IMPROVED CLAWS THROUGH IMPROVED TRACE MINERAL NUTRITION

Michael T. Socha, Ph.D., D. J. Tomlinson, Ph.D. and A. Bruce Johnson, Ph.D. Zinpro Corporation, Eden Prairie, MN 55344

Introduction: Manipulation of the nutritional program of dairy cattle can have a profound effect on the prevalence of laminitis. Providing the proper amounts and forms of fiber, protein, carbohydrates and vitamins clearly affects the incidents of laminitis. Trace minerals also impact claw condition. The objective of this paper is to review the role of trace minerals in maintaining claw integrity.

Iodine (I): Research has shown that feeding I in the form of ethylenediamine dihydriodide (EDDI), in excess of the nutritional requirement, prevents foot rot (8). Only 8.3% of calves on pasture fed a salt mixture containing EDDI had foot rot, while 20.8% of calves receiving a salt mixture without EDDI had foot rot (6). When cattle were inoculated intradermally in the interdigital space with a mixture of Fusobacterium necrophorum and Bacteriodes melaningenicus to induce acute foot rot, cattle receiving 12.5-200 mg/animal/day of EDDI had less lameness than control cattle (1).

A series of studies addressing I supplementation in feedlot diets have concluded (13): 1) I has direct antibacterial properties, but to achieve this level would be toxic to cattle; 2) serum I concentrations of 60-80 mg/dl are thought to be prophylactic; and 3) cellular immune response is improved by feeding EDDI and iodate.

Feeding 0.11 mg/kg BW/d of EDDI has been found to be correlated with serum I concentrations of 20-80 mg/dl and found to be effective in preventing foot rot in cattle (7). However, the maximum legal limit for EDDI in the United States is 10 mg/head/d. The recommended dietary content of I for lactating dairy cattle is 0.6 ppm and 0.25 ppm for non-lactating dairy cows, replacement heifers and calves (11). Soybean, rapeseed and canola increase I requirements of the animal as they contain goitrogenic compounds that reduce I availability (14). High dietary nitrate also inhibits uptake of I by the animal (14).

Selenium (Se): In a study conducted by Larson et al. (5), only 28% of cows fed no supplemental vitamins and 30% of cows receiving supplemental vitamins A, D and E had severe claw problems. In contrast, 48 and 69% of cows receiving 50 mg of injectable Se with and without supplemental vitamins A, D and E, respectively, had severe claw problems (5). It appeared that Se increased the incidents of claw problems, possibly due to over supplementation of Se. Symptoms of a chronic Se toxicity include lameness, sore feet, deformed claws and loss of hair from the tail (14).

The maximum legal limit for Se supplementation in the United States is 0.3 ppm (11). Cadmium, copper, mercury, lead, zinc and sulfur can induce a Se deficiency (14). Dietary calcium levels greater than 0.8% reduce Se absorption (14).

Copper (Cu): Copper's role in the production of a healthy claw horn is related to the Cu enzyme, thiol oxidase. Thiol oxidase increases the structural strength of horn by cross-linking adjoining keratin filaments. In addition, strength of connective tissues such as tendons and laminae is dependent on Cu. The Cu containing enzyme, lysyl oxidase forms the cross linkages between collagen fibers, thus giving connective tissue strength.

Thus, it is not surprising that cattle suffering from a subclinical Cu deficiency are more susceptible to heel cracks, foot rot and sole abscesses (14). The recommended dietary content of Cu for dairy cattle is 10 ppm (11). Copper deficiencies have been observed in cattle fed diets with Cu concentrations in excess of 10 ppm. Bioavailability of Cu is greatly diminished by sulfur and molybdenum as they form an insoluble complex that renders Cu unavailable to the animal (9). Zinc and iron also reduce the availability of Cu to the animal (14). Producers who utilize by-products (i.e. corn gluten products, etc.) need to be aware of possible antagonists and adjust their Cu levels appropriately.

Manganese (Mn): Manganese helps minimize feet problems by maintaining proper leg formation (9). Animals suffering from a Mn deficiency will exhibit skeletal abnormalities, crooked legs and shortening of tendons as noted by knuckling over of feet.

The recommended dietary content of Mn for dairy cattle is 40 ppm (11). Dietary excesses of calcium and potassium increase Mn requirements due to increased fecal loss (9). Iron, magnesium, phosphorus and cobalt also reduce the availability of Mn (14).

Cobalt (Co): The primary physiological role of Co is as a constituent of vitamin B12 (cyanocobalamin). When sufficient dietary Co is fed, synthesis of adequate amounts of vitamin B12 takes place in the rumen. A vitamin B12 deficiency impairs protein and energy metabolism, resulting in laminitis (15).

The recommended dietary content of Co for lactating dairy cattle is 0.1 ppm (11). Current interest in Co is increasing due to the vast array of feedstuffs used in today's TMRs. Many nutritionists are feeding rations containing 1-2 ppm of Co to help increase fiber digestion and nutrient utilization. Manganese, zinc, iodine and monensin may reduce Co availability (14).

Zinc (Zn): It is theorized that Zn improves claw integrity by speeding wound healing, increasing rate of epithelial tissue repair and maintaining cellular integrity. Zinc is also required for the synthesis and maturation of keratin (15).

On dairies with high incidents of foot problems, cows fed 2 to 3 g/d of Zn sulfate for 70 days had fewer claw problems than cows not receiving supplemental Zn (16). In contrast, sheep fed rations medicated with Zn sulfate for up to six months did show a reduction in claw problems (4). The lack of a consistent response to feeding Zn in the form of Zn sulfate can be attributed to antagonists present in the diet reducing the bioavailability of Zn from Zn sulfate. Organic sources of Zn such as Zn methionine have been proven to be more bioavailable than Zn from inorganic sources (17).

Several studies have shown that Zn methionine improves claw integrity. In a year long study conducted at Illinois State University, cows fed an additional 200 mg/d of Zn from Zn methionine had fewer cases of foot rot, heel cracks, interdigital dermatitis and laminitis than cows not fed Zn methionine, (10). Observations on ulcers and white line disease trended towards improvement. Feeding Zn methionine to crossbred steers grazing native grass improved claw integrity (3). Of cattle receiving 216 mg/d of Zn from Zn methionine, 2.45% had foot rot while 5.38% of cattle not receiving Zn methionine had foot rot (3). Sheep fed 80 mg/d of Zn from Zn methionine had a reduction in mean lesion scores per foot (2). Feet were scored for lesions on a scale of 0 to 3, with 0 being no lesions and 3 being undermining of the wall (2). Sheep fed Zn methionine had a 43% improvement in foot lesion scores, while control sheep had no change in foot lesion scores from start to finish of the trial (2).

The recommended dietary content of Zn for dairy cattle is 40 ppm (11). Copper, cadmium, calcium and iron reduce Zn absorption and interfere with Zn metabolism (14).

Combination of trace minerals: There are significant interactions between trace minerals and hence it is imperative that people formulating rations attempt to maintain an appropriate balance of trace minerals in order to maximize animal performance. Research has demonstrated that supplying a combination of complexed trace minerals is more beneficial to claw health than supplying a sole complexed trace mineral. A two year study conducted on five commercial dairy herds in Central New York indicated that cows fed 360 mg of complexed Zn, 200 mg of complexed Mn, 125 mg of complexed Cu and 25 mg of complexed Co had better claw integrity than cows fed only 360 mg of complexed Zn or no complexed trace minerals (12). Supplementation of the diet with a combination of complex trace minerals reduced the incidents of double soling, white line separation, digital dermatitis, sole hemorrhages and ultimately, sole ulceration (12).

Summary: Trace minerals impact claw integrity of cattle. Meeting the true trace mineral requirements of cattle requires not only knowledge of the animal's requirements, but also factors that will affect the amount of trace minerals needed to be added to the diet to meet the true trace mineral requirements of the animal. Feeding organic trace minerals that are research proven is one way to minimize the risk of animals developing subclinical trace mineral deficiencies that compromise claw integrity.

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