不同精粗比下添加维生素B12对体外瘤胃发酵和微生物酶活力的影响

本试验通过体外培养法,研究在不同精粗比饲粮中添加维生素B12对体外瘤胃发酵和微生物酶活力的影响。试验采用3×3双因子试验设计,即3个底物精粗比(玉米∶羊草=35∶65、50∶50和65∶35)和3个维生素B12添加量(0、40和90 ng/mL)。体外试验用瘤胃液取自3只安装有永久性瘤胃瘘管的湖羊。体外培养24 h后测定体外瘤胃发酵参数和微生物酶活力。结果显示:1)随着底物精粗比和维生素B12添加量的提高,体外培养24 h的产气量、潜在产气量和有机物消化率极显著地增加(P<0.01),且维生素B12添加量与上述指标存在线性剂量效应(P<0.01)。2)当底物精粗比为50∶50和65∶35时,添加维生素B12显著提高了发酵液中氨态氮、微生物蛋白、总挥发性脂肪酸、乙酸和丙酸浓度(P<0.05),但对丁酸浓度和乙酸/丙酸无显著影响(P>0.05)。3)当底物精粗比为35∶65和50∶50时,添加40 ng/mL维生素B12使发酵液中羧甲基纤维素酶、木聚糖酶活力显著提高(P<0.05);当精粗比为65∶35时,添加90 ng/mL维生素B12使发酵液中羧甲基纤维素酶、木聚糖酶活力显著提高(P<0.05)。结果提示,底物精粗比和维生素B12添加量影响体外瘤胃发酵。添加维生素B12可增加瘤胃微生物酶的活力,从而提高有机物消化率以及微生物蛋白和总挥发性脂肪酸的产量。当底物精粗比(玉米∶羊草)较高(50∶50和65∶35)时,维生素B12的添加效果更明显,并且具有剂量依赖效应。

In Vitro Rumen Fermentation and Microbial Enzyme Activities Influenced by Vitamin B12 Supplementation in Different Concentrate to Forage Ratios

This study was conducted to investigate the effects of vitamin B12 supplementation in diets with different concentrate to forage ratios on in vitro rumen fermentation and microbial enzyme activities.The trial was carried out using fermentation in vitro with the combinations of three concentrate to forage ratios(corn meal∶Chinese wildrye=35∶65,50∶50 and 65∶35) and three supplemental doses of vitamin B12(0,40 and 90 ng/mL) in a 3×3 factorial design.Rumen fluid was collected from three Hu sheep fitted with permanent rumen fistula.Rumen fermentation parameters and microbial enzyme activities were determined at 24 h incubation in vitro.The results showed as follows: 1) with the increasing of concentrate to forage ratio and supplemental doses of vitamin B12,gas production,potential gas production and organic matter digestibility at 24 h incubation in vitro were enhanced significantly(P<0.01),and vitamin B12 supplementation had a linear dose response relationship in them(P<0.01).2) When the concentrate to forage ratios were 50∶50 and 65∶35,the concentrations of ammonia nitrogen,microbial protein,total volatile fatty acids,acetate and propionate were significantly increased(P<0.05) by vitamin B12 supplementation except the butyrate concentration and acetate/propionate(P>0.05).3) Activities of carboxymethyl cellulase and xylanase were significantly increased at 40 ng/mL vitamin B12 for the concentrate to forage ratios of 35∶65 and 50∶50(P<0.05),while they were significantly increased at 90 ng/mL vitamin B12 for the concentrate to forage ratio of 65∶35 at 24 h incubation(P<0.05).The results of this study indicate that the concentrate to forage ratio and vitamin B12 supplementation have effects on in vitro rumen fermentation.Vitamin B12 supplementation can improve organic matter digestibility and production of microbial protein and total volatile fatty acids through enhancing microbial enzyme activities.When the concentrate to forage ratios(corn meal∶Chinese wildrye) are higher(50∶50 and 65∶35),vitamin B12 has pronounced effects on rumen fermentation in a dose-dependent manner.