本试验旨在通过测定不同粒度脂肪酸钙的在瘤胃发酵过程中干物质降解率和脂肪酸组成的变化,研究粒度对脂肪酸钙瘤胃稳定性的影响。选择4头安装永久瘤胃瘘管的荷斯坦泌乳母牛作为试验动物,饲喂基础饲粮,每天将400 g未经筛分的脂肪酸钙混于每头牛的精料中饲喂。采用尼龙袋法分别测定4种粒度(12目筛上部分,12目筛下、40目筛上部分,40目筛下、60目筛上部分,60目筛下部分)脂肪酸钙在发酵后2、4、8、12、24、36、48 h的瘤胃干物质降解率,并采集降解残渣,测定脂肪酸组成的变化。结果表明:1)试验脂肪酸钙的粒度分布为12目筛上部分40.20%,12目筛下、40目筛上部分50.30%,40目筛下、60目筛上部分4.50%,60目筛下部分5.00%。2)不同粒度脂肪酸钙的脂肪酸组成基本没有差别。3)脂肪酸钙粒度对瘤胃干物质降解率具有极显著影响(P<0.01),60目筛上部分在瘤胃中基本稳定,60目筛下部分干物质降解率较高。4)发酵过程中,C16:0、C18:0脂肪酸比例升高,C18:1、C18:2、C18:3脂肪酸比例下降,60目筛上部分上述变化较小,60目筛下部分变化较大。总之,脂肪酸钙的粒度过小瘤胃稳定性差,不饱和脂肪酸易转化为饱和脂肪酸,提示在生产加工过程中应采用合理的工艺以保证脂肪酸钙的适当粒度与均匀度。

In order to study the effects of particle size on the stability of calcium salt-fatty acids (CSFAs) in rumen, the changes of dry matter degradation rate and fatty acid composition (FAC) of CSFAs with different particle sizes were determined during rumen fermentation. Four lactating Holstein dairy cows installed with permanent fistulas were selected as experimental animals, and were fed a basal diet. A dose of 400 g unscreened CSFAs was mixed in the concentrate per day per cow. CSFAs were screened into four particle sizes (over 12 meshes, 12 to 40 meshes, 40 to 60 meshes and smaller than 60 meshes). Rumen dry matter degradation rate after fermented for 2, 4, 8, 16, 24, 32 and 48 h was evaluated by nylon bag method. Degradation residues were collected at each time point to analyze changes of FAC. The results showed as follows: 1) it was accounted for 40.20%, 50.30%, 4.50% and 5.00% at particle sizes of over 12 meshes, 12 to 40 meshes, 40 to 60 meshes and smaller than 60 meshes, respectively. 2) FAC of the four particle sizes of CSFAs was similar. 3) Particle sizes of CSFAs had extremely significant effects on rumen dry matter degradation rate (P<0.01), the degradation rate of CSFAs over 60 mushes was stable, while CSFAs smaller than 60 mushes were highly degraded. 4) During rumen fermentation, proportions of C16:0 and C18:0 were increased, meanwhile those of C18:1, C18:2 and C18:3 were decreased, which was more obvious on CSFAs smaller than 60 mushes. In conclusion, CSFAs with small particle sizes is not stable in rumen, and the unsatisfied fatty acids are easy to change into satisfied fatty acids. The results indicate that proper manufacture method should be used to obtain CSFAs with more uniform and suitable particle size.