PSV-28 - Effects of the dietary concentrate level and harvest weight on growth performance of Spanish goat wethers and doelings

Abstract: Thirty-six Spanish goat wethers and 36 doelings with initial mean age of 4.3 ± 0.03 months and body weight (BW) of 20.6 and 18.6 kg, respectively (SEM = 0.41), were used in 2 phases to determine effects of dietary concentrate level and harvest weight on growth performance. Three animals of each type were allocated to 12 pens for a total of 6 per pen. The diet in the first phase, 13 weeks in length, had 20% concentrate and 80% forage (20C) with crude protein and neutral detergent fiber (NDF) concentrations of 13 and 50%, respectively. At the end of Phase 1, animals in 2 pens were harvested. In phase 2 that lasted 9-11 weeks, two pens per dietary treatment and animal type continued to be fed diets with different levels of concentrate (20C, 40C, 50C, 60C, and 70C) with the same crude protein concentration of 13% and NDF level of 50, 35, 33, 33, and 31%, respectively. Animals were harvested from treatments of 50C and 70C, 40C and 60C, and 20C after 9, 10, and 11 weeks, respectively. Dry matter intake in Phase 1 was 733 ± 18.1 g/day and 3.39 ± 0.070 % BW, with an average BW during the phase of 21.6 ± 0.26 kg. Average daily gain (ADG) in Phase 2 was not affected by diet or diet × animal type (P = 0.712) but was greater (P < 0.05) for wethers than for doelings (44 and 18 g, respectively; SEM = 5.4). There was a tendency (P = 0.055) for differences in ADG among treatments (4, 44, 43, 17, and 45 g for 20C, 40C, 50C, 60C, and 70C, respectively; SEM = 8.7). Dry matter intake in g/day in Phase 2 was similar among treatments (644, 750, 680, 597, and 621 g/day; SEM = 36.9) but in % BW was greatest among diets (P < 0.05) for 40C (2.73, 3.25, 2.84, 2.62, and 2.63 for 20C, 40C, 50C, 60C, and 70C, respectively; SEM = 0.062). Also, there was a tendency (P = 0.057) for ADG during the entire experiment to differ among treatments (46, 17, 27, 30, 20, and 30 for 20C (phase 1 only) 20C, 40C, 50C, 60C, and 70C (phase 1 and phase 2), respectively; SEM = 5.0). These results suggest that a low concentrate diet followed by diets higher in concentrate containing similar CP and NDF content of 31 to 35% may not influence growth performance of Spanish goat wethers and doelings, but continuous feeding of a low concentrate diet with 50% NDF limit growth rate.