The purpose of this study was to identify biomarkers for fresh grass-clover intake and determine the digestibility and energy value of fresh grass to estimate voluntary fresh grass-clover intake in sows kept on pasture according to organic production practice. A total of sixteen multiparous dry sows (Danish Landrace x Danish Yorkshire) were housed in metabolism cages for 2 periods of 5 d. To study dietary effects, sows were fed one of four mixed treatments where increasing proportions of a basal commercial organic sow compound feed was partly replaced with 0, 2, 4, or 6 kg fresh grass-clover collected 3 wk after the previous cut. Sows were fed similar amounts of metabolizable energy (ME). Total collection of urine and feces was performed on a daily basis for 5d, and blood samples were collected from the jugular vein on the last day of feeding. Plasma metabolites were analyzed using a non-targeted liquid chromatography-mass spectrometry (LCMS) approach. Analyzed plasma metabolites (area under the curve in arbitrary units from the LCMS) were screened for correlation with grass intake. Data on nutrient digestibility and plasma metabolites were analyzed using a MIXED procedure while accounting for repeated measurements. Apparent total tract digestibilities of dry matter, organic matter, nitrogen, and energy of fresh grass-clover were 72, 64, 71, and 68%, respectively, using the regression method. The N intake increased linearly with increasing fresh grass-clover intake (P < 0.001). There was no evidence of altered N deposition and N utilization in response to increasing grass intake (P > 0.05). There was a linear increase in plasma urea content (2.64 to 4.39 mM) when grass intake increased from 0 to 6 kg/d (P = 0.02). Plasma glucose, lactate, creatinine and NEFA, and triglycerides were not affected by increased grass-clover intake. The daily ME contribution from fresh grass-clover (MJ/d) was found to be highly positively correlated with plasma pipecolic acid (Y = 0.0289 X; r² = 0.91; P < 0.001) and a metabolite tentatively identified as plasma bisnorbiotin (Y = 0.482 X; r² = 0.92; P < 0.001). In conclusion, fresh grass-clover intake of sows was highly correlated with plasma pipecolic acid and plasma bisnorbiotin concentration and apparent total tract digestibility of DM, OM, N, and energy estimated for 100% fresh grass-clover intake in dry sows was 64 to 72% using the regression method.

这项研究的目的是确定鲜草三叶草摄入量的生物标志物，并确定鲜草的消化率和能量值，以根据有机生产实践估算草场饲养的母猪自愿摄入鲜草三叶草的摄入量。将总共​​十六只多头干母猪（Danish Landrace x Danish Yorkshire）关在新陈代谢笼中，为期2个5 d。为了研究饮食效果，给母猪喂食四种混合处理之一，其中增加比例的基础商业有机母猪复合饲料的一部分被之前切割后3周收集的0、2、4或6公斤新鲜草三叶草部分替代。给母猪饲喂相似量的代谢能（ME）。每天进行尿液和粪便的总收集，持续5天，在喂养的最后一天从颈静脉收集血样。使用非靶向液相色谱-质谱（LCMS）方法分析血浆代谢物。筛选分析的血浆代谢物（LCMS中任意单位的曲线下面积）与草摄入量的相关性。使用MIXED方法分析营养物消化率和血浆代谢物的数据，同时考虑重复测量。使用回归方法，表观总干物质，有机质，氮和新鲜草草三叶草的总消化率分别为72％，64％，71％和68％。氮的摄入量随着鲜草三叶草的摄入量的增加而线性增加（筛选分析的血浆代谢物（LCMS中任意单位的曲线下面积）与草摄入量的相关性。使用MIXED方法分析营养物消化率和血浆代谢物的数据，同时考虑重复测量。使用回归方法，表观总干物质，有机质，氮和新鲜草草三叶草的总消化率分别为72％，64％，71％和68％。氮的摄入量随着鲜草三叶草的摄入量的增加而线性增加（筛选分析的血浆代谢物（LCMS中任意单位的曲线下面积）与草摄入量的相关性。使用MIXED方法分析营养物消化率和血浆代谢物的数据，同时考虑重复测量。使用回归方法，表观总干物质，有机质，氮和新鲜草草三叶草的总消化率分别为72％，64％，71％和68％。氮的摄入量随着鲜草三叶草的摄入量的增加而线性增加（P <0.001）。没有证据表明，随着草摄入量的增加，氮的沉积和氮的利用发生了变化（P > 0.05）。当草摄入量从0千克/天增加到6千克/天时，血浆尿素含量呈线性增加（2.64至4.39 mM）（P  = 0.02）。血浆葡萄糖，乳酸盐，肌酐和NEFA以及甘油三酸酯不受草三叶草摄入量增加的影响。发现新鲜草草三叶草的每日ME贡献（MJ / d）与血浆哌考酸（Y = 0.0289 X; r ²  = 0.91; P <0.001）高度相关，初步确定为血浆双降生物素（Y = 0.482 X; r ²  = 0.92; P<0.001）。总之，母猪新鲜草三叶草的摄入量与血浆哌考酸和血浆双降生物素浓度以及表观DM，OM，N的表观总道消化率高度相关，估计干母猪100％新鲜草草三叶草摄入量的能量为64至72％使用回归方法。