Jones A L, Goetsch A L
University of Arkansas, Fayetteville 72701.
Arch Tierernahr. 1987 Jul-Aug;37(7-8):685-99. doi: 10.1080/17450398709425382.
Five crossbred beef cows (Hereford X Angus, 422 kg) with ruminal and duodenal cannulae were used in a Latin square experiment to determine the effects of dietary proportions of fescue and clover hays (0:1, .25: .75, .5:.5, .75:.25 and 1:0) on digestive function. Feed intake was 85% of ad libitum intake of fescue alone (1.03% of body weight). Fescue contained 1.26% nitrogen (N), 71.0% neutral detergent fibre (NDF) and 7.6% acid detergent lignin (ADL), and clover contained 2.43% N 50.0% NDF and 5.8% ADL in DM. Ruminal fluid ammonia-N concentration increased linearly (P less than .05) with declining dietary fescue level. Total concentration of volatile fatty acids in ruminal fluid and duodenal and rectal digesta mean particle size were not affected by fescue level. Ruminal fluid volume and flow rate increased linearly (P less than .05) with increasing dietary fescue, but fluid and particulate digesta passage rates were unchanged. Apparent ruminal organic matter (OM) digestion decreased quadratically (P less than .05) as fescue increased (74.5, 54.3, 49.8, 46.2 and 42.4% for 0, 25, 50, 75 and 100% fescue, respectively). Postruminal OM digestion as a percentage of intake was partially compensatory, increasing linearly (P less than .05) as dietary fescue level rose (2.3, 3.5, 5.1, 8.6 and 11.1% of intake). Thus, total tract OM digestion declined less as fescue replaced clover (76.8, 57.8, 55.0, 54.8 and 53.5%; linear and quadratic, P less than .05) than did apparent ruminal OM disappearance. Changes in ruminal NDF, acid detergent fibre and cellulose digestibilities were similar to those for OM. Microbial growth efficiency increased quadratically (P less than .10) as fescue intake increased. These results indicate that with low feed intake, ruminal and total tract digestion of an all-legume hay diet is greater than that of a grass hay diet. Little or no digestive advantage was achieved by substituting clover for fescue, except in the case of total replacement of fescue with clover, because of concurrent decreases in microbial growth efficiency, microbial N flow to the intestines and OM digestion in the postruminal tract. Negative associative effects in digestion observed between clover and fescue hays in this experiment deserve further study.
选用5头装有瘤胃和十二指肠瘘管的杂交肉牛（赫里福德×安格斯，体重422千克）进行拉丁方试验，以确定羊茅和三叶草干草不同日粮比例（0:1、0.25:0.75、0.5:0.5、0.75:0.25和1:0）对消化功能的影响。采食量为随意采食羊茅时采食量的85%（占体重的1.03%）。羊茅含氮（N）1.26%、中性洗涤纤维（NDF）71.0%、酸性洗涤木质素（ADL）7.6%，三叶草在干物质中含氮2.43%、NDF 50.0%、ADL 5.8%。随着日粮中羊茅水平的降低，瘤胃液氨氮浓度呈线性增加（P<0.05）。瘤胃液中挥发性脂肪酸的总浓度以及十二指肠和直肠食糜的平均粒径不受羊茅水平的影响。瘤胃液体积和流速随着日粮中羊茅含量的增加呈线性增加（P<0.05），但液体和颗粒食糜的通过率不变。随着羊茅比例的增加，瘤胃表观有机物（OM）消化率呈二次下降（P<0.05）（羊茅比例为0、25、50、75和100%时，分别为74.5%、54.3%、49.8%、46.2%和42.4%）。瘤胃后段OM消化率占摄入量的百分比具有部分补偿性，随着日粮中羊茅水平的升高呈线性增加（P<0.05）（分别占摄入量的2.3%、3.5%、5.1%、8.6%和11.1%）。因此，随着羊茅替代三叶草，全消化道OM消化率的下降幅度（76.8%、57.8%、55.0%、54.8%和53.5%；线性和二次，P<0.05）小于瘤胃表观OM消失率。瘤胃NDF、酸性洗涤纤维和纤维素消化率的变化与OM相似。随着羊茅摄入量的增加，微生物生长效率呈二次增加（P<0.10）。这些结果表明，在低采食量情况下，全豆科干草日粮的瘤胃和全消化道消化率高于禾本科干草日粮。用三叶草替代羊茅几乎没有消化优势，除非完全用三叶草替代羊茅，因为同时微生物生长效率、微生物氮向肠道的流动以及瘤胃后段的OM消化率都会降低。本试验中观察到的三叶草和羊茅干草之间的负协同消化效应值得进一步研究。
