Vieira Daniel J C, Grigoletto Nathália T S, Poletti Guilherme, Chesini Rodrigo G, Diepersloot Evan C, Takiya Caio S, Ferraretto Luiz F, Rennó Francisco P
Department of Animal Production and Animal Nutrition, University of São Paulo, Pirassununga, 13635-900, Brazil.
Department of Dairy Science, University of Wisconsin-Madison, Madison, WI 53706.
J Dairy Sci. 2025 Aug;108(8):8462-8475. doi: 10.3168/jds.2025-26388. Epub 2025 Jun 11.
The objective of this study was to evaluate the effects of decreasing concentrations of undigested NDF after 288 h of incubation (uNDF288) in corn silage-based diets for dairy cows on nutrient intake and digestibility, feed sorting index, ingestive behavior, ruminal fermentation, milk yield, and milk composition. Twenty-four Holstein cows were used, including 8 primiparous and 16 multiparous cows, in a replicated 4 × 4 Latin square experiment. Cows were blocked based on milk yield (37.1 ± 4.28 kg/d), DIM (110 ± 60.0 d), and BW (669 ± 74.2 kg). Each period lasted 21 d, with the last 7 d designated for data collection. Treatments consisted of dietary uNDF at 11.1%, 10.4%, 9.7%, and 9.0% diet DM. The dietary uNDF concentration was manipulated by ensiling corn plants cut at 40 cm and 65 cm above the ground, provided in different proportions in the diet. Increasing the cutting height of corn silage from 40 to 65 cm resulted in a reduction in the uNDF288 concentration from 21.2% to 16.8% DM, and increased estimated in vitro ruminal NDF digestibility and total-tract NDF digestibility for silage with a cutting height of 65 cm. Results showed that reducing dietary uNDF concentration linearly increased intake and apparent total-tract digestibility of DM, OM, CP, and NDF. Cows fed diets with greater uNDF concentration rejected larger particles, whereas lower uNDF diets tended to decrease ruminal ammonia concentration. Milk yield and FCM yield increased linearly with decreasing diet uNDF. A 1 unit increase in uNDF was negatively associated with -0.59 kg/d in DMI and -0.48 kg/DIM yield and -0.75 kg/d in FCM yield, as well as decreases of 1.79% in DM digestibility and 1.73% in amylase-treated NDF digestibility. In conclusion, reducing the dietary uNDF concentration from 11.1% to 9.0% improved performance due to increased nutrient intake and digestibility, as well as altering the ruminal fermentation.
本研究的目的是评估在以玉米青贮为基础的奶牛日粮中，将288小时培养后的未消化中性洗涤纤维（uNDF288）浓度降低，对营养物质摄入量和消化率、饲料分选指数、采食行为、瘤胃发酵、产奶量和牛奶成分的影响。在一项重复的4×4拉丁方试验中，使用了24头荷斯坦奶牛，其中包括8头初产奶牛和16头经产奶牛。根据产奶量（37.1±4.28千克/天）、泌乳天数（110±60.0天）和体重（669±74.2千克）对奶牛进行分组。每个试验期持续21天，最后7天用于数据收集。处理组日粮的uNDF含量分别为日粮干物质的11.1%、10.4%、9.7%和9.0%。通过青贮不同比例的、分别从地面以上40厘米和65厘米处刈割的玉米植株，来调控日粮中的uNDF浓度。将玉米青贮的刈割高度从40厘米提高到65厘米，导致uNDF288浓度从干物质的21.2%降至16.8%，并提高了65厘米刈割高度青贮料的体外瘤胃中性洗涤纤维消化率和全消化道中性洗涤纤维消化率的估计值。结果表明，降低日粮uNDF浓度可使干物质、有机物、粗蛋白和中性洗涤纤维的摄入量和表观全消化道消化率呈线性增加。采食较高uNDF浓度日粮的奶牛会拒绝较大颗粒，而较低uNDF日粮往往会降低瘤胃氨浓度。产奶量和乳脂校正乳产量随日粮uNDF的降低呈线性增加。uNDF每增加1个单位，干物质采食量下降0.59千克/天，日产奶量下降0.48千克，乳脂校正乳产量下降0.75千克/天，干物质消化率下降1.79%，淀粉酶处理的中性洗涤纤维消化率下降1.73%。总之，将日粮uNDF浓度从11.1%降至9.0%可提高生产性能，这是由于营养物质摄入量和消化率增加，以及瘤胃发酵改变所致。
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