 60 days old. Early weaning of 40 to 50 pound lambs can be successful, provided the lambs are consuming adequate amounts of feed. Research has shown that the ewe's milk production reaches a peak at about four weeks following lambing, and steadily declines to about half as much by the 10th week of lactation. About 74 percent of all milk is produced in the first eight weeks of lactation.
Feeding Lambs. If the farm enterprise is geared to producing marketable lambs in the shortest possible time, creep feeding the lambs early in life is essential to early weaning and to subsequent rapid development in the feedlot. The size of the lamb at weaning is more important than its actual age. Generally, lambs should weigh at least 50 pounds before weaning. Lambs that are on full feed at weaning generally have little difficulty adjusting to a feedlot environment.
After weaning, ewes can be placed on lower quality pasture because their nutritional requirements are low.
One of the biggest advantages of not pasturing the lamb with the ewe is that lambs have less chance of internal parasite infestation. In some situations, it can be more economical to wean lambs and place them on clean, high-quality, fresh pasture, while continuing to provide them supplemental feed. However, this method of finishing lambs does not maximize growth rate under most situations. Ordinarily, pastures are most efficiently used by old-crop lambs. Typically, older lambs can more economically use alfalfa, grain sorghum stubble, wheat pasture, and corn fields. Temporary woven-wire fences or electric fences can be used to effectively control grazing on such fields.
Usually, the lambs must be placed in a feedlot to be adequately finished for market. Intensive management is the key to success in lamb feeding.
In the feedlot, the first few days are the most critical. Generally, lambs have been transported long distances without adequate feed or water, and they often are highly stressed when they arrive at the feedlot.
Range lambs sometimes refuse to drink or eat. For this reason, drylot range-raised lambs for three to four weeks on the ranch so that the lambs know how to eat feed from a bunk and drink from a trough.
Feed newly arrived lambs a high-roughage ration (unless they have previously been adapted to a high-grain diet) and allow them to rest. Lambs should be placed on feed cautiously and gradually adapted to the desired concentrate level.
As soon as the lambs are over the stress of relocation, treat them for internal and external parasites. Also, vaccinate them for enterotoxemia type D, and sore mouth.
Adequate feeding pens should be available so that the lambs can be sorted by size and fed accordingly. Immediately isolate weak or sick lambs. Size and age of lambs influence the ration composition. Heavy lambs must be finished more rapidly, so they need a ration with a higher level of grains for energy. Lighter lambs can be fed rations containing more roughage. Generally, lambs are started on rations containing 60 to 70 percent roughage. For general lamb feeding, where both legume hay and feed-grains are readily available, a ration of 50 to 60 percent grain and 40 to 50 percent hay can produce very economical gains while minimizing the occurrence of digestive disturbances. Growth stimulants such as Ralgro┬« also can be beneficial in improving lamb performance in the feedlot. Ralgro┬« has been shown to stimulate growth rate and to improve feed efficiency.
Lasalocid (Bovatec) also can be incorporated into feedlot diets. Lasalocid will help prevent coccidiosis while promoting growth and improving feed efficiency.