Abstract :
Eight yearling Spanish wethers (29.6±1.10 kg initial BW) were used in an experiment with a 2×4 factorial arrangement
of treatments and two simultaneous 4 × 4 Latin squares to determine effects on feed intake and digestion of supplementing
wheat straw treated (ammoniated) with urea (T) or untreated (U) with soybean meal or broiler litter. Supplements were C
(ground corn-based and fed at 0.64% BW, DM), S (C plus 0.25% BW of soybean meal) and LL and HL (C plus 0.5 or 1.0%
BWof broiler litter). The N concentration was 0.4 and 2.3% and in vitro digestibility was 48 and 63% in U and T, respectively.
There were no significant interactions between straw type and supplement treatment except for NDF digestion and digestible
NDF intake. Ruminal fluid ammonia N concentration was greater for T than for U (P < 0.05) but was not influenced by
supplement treatment (4.1, 7.9, 5.1, 3.8, 11.7, 12.4, 10.8 and 15.6 mg/dl; S.E. = 1.53); plasma urea N concentration was
greater for T vs. U (P < 0.05) and lowest among treatments (P < 0.05) for C (7.8, 17.1, 16.5, 18.9, 21.5, 25.1, 28.6 and
26.6 mg/dl for U-C, U-S, U-LL, U-HL, T-C, T-S, T-LL and T-HL, respectively; S.E. = 1.71). Straw DM intake was not
influenced by supplement treatment and tended to be greater (P < 0.13) for U vs. T (212, 261, 274, 277, 406, 404, 432 and
423 g per day for U-C, U-S, U-LL, U-HL, T-C, T-S, T-LL and T-HL, respectively; S.E. = 24.6). Total OM intake ranked
(P < 0.05) C < S < LL < HL (476, 566, 649 and 739 g per day); apparent total tractOMdigestibility was greater (P < 0.10)
for C and S vs. LL and HL (67.9, 68.3, 61.9 and 60.7% for C, S, LL and HL, respectively); digestible OM intake was lowest
among treatments (P < 0.05) for C, similar between S and LL and greater for HL than for S (P < 0.05) and LL (P < 0.13;
249, 331, 342, 386, 380, 423, 450 and 495 g per day for U-C, U-S, U-LL, U-HL, T-C, T-S, T-LL and T-HL, respectively). In
summary, apparently with considerable N recycling by yearling Spanish goat wethers, improvements in digestible OM intake
by supplementation were achieved through the additional consumption of digestible OM in soybean meal and broiler litter,
without substitution for wheat straw intake. Effects of ammoniation and N supplementation on digestible OM intake were
additive, with greater magnitude of change via ammoniation than addition of soybean meal or broiler litter to a moderate level
of a grain-based supplement.
© 2003 Elsevier B.V. All rights reserved
