Gallo A, Giuberti G, Masoero F
Feed and Food Science and Nutrition Institute, Facoltà di Scienze Agrarie, Alimentari e Ambientali, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy.
Feed and Food Science and Nutrition Institute, Facoltà di Scienze Agrarie, Alimentari e Ambientali, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy.
J Dairy Sci. 2016 Jun;99(6):4347-4359. doi: 10.3168/jds.2015-10779. Epub 2016 Mar 16.
The objective of this study was to verify the effect of mean particle size (mPS) on both gas production and in vitro rumen starch degradability (IVSD) of corn and barley meals (Cm and Bm, respectively). Batches of the same Cm or Bm were separately processed through 2 different mills (i.e., a cutter mill or a rotor speed mill) equipped with or without different screens to achieve different mPS for each tested meal. Samples were analyzed accordingly to a completely randomized design and the main tested effect of model was mPS (n=11, from 0.46 to 3.50mm mPS for Cm or n=10, from 0.11 to 2.98mm mPS for Bm). For both in vitro assays, the rumen inocula were collected from 2 rumen-fistulated Holstein lactating dairy cows fed a total mixed ration with 16.2% crude protein, 28.5% starch, and 35.0% neutral detergent fiber on a dry matter basis. To fit gas production data, 1-pool exponential model and 1-pool or 2-pool Gompertz models were adopted. The rate of gas production decreased and lag increased by increasing mPS of both Cm and Bm, irrespective of adopted 1-pool models. When the 2-pool Gompertz model was used to fit gas production data, a shift of particles from fast to slow fermentable pools was measured by increasing mPS. In particular, the ratio between fast and slow final volumes ranged from 0.90 at 0.11mm mPS to 0.10 at 2.98mm mPS for Bm. For Cm, the ratio between fast and slow final volumes decreased quadratically by increasing mPS, with the highest value (i.e., 0.58) measured at the lowest tested mPS. Values lower than 0.10 were measured for mPS greater than 1.93mm for Cm. Concerning IVSD data, linear decreases in rate of starch degradation equal to -0.049 or -0.092h(-1) for each 1-mm increase in mPS were achieved for Cm and Bm, respectively. The 7-h IVSD decreased by 6.3 or 6.5% starch for each 1-mm increase in mPS of Cm or Bm, respectively. Present findings supported the hypothesis that different particle sizes within the same starch source represent an important factor influencing both fermentation kinetic parameters and IVSD.
本研究的目的是验证平均粒径（mPS）对玉米粉和大麦粉（分别为Cm和Bm）产气率及体外瘤胃淀粉降解率（IVSD）的影响。将相同批次的Cm或Bm分别通过配备或不配备不同筛网的2种不同磨机（即切碎机或转子速度磨机）进行加工，以使每种受试粉样达到不同的mPS。根据完全随机设计对样品进行分析，模型的主要受试效应为mPS（Cm的mPS为0.46至3.50mm，n = 11；Bm的mPS为0.11至2.98mm，n = 10）。对于两种体外试验，瘤胃液接种物均采自2头装有瘤胃瘘管的荷斯坦泌乳奶牛，这2头奶牛饲喂的全混合日粮干物质基础上含有16.2%的粗蛋白、28.5%的淀粉和35.0%的中性洗涤纤维。为拟合产气数据，采用了单池指数模型以及单池或双池Gompertz模型。无论采用哪种单池模型，Cm和Bm的产气率均随mPS的增加而降低，滞后期增加。当使用双池Gompertz模型拟合产气数据时，随着mPS的增加，可观察到颗粒从快速发酵池向慢速发酵池的转移。具体而言，Bm快速和慢速最终体积之比在mPS为0.11mm时为0.90，在mPS为2.98mm时为0.10。对于Cm，快速和慢速最终体积之比随mPS的增加呈二次方下降，在受试的最低mPS时测得最高值（即0.58）。对于Cm，当mPS大于1.93mm时，该比值低于0.10。关于IVSD数据，Cm和Bm的淀粉降解率分别随mPS每增加1mm线性下降，下降幅度分别为-0.049或-0.092h⁻¹。Cm或Bm的mPS每增加1mm，7小时IVSD的淀粉降解率分别下降6.3%或6.5%。目前的研究结果支持以下假设：同一淀粉来源内的不同粒径是影响发酵动力学参数和IVSD的重要因素。
