烟酸对锦江黄牛瘤胃乳酸、挥发性脂肪酸浓度及相关酶活性的影响

摘要

本试验旨在探讨在高精料饲粮条件下,添加烟酸对锦江黄牛瘤胃乳酸、挥发性脂肪酸浓度及相关酶活性的影响.选用3头平均体重为(275±20)kg、安装有永久性瘤胃瘘管的锦江黄牛,采用精料比例逐步提高来诱导酸中毒的试验方法,试验分4期,每期10 d,第Ⅰ、Ⅱ、Ⅲ期依次饲喂精料比例分别为60％、70％、80％的饲粮；第Ⅳ期饲喂精料比例80％+烟酸800 mg/kg的饲粮.结果表明:1)在试验第Ⅰ、Ⅱ、Ⅲ期,未添加烟酸条件下,随精料比例的提高,瘤胃pH显著下降(P＜0.05)；瘤胃中的乙酸、丙酸、丁酸、总挥发性脂肪酸浓度随着精料比例的提高而提高,60％精料比例与70％和80％精料比例之间差异显著(P＜0.05),但70％和80％精料比例之间差异不显著(P＞0.05)；瘤胃中的丙酮酸、乳酸浓度及乳酸/丙酮酸也随着精料比例的提高而提高,60％与70％精料比例之间差异不显著(P＞0.05),80％精料比例与60％、70％精料比例之间差异显著(P＜0.05)；各精料比例对瘤胃氧化型烟酰胺腺嘌呤二核苷酸(NAD+)、还原型烟酰胺腺嘌呤二核苷酸(NADH)浓度和NADH/NAD+没有显著影响(P＞0.05),但NAD+浓度随着精料比例的提高有降低的趋势,而NADH浓度和NADH/NAD+有提高的趋势.2)在试验第Ⅲ、Ⅳ期,精料比例为80％条件下,与未添加烟酸相比,添加烟酸显著提高了瘤胃pH及丙酸、总挥发性脂肪酸浓度(P＜0.05),显著降低了丙酮酸、乳酸浓度及乳酸/丙酮酸(P＜0.05),而乙酸、丁酸浓度及乙酸/丙酸差异不显著(P＞0.05)；与未添加烟酸相比,添加烟酸对瘤胃中总脱氢酶活性、NAD+、NADH浓度及NADH/NAD+均无显著影响(P＞0.05),但有提高NAD+浓度,降低NADH浓度及NADH/NAD+的趋势.3)第Ⅰ、Ⅱ、Ⅳ期瘤胃中均未检出乳酸脱氢酶活性,而在试验第Ⅲ期,精料比例为80％(未添加烟酸)条件下,瘤胃中检出了乳酸脱氢酶,其活性为132.9 U/mL.结果提示,添加烟酸提高了瘤胃NAD+浓度,降低了NADH浓度及NADH/NAD+,抑制了乳酸脱氢酶活性和乳酸产生,从而缓解瘤胃酸应激或酸中毒.%The effects of nicotinic acid (NA) on lactate and volatile fatty acid (VFA) concentrations,and related enzyme activities in rumen of Jinjiang cattle were studied in this experiment.Three healthy Jinjiang cattle with permanent rumen cannulas and an average body weight of (275 ± 20) kg were selected.Using rumen acidism method induced by gradually increasing concentrate ratio,the experiment was divided into four test periods:test periods Ⅰ,Ⅱ and Ⅲ were fed diets with the concentrate ratios of 60％,70％ and 80％,respectively; test period Ⅳ was fed the diet with 80％ concentrate ratio + 800 mg/kg NA,and every test period lasted for 10 days.The results showed as follows:1) in test periods Ⅰ,Ⅱ and Ⅲ,under the condition of diets without NA,pH in rumen was significantly decreased with the increase of concentrate ratio (P ＜ 0.05) ; the concentrations of acetate,propionate,butyrate and total VFA were significantly increased with the increase of concentrate ratio (P ＜0.05),there was significant difference between 60％ and 70％ or 80％ concentrate ratio (P ＜0.05),but no significant difference was found between 70％ and 80％ concentrate ratio (P ＞0.05).Rumen pyruvate and lactate concentrations,and lactate/pyruvate were increased with the increase of concentrate ratio,no significant difference was found between 70％ and 60％ concentrate ratio (P ＞ 0.05),but there was significant difference between 80％ and 70％ or 60％ concentrate ratio (P ＜0.05).There were no significant differences in the concentrations of oxidized nicotinamide adenine dinucleotide (NAD +) and reduced nicotinamide adenine dinucleotide NADH,and NADH/NAD + in this three test periods (P ＞ 0.05),but with the increase of concentrate ratio,NAD + concentration was reduced,and NADH concentration and NADH/NAD + were increased.2) In test periods Ⅲ and Ⅳ,under the condition of 80％ concentrate ratio,the supplementation of NA significantly increased rumen pH,propionate and total VFA concentrations (P ＜ 0.05),and significantly decreased pyruvate and lactate concentrations,and lactate/pyruvic compared with no NA supplementation (P ＜ 0.05),but there were no significant differences in the concentrations of acetate and butyrate,and acetate/propionate (P ＞ 0.05).The supplementation of NA did not significantly affect NAD + and NADH concentrations and lactate dehydrogenase activity compared with no NA supplementation (P ＞ 0.05),but there was a trend to increase NAD + concentration and decrease NADH concentration and lactate dehydrogenase activity (P ＞ 0.05).3) The lactate dehydrogenase activity in rumen was not detected in test periods Ⅰ,Ⅱ and Ⅳ,and only found in the test period Ⅲ of 80％ concentrate ratio (without NA),and the activity was 132.9 U/mL.In conclusion,the supplementation of NA can increase NAD + concentration,decrease NADH concentration and lactate dehydrogenase activity,and inhibit lactate dehydrogenase activity and lactic acid concentration.Therefore,NA may be play a role in alleviate acid shock or acidosis in rumen.