Evaluating Body Condition of Group-Housed Gestating Sows: Sow Caliper Measurements Vs. Backfat Thickness and Visual Scores

This study was designed to evaluate body condition of gestating sows using the following approaches: objective body condition measurement (sow caliper), backfat depth, and subjective body condition scores (BCS). Sows (n=928, Parity 1-9) from 20 breeding groups were group-housed in pens (42 to 51 sows/pen) with an electronic sow feeder at wk 5 postmating until d 109 of gestation. Backfat depth, body condition, and BW were measured for all sows upon entry and exit of gestation pens. Sow caliper measurements were recorded at the P2 location and backfat depth using an ultrasonic scanner (Renco Leanmeater®) was recorded at the same location on both sides of the body. A scoring system of 1 (emaciated) to 5 (obese) was used for BCS. At entry to gestation pens, 8% of sows across parities had caliper measurements between 14.5 and 18 (Fat), 54% of sows between 10.5 and 14 (Fit), 24% of sows between 8.5 and 10 (Thin), and 14% of sows between 4 and 8 (Very Thin). The corresponding backfat depth (median) for Fat, Fit, Thin, and Very Thin sows were 19, 16, 13, 11, and 10 mm, respectively, and the corresponding BCS were 4.0, 3.5, 3.0, 3.0, and 2.5, respectively. There were correlations (all P < 0.0001) between entry and exit of gestation pens for caliper measurements (r=0.826), backfat depth (r=0.858), BCS (r=0.844), and BW (r=0.888), suggesting that caliper measurements assessed body condition of sows at the two observation times similar to other measurements of body condition. Across parities at entry (r₁) and exit (r₂) of gestation pens, caliper measurements were correlated with backfat depth (r₁ = 0.714; r₂ = 0.739), BCS (r₁ = 0.665; r₂ = 0.742), and BW (r₁ = 0.532; r₂ = 0.539; all P < 0.0001). For sows in each parity category at entry to gestation pens, meaningful correlations (all P < 0.0001) between caliper measurements with backfat depth (r₁ = 0.685 for parity 1-2; r₁ = 0.697 for parity 3-4; r₁ = 0.736 for parity 5-6; and r₁ = 0.685 for parity 7-9), BCS (r₁ = 0.629, r₁ = 0.673; r₁ = 0.635, and r₁ = 0.627), and BW (r₁ = 0.555; r₁ = 0.719; r₁ = 0.745; and r₁ = 0.676), respectively. These data indicate that caliper measurements correspond to backfat depth and BCS, and can be used as a tool to evaluate body condition of gestating sows.