肉牛常见饲料干物质和蛋白质瘤胃降解特性和小肠消化率研究

[方法]选用装有瘤胃瘘管和小肠瘘管的肉牛作为试验动物,尼龙袋法测定肉牛常见饲料干物质(DM)和粗蛋白(CP)的瘤胃降解特性和小肠消化率。[结果]结果表明,DM瘤胃有效降解率由高到低为玉米粉、麦麸、苜蓿干草、豆粕、菜籽粕、玉米青贮、醋糟、白酒糟;CP瘤胃有效降解率由高到低为苜蓿干草、麦麸、豆粕、醋糟、玉米粉、玉米青贮、菜籽粕、白酒糟;DM小肠消化率由高到低为豆粕、菜籽粕、玉米粉、白酒糟、醋糟、麦麸、苜蓿干草、玉米青贮;CP小肠消化率由高到低为豆粕、菜籽粕、玉米粉、苜蓿干草、麦麸、白酒糟、玉米青贮、醋糟。[结论]试验表明,不同饲料瘤胃降解特性不同,为小肠提供过瘤胃可消化蛋白的能力不同,且饲料的DM小肠消化率小于CP小肠消化率。     

秦川肉牛5种常用精饲料的瘤胃降解特性研究

试验旨在研究秦川肉牛常用饲料的瘤胃降解特性,为秦川肉牛的科学养殖提供理论支持。试验选用3头装有永久性瘤胃瘘管的秦川肉牛(公牛),采用尼龙袋法评定秦川肉牛常用饲料的干物质(DM)、有机物(OM)和粗蛋白质(CP)的瘤胃降解率和有效降解率。DM的瘤胃有效降解率为麸皮玉米豆粕棉粕菜籽粕(P0.05)。OM瘤胃有效降解率依次为:麸皮玉米豆粕,各饲料间差异显著(P0.05),而菜籽粕与棉粕的有效降解率最低,两者之间差异不显著(P0.05)。CP有效降解率麸皮最高,玉米次之,豆粕最低,各饲料间差异显著(P0.05)。棉粕和菜籽粕均比豆粕高,且两者较为接近(P0.05)。结果表明:不同种类饲料瘤胃的有效降解率与饲料原料的养分组成有关。在5种饲料中,豆粕的CP含量最高,玉米的OM含量最高。麸皮的CP瘤胃有效降解率高于玉米,棉粕和菜籽粕的DM、OM、CP的瘤胃有效降解率均相似。     

奶牛对不同糟渣类饲料营养成分的瘤胃降解率和小肠消化率对比研究

本试验旨在对比奶牛对不同糟渣类饲料(玉米酒糟、高粱酒糟、醋糟、糖糟、啤酒糟)的营养成分瘤胃降解率和小肠消化率.选用3只装有永久性瘤胃瘘管的中国荷斯坦奶牛,用尼龙袋法测定干物质(DM)、粗蛋白质(CP)、必需氨基酸(EAA)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)在不同时间点的瘤胃降解率和小肠消化率.结果表明:1...     

酒糟与肉羊常用粗饲料的营养价值及瘤胃降解特性的对比研究

试验旨在研究酒糟与肉羊常用粗饲料(玉米秸秆和高粱秸秆)的营养价值及瘤胃降解特性。选择3只安装永久性瘤胃瘘管的杜×寒杂交F1阉割公羊,采用尼龙袋法测定3种粗饲料的粗蛋白(CP)、干物质(DM)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的瘤胃降解参数,并对其常规养分及能量价值进行分析。结果表明:酒糟的CP含量和肉羊饲用价值均高于玉米秸秆和高粱秸秆,而NDF含量低于这两种粗饲料;酒糟的CP瘤胃有效降解率显著高于此两种秸秆类粗饲料(P0.05),而DM、ADF和NDF的瘤胃有效降解率均显著低于这两种粗饲料(P0.05)。综合比较,酒糟的CP含量、肉羊饲用的能量价值和CP瘤胃降解率均较高,是补充CP的优质粗饲料。     

4种非常规饲料在肉牛瘤胃内降解特性的研究

试验旨在研究全株甘蔗青贮、木薯茎叶、香蕉茎叶青贮和白酒糟等4种非常规粗饲料在肉牛瘤胃中的降解特性。试验采用尼龙袋法,以3头装有永久瘘管的肉牛（云岭牛）为试验对象,每头牛做3个平行。4种非常规粗饲料通过瘤胃瘘管送至瘤胃腹囊中,分别在6、12、24、36、48、72 h取出,测定4种非常规粗饲料在不同时间点消化后的干物质（DM）、粗灰分（Ash）、粗蛋白质（CP）、中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）、粗脂肪（EE）含量。结果显示：白酒糟的DM、CP含量显著高于其他3组（P<0.05）。香蕉茎叶青贮的Ash、NDF和ADF含量显著高于其他3种粗饲料（P<0.05）。木薯茎叶和白酒糟的EE含量均显著高于其他2种粗饲料（P<0.05）。DM、有机物（OM）、CP有效降解率均为白酒糟>全株甘蔗青贮>木薯茎叶>香蕉茎叶青贮。NDF有效降解率排序为香蕉茎叶青贮>木薯茎叶>白酒糟>全株甘蔗青贮。香蕉茎叶青贮和木薯茎叶的ADF有效降解率显著高于白酒糟和全株甘蔗青贮（P<0.05）。研究表明,4种粗饲料均表现出良好的饲喂效果,以白酒糟和...     

不同类型酒糟营养成分组成差异的比较研究

本研究旨在比较不同类型酒糟营养成分组成差异并评定其营养价值。采集了5类酒糟样品共24个,其中浓香型高粱酒糟8个,酱香型高粱酒糟4个,青稞酒糟4个,玉米酒糟3个,啤酒糟5个,分析其养分组成,并应用康奈尔净碳水化合物-蛋白质体系(CNCPS)对其瘤胃降解特性进行评定,利用原子吸收法测定其铁、铜、锰、锌含量,并测定其抗营养因子单宁和硅含量。结果表明:1)啤酒糟pH和初水含量显著高于其他酒糟(P0.05)。2)啤酒糟粗蛋白质含量最高,显著高于浓香型高粱酒糟、青稞酒糟和玉米酒糟(P0.05)。啤酒糟和酱香型高粱酒糟中性洗涤不溶蛋白质(NDIP)含量显著高于其他酒糟(P0.05)。浓香型高粱酒糟和酱香型高粱酒糟酸性洗涤不溶蛋白质(ADIP)含量显著高于其他酒糟(P0.05)。玉米酒糟粗脂肪含量显著高于其他酒糟(P0.05)。浓香型高粱酒糟的粗纤维、中性洗涤纤维、酸性洗涤纤维和酸性洗涤木质素含量显著高于其他酒糟(P0.05)。玉米酒糟淀粉含量显著高于其他酒糟(P0.05),啤酒糟淀粉含量显著低于其他酒糟(P0.05)。3)按CNCPS划分,啤酒糟快速降解碳水化合物(CA)比例显著高于其他酒糟(P0.05),玉米酒糟中速降解碳水化合物(CB1)比例显著高于其他酒糟(P0.05),浓香型高粱酒糟不可降解碳水化合物(CC)比例显著高于其他酒糟(P0.05),啤酒糟慢速降解真蛋白质(PB3)比例显著高于其他酒糟(P0.05),浓香型高粱酒糟不可降解真蛋白质(PC)比例显著高于其他酒糟(P0.05)。4)浓香型高粱酒糟和酱香型高粱酒糟铁和锰含量显著高于其他酒糟(P0.05),啤酒糟铜和锌含量显著高于其他酒糟(P0.05)。5)啤酒糟单宁含量显著低于其他酒糟(P0.05),浓香型高粱酒糟硅含量显著高于其他酒糟(P0.05)。由此可见,不同类型酒糟营养成分组成差异较大。玉米酒糟提供了最优质的碳水化合物组分,啤酒糟提供了最优质的蛋白质组分,青稞酒糟和酱香型高粱酒糟品质较优,浓香型高粱酒糟品质最差,应根据实际生产需求合理添加。     

反刍家畜常用饲料蛋白质和氨基酸瘤胃降解特性和小肠消化率评定研究

本试验探讨了常用饲料在瘤胃的降解特性及非降解饲料的小肠消化率,旨在为研究反刍动物的营养平衡和消化规律及科学配制日粮提供依据。试验选用3头装瘤胃瘘管和十二指肠瘘管的肉牛,采用尼龙袋法研究反刍动物常用饲料粗蛋白质和氨基酸瘤胃降解参数和表观小肠消化率。结果表明,在本试验中粗蛋白质降解率由低到高的顺序为:酒糟蛋白、黄玉米、羊草、玉米胚芽饼、菜粕、棉粕、豆粕、花生饼、啤酒糟、苜蓿、米糠、小麦麸;总氨基酸瘤胃降解率由低至高的顺序依次为:酒糟蛋白、黄玉米、羊草、玉米胚芽饼、菜粕、豆粕、棉粕、啤酒糟、花生饼、苜蓿、米糠、小麦麸。除花生饼、酒糟蛋白和黄玉米外,粗蛋白质和总氨基酸的有效降解率差异不显著(P>0.05)。粗蛋白质的表观小肠消化率由低至高的顺序依次为:苜蓿、羊草、米糠、小麦麸、啤酒糟、玉米胚芽饼、棉粕、菜粕、玉米、酒糟蛋白、花生饼、豆粕;总氨基酸的小肠消化率由低至高的顺序依次为:羊草、苜蓿、米糠、小麦麸、啤酒糟、玉米胚芽饼、菜粕、棉粕、花生饼、玉米、酒糟蛋白、豆粕。由此可见,不同的饲料瘤胃降解特性是不同的,并且为小肠提供的各种可吸收氨基酸潜力也是不同的。     

应用康奈尔净碳水化合物-蛋白质体系和瘤胃降解特性比较糟渣类粗饲料的营养价值

本试验旨在应用康奈尔净碳水化合-蛋白质体系(CNCPS)和瘤胃降解特性比较3种糟渣饲料营养价值及其作为肉羊粗饲料资源的可行性。采集山西晋中地区有代表性的酿酒葡萄皮渣、醋糟和酒糟,每种样品各采集3个样本,利用CNCPS模型测定营养成分进行碳水化合物和蛋白质组分的剖分,同时利用尼龙袋法测定3种粗饲料的干物质(DM)、粗蛋白质(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的瘤胃降解参数。结果表明:酒糟的CP含量显著高于葡萄皮渣和醋糟(P<0.05),NDF、ADF和酸性洗涤木质素(ADL)显著低于其他两者(P<0.05);蛋白质组分中不可降解氮三者差异不显著;酒糟快速降解碳水化合物和中速降解碳水化合物显著高于其他两者(P<0.05),不可利用碳水化合物显著低于其他两者(P<0.05);酒糟的CP、DM和NDF有效降解率显著高于醋糟(P<0.05)。可见,酒糟的营养价值高于葡萄皮渣和醋糟,可替代部分常规粗饲料添加到肉羊日粮中。     

不同来源蛋白质饲料瘤胃降解特性研究

文章旨在研究豆粕、牡丹籽粕、棉籽粕、棕榈粕、啤酒糟、豆渣、味精渣、玉米酒精糟（DDGS）、芝麻饼粕和葵花饼共10种蛋白质饲料原料的瘤胃降解特性。试验选用3头装有永久性瘤胃瘘管的鲁西牛×利木赞杂交牛为试验动物,采用尼龙袋法测定10种蛋白质饲料的干物质（DM）、粗蛋白质（CP）、中性洗涤纤维（NDF）和酸性洗涤纤维（ADF）瘤胃降解率。结果表明：味精渣DM有效降解率最高,芝麻饼粕最低,各原料间差异显著（P <0.05）;CP有效降解率为棉籽粕>牡丹籽粕>豆粕>味精渣>豆渣> DDGS>葵花粕>啤酒糟>棕榈粕>芝麻饼粕,各原料间显著差异（P <0.05）;味精渣、棉籽粕和豆粕的NDF有效降解率较高,棕榈粕、啤酒糟和芝麻饼粕较低,各原料间差异显著（P <0.05）;味精渣ADF有效降解率最高,其次为豆粕、棉籽粕和牡丹籽粕,均显著高于其他原料（P <0.05）。综上所述,不同来源蛋白质饲料具有不同的瘤胃降解特性,采用隶属函数进行综合营养评价,排序为味精渣>豆粕>棉籽粕> DDGS>牡丹籽粕>...     

陕北白绒山羊常用饲料干物质和粗蛋白质瘤胃降解特性研究

本试验旨在研究陕北白绒山羊常用4种精料和5种粗饲料的瘤胃降解特性。选用3只装有永久性瘤胃瘘管的陕北白绒山羊,采用尼龙袋法测定9种饲料原料的干物质(DM)和粗蛋白质(CP)瘤胃消失率与有效降解率。结果表明:豆腐渣在48 h的DM降解率显著高于其他3种精料(P<0.05),谷糠和豆腐渣DM有效降解率显著高于其他2种精料(P<0.05);粗饲料在72 h的DM降解率和有效降解率均以柠条最高,醋糟最低。精料CP有效降解率从大到小依次是谷糠>酵母>棉籽粕>豆腐渣,且差异显著(P<0.05)。粗饲料在72 h的CP消失率和CP有效降解率以柠条最高。综合来看,精料中谷糠的降解性能最高;粗饲料中柠条的降解性能最高。     

奶牛和肉牛日粮淀粉和葡萄糖的营养调控及其评定的建议

谷物饲料干物质中的淀粉含量多在50%以上,全株玉米青贮的淀粉含量亦有30%。牛的玉米日粮生淀粉消化率比熟淀粉低,但熟淀粉由于瘤胃消化率很高,所以瘤胃后的可消化淀粉量很低。生糖前体能量(瘤胃丙酸 肠可消化淀粉)能明显提高产奶量和乳蛋白率,但导致乳脂率下降。须对生糖前体能量进行评定和调节,以提高产奶效率。对真胃灌注不同梯度的葡萄糖或淀粉均显着地提高了Kf和体脂肪及体蛋白质沉织,因此我国肉牛饲养标准提出的Kf(%)=11.7645 55.756(IDOM/FNDF)仍适用,但可进一步增加IDOM中的淀粉调控。     

Methodological impact of starch determination on starch content and ileal digestibility of starch in grain legumes for growing pigs

Background: Grain legumes represent a valuable energy source in pig diets due to their high starch content. The present study was conducted to determine the content and apparent ileal digestibility(AID) of starch in different grain legume cultivars for pigs by means of both a polarimetric and enzymatic method for starch determination.Methods: Three experiments were conducted with six barrows each which were fitted with ileal T-cannulas. In total, 18 diets including six different cultivars of faba beans(Vicia faba L.) and peas(Pisum sativum L.), five different cultivars of lupins(Lupinus luteus L., Lupinus angustifolius L.), and one diet with a soybean meal(SBM) were fed.Results: The starch content of faba beans and peas was greater(P 0.05) when determined polarimetrically than enzymatically(438 vs. 345 g/kg dry matter(DM) in faba beans and 509 vs. 390 g/kg DM in peas, respectively).Considerable lower starch contents were obtained in lupins and SBM, with 82 and 48 g/kg DM(analyzed polarimetrically) and 1.1 and 3 g/kg DM(analyzed enzymatically), respectively. Mean values for contents of neutral detergent fiber(NDF) and acid detergent fiber(ADF) in grain legumes ranged from 111 and 79 g/kg DM in peas to248 and 207 g/kg DM in lupins, respectively. Contents of condensed tannins in the colored flowered faba bean cultivars ranged from 2.1 to 7.4 g/kg DM. The AID of starch was greater(P 0.05) in pea than in faba bean cultivars,and using the polarimetric starch determination method resulted in greater(P 0.05) digestibility values than using enzymatic starch analysis(84 vs. 80% in faba beans and 86 vs. 83% in peas). Moreover, AID of starch differed(P 0.05)within pea cultivars and starch digestibility in faba beans decreased linearly(P 0.05) as the content of condensed tannins increased. However, there was no relationship between contents of NDF and ADF and AID of starch in pea and faba bean cultivars.Conclusion: Both contents and AID of starch in grain legumes can vary as influenced by the analytical method used for starch determination. Generally, starch digestibility is greater when measured by polarimetric rather than enzymatic methods.     

Effects of six carbohydrate sources on dog diet digestibility and post-prandial glucose and insulin response

The effects of six extruded diets with different starch sources (cassava flour, brewer's rice, corn, sorghum, peas or lentils) on dog total tract apparent digestibility and glycemic and insulinemic response were investigated. The experiment was carried out on thirty-six dogs with six dogs per diet in a completely randomized design. The diets containing brewer's rice and cassava flour presented the greatest digestibility of dry matter, organic matter and gross energy (p < 0.05), followed by corn and sorghum; pea and lentil diets had the lowest. Starch digestibility was greater than 98% in all diets and was greater for brewer's rice and cassava flour than for lentils and peas diets (p < 0.05). Dogs' immediate post-prandial glucose and insulin responses (AUC < or = 30 min) were greater for brewer's rice, corn, and cassava flour diets (p < 0.05), and later meal responses (AUC > or = 30 min) were greater for sorghum, lentil and pea diets (p < 0.05). Variations in diet digestibility and post-prandial response can be explained by differences in chemical composition of each starch source including fibre content and starch granule structure. The nutritional particularities of each starch ingredient can be explored through diet formulations designed to modulate glycemic response. However, more studies are required to support these.     

蒸汽压片玉米加工工艺及其在肉牛生产中应用的研究进展

玉米是肉牛生产中的主要能量饲料,蒸汽压片处理可以提高玉米的淀粉消化率,并对玉米的淀粉糊化度和能值等产生一定影响,对肉牛的瘤胃发酵模式、生产性能、牛肉品质及其经济效益有积极的影响。本文综述了蒸汽压片技术、经蒸汽压片处理后玉米营养价值的变化以及饲喂蒸汽压片玉米对肉牛生产性能及肉品质影响等方面的研究进展,以期为蒸汽压片玉米在肉牛生产中的进一步推广应用提供参考。     

Performance and digestibility characteristics of finishing diets containing distillers grains, composites of corn processing coproducts, or supplemental corn oil

Three experiments evaluated the lipids in distillers grains plus solubles compared with corn or other sources of lipid in finishing diets. Experiment 1 utilized 60 individually fed yearling heifers (349 +/- 34 kg of BW) fed treatments consisting of 0, 20, or 40% (DM basis) wet distillers grains plus solubles (WDGS), or 0, 2.5, or 5.0% (DM basis) corn oil in a finishing diet based on high-moisture corn (HMC) and dry-rolled corn. Cattle fed 20 and 40% WDGS had greater (P < 0.10) G:F than cattle fed 0% WDGS. Cattle fed the 5.0% corn oil had less overall performance than cattle fed the other diets. Results from Exp. 1 indicated that adding fat from WDGS improves performance, whereas supplementing 5.0% corn oil depressed G:F, suggesting that the fat within WDGS is different than corn oil. Experiment 2 used 234 yearling steers (352 +/- 16 kg of BW) fed 1 of 5 treatments consisting of 20 or 40% (DM basis) dry distillers grains plus solubles, 1.3 or 2.6% (DM basis) tallow, or HMC. All diets contained 20% (DM basis) wet corn gluten feed as a method of controlling acidosis. No differences between treatments for any performance variables were observed in Exp. 2. The dry distillers grains plus solubles may be similar to tallow and HMC in finishing diets containing 20% wet corn gluten feed. Experiment 3 used 5 Holstein steers equipped with ruminal and duodenal cannulas in a 5 x 5 Latin square design. Treatments were a 40% WDGS diet, 2 composites, one consisting of corn bran and corn gluten meal; and one consisting of corn bran, corn gluten meal, and corn oil; and 2 dry-rolled corn-based diets supplemented with corn oil or not. Cattle fed the WDGS diet had numerically less rumen pH compared with cattle fed other treatments. Cattle fed WDGS had greater (P < 0.10) molar proportions of propionate, decreased (P < 0.10) acetate:propionate ratios, greater (P < 0.10) total tract fat digestion, and a greater (P < 0.10) proportion of unsaturated fatty acids reaching the duodenum than cattle fed other treatments. Therefore, the greater energy value of WDGS compared with corn may be due to more propionate production, greater fat digestibility, and more unsaturated fatty acids reaching the duodenum.     

调制方式对粮饲兼用型玉米肉牛瘤胃降解规律影响的研究

试验选同一玉米品种、地块,分别制作全株玉米青贮、玉米黄贮、玉米秸秆,利用尼龙袋试验研究其对肉牛瘤胃降解规律,为其在生产中有效利用提供依据.结果显示:全株玉米青贮干物质(DM)瘤胃快速降解部分a、慢速降解部分b、有效降解率(ERD)显著高于玉米秸秆(P＜0.05);全株玉米青贮和玉米黄贮粗蛋白(CP)瘤胃快速降解部分a和...     

Comparison of wheat or corn dried distillers grains with solubles on rumen fermentation and nutrient digestibility by feedlot heifers

A 5 × 5 Latin square design trial was conducted to evaluate rumen fermentation and apparent nutrient digestibility in 5 rumen-cannulated heifers (420 ± 6 kg) fed a barley-based finishing diet supplemented with 20 or 40% wheat or corn dried distillers grains with solubles (DDGS). The composition of the control diet was 88.7% rolled barley grain, 5.5% supplement, and 5.8% barley silage (DM basis). Increasing the quantity of corn DDGS in the ration resulted in a quadratic decrease in DMI (P = 0.04) and OM intake (P = 0.05). Rumen pH, pH duration, and area under rumen pH thresholds of 5.8 or 5.5 were not affected (P > 0.05) by treatment. Inclusion of wheat DDGS resulted in a quadratic increase (P = 0.05) in pH area below the cutoff value of 5.2, with the most pronounced effect at 20% inclusion. Wheat DDGS linearly increased (P = 0.01) rumen NH(3)-N concentrations. Increasing the inclusion rate of wheat and corn DDGS resulted in quadratic (P = 0.05) and linear (P = 0.04) decreases in rumen propionate, whereas butyrate increased quadratically (P < 0.01) and linearly (P < 0.01), respectively. Feeding wheat DDGS linearly decreased (P < 0.01) DM and OM digestibility values. Inclusion of corn DDGS increased the digestibility values of ether extract (P = 0.05; quadratic response) and CP (P < 0.01; linear response). Neutral detergent fiber digestibility increased in a linear fashion (P = 0.01) as both wheat and corn DDGS inclusion increased, whereas ADF digestibility increased linearly (P = 0.03) for wheat and quadratically (P = 0.02) for corn DDGS. Increased inclusion of wheat DDGS resulted in a linear decrease in GE digestibility (P = 0.01), whereas increasing corn DDGS inclusion linearly increased (P < 0.01) the DE content of the diet. Feeding both wheat and corn DDGS linearly increased (P = 0.01) the excretion of N and P. In summary, replacement of barley grain with up to 40% wheat or corn DDGS did not mitigate rumen pH conditions associated with mild to moderate acidosis in heifers fed a barley-based finishing diet. Supplementing corn DDGS increased nutrient digestibility of all nutrients and, as a result, led to greater DE content. Supplementation of wheat DDGS reduced DM and OM digestibility values, with no effect on DE content. Increased N and P excretion by heifers fed DDGS at 20 or 40% of dietary DM presents a challenge for cattle feeders with respect to nutrient management.     

3种不同瘤胃缓冲剂对肉牛消化利用的影响

[目的]评价3种瘤胃缓冲剂对肉牛的采食量和消化利用率的影响。[方法]试验对24头425 kg左右西门塔尔肉牛服用缓冲剂后的采食量、粪筛数据以及养分表观消化率进行分析。[结果]日粮中添加0.8%巴菲特处理的采食量较日粮中添加2%小苏打和1%瘤胃缓冲剂分别增加了2.6%和1.94%,日粮中添加0.8%巴菲特处理粪便筛上层、中层、下层占比试验后较试验前分别降低了44.7%,59.14%以及增高了55.92%。日粮中添加0.8%巴菲特处理肉牛的DM、GE、CP、NDF和ADF的表观消化率都有不同程度提高(P<0.05)。[结论]日粮中添加0.4%巴菲特瘤胃修复剂可提高肉牛的采食量,对其饲料表观消化率有明显的促进作用。     

Grain processing effects on starch utilization by ruminants

Starch utilization may be markedly enhanced by proper grain processing; however, extent of improvement is primarily dependent upon the ruminant species, grain source and method of processing. Grain processing has less impact on starch digestion by sheep than cattle. The magnitude of improvement is inverse to the starch digestion values for nonprocessed (or minimally processed) grains. Utilization of sorghum grain starch is improved most by extensive processing, and then corn, with little improvement in barley starch digestion. Studies comparing processing effects on barley or wheat starch utilization by cattle were not found. Steam-flaking consistently improves digestibility of starch by cattle fed corn- or sorghum grain-based diets over whole, ground or dry-rolled processes. Other extensive processing methods appear to enhance starch digestibility of corn and sorghum grain to a similar extent as steam-flaking, but comparative data are too limited to quantitate adequately effects of these methods. This improvement in starch utilization appears to be the primary reason for enhanced feed conversion of cattle fed diets high in these processed grains. The major site of cereal grain starch digestion is usually the rumen. Processing increases microbial degradation of starch in the rumen and decreases amounts of starch digested post-ruminally. Rates of in vitro amylolytic attack of starch in cereal grains by both ruminal microbial and pancreatic enzyme sources are improved by processing methods employing proper combinations of moisture, heat and pressure. In vitro and in situ studies suggest that much of the increase in ruminal starch fermentation with steam-flaking is due to changes in starch granular structure, which produces additive effects beyond those of decreasing particle size. Thus, efficiency of ruminal starch fermentation by cattle appears to be improved by proper processing of corn and sorghum grain. Processing and grain source studies both suggest that maximal total tract starch digestibility is positively related to the extent of digestion in the rumen.