Performance of Spanish and Boer × Spanish doelings consuming diets with different levels of broiler litter

Sixty Spanish (S) and 40 Boer × Spanish (BS) doelings (14.9 ± 3.8 kg and 21.9 ± 3.8 kg initial BW, respectively, and approximately 6 months of age) were used in an experiment with four 3-week periods to determine effects of dietary broiler litter (L) level on growth performance. There were two groups per treatment with six S and four BS doelings in each. Dietary treatments were 20% coarsely ground millet hay and 80% concentrate, which consisted of 0 (0L), 20 (20L), 40 (40L), or 60% L (60L; total dietary level). An additional treatment was 80% hay and 20% concentrate (80F). Concentrate (primarily corn and L when included) DM intake (DMI) was 700, 593, 652, 387, and 165 g/d (S.E. = 20.3) and total DMI was 883, 755, 825, 490, and 696 g/d (S.E. = 35.5) for 0L, 20L, 40L, 60L, and 80F, respectively. There was a dietary treatment × period interaction in ADG (period 1: 104, 29, 36, −44, and 47 g; period 2: 124, 102, 53, −74, and 12 g; period 3: 175, 126, 126, 87, and 80 g; period 4: 161, 151, 136, 66, and 51 g for 0L, 20L, 40L, 60L, and 80F, respectively (S.E. = 12.2)). Treatment and genotype also interacted in ADG (S: 107, 85, 72, 8, and 36 g; BS: 174, 118, 103, 10, and 60 g for 0L, 20L, 40L, 60L, and 80F, respectively (S.E. = 9.2)). ADG:DMI ranked (P < 0.06) 0L > 20L > 40L > 80F > 60L (152, 130, 102, 18, and 65 g/kg for 0L, 20L, 40L, 60L, and 80F, respectively; S.E. = 6.12). The acetate:propionate ratio in ruminal fluid was greater (P < 0.05) for 60L and 80F than for other treatments (1.60, 1.73, 2.18, 3.80, and 3.67 for 0L, 20L, 40L, 60L, and 80F, respectively; S.E. = 0.27). Liver Cu concentration at the end of the experiment was influenced by dietary treatment (88, 275, 478, 286, and 47 ppm for 0L, 20L, 40L, 60L, and 80F, respectively; S.E. = 53.2). In conclusion, L can be effectively used in diets for growing meat goats, but high levels, such as above 40% of dietary DM, may restrict performance primarily via limited feed intake. However, the level of L below this threshold impacts efficiency of feed utilization.