添加复合缓冲剂对高精料饲喂泌乳奶山羊乳品质的改善及机制

Improvement and Underlying Mechanism of Milk Quality of Lactating Goats Fed High Concentrate Diet by Dietary Supplementation of Composite Buffer

目的:探讨复合缓冲剂对高精料饲喂泌乳期奶山羊乳品质及机体健康状态的影响。方法:选取8只体质量接近的泌乳中期萨能奶山羊,随机分为高精料组(high concentrate diet group,HG)(精粗质量比60∶40)和缓冲剂组(buffering concentrate group,BG)(高精料中添加复合缓冲剂)。实验共20周,每周统计奶山羊产乳量,每周检测乳成分含量;至第19周,采集瘤胃液和血液样品,测定瘤胃液p H值及脂多糖(lipopolysaccharides,LPS)含量及血液中相关生化指标。结果:与HG相比,BG的奶山羊平均日产乳量、乳中乳蛋白率、乳脂率及乳糖含量都高于HG,其中乳脂率显著高于HG(P<0.05)。HG奶山羊瘤胃p H值一直低于BG,且出现了亚急性瘤胃酸中毒症状,其中瘤胃液中LPS含量极显著高于BG(P<0.01);生化指标检测结果显示:HG奶山羊血液中碱性磷酸酶、谷丙转氨酶、谷草转氨酶的活性都高于BG,且差异显著(P<0.05)。结论:给泌乳奶山羊高精料饲料中添加复合缓冲剂可以改善泌乳期奶山羊乳品质和产乳量,其机理可能与复合缓冲剂缓解高精料所致的瘤胃p H值下降、减少代谢异常产物的产生,从而改善机体的健康状态有关。

Objective: To investigate the effect of dietary supplementation of composite buffer on the milk quality and health status of lactating goats fed a high concentrate diet. Methods: Eight mid-lactating Saanen dairy goats with similar body weights were randomly divided into high concentrate diet group (HG, concentr ate:forage ratio = 60:40)and buffering agent group (BG, fed high concentrate diet added with). The experiment lasted for 20 weeks. The milkproduction and milk composition were measured weekly during the period, and on week 19, rumen fluid and bloodsamples were collected for the measurement of rumen fluid pH and lipopolysaccharide (lipopolysaccharides, LPS) contentas well as blood biochemical indices. Results: The average daily milk yield, and protein, fat and lactose percentages ofdairy goats from the BG were higher than those of the HG, especially milk fat percentage (P < 0.05). The rumen fluidpH of dairy goats in the HG was persistently lower than that of the BG and the occurrence of subacute ruminal acidosiswas found in the former. Additionally, the LPS content of the rumen fluid of dairy goats in the HG was significantlyhigher than that in the BG (P < 0.01). Biochemical analysis showed that the activities of alkaline phosphatase and alanineaminotransferase and aspartate transaminase in the blood of HG goats were significantly higher than those in BG goats(P < 0.05). Conclusion: Dietary supplementation of composite buffer could improve the milk quality and yield of lactating goats fed a high concentrate diet. The mechanism involved may be due to decreased rumen fluid pH, reduced production of abnormal metabolites and consequent improved health status in response to dietary composite buffer.