Digital Dermatitis Stymies Feed Efficiency in the Feedlot

Digital dermatitis, also known as hairy heel warts, takes its toll in growing-finishing feedlot cattle. It reduces market weights and hot carcass weights in infected cattle, according to beef feedlot research conducted in commercial feedlots located in Iowa and Illinois, where digital dermatitis is an endemic problem. The studies evaluated the differences between cattle fed a novel nutritional supplement that included Zinpro Performance Minerals^® (zinc, manganese, copper) and iodine to a supplement that had a similar profile from predominantly inorganic trace mineral sources (zinc, manganese, copper) which also included iodine.

In one study, cattle fed performance trace minerals had an average increase in total final weight gain of 17.6 pounds (8 kg), and a calculated average increase in hot carcass weight of 26 pounds (11.8 kg) per animal compared to the animals fed an inorganic source of trace minerals. Likewise, cattle fed the inorganic trace minerals had a greater prevalence of total digital dermatitis lesions by the time cattle were shipped to market.

Digital Dermatitis Impacts Beef Cattle Nutrition

Digital dermatitis is a growing health and animal welfare concern in feedlots located in some geographic regions of the United States and Canada.  Digital dermatitis may commonly be misdiagnosed as foot rot; however, treatment and prevention strategies are different. So, it is important that an accurate diagnosis be made as soon as possible to help reduce the incidence and severity of the disease and its adverse effects.

Digital dermatitis begins as lesions around the claw. They are raw, bright-red or black circular erosions of the skin just above the heel bulbs. The edges form a white margin that surrounds sores or are adjacent to thick, hairy wart-like growths. There are five stages of digital dermatitis, ranging from M1 (early/subclinical) to M4.1 (chronically recurring). It starts to impact animal health at the M2 stage, which is the more painful, ulcerated lesion.

The pain and chronic lameness from the M2 lesions are such that cattle are very reluctant to move. They’ll either stand longer or they’ll lay down longer than their pen mates that don’t have M2 lesions. The result of this suppressed movement is that they basically do not get to the bunk as much as they normally would.

Trace Mineral Research

Digital dermatitis has been recognized for many years in dairy herds, and research using Zinpro products has shown efficacy in controlling or mitigating the prevalence of digital dermatitis lesions. Based on the observed responses in dairy cattle, two studies have been conducted in beef cattle feedlots to evaluate the efficacy of the Availa^® Plus DD Formula. Both research studies were conducted with Dorte Dopfer, DVM, Ph.D, University of Wisconsin School of Veterinary Medicine, as the principle investigator, and in cooperation with the management at both facilities.

The first study was conducted at a commercial feedlot located in northern Illinois involving 1,077 growing-finishing steers. The cattle had been in the feedlot prior to beginning of the study and it was determined during the initial digital dermatitis evaluation that a substantial percentage of the cattle already exhibited digital dermatitis lesions. Steers were fed either a Control supplement providing similar levels of trace minerals (Cu, Co, I, Mn, Se and Zn) from primarily inorganic sources or the Availa-Plus DD Formula. Cattle were individually scored for digital dermatitis lesions throughout a 60-day adaption phase, and until steers were shipped to the harvesting plant. 

The study found that 54.03 percent of steers fed the inorganic trace minerals diet developed digital dermatitis lesions, while only 26.72 percent of the steers fed the Availa-Plus DD Formula had digital dermatitis lesions. Growth performance, final live weight and hot carcass weights were negatively impacted when steers were observed to have active digital dermatitis lesions (M2 lesions) compared to steers with no M2 lesions over the study period.

• When a similar healthy animal is compared to an animal with just one M2 lesion, the steer with the lesion had a significant body weight loss of approximately 23.2 pounds (10.06 kg) and a mean reduction in hot carcass weight of 12.1 pounds (5.5 kg).
• Average daily gain of lame beef cattle was reduced by 5.5 percent when compared to similarly sound cattle — 3.41 pounds/day vs. 3.53 pounds/day (1.55 kg/day vs. 1.6 kg/day).
• Lameness diagnosed in the finishing phase (121 days on feed until harvest) adds an average of 14.3 additional days on feed for infected animals.

The second study was conducted at a commercial feedlot in northwestern Iowa with a history of digital dermatitis. Following a 30-day starting period, 1,120 growing-finishing heifers with an average initial body weight of 610.7 pounds (277 kg) were randomly assigned to eight pens. Four pens of 140 head/pen were fed the control diets, including an inorganic trace mineral diet and four pens (140 head/pen) received the performance trace mineral Availa-Plus DD Formula diet throughout the growing and finishing periods until they were shipped to the harvesting plant.  All heifers were fed ractopamine for approximately the last 30 days prior to harvest.

At four times in the study, the heifers were visually evaluated and scored for prevalence of digital dermatitis lesions using the M-stage system. While the baseline (at 70 days) prevalence of total M2 lesions was negligible and similar in both groups, overall prevalence was observed to increase throughout the study with the greatest prevalence at day 189. The pens fed the Availa-Plus DD Formula had a reduced overall prevalence and rate of increase in lesion development as compared to the groups fed inorganic trace minerals.

Other results for the Availa-Plus DD Formula heifers were:

• Increased total weight gain per animal of 17.6 pounds (8 kg).
• When using pen comparisons, increased hot carcass weight per animal of 13 pounds (5.9 kg).
• An increase in individual animal hot carcass weight of 26 pounds (11.8 kg) as a departure from the overall centered mean value. This suggests that improvements in carcass weight due to Availa-Plus DD Formula supplementation could range from 11.9 pounds (5.4 kg) to 41.2 pounds (18.7 kg) based on a calculated 95 percent confidence interval.

Prevention and Control of Digital Dermatitis

There is a significant economic cost related to digital dermatitis. However, feedlots that integrate a prevention strategy that includes management, hygiene and beef cattle nutrition that includes performance trace minerals like the Availa-Plus DD Formula can mitigate the impacts of digital dermatitis on feed efficiency, body weight and hot carcass weight, as well as limit the prevalence of digital dermatitis.

• Management
  • Take biosecurity measures to prevent infected animals from being introduced to the feed yard.
  • Regularly inspect hind feet for signs of digital dermatitis in pen walks.
  • Identify M2 lesions early and treat promptly.
• Hygiene
  • Promote a clean, dry environment and use footbaths as needed.
• Nutrition
  • Consider inclusion of performance trace minerals like the Availa-Plus DD Formula in beef cattle nutrition to help prevent digital dermatitis.

To learn more, contact a Zinpro representative near you.

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