1Department of Animal Production,Welfare and Veterinary Sciences,Harper Adams University,Edgmond,Newport,ShropshireTF10 8NB,UK.
2School of Agriculture,Policy and Development,University of Reading,Earley Gate,Reading,RG6 6ARBerkshire,UK.
Animal. 2019 Mar;13(3):524-532. doi: 10.1017/S1751731118001568. Epub 2018 Jul 9.
The particle size of the forage has been proposed as a key factor to ensure a healthy rumen function and maintain dairy cow performance, but little work has been conducted on ryegrass silage (GS). To determine the effect of chop length of GS and GS:maize silage (MS) ratio on the performance, reticular pH, metabolism and eating behaviour of dairy cows, 16 multiparous Holstein-Friesian cows were used in a 4×4 Latin square design with four periods each of 28-days duration. Ryegrass was harvested and ensiled at two mean chop lengths (short and long) and included at two ratios of GS:MS (100:0 or 40:60 dry matter (DM) basis). The forages were fed in mixed rations to produce four isonitrogenous and isoenergetic diets: long chop GS, short chop GS, long chop GS and MS and short chop GS and MS. The DM intake (DMI) was 3.2 kg/day higher (P<0.001) when cows were fed the MS than the GS-based diets. The short chop length GS also resulted in a 0.9 kg/day DM higher (P<0.05) DMI compared with the long chop length. When fed the GS:MS-based diets, cows produced 2.4 kg/day more (P<0.001) milk than when fed diets containing GS only. There was an interaction (P<0.05) between chop length and forage ratio for milk yield, with a short chop length GS increasing yield in cows fed GS but not MS-based diets. An interaction for DM and organic matter digestibility was also observed (P<0.05), where a short chop length GS increased digestibility in cows when fed the GS-based diets but had little effect when fed the MS-based diet. When fed the MS-based diets, cows spent longer at reticular pH levels below pH 6.2 and pH 6.5 (P<0.01), but chop length had little effect. Cows when fed the MS-based diets had a higher (P<0.05) milk fat concentration of C18 : 2n-6 and total polyunsaturated fatty acids compared with when fed the GS only diets. In conclusion, GS chop length had little effect on reticular pH, but a longer chop length reduced DMI and milk yield but had little effect on milk fat yield. Including MS reduced reticular pH, but increased DMI and milk performance irrespective of the GS chop length.
草料的粒径被认为是确保健康瘤胃功能和维持奶牛生产性能的关键因素，但对黑麦草青贮（GS）的研究却很少。为了确定 GS 的切割长度和 GS:玉米青贮（MS）比例对奶牛生产性能、网胃 pH 值、代谢和采食行为的影响，采用 4×4 拉丁方设计，每个周期 28 天，选择 16 头经产荷斯坦弗里生奶牛进行 4 个周期的试验。黑麦草在两种平均切割长度（长和短）下收获和青贮，并在 GS:MS 比例（干物质（DM）基础上 100:0 或 40:60）下进行处理。将这些饲料混合在日粮中，制成四种等氮和等能的日粮：长切 GS、短切 GS、长切 GS 和 MS、短切 GS 和 MS。与 GS 基础日粮相比，奶牛饲喂 MS 日粮的干物质采食量（DMI）每天高出 3.2kg（P<0.001）。短切长度 GS 也使 DMI 每天增加 0.9kg（P<0.05），与长切长度相比。当饲喂 GS:MS 基础日粮时，奶牛的产奶量比仅饲喂 GS 日粮时每天多 2.4kg（P<0.001）。切割长度和饲草比例对产奶量存在互作（P<0.05），短切长度 GS 增加了饲喂 GS 但不饲喂 MS 日粮的奶牛的产奶量。DM 和有机物消化率也存在互作（P<0.05），短切长度 GS 增加了饲喂 GS 日粮的奶牛的消化率，但饲喂 MS 日粮时几乎没有影响。当饲喂 MS 日粮时，奶牛的网胃 pH 值低于 6.2 和 6.5 的时间更长（P<0.01），但切割长度影响不大。与仅饲喂 GS 日粮相比，饲喂 MS 日粮的奶牛的乳脂中 C18:2n-6 和总多不饱和脂肪酸的浓度更高（P<0.05）。总之，GS 的切割长度对网胃 pH 值影响不大，但较长的切割长度降低了 DMI 和产奶量，但对乳脂产量影响不大。添加 MS 降低了网胃 pH 值，但增加了 DMI 和产奶性能，而与 GS 的切割长度无关。
