An area of nutrition that is commonly overlooked in foot health managment is the role trace minerals play in improving claw health, structural integrity and reducing incidence of lameness. Trace minerals are important to production and maintenance of healthy keratinized tissues (Mulling et al., 1999). Increasing the bioavailability of trace minerals improves their utilization and thus may help improve claw horn production (Ballantine et al., 2002).
Relationship between Trace Minerals and Claw Integrity
A discussion on trace mineral functions and claw horn development would be incomplete without first noting calcium, a macro mineral, and its importance to claw horn formation. Calcium is integral to the keratinization and cornification process. Calcium is needed for activation of epidermal transglutaminase (TG), which is active in cross-linkage of cell envelope keratin fibers and is involved in initiation and regulation of terminal differentiation of epidermal cells. It may be probable that some laminitic insults seen in high producing dairy cows (typically moderately hypocalcemic) and those that have suffered from hypocalcemia may be in part related to impaired TG activity and its impact on differentiation control and formation of healthy claw horn.
Similar to calcium the trace minerals zinc, manganese, copper, cobalt, selenium and iodine are essential to enzymatic functions relating to catalytic, structural and regulatory control of keratinization processes. Zinc is an essential component of hundreds of enzyme systems. The metabolic actions of these include carbohydrate and energy metabolism, protein synthesis, nucleic acid metabolism, epithelial tissue integrity, cell repair and division, and vitamin A transport and utilization (NRC, 2001).
It is theorized that zinc improves claw integrity by increasing rate of epithelial tissue repair, maintaining cellular integrity and speeding wound healing (Weaver et al., 1978). Zinc is also required for the synthesis and maturation of keratin proteins (Mulling 1999, Mulling 2000, Smart and Cymbaluk, 1997).
On dairies with high incidence of foot problems, cows fed 2 to 3 g/d of zinc sulfate for 70 days had fewer claw problems than cows not receiving supplemental zinc (Dembinski and Wieckowski, 1987). Inconsistent responses to feeding inorganic zinc may be attributed to dietary antagonists reducing zinc bioavailability. Complexed sources of zinc, such as zinc methionine, are proven to be more bioavailable than inorganic zinc sources as they are less affected by dietary antagonists (Paripatananont and Lovell, 1995;Wedekind et al., 1992).
Several studies have shown that complexed zinc improves claw integrity. In a year-long study conducted at Illinois State University, cows fed complexed zinc had fewer cases of heel cracks, interdigital dermatitis and laminitis than cows fed inorganic zinc (Table 1), (Moore et al., 1989). Incidence of sole ulcers and white line disease tended to be reduced.
Researchers at Kansas State University found feeding complexed zinc improved claw quality of crossbred steers grazing native grass (Brazle, 1993). Of cattle receiving 216 mg per day of complexed zinc, 2.45% had foot rot vs. 5.38% infection in cattle not receiving complexed zinc.
Research in dairy cattle indicates that cows supplemented with 360 mg of zinc from complexed sources (ZINPRO, zinc methionine) had 15% higher zinc content than cows supplemented with only inorganic sources of zinc (Smith et al., 1999). Diets in this study contained over 170 mg zinc/kg of DM. British workers reported findings of lower Zn concentration in claws of lame cows than those with no history of lameness (Baggott et al., 1988). Claws of lame cows were also softer than non-lame animals.
Table 1. Claw evaluation scores of lactating dairy cows fed complexed zinc (Moore et al., 1989)
Similar to zinc, copper is also important to production of healthy claw horn as it is a key component in lysyl and thiol oxidases. These enzymes are responsible for formation of the disulfide bonds between Cys residues of keratin filaments (O'Dell, 1990). This process is responsible for building structural strength and rigidity at the cellular level. Cattle receiving insufficient copper often suffer from heel cracks, foot rot and sole abscesses (Puls, 1984).
Manganese is active in a number of enzyme systems required for cartilage and collagen formation and bone growth (Miller et al., 1988). Animals suffering from a clinical manganese deficiency will exhibit skeletal abnormalities, crooked legs and shortening of tendons as noted by knuckling over of feet (Miller et al., 1988). Manganese helps minimize feet problems by maintaining proper leg formation.
The primary physiological role of cobalt is as a constituent of vitamin B12 (cyanocobalamin). A vitamin B12 deficiency impairs protein and energy metabolism, resulting in poor horn production and lameness (Smart and Cymbaluk, 1997).
Iodine is required for synthesis of thyroxin which regulates metabolic rate (NRC, 2001). Subclinical iodine deficiency results in suppressed immune function and may result in increased incidence of foot rot and respiratory diseases (Puls, 1994). Several studies have shown benefits of feeding iodine as ethylenediamine dihydriodide (EDDI) in excess of nutritional requirements to prevent foot rot (Miller and Tillapaugh, 1967).
Selenium is recognized as an essential element that defends the body against oxidative stress. Symptoms of selenium deficiency include a suppressed immune system, reduced fertility and weak or silent heats. Symptoms of chronic selenium toxicity include lameness, sore feet, deformed hooves and loss of hair from the tail (Puls, 1994).
Effect of feeding a combination of complexed trace minerals on claw health
Feeding a combination of complexed zinc, manganese, copper and cobalt results in further reduction in claw disorders when compared to only complexed zinc or only inorganic trace minerals. A 3000 cow study conducted in Central New York indicates that feeding a combination of complexed zinc, manganese, copper and cobalt, instead of only complexed zinc or only inorganic trace minerals reduced incidence of double soling (4.0 vs. 9.8%), white line separation (28.9 vs. 43.9%), sole hemorrhages (64.1 vs. 72.5%) and ultimately, sole ulceration (13.2 vs. 14.8%), (Nocek et al., 2000). Supplementation with complexed trace minerals also reduced incidence of digital dermatitis (8.3 vs. 12.4%).
Researchers in Florida found that replacing inorganic zinc, copper, manganese and cobalt with similar amounts from complexed sources resulted in a decrease in claw lesions (Ballantine et al., 2002). Feeding complexed trace minerals tended to decrease the incidence of claw disorders at 75 d postpartum (23.6 vs. 34.1%) and the incidence of white line disease at 75 (9.5 vs. 14.6%) and 250 d postpartum (4.9 vs. 8.8%).
Meeting the true trace mineral requirements of dairy cows requires not only knowledge of the animal's requirements, but also factors that will affect the amount of trace minerals needed to meet requirements. 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 and may lead to lameness.
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This presentation was given at Dairy Focus Asia 2010. Engormix.com thanks the authors and the organizing committee for the contribution.