Huhtanen P, Jaakkola S
Department of Animal Science, University of Helsinki, Finland.
Arch Tierernahr. 1994;47(2):153-67. doi: 10.1080/17450399409381802.
The effects of, and interactions between, the diet and maturity of grass were studied in cattle in a 6 x 6 Latin square experiment with a 2 x 3 factorial arrangement of treatments. Barn-dried grass or direct-cut silage from the same sward were fed together with 250 (L), 500 (M) or 750 (H) g concentrate dry matter (DM) kg-1 total DM. Six timothy-meadow fescue grasses, cut at 7 d intervals, were incubated in nylon bags in the rumen for 6, 12, 24, 48, 72 and 96 h, and the kinetics parameters for DM and neutral detergent fibre (NDF) digestion were estimated. Ruminal NDF digestibility was calculated using a value of 0.02 for the rate of passage. With increasing maturity of grass, crude protein content and in vitro digestibility decreased with associated increases in the contents of cell wall constituents. Both the rate and extent of DM and NDF digestion decreased with maturity. The changes were curvilinear with an increasing depression in the extent of digestion and a decreasing depression in the rate of digestion with maturity. Ruminal NDF digestibility averaged over the diets decreased from 61.2 to 39.7% with the maturity. DM and NDF disappearance and calculated NDF digestibility decreased as the proportion of concentrate in the diet increased. This adverse effect of concentrate increased more rapidly as the proportion of concentrate increased from M to H and rumen pH dropped from 6.2 to 6.0 than as the proportion of concentrate increased from L to M with a consequent reduction in rumen pH from 6.4 to 6.2. The minimum rumen pH explained more of the variation in NDF digestibility than mean pH, duration or summation (pH x time) of the pH depression below 6.2, 6.0 or 5.8. Predicted NDF digestibility was higher in cattle given the dried grass diets than in those given the silage diets. The adverse effect of the concentrate level on NDF digestibility increased with the maturity of the grass. The decrease was 0.54, 0.59, 0.72% units per one day delay in cutting for low, medium and high levels of concentrate, respectively.
在一项采用2×3析因处理安排的6×6拉丁方试验中，研究了日粮和牧草成熟度对牛的影响及其相互作用。将来自同一草地的烘干牧草或直接青贮的青贮料与250（低）、500（中）或750（高）克精料干物质（DM）/千克总干物质一起饲喂。以7天为间隔收割的6种梯牧草-草地羊茅，置于瘤胃尼龙袋中培养6、12、24、48、72和96小时，并估算干物质和中性洗涤纤维（NDF）消化的动力学参数。瘤胃NDF消化率采用0.02的通过率值计算。随着牧草成熟度增加，粗蛋白含量和体外消化率下降，细胞壁成分含量相应增加。干物质和NDF的消化速率和程度均随成熟度下降。这些变化呈曲线关系，随着成熟度增加，消化程度的下降幅度增大，消化速率的下降幅度减小。日粮平均瘤胃NDF消化率随成熟度从61.2%降至39.7%。随着日粮中精料比例增加，干物质和NDF消失量以及计算得出的NDF消化率下降。当精料比例从M增加到H且瘤胃pH从6.2降至6.0时，精料的这种不利影响比精料比例从L增加到M且瘤胃pH从6.4降至6.2时增加得更快。最低瘤胃pH比平均pH、pH低于6.2、6.0或5.8的持续时间或总和（pH×时间）能更好地解释NDF消化率的变化。饲喂干草日粮的牛预测NDF消化率高于饲喂青贮日粮的牛。精料水平对NDF消化率的不利影响随牧草成熟度增加而增大。对于低、中、高精料水平，分别每延迟一天收割，NDF消化率下降0.54、0.59、0.72个百分点。
