By Hubert J. Karreman, V.M.D.
Nutritional deficiencies in cattle herds probably revolve more around micronutrient minerals than protein or energy, although poor energy intake will definitely hinder conception. Poor energy intake is usually obvious by seeing skinny cows for months on end. This may be seen on grazing farms when not enough effective fiber is being fed, or the fresh grass is exiting the digestive tract too quickly and cows have too loose manure (diarrhea) for too long. Keep in mind that if you spot skinny cows, there will likely be micronutrient deficiencies as well. The animals are depleting their mineral stores from their bones (the skeleton is the major bank of minerals in the body). An obvious symptom of mineral imbalance is when animals licking the soil, stones, concrete, or walls in attempts to regain minerals not available in their feed.
Some of the important microminerals include selenium, zinc, copper, manganese, and cobalt. Selenium deficiency is classically seen in newborn calves with white muscle disease; however, it is more often seen as retained placentas without a problem calving (i.e., no twins, not early, not a hard calving). Selenium also helps the immune system and can help if high somatic cell counts are a problem.
Zinc deficiency may show in reduced conception rates, increased retained placentas, hoof problems (strawberry heel, laminitis, heel cracks), low-quality milk due to high somatic cell count, and slow wound healing.
Copper deficiency may show reduced conception although heats are being seen, early embryonic death (although BVD can certainly cause early embryonic death as well), possible increase in retained placenta, and diarrhea.
Manganese deficiency may be seen as no heats or silent heats, reduced conception rate, slow or delayed ovulation, and increased abortion (although BVD, lepto, and neospora may also cause abortions).
Cobalt deficiency, which is required for production of vitamin B12, may result in reduced fertility but is more associated with increased early calf mortality.
Deficiencies of any of these micronutrients can cause an animal, especially a younger one, to have a poor hair coat and poor growth of the skeleton, legs, and joints (although parasitism can also cause symptoms of animals looking rough and not thriving). Chronically loose manure (diarrhea) will certainly deplete the animal’s system of minerals as well as protein, and in adults we usually think of Johne’s disease or inadequate dry hay being fed. Either way, minerals are being wasted.
Obviously, your nutritionist will be able to advise you on the proper levels of the micronutrients to feed based on what is being provided by your forages. Please keep in mind that most minerals are absorbed better through the digestive tract than by syringe and needle. Generally speaking, if the animals in your herd look sleek, have shiny hair coats, and are in proper body condition for their stage of lactation, they will most likely be able to get bred back in the time period that you would like. In short, doing your part in watching for heats, breeding them in time, feeding them well, and doing regularly scheduled reproductive examinations will enable your cows to freshen according to your schedule.
Source: Four-Seasons Organic Cow Care