The success of any type of livestock farming is determined by the yield produced, meat quality and the maintenance of excellent herd health conditions. Therefore, adequate and proper nutrition is key to the welfare, health and productivity of all animals. Apart from nutrition, other factors like temperature, humidity, solar radiation and wind also have direct effects on animals as well, especially in tropical climates such as the Middle East.
Feeding should never be considered as the act of merely providing for the animals immediate needs, because it has a great impact on future production, yield and meat quality. Inadequate feeding regimes during key periods of embryonic, foetal and early postnatal growth leads to poor herd health, low yield and poor meat quality. A well-planned diet with the correct levels of nutrients can reduce overall feed costs.
Sheep are ruminant animals. The bacteria, protozoa and fungi in the rumen of the sheep is responsible for helping them digest the fibrous foods, such as forages, that they consume. Hence, feeding the microorganism-filled rumen should be the most important consideration while formulating diets for sheep.
In tropic and subtropic environments such as the Middle East, natural pasture has both lower nutritional value and lower tiller density than in temperate regions. Hence, most of the animals (sheep) in this region are largely impacted by nutritional stress.
A good diet for optimum growth should consist of adequate quantities of water, carbohydrates and fats (Energy), Proteins, Vitamins and Minerals. In regions where there is environmental stress, additional nutrients may have to be added to their regular diet.
The usual recommendations for sheep in moderate climates are approximately 3.8 litres of water/day for ewes on dry feed, 5.7 litres/day for ewes nursing lambs, and 1.9 litres/day for finishing lambs.
However, animals in hotter climates (like ours) use more water for evaporative cooling. Sheep adjust to the excessive heat stress by increasing evaporative cooling through panting. Even with the provision of good quality water and shade for the sheep, water consumption can be higher by about 40 percent than in winter. In extreme conditions, the water consumption can be 70 percent above that in winter. For optimum productivity, it is absolutely essential that the water availability to the sheep is monitored daily during all weather conditions.
It’s not the quantity of forage but the quality of forage that determines whether energy for maintenance and production are met. Higher the forage quality, higher the feed intake. For Ewes, the greatest requirement for energy is during the first 8- 10 weeks of lactation. This is because milk production gradually starts declining after that, as the lambs start foraging on their own.
A body scoring system is usually employed to assess energy adequacy in sheep using an objective 1-5 scoring system, with 1 being extremely thin and 5 being extremely obese. This is determined by palpating the amount of fat covering on the spinous processes and transverse processes in the lumbar region of the sheep. Most healthy productive ewes will have a score ranging between 2 to 3.5. Sheep with a score lesser than 2 should be examined thoroughly and fed up to attain a higher score, and ewes with a score of less than 1 should not be considered for immediate breeding. Those sheep with a score that is greater than 3.5 should be fed less. Changes in diet should always be done gradually, and drastic reduction in total energy intake should be avoided, especially if an ewe is in middle to late gestation. Adequate feed space ranging from 300mm to 450 mm must be allocated for the ewes in order to ensure all animals are fed well. Rams should have a target body condition score of 3.5 before tupping. Testes size and sperm production are highly responsive to nutrition. It is recommended that there must be an increase in the ram’s nutrtion atleast 7 weeks prior to tupping, inorder to achieve good sperm quality and quantity. As supplementation with concentrates increases, the intake of forage is likely to decrease.
Usually good-quality pasture and forage provide sufficient protein for mature sheep. However, it is recommended to add a protein supplement along with the forage. The stage of the ewe must be taken into consideration while supplementing protein. While 7% dietary crude protein is needed for maintenance in most sheep, this quantity will vary during periods of growth, gestation and lactation etc. Alternatively, protein supplements, such as oilseed meals, cottonseed meal, soybean meal or commercially blended supplements can be fed to meet the necessary protein requirement.
The major minerals required in the diet of a sheep include Sodium, Chlorine, Calcium, Phosphorus, Magnesium, Sulphur and Pottasium. The trace minerals required in the diet are Cobalt, Copper, Iodine, Iron, Mangnese, Molybdenum, Zinc and Selenium.
Sodium and Chlorine (as salt): Sheep need salt especially during stages of reproduction and lactation. Adult sheep will consume approximately 9 g of salt daily, and lambs will consume 4.5g of salt.
Calcium and Phosphorus: In plants, generally the leafy parts are relatively high in calcium and low in phosphorus, whereas the reverse is true of the seeds. Legumes, in general, have a higher calcium content than grasses. As grasses mature, phosphorus is transferred to the seed. Deflourinated rock phosphate and ground limestone are used in cases where there is a low phosphorus and calcium content in the diet.
Iodine : A deficiency of iodine is usually manifested as goiter in the adult and as lack of wool and/or goiter in lambs. This can be prevented by feeding iodized salt to pregnant ewes.
Cobalt & Copper: Adult sheep require ~0.1 ppm of cobalt in their diet, whereas pregnant ewes require approximately 5 mg of copper daily. Sheep are more susceptible to copper toxicity, hence care must be taken to avoid excessive copper intake.
Selenium : This element is effective in at least partially controlling nutritional muscular dystrophy. The dietary requirement is ~0.3 ppm. It also plays an important role in sperm quality of the ram.
Zinc : Lambs usually require ~30 ppm of zinc in the diet on a drymatter basis. Zinc is also an essential trace mineral requirement in rams for testicular development and for sperm quantity and quality.
Sheep diets usually contain adequate supply of Vitamins A, D and E. When fed diets rich in carotenes, sheep can store large quantities of Vitamin A in the liver to meet their requirements for as long as 6 months.
Vitamin E is poorly stored in the body; hence a daily intake is essential. Green feeds and germ of seeds are excellent sources of Vitamin E. Its deficiency coupled with low intake of Selenium can lead to nutritional muscular dystrophy. The rumen microorganisms usually synthesize Vitamin B and Vitamin K and hence, these supplements are not necessary always. The tissues of the sheep synthesize Vitamin C , however, a steady supply of the same can also be added in the diet to improve conditions of the sheep. Vitamin D2 is derived from sun-cured forage, and vitamin D3 from exposure of the skin to ultraviolet light.
Finally, in order to ensure greater productivity, it is important to know the exact constituents in the feed and ascertain the level of protein, energy, vitamin and mineral enrichment it is providing to the sheep. This can be achieved by conducting regular feed analysis of samples sent to local food testing laboratories.
Dr. Hansel Geo Thomas is the director and founder of Charis Vets. He is a licenced veterinary practitioner in the kingdom of Bahrain.