Reproduction and Laminitis

Lame cows tend to have lower dry matter intake, milk production and extended days open as a result of the laminitic insult. Lameness in bulls has the potential for loss of use in two general areas (12). First, lameness results in bulls failing to follow, mount and serve cows. Secondly, lameness can result in testicular degeneration, and thus poor semen quality (12). Lameness in cows also affects fertility. Cornell research indicates that lame cows have 28 more days open (27). British studies reported that cows lame between 36 and 70 days postpartum had 17 days more to first service and 30 days more open.

It is theorized that zinc improves claw (hoof) 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 (55). On dairies with high incidence of foot problems, feeding 2 or 3 grams per day of zinc sulfate for 70 days reduced claw disorders (64). In contrast, sheep fed rations supplemented with zinc sulfate for six months did not show a reduction in claw problems (16). The lack of a consistent response to feeding zinc in the form of zinc sulfate can be attributed to antagonists present in the diet reducing the bioavailability of zinc from zinc sulfate. Complexed sources of zinc have proven to be more bioavailable than zinc from inorganic sources in part because the absorption of complexed trace minerals is only minimally affected by antagonists (65).

Feeding complexed zinc has been shown to reduce incidence of claw disorders in sheep and cattle. In a year long study conducted at Illinois State University, cows fed an additional 200 mg/d of zinc from Zinpro complexed zinc had fewer cases of foot rot, heel cracks, interdigital dermatitis and laminitis than control cows (42; Figure 6).

Figure 6.

Complexed zinc also improved claw quality of crossbred steers grazing native grass (7). Of cattle receiving 216 mg per day of zinc from Zinpro complexed zinc, 2.45% had foot rot while 5.38% of cattle not receiving complexed zinc had foot rot (7). The reduction in foot rot may have partially contributed to the higher average daily gain for cattle fed complexed zinc (1.27 kg vs. 1.23 kg), (7).

Sheep fed 80 mg per day of complexed zinc had a reduction in mean lesion scores per foot (4). Feet were scored for lesions on a scale of 0 to 3, with 0 being no lesions and 3 being under-mining of the wall (4). Sheep fed complexed zinc 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 (4).

In addition to zinc, manganese, copper and cobalt play important roles in maintenance of claw integrity (55). Copper plays an important role in keratin maturation and formation of connective tissue. Manganese plays an integral role in maintaining foot and leg condition (41). In addition, increased claw problems are observed in a cobalt deficiency due to decreased protein synthesis.

Research conducted in Central New York indicated that feeding Zinpro complexed zinc, manganese, copper and cobalt resulted in fewer claw disorders than feeding no organic trace minerals or only complexed zinc (50). Supplementation of the diet with complexes reduced the incidence (P<0.05) of double soles, white line separation, sole hemorrhages and ultimately, sole ulceration (50). Supplementation with complexes also reduced the incidence (P<0.05) of digital dermatitis (50). Incidence of dorsal wall ridges tended to be reduced (P<0.15) by complexed trace minerals (50). The addition of Zinpro complexes to diets of lactating dairy cows improved claw condition compared to feeding no complexed trace minerals or only Zinpro complexed zinc (50; Figure 7).

Figure 7.

Similarly, Florida researchers found that replacing inorganic zinc, manganese, copper and cobalt with similar amounts of these trace minerals from Zinpro complexes resulted in reductions in total claw lesions (2). Feeding Availa-4 tended to reduce the incidence of foot rot and white line disease (2). If cows did exhibit a claw lesion such as white line disease, heel erosion or sole ulcers, Availa-4 supplementation reduced the severity of the lesion. (2; Figure 8 and 9).

An interesting footnote to this study is that source of trace mineral had no effect on trace mineral content of the liver. Levels of zinc, manganese and copper in the liver were above levels considered to be adequate and were similar both statistically and numerically for both Availa-4 and sulfate groups. However, cows fed Availa-4 had not only improved feet but also better reproduction and milk production (2). These results indicate that trace mineral content of liver may only be useful to identify deficiencies, not ability of trace mineral source to impact animal performance.

Figure 8.

Figure 9.