PS4-1. Changes in Steer Gait and Joint Physitis During the Finishing Phase.

Abstract

The objective of this study was to evaluate changes in gait and rear leg physitis development during the finishing phase of feedlot cattle in a slatted floor facility. Inherent individual differences in structural conformation and changes over time may be related to cattle mobility and growth performance in a slatted floor facility. Accelerated growth of feedlot cattle may also present challenges for proper joint development. Simmental × Angus steers (n = 22; body weight = 284 kg) were evaluated during the early (d 61) and mid-finishing (d 144) phases in an indoor slatted facility. Individual steers videos were recorded using a Panasonic Lumix DMC-FZ1000 recording at 120 frames per second camera and four frames were selected to estimate gait traits in ImageJ. Additionally, body morphometric measurements were determined for hip height and cannon bone length to generate a pixel-to-centimeter conversion for each animal. Hock and cannon bone circumference were also measured. Radiographic imaging was used to assess structural conformation of the rear leg, including dorsoplantar (DP) and lateral views of both hock and fetlock joints. Images were evaluated for physitis and classified as none, very mild, mild, moderate, or severe. Data were analyzed using the MIXED procedure of SAS 9.4. Hip-to-hock length increased (P < 0.01) from 63.5 cm on d 61 to 80 cm on d 144 and corresponded with cattle growth. However, there was no change (P > 0.32) over time for front and rear step length. There was also no change (P > 0.17) in front and rear stride length from d 61 to 144. Hock circumference increased (P < 0.01) over time from 43.9 cm on day 61 to 48 cm on day 144. Cannon bone circumference increased (P < 0.01) over time from 22.6 cm on day 0 to 24.1 cm on d 144. On d 61, radiographs indicated 80% of steers had very mild or mild physitis in rear fetlock joints, but this did not increase by d 144. On d 61, 50% of steers had mild physitis and 30% had moderate physitis in rear hock joints. However, physitis severity increased by d 144 such that moderate or severe physitis was observed in more than 80% of rear hock radiographs. In conclusion, step and stride length did not increase with time during the finishing phase and may be related to greater severity of physitis observed in the rear hock joints of feedlot cattle in slatted floor facilities.