Visceral organ mass in wethers consuming low- to moderate-quality grasses

Crossbred wethers (72; 31 k 0.5 kg) were used to determine effects of different grass sources and qualities on visceral organ mass after 42 and 84days. Wethers consumed ad libitum bermudagrass (BER; Cynodon dactylon) (H, 24-day regrowth; M, 42-day regrowth; L, full-season growth) or orchardgrass (ORC; Dactylis glomeruta) (H, late vegetative to pre-anthesis; M, post-anthesis; L, seed in dough stage). DOMI averaged 730, 603, 550, 592, 514 and 387 gday-’ (SE 32.4) for BER-H, BER-M, BER-L, ORC-H, ORC-M and ORC-L, respectively. Total gastrointestinal tract digesta mass (fresh weight) was greater (P = 0.01) for BER than for ORC (8.14, 8.36, 8.00, 7.64, 7.21 and 6.71 kg for BER-H, BER-M, BER-L, ORC-H, ORC-M and ORC-L, respectively). Mass of the reticula-rumen (722, 675, 617, 606, 577 and 512 g; SE 20.6) and small intestine (659, 620, 548, 585, 521 and 484g; SE 25.9) were greater (P < 0.01) for BER than for ORC, and liver mass generally differed similarly (period 1: 389, 406, 318, 390, 321 and 2868 (SE 10.2); period 2: 405, 392, 346, 372, 369 and 2898 (SE 10.6) for BER-H, BER-M, BER-L, ORC-H, ORC-M and ORC-L, respectively). A slightly greater proportion of variability in reticula-ruminal mass was attributable to digesta mass than to DOMI, although DOMI but not digesta mass was related to small intestinal tissue mass. Liver mass was more highly related to gastrointestinal tract tissue mass than to DOMI. In conclusion, physical attributes of digesta that differ among lowto moderate-quality grasses may affect mass and energy consumption by splanchnic tissues.