Topical zinc oxide improves shoulder lesion healing compared with other treatments

A shoulder lesion is formed when the scapular spinal process is placed under prolonged pressure reducing blood supply and eventually causing tissue necrosis (Rolandsdotter et al. 2009). Shoulder lesions are developed primarily in the farrowing unit, and are more typical of sows with poor body condition, lameness, and scars from previous incidence (Kaiser et al. 2013). These lesions negatively impact sow welfare, and adversely affect consumer opinion of current conventional farrowing systems. The aim of this study was to assess the effectiveness of four treatments on the healing of shoulder lesions. We hypothesised that topical zinc oxide administration would improve the healing of lesions compared with cetrimide, benzalkonium and aluminium sprays.

A total of 399 lesions were graded (BPEX 2011) and measured for lesion diameter pre-treatment (~d 12 lactation), d 7 post-treatment and again at weaning (~d 25 lactation). Each shoulder lesion was randomly allocated using the Rand function in excel to one of the following treatments: 0.8% cetrimide solution (n = 103), 0.2% benzalkonium solution (n = 104), 4% aluminium powder ointment (n = 90) and, 15.25% zinc oxide (n = 102). All groups were topically treated daily until weaning. Lesion grade and diameter were analysed using a general linear model, shed was fitted as a random term, with farrowing month, parity, body condition score, and treatment as fixed effects (SPSS v24.0, IBM, Armonk, NY, USA). Percentage of sows with sores at weaning was analysed using binary logistic regression with the same model.

There was no significant difference in shoulder lesion grading or diameter before treatment. At both the post treatment measurements (d 7 post-treatment and at weaning), zinc oxide had significantly reduced the diameter of the lesion compared with cetrimide, with the other two treatments being intermediate (Table 1). A similar pattern was observed for lesion grade. Fewer sows from the zinc oxide treatment presented with lesions at weaning compared with cetrimide and benzalkonium, with aluminium being intermediate.

Table 1.  Lesion diameter (cm) and grade (0 to 5) pre-treatment, d 7, and weaning and lesion presence at weaning for sows treated with cetrimide, benzalkonium, aluminium and zinc oxide daily

Using a 15.25% zinc oxide ointment to treat shoulder lesions improved healing compared with other available treatment options such as antiseptic sprays and aerosol band aids.