The nutritional needs of captive laying ducks are entirely dependent on the supply of full-priced commercial feed. It is important to maintain the egg production rate of the captive ducks and increase the commodity rate of the eggs. In addition to meeting the needs of protein and energy nutrition, calcium supplementation is particularly important. First, as long as the normal development of calcium, part of the circle of laying ducks began to produce eggs around the age of 100 days, therefore, 15 weeks of age is the best time to start calcium supplementation. Calcium should be between the young duck and the laying duck, with an appropriate rate of 2.5%, and gradually increase thereafter. Second, the best calcium in each stage of egg production The utilization rate of calcium in duck is about 65%, and the production of one egg requires 4.8g to 5.12g of calcium. Practice has proved that the reasonable supply of calcium to duck is: When the egg rate is below 65%, calcium is 2.5%; when the egg production rate is between 65% and 80%, calcium is 3%; when the egg production rate is above 80%, calcium is between 3.21% and 3.5%. Third, choose a good source of calcium Calcium source is more extensive, generally limestone, shells as a major source of calcium, and more economical, but the proportion should be appropriate. Practice has proved that: the ratio of stone powder and shell powder is appropriate to 2:3, plus 1% of bone powder, the strength and smoothness of eggshell are the best. Fourth, the shape of calcium supplements Calcium particles stay in the digestive tract for a long time, in the eggshell formation stage can evenly provide calcium, at the same time, granular calcium in the stomach have similar grinding effect of sand, can promote the digestion and utilization of feed. Experiments have shown that using 50% of the shells in combination with 50% limestone can help the duck to absorb calcium well. 5. Factors Affecting Calcium Absorption 1. Calcium Phosphorus Ratio: Phosphorus can interfere with the metabolism of calcium and its deposition in the eggshell. The level of serum phosphorus is closely related to the formation of the best eggshell, and the optimum ratio of calcium to phosphorus is 5 to 6.5:1. 2, the role of VD: VD and duck body calcium and phosphorus metabolism, can help calcium, phosphorus absorption, is conducive to bone calcification and eggshell formation. And the absorption rate of calcium in the diet is proportional to the pH of the intestinal tract, and VD can reduce the intestinal pH. When egg ducks lack VD, the quality of egg shells declines, and soft shell eggs are produced. The hatching rate of eggs is low. 3. The relationship with the light: The sunlight of the duck body can change the ergosterol in the feather and skin blood to VD. Therefore, according to the egg production rate, 14 hours to 17 hours of light should be guaranteed, which is beneficial to calcium. Absorption and utilization, increase egg production rate. 4. The relationship with temperature: When the temperature is high, the carbon dioxide emitted from the ducks and the harmful gas such as nitrogen and sulfur dioxide produced in the duck houses are large, which is not conducive to the absorption of calcium. In the summer and fall season, it is necessary to do a good job in preventing the heat and cooling and ventilation in the duck house. 5. Relationship with Metabolisable Energy: When the diet of ducks and ducks contains high metabolic energy (3000 kcal/kg), the calcium content in the feed should also be increased to 4% to 4.5%; the metabolic energy in the diet should be 2650 kcal In the case of kilograms to 2750 kcal/kg, the calcium content is also reduced to 3.12% to 3.5%.
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