| Abstract | Twenty-five Dorper (D), 27 Katahdin (K), and 33 St. Croix (S) ewes were used to characterize changes in BW, body condition score (BCS), body mass index (BMI), and body composition with different nutritional planes before breeding. Supplement treatments were soybean meal fed at 0.16% BW and 25% soybean meal and 75% ground corn at 0.8% BW (DM; L and H, respectively). There were two animal groups and pens per breed and supplement treatment. Shrunk BW (20 h without feed and water), BCS (1-5), linear measures including wither height and length from the point of the shoulder to pin bone, and body composition via urea space were determined after 0, 4, and 8 wk. Initial values were 62.10, 59.99, 61.57, 62.25, 50.23, and 52.98 kg shrunk BW (SEM=3.601); 35.82, 34.81, 35.57, 36.41, 33.77, and 34.09% fat (SEM=1.043); 17.06, 16.72, 16.98, 17.27, 16.38, and 16.49 MJ/kg energy (SEM=0.357); 3.29, 3.41, 3.29, 3.29, 2.99, and 3.18 BCS (SEM=0.139); and 13.72, 14.22, 12.69, 12.81, 11.53, and 11.50 g/cm2 BMI (BW/(height×length); SEM=0.463) for D-L, D-H, K-L, K-H, S-L, and S-H, respectively. Change from wk 0 to 8 was -0.80, 2.90, -2.74, 3.33, -2.02, and 3.36 kg shrunk BW (SEM=0.842); -0.14, 2.03, -1.45, 1.70, -0.85, and 2.10 kg fat (SEM=0.862); -8.4, 83.7, -62.5, 73.8, -38.4, and 88.1 MJ energy (SEM=33.30); -0.02, 0.20, 0.04, 0.29, -0.08, and 0.17 BCS (SEM=0.070); and -0.265, 0.297, -0.185, 0.491, -0.571, and 0.587 g/cm2 BMI (SEM=0.488) for D-L, D-H, K-L, K-H, S-L, and S-H, respectively. Correlation coefficients between change in BCS and mass of water, fat, and energy were 0.35 and 0.44 (P≤0.004), and those for BMI were 0.54 and 0.56, respectively (P<0.001). In conclusion, a BMI can be more highly related to and predictive of change in body composition of hair sheep resulting from different nutritional planes compared with BCS. |
