本试验旨在研究多聚甲醛对牛瘤胃消化酶活性及营养物质消化的影响。选取4头2岁、体重为（283.5±5.4）kg、装置永久性瘤胃瘘管的新疆褐牛×西门塔尔F₁代空怀母牛，在饲粮精粗比为4：6的条件下，采用4×4拉丁方设计，每期给每头牛分别饲喂添加0（对照）、150、300和600 mg/kg多聚甲醛的饲粮。结果表明：与对照组相比，牛的干物质自由采食量随多聚甲醛添加量的增加呈先升后降的变化，添加量为300 mg/kg时效果最好，较对照组增加25.6%（P<0.01）；随多聚甲醛添加量的增加，牛瘤胃液内纤维素酶、外纤维素酶、纤维二糖酶和木聚糖酶活性呈先升后降的变化，添加量为300 mg/kg时最高，较对照组分别提高38.1%（P<0.01）、37.0%（P<0.01）、45.9%（P<0.01）和25.0%（P<0.05），但添加多聚甲醛对瘤胃液内果胶酶、淀粉酶和蛋白酶活性无显著影响（P>0.05）；与对照组相比，添加多聚甲醛时，牛饲粮干物质、有机物和纤维素表观消化率显著下降（P<0.05），而粗蛋白质表观消化率显著升高（P<0.05）；但干物质、有机物、粗蛋白质、纤维素和能量消化量却均随多聚甲醛添加量呈先升后降的变化，添加量为300 mg/kg时最高，较对照组分别增加18.5%（P<0.01）、18.7%（P<0.01）、20.4%（P<0.01）、17.9%（P<0.01）和和14.6%（P<0.01）；牛氮、钙、磷保留量也随多聚甲醛添加量呈先升后降的变化，添加量为300 mg/kg时最高，较对照组分别增加66.1%（P<0.01）、19.3%（P<0.01）和16.2%（P<0.01）。综上所述，添加多聚甲醛（300 mg/kg）可提高牛饲粮自由采食量和消化量，提高瘤胃纤维素酶活性和增加氮保留量，有利于改善牛对饲粮营养物质的消化与利用。

This experiment was aimed to investigate the effects of paraformaldehyde on activities of digestive enzymes of rumen and nutrient digestion in cattle. Four of Xinjiang brown×Simmental F₁ non-pregnant cattle, 2-year-old, with body weight of (283.5±5.4) kg, were fitted with permanent ruminal fistula, and were fed a diet with a ratio of 4:6 of concentrate to roughage ad libitum. By 4×4 Latin square design, each animal was supplemented with paraformaldehyde (PFD) at the additive amount of 0 (control), 150, 300 and 600 mg/kg, respectively in each phase. The results showed that the dry matter voluntary intake of cattle was up-down changed with PFD supplementation, and was the highest at the PFD additive amount of 300 mg/kg, increasing by 25.6% (P<0.01) compared with the control group. The activities of ruminal endocellulase, exocellulase, cellobiase and xylanase were up-down changed with the increasing of PFD additive amount, and were the highest at the PFD additive amount of 300 mg/kg, increasing by 38.1% (P<0.01), 37.0% (P<0.01), 45.9% (P<0.01) and 25.0% (P<0.05), respectively. However, adding PFD had no significant effect on the activities of pectinase, amylase and protease (P>0.05). The apparent digestibility of dry matter, organic matter and cellulose, rather than crude protein, decreased significantly by PFD supplementation (P<0.05). However, the amounts of digested dry matter, organic matter, crude protein, cellulose and energy were up-down changed with PFD supplementation, being the highest at 300 mg/kg, by 18.5% (P<0.01), 18.7% (P<0.01), 20.4% (P<0.01), 17.9% (P<0.01) and 14.6% (P<0.01). The retention of nitrogen, calcium and phosphorus also were up-down changed with PFD supplementation, being the highest at 300 mg/kg, by 66.1% (P<0.01), 19.3% (P<0.01) and 16.2% (P<0.01), respectively. It is concluded that supplementation with PFD (300 mg/kg diet) increases the activities of ruminal cellulase, voluntary feed intake, the digested amounts of diets, and the nitrogen retention, so being beneficial for digestion and nutrition of cattle.