Exposing ensiling forage to oxygen can result in dry matter deterioration and reduce silage intake by animals. This study was conducted to investigate the effects of two different wrapping sources and time intervals between baling and wrapping on N utilization in gestating sheep offered alfalfa silage. Alfalfa silage was baled in large round bales (moisture concentration = 591 ± 43.0 g/kg), then wrapped with plastic using either an enhanced oxygen-limiting barrier (EOB) or no additional barrier (conventional wrap; CW) on the day of baling or 1, 2 or 3 d after baling. After 5 months of storage, silages were chopped, then offered randomly for ad libitum consumption to 16 gestating ewes [63.5 ± 1.71 kg body weight] to provide 2 observations per treatment for each of 3 experimental total collection periods. Each study period consisted of a 10-d dietary adaptation period followed by 7 d of total fecal and urine collection. Blood was collected immediately prior to feeding and four hours after feeding on the last day of each period. Data were analyzed using PROC MIXED of SAS for a 2 × 4 factorial treatment arrangement, while blood data were treated as repeated measures. When expressed as a portion of total N, neutral detergent insoluble N (NDIN) content of silage increased (P ≤ 0.02) linearly and quadratically, and acid detergent insoluble N (ADIN) concentrations increased (P < 0.01) linearly with longer wrapping delays. Nitrogen apparent absorption (g/d and g/kg N intake) and urinary N (g/d) decreased (P ≤ 0.04) linearly with extended time delays between baling and wrapping. Retained N (g/kg of N intake and of absorbed N) was greater (P = 0.04) from silage wrapped with EOB. Blood urea N concentrations (mg/dL) decreased (P = 0.02) quadratically with extended delay between baling and wrapping. Digestion of NDIN (g/kg NDIN intake) increased (P = 0.03) linearly with extending time delay when silage was wrapped with EOB and linearly and quadratically (P < 0.01) when wrapped with CW. Digestion of ADIN increased (P = 0.02) quadratically with increasing delay between baling and wrapping averaged across wrap types. Therefore, management practices to limit oxygen exposure during packaging and ensiling can prevent a decline in N utilization by ruminants.

将青贮饲草暴露于氧气会导致干物质变质并减少动物摄入青贮饲料。进行这项研究以研究两种不同的包裹来源以及打包和包裹之间的时间间隔对提供苜蓿青贮的妊娠绵羊氮素利用的影响。将苜蓿青贮饲料打包成大捆（水分浓度为591±43.0 g / kg），然后在打包当天用增强的限氧屏障（EOB）或不使用其他屏障（常规包装； CW）将其用塑料包裹或打包后1、2或3 d。储存5个月后，将青贮饲料切碎，然后随机提供给16头妊娠母羊[63.5±1.71 kg体重]，以随意采食，以便在每个实验的3个实验总收集期中分别进行2次观察。每个研究阶段包括10天的饮食适应期，然后是7天的粪便和尿液收集总量。在每个时期的最后一天，在进食前和进食后四个小时采集血液。使用SAS的PROC MIXED对2×4阶乘处理方案进行数据分析，同时将血液数据作为重复测量。当表示为总氮的一部分时，青贮饲料中性洗涤剂的不溶氮（NDIN）含量增加（P ≤0.02）线性和二次曲线，和酸洗涤不溶N（ADIN）浓度的增加（P <0.01），线性长包裹延迟。氮表观吸收（克/ d和g /千克氮摄入）和尿N-（克/ d）降低（P ≤0.04）线性地打包和包装之间延长的时间延迟。包裹有EOB的青贮饲料的残留氮（g / kg氮摄入量和吸收的N）更大（P = 0.04）。血尿素氮浓度（mg / dL ）呈二次下降（P = 0.02），并且打包和包裹之间的延迟时间延长。当青贮饲料用EOB包裹时，NDIN的消化（克/千克NDIN摄入量）随着时间的延长线性增加（P = 0.03），并且线性和二次方增加（P<0.01）用CW包裹时。随着打包类型之间打包和打包之间的延迟增加，ADIN的消化率呈二次方增加（P = 0.02）。因此，在包装和封口过程中限制氧气暴露的管理措施可以防止反刍动物对氮的利用下降。