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Should you be concerned about low iron status in your calves?

Amanda Kerr for Progressive Dairy Published on 28 July 2022

Iron status is a classic study point to the importance of mineral and vitamin nutrition for young calves. It has been reported approximately 20% of neonatal calves experience iron deficiency anemia.

An iron-deficient calf will show poor growth, dullness, with increased risk for disease due to a suppressed immune system. There are several vital roles iron plays within the body; the most noted one, of course, is as a component of hemoglobin, allowing oxygen to be transported to cells throughout the body. However, iron is also a component of enzymes involved in mitigating negative effects of free radicals generated during oxidative stress responses and other metabolic pathways requiring electron transport.

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Hemoglobin represents a large pool of iron within the body and stored reserves found within the liver, spleen and bone marrow. There are various measures to monitor iron status, with hemoglobin and serum ferritin as two common focal points in calves. Ferritin is a protein found in blood which “holds” iron and can be a useful representation of physiological stores of iron. Iron is drawn from these stores when serum levels fall, such as a bleeding event, lack of dietary sources or under high-demand conditions such as growth and active immune response to acute or chronic challenges. Considering the pre-weaning period, a fast-growing calf will have increased demands for iron, in addition to calves experiencing health challenges or other forms of chronic physiological stress. With maturity, the dietary need for iron is less and risk of deficiency a negligible concern.

At birth, increased risk for low hemoglobin levels have been found if a calf is a twin, a bull or is born to a first-calf heifer. The amount of iron capable of being transferred across the placenta during late gestation is suspected to be one cause of anemia at birth, and it seems independent of the cow’s hemoglobin status. It is not clear the proportion of dairy calves which may be impacted by low iron status at birth (clinically anemic or subclinical low iron levels), nor the implication this may have on downstream risk factors.

Young calves are very efficient at absorbing iron from their diet; thus providing a milk replacer fortified with all essential vitamins and minerals is an easy solution to alleviate neonatal calf anemia. However, when only offering whole milk, calves can be quick to become deficient, whether clinically with anemia or with suboptimal levels which may impair metabolic responses. Although whole milk offers many essential micronutrients, iron content of whole milk is negligible. Under natural conditions, nursing calves on pasture would obtain needed iron missing from milk by accidental ingestion of soil, insects, etc., in addition to stores present at birth.

Providing a vitamin and mineral supplement to young calves fed whole milk can be a useful nutritional approach, along with good management practices, to ensure the best health and growth for calves. Moreover, if calf starter is not provided in the first days or week of life, the opportunity to gain minor dietary amounts of iron is not available. When low, early starter voluntary intake is coupled with a high iron demand period, the calf’s health can be negatively impacted. Figure 1 illustrates this according to adequate intake for iron as prescribed in the NASEM Nutrient Requirements of Dairy Cattle 2021 based on typical calf growth rates and calculated calf starter intake in relation to the amount of milk fed.

Predicting amount of dietary Iron

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Iron’s immunological role may in part explain an increased incidence of diarrhea in calves with low serum iron status. This is significant, as research has indicated calfhood scours, among others, is an interlaced risk factor for pneumonia, a clear animal welfare and farm economic issue. In an unpublished research trial, Grober Nutrition Inc. noted calves with lower hemoglobin status experienced a greater number of days with a fecal score of 3 (watery scour) compared to calves with hemoglobin in a normal range. Research in other species, and in calves, have provided an association between iron status and insulin-like growth factors (IGF), which with further study may help to better elucidate factors impacting the gut environment towards a healthy state or a diarrheic one.

Typically a condition associated with milk-fed white veal calf production, low iron status can affect neonatal calves of any production type. Considering iron status, therefore, is another metric to monitor in calves to ensure full growth, health and profitability potentials are met. end mark

Amanda Kerr is a senior nutritionist with Grober Nutrition Inc.

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