Identifying the Best Strategies for Treating Toe Tip Necrosis and Digital Dermatitis in Feedlot Cattle

Background

Lameness, defined as an abnormal gait caused by disease or injury in the feet or limbs, is a major economic, labour, and welfare concern for the feedlot industry. It is the second highest (40%) reason for treatments in western Canadian feedlot cattle, after bovine respiratory disease (42%). Hoof-related lameness (HRL) including foot rot (FR), toe tip necrosis syndrome (TTNS), digital dermatitis (DD) and mechanical injuries account for roughly 70% of all lameness cases. Lame cattle weigh on average 48 lbs less than cattle who are not lame. This means for 1400 lb steers, approximately $80/hd will be left on the table. Despite its impact, there is still much we do not know about the prevention, control, and treatment of HRL. 

Objectives

• Describe the causes and outcomes of hoof-related lameness in western Canadian feedlot cattle
• Characterize the hoof microbiome of feedlot cattle diagnosed with two common causes of infectious lameness (digital dermatitis and foot rot)

What They Did

The original plan to collect samples and data from commercial feedlots between 2018 and 2022 was derailed by COVID-19 related travel restrictions, so the objectives were altered to use historical data collected by consulting veterinarians as well as hoof swab samples that the team had collected previously. 

The first study analyzed animal lameness data from 1,772,565 cattle on 28 western Canadian feedlots collected over five-years (2014-2018). Various risk factors potentially associated with DD, FR or TTNS diagnosis were assessed: feedlot ID, animal ID, lot number, placement date, placement year, age, class (calf/yearling), breed, gender (heifer, steer, bull), acquisition source (auction, backgrounded, grass-backgrounded, ranch direct, or unknown), treatment date, and days on feed (DOF) at the time of treatment.  

In the second study the research team obtained hoof swabs from 101 lame cattle located at three commercial feedlots in southern Alberta of which 48 were diagnosed with FR, 23 with DD and 25 with a combination of FR+DD (in the same hoof) and 5 completely healthy controls. A technique known as 16S rRNA sequencing was used to characterize the hoof microbiome of cattle affected with the three types of lesions and were then compared to healthy hooves on the same animal as well as well as non-lame (controls) cattle. This allowed them to characterize the differences in the microbiome of affected vs. healthy hooves.  

What THey Learned

Lameness accounted for 26% of all treatments in the historical data (72% of which were HRL cases, representing 19% of all treatments). The most common causes of HRL were foot rot (90%), followed by digital dermatitis (8%) and toe tip necrosis (2%). Cases of FR occurred at a relatively steady rate throughout the feeding period while DD was more common between 80 and 190 days on feed and TTNS was most common during the first 100 days on feed.  

Cattle sourced from backgrounding and grass-backgrounding operations had a higher risk of developing HRL than cattle sourced from ranches or auction marts. Calves were at higher risk of HRL than yearlings and females. Cattle from small feedlots (<10,000 head) were at higher risk of HRL than large (>10,000 head) feedlots. Finally, cattle arriving at the feedlot from January to June were at higher risk of developing HRL compared to those arriving between July and December. Breed had no effect on risk of FR or DD though heifers appeared to be at higher risk for DD than steers.  

When studying the microbiome of the hooves of lame animals, they found that cattle diagnosed with DD, FR, DD+FR had reduced bacterial diversity compared to healthy hooves. While the impact of feedlot was minimal (7.4%), having a lesion contributed to 22% of the observed variations of the hoof bacterial communities. Analysis of the swabs found different bacterial profiles in hooves infected with FR, DD, FR+DD compared to the healthy controls. Fusobacteria were higher in FR and DD+FR cases and Spirochaetota were higher in DD.  The microbiome of hooves affected with both DD and FR closely resembled what was observed for FR cases. This is the first study to describe the bacterial community of combined DD+FR lesions. Not only did DD and FR lesions have altered bacterial communities compared to healthy skin, but some bacteria were also more likely to be present in one type of lesion than the other. Another important finding was that the method of surface swabbing the lesions was enough to differentiate between lesion and control samples. This means that taking a biopsy (gold standard for characterizing the hoof microbiome) which is more invasive, expensive, time consuming and difficult to obtain under commercial conditions, is not necessary.    

What It Means

Lameness is a significant cause of disease as well as an economic and welfare concern for Canadian feedlots. Understanding factors that may increase cattle’s risk of HRL (cattle source, feedlot size, and age) and the bacteria playing a role in the microbiome of infected hooves can help develop new diagnostic, preventative and treatment strategies as well as guide feedlots on which management practices can be altered to best mitigate hoof-related lameness on-farm.