新鲜黑麦草对奶山羊乳脂肪酸组成的影响及机制研究

Effect and Mechanism of Fresh Ryegrass on Milk Fatty Acid Composition of Dairy Goats

试验旨在研究用新鲜黑麦草不同比例地替代饲粮中的粗饲料对奶山羊乳脂肪酸组成影响和可能机制的探究。采用一个单因素完全随机设计和一个4×4拉丁方设计,将24只泌乳奶山羊和4只安装永久性瘤胃瘘管的奶山羊随机分为4组。试验共4个处理组,基础饲粮组(精粗比为50∶50,粗饲料为玉米青贮和苜蓿干草),用新鲜黑麦草50%和100%地取代基础饲粮中粗饲料组,全部饲喂新鲜黑麦草的全黑麦草组。结果表明:饲粮中新鲜黑麦草的添加显著降低了C18:2n-6的摄入量(P<0.05),显著增加了C18:3n-3的摄入量(P<0.05);新鲜黑麦草的添加对乳常规成分无显著影响(P>0.05),100%取代组总VFA浓度和全黑麦草组乙酸含量均显著增加(P<0.05),NH3-N和pH无显著变化(P>0.05)。对瘤胃脂肪酸组成,50%和100%取代组影响较小,而全黑麦草组显著增加了C18:3n-3的比例,降低了C18:2n-6的比例(P<0.05)。所有黑麦草组乳脂肪酸组成均发生了显著变化,C18:3n-3和不饱和脂肪酸显著增加(P<0.05),乳腺9-去饱和酶指数显著升高(P<0.05),乳中C14:0、C16:0和饱和脂肪酸和致动脉粥样硬化指数显著降低(P<0.05)。研究结果表明,用新鲜黑麦草取代饲粮中的玉米青贮和苜蓿干草可以改善奶山羊乳脂肪酸组成,而这种改善作用主要与新鲜黑麦草增加了C18:3n-3摄入量,影响了瘤胃发酵和脂肪酸代谢有关。

This study investigates the effects and mechanisms of replaing roughage with different percentage of fresh rygrass on profile of milk fatty acids of dairy goats.The trial was conducted by two designs:effects of treatments on milk yield and milk fatty acid profile were investigated in a completely random design with 24 lactation dairy goats while the influence of treatments on rumen fermentation and rumen fatty acid metabolism was studied using a 4×4 latin square design with 4 ruminally-cannulated dairy goats.The treatments were replacing 0,50% and 100% of roughage(maize silage+alfalfa hay)in a concentrated based diet(concentrate to forage=50:50)with fresh ryegrass,and a negative control(goats receiving fresh ryegrass only).The results are shown as follows:compared to the basic ration group,daily intake of C18:2n-6 is significantly decreased in all replacing groups(P<0.05),while the daily intake of C18:3n-3 is opposite(P<0.05);the rumen pH and NH 3-N concentration are not affected significantly by treatments(P >0.05).VFA in all groups feeding fresh ryegrass is higher compared to the basal diet group(P<0.05).The fatty acid composition in the rumen content is just affected by ryegrass only treatment,which significantly increased the C18:3n-3 proportion and decreased the C18:2n-6 proportion(P<0.05).The proportions of C18:3n-3,UFA and the△9-desaturase index in the milk are increased(P<0.05)while the proportions of C14:0,C16:0 and SFA are decreased(P<0.05)in all fresh ryegrass groups.The above results indicate that replacing dietary roughage in a concentrate based diet with fresh ryegrass can improve the milk fatty acid composition,which is mainly due to the increased intake of C18:3n-3 and its influence on rumen fermentation and rumen fatty acid metabolism.