How big an issue is foot rot in southern Alberta lamb feedlots: A preliminary look at incidence and associated risk factors

May

By Wiolene Nordi^*, Désirée Gellatly^§, Daniela Meléndez^*, Sonia Marti^‡, Doerte Dopfer^††, Kathy Parker^†, Joyce Van Donkersgoed^╪, and Karen Schwartzkopf-Genswein^*

Sheep production is on the rise in Canada, largely due to the growing ethnic market. This means that the number of lamb feedlots is also increasing to meet this demand. As with most intensive production systems, some health and welfare issues are reduced as a result of greater ability and opportunity to manage animal health while other issues may increase since disease can be more easily spread. This is true in the case of lameness, which can be caused by either infectious or non-infectious sources. Regardless of the cause, lameness is a significant animal welfare and economic concern known to be painful for the animals and costly to producers due to production losses and increased treatment and labour costs.

Recent producer reports indicate that lameness is a growing problem in Canadian lamb feedlots. Foot rot has been identified as one of the three main causes of infectious lameness in sheep along with interdigital dermatitis. Although some research on the most common causes of lameness in sheep has been done, no studies have been conducted in Canada, taking into account animal genetics, nutrition, housing and environmental conditions unique to this country.

An important first step in reducing lameness in feedlot lambs is identifying the cause (correct diagnosis) as well as understanding which animal, managerial or environmental risk factors can exacerbate it. To address this, our research group conducted a 1.5 year study (funded by Alberta Agriculture and Forestry and the Alberta Lamb Producers) at one large lamb feedlot in Alberta. Lambs were assessed by our research team every 2 weeks (minimum of 10 pens per feedlot visit) over the duration of the study. By the end of the study we had observed a total of 73,150 lambs, 473 of which had been identified as lame. All lame lambs were visually evaluated and given a “mobility” score (1 = mild, 2 = moderate, and 3 = severe lameness) describing the severity of their lameness. Once the visual score was completed, a physical examination of their feet and limbs was conducted so that a lameness diagnosis could be made. The risk factor information we recorded for all lame lambs included gender, days on feed, diet composition, and season.

We found that the incidence of lameness due to foot rot was 22.6% (107/473 lame animals). Lambs affected by foot rot had significantly higher (≥ 2) mobility scores than all other lameness diagnoses. Ewe lambs were 4.4 times more likely than ram lambs to be diagnosed with foot rot while wethers were only 0.10 times more likely. As expected, season had an effect on foot rot diagnosis; it was 0.60 times more likely to occur in the fall compared to the winter and 0.23 times more likely in the summer than in the spring. We also saw an association between the number of days the lambs had been in the feedlot and the amount of concentrate or mineral supplement in their diet. For example, the odds of being diagnosed with foot rot increased for each additional day on feed and each kg increase of barley in the diet, while the odds decreased for each additional kg of supplement in their diet.

The findings of this study provide some evidence that foot rot may be a significant issue in Canadian lamb feedlots. Some risk factors associated with being diagnosed with foot rot include being female, feeding higher grain rations with lower supplement as well as pen conditions related to season. More studies looking at a greater number of feedlots across Canada are warranted and should include the assessment of other potential risk factors such as pen condition and density, use of bedding, and pen cleaning to name a few. These studies will provide producers with a better understanding of which factors have the greatest impact on the incidence of foot rot in feedlot lambs so that strategies to control it can be developed. Mitigation strategies will become more important with the increasing number a feedlot reared lambs as well as increased pressure to reduce the use of antimicrobials and improve overall lamb welfare. The results presented in this article are only a portion of a larger study to be shared at a later date.

Figure 1. Image of a foot rot affected hoof (left picture) and a healthy hoof (right picture).

^*Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, Alberta T1J 4B1, Canada; ^§Technology Access Centre for Livestock Production, Olds College, Olds, Alberta, T4H 1R6, Canada;^‡IRTA, Ruminant Production, 08140 Caldes de Montbui, Spain; ^††Department of Medical Sciences, University of Wisconsin, Madison, WI 53706, EUA; ^╪Alberta Beef Health Solutions, Picture Butte, Alberta T0K 1V0, Canada; and ^†Valley Veterinary Services (Three Hills), Alberta T0M 2A0, Canada.