VISCERAL ORGAN MASS IN WETHERS CONSUMING LOW-QUALITY TO MODERATE-QUALITY GRASSES

Crossbred wethers (72; 31 +/- 0.5 kg) were used to determine effects o f different grass sources and qualities on visceral organ mass after 4 2 and 84days. Wethers consumed ad libitum bermudagrass (BER; Cynodon d actylon) (H, 24-day regrowth; M, 42-day regrowth; L, full-season growt h) or orchardgrass (ORC; Dactylis glomerata) (H, late vegetative to pr e-anthesis; M, post-anthesis; L, seed in dough stage). DOMI averaged 7 30, 603, 550, 592, 514 and 387 g day(-1) (SE 32.4) for BER-H, BER-M, B ER-L, ORC-H, ORC-M and ORC-L, respectively. Total gastrointestinal tra ct digesta mass (fresh weight) was greater(P=0.01) for EER than for OR C (8.14, 8.36, 8.00, 7.64, 7.21 and 6.71 kg for BER-H, BER-M, BER-L, O RC-H, ORC-M and ORC-L, respectively). Mass of the reticulo-rumen (722, 675, 617, 606, 577 and 512 g; SE 20.6) and small intestine (659, 620, 548, 585, 521 and 484 g; SE 25.9) were greater (P < 0.01) for EER tha n for ORC, and liver mass generally differed similarly (period 1: 389, 406, 318, 390, 321 and 286g (SE 10.2); period 2: 405, 392, 346, 372, 369 and 289 g (SE 10.6) for BER-H, BER-M, BER-L, ORC-K, ORC-M and ORC- L, respectively). A slightly greater proportion of variability in reti culo-ruminal mass was attributable to digesta mass than to DOMI, altho ugh DOMI but not digesta mass was related to small intestinal tissue m ass. Liver mass was more highly related to gastrointestinal tract tiss ue mass than to DOMI. In conclusion, physical attributes of digesta th at differ among law-to moderate-quality grasses may affect mass and en ergy consumption by splanchnic tissues. (C) 1997 Elsevier Science B.V.