Tafaj Myqerem, Zebeli Qendrim, Maulbetsch Anja, Steingass Herbert, Drochner Winfried
University of Hohenheim, Institute of Animal Nutrition, Stuttgart, Germany.
Arch Anim Nutr. 2006 Jun;60(3):254-66. doi: 10.1080/17450390600679322.
Four multiparous ruminally cannulated Holstein cows (mean bodyweight [BW] 615 kg) in mid-lactation (103 days in milk and 32 kg milk x d(-1) at start of the experiment) were used in an one-factorial experiment to evaluate the effects of fibre level (19, 24, 28, 32 and 39% physically effective NDF [peNDF] in dry matter [DM]) in diets consisting of hay and slowly degradable concentrate on rumen fermentation patterns and digesta particle size, under a constant intake level (146 g DM x kg(-0.75). The different fibre concentrations in the diet were achieved by adjusting the hay to concentrate ratio. The above-mentioned levels of peNDF corresponded to 70, 60, 50, 40 and 25% concentrate in diet DM, respectively, and followed the lactation curve of the cows. The ruminal pH was positively and linearly correlated to the percentage of fibre (peNDF, NDF or CF) in ration DM with R2 of 0.76-0.88 (p < 0.001) for solid digesta (particle-associated rumen fluid, PARL), and R2 of 0.26-0.29 (p < 0.05) for fluid digesta (free rumen liquid, FRL). The lowest fibre level in the diet (19% peNDF) or the highest level of concentrate (70% on DM basis) caused pH values lower than 6.0 at almost all sampling times only in PARL but not in FRL, and significantly increased the proportion of large particles in rumen digesta, which in turn was reflected by a depression of fibre digestibility. A level of 24% peNDF or 60% concentrate in the diet maintained the ruminal pH higher than 6.0 and 5.8 in FRL and PARL, respectively. Therefore, the inclusion of more than 60% slowly degradable concentrate in dairy cows diets fed approximately 18 kg DM x d(-1) is discouraged. Based on the response of ruminal solid digesta to dietary fibre, it can be concluded that the recommendations of feeding a structural value > or =1 per kg DM (De Brabander et al. 1999) underestimated, and 400 g CF per 100 kg BW (Hoffmann 1990) overestimated the evaluation of structural effectiveness of the present diet.
选用4头经产的安装有瘤胃瘘管的荷斯坦奶牛（平均体重[BW]615千克），处于泌乳中期（实验开始时产奶103天，日产奶量32千克），进行单因素实验，以评估由干草和慢速降解精料组成的日粮中纤维水平（干物质[DM]中物理有效中性洗涤纤维[peNDF]含量分别为19%、24%、28%、32%和39%）对瘤胃发酵模式和消化物颗粒大小的影响，采食水平恒定（146克DM×千克-0.75）。通过调整干草与精料的比例来实现日粮中不同的纤维浓度。上述peNDF水平分别对应日粮DM中70%、60%、50%、40%和25%的精料，且符合奶牛的泌乳曲线。瘤胃液pH值与日粮DM中纤维（peNDF、中性洗涤纤维或酸性洗涤纤维）百分比呈正线性相关，固体消化物（颗粒相关瘤胃液，PARL）的R2为0.76 - 0.88（p < 0.001），液体消化物（游离瘤胃液，FRL）的R2为0.26 - 0.29（p < 0.05）。日粮中最低纤维水平（19% peNDF）或最高精料水平（以DM计70%）仅在PARL中几乎所有采样时间导致pH值低于6.0，而在FRL中未出现，且显著增加瘤胃消化物中大颗粒的比例，进而导致纤维消化率降低。日粮中24% peNDF或60%精料水平分别使FRL和PARL中的瘤胃液pH值维持在高于6.0和5.8的水平。因此，不建议在日采食约18千克DM×天-1的奶牛日粮中添加超过60%的慢速降解精料。基于瘤胃固体消化物对日粮纤维的反应，可以得出结论，每千克DM结构值≥1的建议（De Brabander等人，1999年）低估了，而每100千克体重400克酸性洗涤纤维的建议（Hoffmann，1990年）高估了本日粮结构有效性的评估。
