Source: Manitoba Agriculture Food, and Rural Initiatives
Retained placentas are defined as failure of the cow to expel the placenta within 12 hours of calving. The usual incidence of retained placentas in a herd is less than 5%. Although difficult calvings are associated with retained placentas, the cause is quite often nutritional. Low dietary levels of selenium, vitamin E, vitamin A, calcium and protein prior to calving have been implicated.
Selenium and vitamin E are both important for proper smooth muscle function. Ensure selenium is present at 0.3 mg/kg dry feed (6 mg/day). Daily intake of vitamin E during the dry period should be 800-1000 IU. Both vitamin E and selenium should be supplemented through the feed. Commercial mineral mixes or supplements will contain added selenium. Vitamin E levels are generally inadequate in these products and the addition of a vitamin E premix (eg. Vitamin E 40,000) will be needed. Feeding 25g of vitamin E 40,000 will provide 1,000 IU of vitamin E.
Injections of Vitamin E/selenium can be given 2-3 weeks before calving but they should be used only as a short-term measure. The vitamin E is effective for 2-3 weeks necessitating repeat injections. Remember that adequate vitamin E is essential for the immune system.
Vitamin A deficiency can result in a high incidence of retained placentas due to the role of vitamin A in maintaining the lining of the reproductive tract. Dry cows should receive 55,000 IU/day. This corresponds to an intake of 6g/cow/day of a vitamin A premix containing 10,000,000 IU vitamin A/kg.
Calcium is essential for smooth muscle function and nerve transmission. Calcium levels in dry cow diets should be between 0.4 and 0.75%. Remember that high calcium intakes during the dry period cause milk fever and milk fever cows are four times more likely to develop retained placentas. It is important not to overfeed calcium during this time.
Low protein levels during the dry period have been associated with retained placentas. Low protein intake causes the placenta to increase in size to try and absorb sufficient quantities of protein. Heavier placentas are associated with retained placentas. Protein in close up dry cow diets should be approximately 15%.
For further information contact:
Farm Production Extension, Animal Nutritionist
Manitoba Agriculture Food, and Rural Initiatives
204-545 University Crescent
Winnipeg, MB R3T 5S6