【作者】 乔良；

【导师】 闫素梅；

【作者基本信息】 内蒙古农业大学 ， 动物营养与饲料科学， 2008， 博士

【摘要】 本论文共分9个试验对奶牛维生素A的瘤胃降解规律进行研究,并对过瘤胃保护维生素A的效果进行评价。研究结果为过瘤胃保护维生素A的研制与应用提供了理论依据,为奶牛日粮中维生素A的合理补加、营养状况的保证与奶牛生产性能、免疫机能的进一步提高奠定了理论基础;同时对丰富反刍动物的维生素A营养理论具有重要的学术意义。试验1、2研究不同精粗比日粮条件下,不同添加剂量的两种维生素A在奶牛瘤胃内的降解率及其对瘤胃发酵参数的影响。试验采用2×2×3完全随机试验设计,第一因素为培养底物的精粗比,设2:8和5:5两个水平,第二因素为维生素A来源,设国产和进口两种,第三因素为维生素A的添加剂量,设3个水平,分别为每毫升培养液中5.8、11.7和23.3IU。试验共分12个处理组,每处理组均进行4、8、12及24h 4个时间点的体外批次培养,每个时间点3个重复。试验3利用瘤胃微生物驱除技术研究瘤胃微生物对维生素A降解的影响;在试验3的基础上,试验4利用细菌分离技术进一步研究瘤胃不同菌群对维生素A降解的影响,初步揭示维生素A的瘤胃降解机理。试验5利用喷雾干燥法制备过瘤胃保护维生素A微胶囊,并利用体外法测定其瘤胃降解率。在试验5的基础上,试验6采用2×2完全随机试验设计,按照体重,泌乳量及胎次相近的原则,将20头奶牛随机分为4组,每组5头。各组在基础日粮中添加不同处理(过瘤胃保护维生素A、未处理维生素A)及水平(110IU/kgBW、165IU/kgBW)的维生素A。试验预饲期15天,正试期60天。于正试期结束的前2天采集各处理组每头牛的瘤胃液,以测定不同处理及添加水平的维生素A对瘤胃维生素A浓度及瘤胃发酵的影响,为过瘤胃保护维生素A微胶囊的科学研制及其在奶牛生产中的推广应用提供理论基础。试验7～9通过饲养试验的手段,研究不同处理及添加剂量的维生素A对奶牛泌乳性能、免疫机能、抗氧化功能及机体维生素A营养状况的影响。试验采用2×2随机试验设计,按照体重,泌乳量及胎次相近的原则,将24头奶牛随机分为4组,每组6头。各组在基础日粮中添加不同处理(过瘤胃保护维生素A、未处理维生素A)及水平(110IU/kgBW、165IU/kgBW)的维生素A。试验预饲期15天,正试期60天。在本研究的试验条件下初步得出以下结果:1)不论精料比例高低,进口与国产维生素A在体外培养液中均有较高的降解率,在8h培养时间点,降解率达60%左右;在24h培养时间点达70%以上。2)高精料组维生素A的降解率显著高于低精料组;维生素A的添加剂量在5.8~23.3IU/mL范围内,其降解率随维生素A添加剂量的增加呈一定增加趋势,但对奶牛瘤胃体外发酵参数的影响较小。3)维生素A的降解主要与瘤胃细菌有关,其中分解纤维菌与分解淀粉菌对于维生素A均有一定的降解作用,但分解淀粉菌的降解作用更大,是维生素A在瘤胃内降解的主要因素。瘤胃内环境对维生素A在瘤胃中的降解也有一定的影响。4)与未处理的维生素A相比,过瘤胃保护维生素A微胶囊有较高的瘤胃稳定性,在体外培养进行到24h时,其降解率只有30.38%;而未处理的维生素A的降解率高于70%。5)与未处理维生素A相比,日粮中添加110、165IU/kgBW的过瘤胃保护维生素A微胶囊,可显著降低奶牛瘤胃液中维生素A的浓度,增加瘤胃液中乙酸与TVFA的浓度,对瘤胃其它发酵参数无明显影响。日粮中添加165IU/kgBW的高剂量未处理维生素A,对瘤胃代谢无明显影响。6)与未处理维生素A组相比,日粮中添加110、165IU/kgBW过瘤胃保护维生素A微胶囊,可以显著改善奶牛维生素A营养状况,增加奶牛日产奶量与乳中维生素A浓度,增强免疫机能与抗氧化功能;在试验所设的4个处理组中,尤以165IU/kgBW的过瘤胃保护维生素A组效果最好,而以110IU/kgBW未处理维生素A组效果最差。7)添加过瘤胃保护维生素A微胶囊与或单纯增加未处理维生素A的添加剂量对奶牛产奶性能、免疫机能、抗氧化功能及乳维生素A浓度方面均有一定促进效果,但前者优于后者。更多还原

【Abstract】 The present study was divided into 9 trials to discuss the rule of degradation of vitamin A in rumen and evaluate the effects of ruminal protected vitamin A on dairy cows. All of the results obtained were very important to enrich the theoretics of ruminant vitamin A nutrition, and to provide foundation to prepare and use ruminal protected vitamin A. and to propose reasonable adding levels of vitamin A in order to improve body vitamin A status and enhance the performance and immune function of dairy cows.Trial 1 and 2 were conducted to study the influences of different sources and levels of vitamin A and different concentrate to forage ratio diets on the ruminal vitamin A degradability and the rumen fermentation during in vitro ruminal fermentation. The experiment was a 2×2×3 factorial arrangement, and the first factor was concentrate to forage ratio of incubating substrate(2:8 and 5:5), and the second factor was the source of vitamin A (domestic and imported). The third factor was vitamin A level added to incubating system (5.8, 11.7, 23.3 IU per milliliter medium).In order to discuss the degradation mechanism of VA in rumen, trial 3 was conducted to study the effect of ruminal microbe on degradation of vitamin A during in vitro ruminal fermentation and trial 4 was conducted to test the effect of different types of microflora in rumen on the degradation of vitamin A during in vitro ruminal fermentation. Microcapsules of ruminal protected vitamin A were prepared in trial 5 by using spray-dried technology and its degradability during in vitro ruminal fermentation was determined.Trial 6 was a 2×2 factorial arrangement. 20 dairy cows which were similar in weight and milk performance were randomly divided into 4 groups, with 5 each group. Different groups were fed the different diets in vitamin A treatments (ruminal protected vitamin A, untreated vitamin A) and levels (110IU/kgBW, 165IU/kgBW) . Pre-trial period was 15 d and the experimental period was 60 d. The rumen fluid was collected from the cows in different groups in the last two days of the experimental periods to evaluate the effect of the different treatments and levels of vitamin A on ruminal vitamin A content and rumen fermentation in dairy cows.Trial 6 was a 2×2 factorial arrangement. 20 dairy cows which were similar in weight and milk performance were randomly divided into 4 groups, with 6 each group. Different groups were fed the different diets in vitamin A treatments (ruminal protected vitamin A, untreated vitamin A) and levels (110IU/kgBW, 165IU/kgBW). Pre-trial period was 15 d and the experimental period was 60 d. The purpose of these experiments was to discuss the influences of different treatments and levels of vitamin A in dairy cows diet on milk yield, immune function, anti-oxidation function and vitamin A nutritional status.Under the present experimental conditions, the results showed as follows:1) The degradability of both the vitamin A sources was all higher for high or low concentrates dies during in vitro ruminal fermentation, and it was about 60% at 8h and was more than 70% at 24h.2) The vitamin A degradability during in vitro ruminal fermentation for the high concentrates diet was significantly higher than for the low concentrates diet. With the increasing level of vitamin A in incubating system from 5.8 to 23.3 IU/mL, the disappearance of vitamin A had a certain attendency to be increased..3) The degradation of vitamin A in rumen was mainly related to ruminal bacteria. Both amylolytic bacteria and cellulose-digesting bacteria could result in the degradation of vitamin A, but amylolytic bacteria had a dominant effect for vitamin A degradation. The results also showed that rumen environment had a little effect on the degradation of vitamin A.4) Microcapsule of ruminal protected vitamin A was more stable in rumen than untreated vitamin A. During in vitro fermentation the degradation rate of vitamin A was 30.38% fro ruminal protected vitamin A at 24h, but it was more than 70% for untreated vitamin A.5) Supplementation of ruminal protected vitamin A(110IU/kgBW and 165IU/kgBW)in diet significantly reduced the vitamin A content and increased acetic acid and TVFA concentrations in rumen, but had little effect on the other fermentation parameters. The supplementation of high dose of untreated vitamin A (165IU/kgBW) had little effect on rumen fermentation.6) Supplementation of microcapsules of ruminal protected vitamin A(110IU/kgBW and 165IU/kgBW, respectively)in diet resulted in an significant improvement in milk yield , immune function ,anti-oxidation function and vitamin A nutritional status of dairy cows and vitamin A content of milk. The 165 IU/kgBW ruminal protected vitamin A group had the best effect on above indexes, but 110IU/kgBW untreated vitamin A group had the worst effect.7) Either supplementation of ruminal protected vitamin A microcapsules or increasing untreated vitamin A level in diet could promote the performance and immune fuction and anti-oxidation function of dairy cows, but the effect was better for microcapsules of ruminal protected vitamin A.更多还原