Bohnert D W, Schauer C S, DelCurto T
Eastern Oregon Agriculture Research Center, Oregon State University, Burns 97720, USA.
J Anim Sci. 2002 Jun;80(6):1629-37. doi: 10.2527/2002.8061629x.
Two studies were conducted to determine the influence of CP degradability and supplementation frequency (SF) on ruminant performance and N efficiency. Treatments included an unsupplemented control (CON) and degradable intake protein (DIP; 82% of CP) or undegradable intake protein (UIP; 60% of CP) provided daily, every 3 d, or every 6 d. Seven wethers (36+/-1 kg BW) were used in the digestibility study with DIP and UIP treatments formulated to meet CP requirements. Eighty-four Angus x Hereford cows (512+/-42 kg BW) in the last third of gestation were used for the performance study. The DIP treatments were calculated to provide 100% of the DIP requirement and UIP treatments were provided on an isonitrogenous basis compared with DIP. Basal diets consisted of low-quality (5% CP) meadow hay. Forage DMI and N intake by lambs decreased (P < 0.05) linearly as SF decreased. Additionally, DMI, OM intake, N retention, N digestibility, and digested N retained were greater (P < 0.01) for supplemented wethers than for controls with no difference due to crude protein degradability. Nitrogen balance, DMI, and OM intake decreased linearly (P < 0.05) as SF decreased. Plasma urea (PU; mM) was measured over a 6-d period and supplemented lambs had increased (P < 0.01) PU compared with CON. Plasma urea linearly decreased (P < 0.01) as SF decreased. Pre- and postcalving (within 14 d and 24 h of calving, respectively) cow weight and body condition score change were more positive (P < 0.05) for supplemented groups than for controls. Results suggest CP supplements consisting of 20 to 60% UIP can be effectively used by ruminants consuming low-quality forage without adversely affecting N efficiency and animal performance, even when provided as infrequently as once every 6 d.
开展了两项研究以确定粗蛋白（CP）降解率和补充频率（SF）对反刍动物生产性能和氮效率的影响。处理方式包括不补充的对照组（CON）以及每日、每3天或每6天提供一次的可降解摄入蛋白（DIP；占CP的82%）或不可降解摄入蛋白（UIP；占CP的60%）。在消化率研究中使用了7只阉羊（体重36±1千克），DIP和UIP处理的配方满足CP需求。在性能研究中使用了84头处于妊娠后期三分之一阶段的安格斯×赫里福德母牛（体重512±42千克）。计算得出DIP处理提供100%的DIP需求量，与DIP相比，UIP处理在等氮基础上提供。基础日粮由低质量（5% CP）的草地干草组成。随着SF降低，羔羊的饲草干物质采食量（DMI）和氮摄入量呈线性下降（P < 0.05）。此外，补充组阉羊的DMI、有机物摄入量、氮保留量、氮消化率和消化氮保留量均高于（P < 0.01）对照组，且粗蛋白降解率无差异。随着SF降低，氮平衡、DMI和有机物摄入量呈线性下降（P < 0.05）。在6天时间内测量血浆尿素（PU；毫摩尔），与CON相比，补充组羔羊的PU升高（P < 0.01）。随着SF降低，血浆尿素呈线性下降（P < 0.01）。补充组母牛在产犊前（产犊前14天内）和产后（产犊后24小时内）的体重和体况评分变化比对照组更积极（P < 0.05）。结果表明，即使每6天仅提供一次，由20%至60% UIP组成的CP补充剂也可被采食低质量饲草 的反刍动物有效利用，且不会对氮效率和动物生产性能产生不利影响。
