341 Determining the optimum duration of performance testing for daily feed intake, growth rate, and residual feed intake in growing goats using Grow Safe Feeding System.

Abstract The study aimed to determine the optimum duration of performance testing length for daily feed intake, growth rate, and residual feed intake in two breeds of growing goats. Nineteen female goats, 10 Alpine and 9 Spanish, with average initial ages of 360-d and 352-d and IBW of 38.8 ± 2.8 kg and 35.5 ± 3.1 kg, respectively, were randomly assigned within the breed to one of two non-adjacent pens (5 goats/pen), each equipped with GrowSafe feed bunks. Goats received a pelletized total mixed ration twice a day and had an ad libitum access to feed, water, and mineral block throughout the 84-d trial period. In determining the length of days on trial for different phenotypic traits for goats, changes and relative changes of phenotypic residual variances, Pearson and Spearman correlations for ADG, DMI, and RFI of shortened tests 28-, 42-, 56-, 70, and the full-test 84-d were determined. The relative residual variance for DMI was 0.0399 at 28-d; it increased, over the increasing test length, to 0.0463, 0.0613, and 0.0634 at 42, 56, and 70 d tests, respectively. At the full test (84-d), the relative residual variance dropped to 0.0574. For DMI, the lowest relative residual variance was observed at the 28-d test period, and the Pearson Correlation coefficient for the DMI reached 0.946 (p < 0.0001) at 28-d. Relative residual variance (RRV) for ADG at 28 d test was 0.00437; it decreased over increasing test period to 0.00406 at 42-d, attained a peak value of 0.0050 at 56-d, and dropped to 0.00268 and 0.000237 at 70-d and 84-d, respectively. The lowest variation for ADG was observed at the full-test period of 84-d. In addition, the Pearson correlation coefficient reached its highest (>0.95) (p <.0001) at 84-d and relatively low 0.946 (p < 0.0001) at 56-d. According to the RRV and Pearson r2 results, the 84-d test length was sufficient to measure ADG in Alpine and Spanish goats. For RFI, the relative residual variance at 28 d and 42 d tests was comparable (0.018); slightly decreased over the increasing test period to 0.017 at 56 and increased to 0.031 and 0.030 at 70 and 84 d, respectively. The lowest variation for RFI was at 56 d test length. However, Pearson correlations between shortened tests (28-, 42-, 56-, and 70-day) and the full-length 84-day test for RFI was 0.83 (p< 0.0001) at 56-d, which is lower than the other shortened tests 28-d, 42-d, and 70-d with R of 0.93, 0.90, and 0.96, respectively. Based on both RRV and r2 results, the 56-d test length should be sufficient to measure the RFI in goats accurately. The current results are inconsistent with previous results and their application warrants further research.