Arthington J D, Rechcigl J E, Yost G P, McDowell L R, Fanning M D
University of Florida, Range Cattle Research and Education Center, Ona 33865, USA.
J Anim Sci. 2002 Oct;80(10):2507-12. doi: 10.2527/2002.80102507x.
To assess the impact of S fertilization on bahiagrass (Paspalum notatum) quality and Cu metabolism in cattle, two studies were conducted during the summer grazing season (1999 and 2000). Pasture replicates (16.2 ha; n = 2/treatment) received the same fertilizer treatment in each growing season, consisting of 1) 67 kg N/ha from ammonium sulfate (AS), 2) 67 kg N/ha from ammonium nitrate (AN), and 3) control (no fertilizer; C). Forage sampling was conducted at 28-d intervals following fertilization by the collection of whole plants (four samples/pasture) in randomly distributed 1-m2 grazing exclusion cages and analyzed for CP, in vitro organic matter digestibility, S, P, Ca, K, Mg, Na, Fe, Al, Mn, Cu, and Zn. To determine the effect of fertilizer treatment on liver trace mineral concentrations in grazing cattle, random liver tissue samples were collected (n = 12; four/treatment) at the start and end of the study period in 2000. Ammonium sulfate fertilization increased (P < 0.001) forage S concentration in both years. Plant tissue N concentrations were increased by N fertilization, regardless of source, in 2000, but not in 1999. Cows grazing AS pastures had lower (P < 0.05) liver Cu concentrations at the end of the study period in 2000 compared to AN and C. In Exp. 2, 37 Cu-deficient heifers grazing AS fertilized pastures were obtained from the same location and allocated to one of two treatments, consisting of supplements providing 123 mg/d of either inorganic (Cu sulfate; n = 12) or organic (Availa-Cu; n = 15) Cu. Treatments were delivered for 83 d. Liver Cu increased over time in all heifers regardless of treatment; however, heifers supplemented with Availa-Cu tended (P = 0.09) to have higher mean liver Cu concentrations than those receiving Cu sulfate. The results of these studies indicate that AS fertilization of bahiagrass increases forage S concentrations. When provided free-choice access to a complete salt-based trace mineral supplement, cows grazing AS-fertilized pastures had lower liver Cu concentrations than cows grazing pastures fertilized with AN; upon removal from high-S pastures, cattle were able to respond to Cu supplementation.
为评估施硫肥对牛鞭草（雀稗）品质及牛体内铜代谢的影响，于夏季放牧季节（1999年和2000年）开展了两项研究。每个生长季，牧场重复区（16.2公顷；每个处理n = 2）接受相同的施肥处理，包括：1）硫酸铵提供67千克氮/公顷（AS）；2）硝酸铵提供67千克氮/公顷（AN）；3）对照（不施肥；C）。施肥后每隔28天进行一次牧草采样，通过在随机分布的1平方米放牧排除笼中采集整株植物（每个牧场4个样本），并分析其粗蛋白（CP）、体外有机物消化率、硫、磷、钙、钾、镁、钠、铁、铝、锰、铜和锌。为确定施肥处理对放牧牛肝脏微量矿物质浓度的影响，在2000年研究期开始和结束时采集随机的肝脏组织样本（n = 12；每个处理4个）。两年中，硫酸铵施肥均提高了（P < 0.001）牧草硫浓度。2000年，无论氮源如何，施氮肥均提高了植物组织氮浓度，但1999年未出现这种情况。与AN和C处理相比，2000年研究期末，放牧于AS处理牧场的奶牛肝脏铜浓度较低（P < 0.05）。在实验2中，从同一地点获取37头铜缺乏的小母牛，它们放牧于施AS肥的牧场，并分配到两种处理之一，即分别提供每日123毫克无机铜（硫酸铜；n = 12）或有机铜（Availa-Cu；n = 15）的补充剂。处理持续83天。无论处理方式如何，所有小母牛的肝脏铜含量均随时间增加；然而，补充Availa-Cu的小母牛肝脏铜平均浓度往往（P = 0.09）高于补充硫酸铜的小母牛。这些研究结果表明，牛鞭草施AS肥可提高牧草硫浓度。当自由选择获取完整的盐基微量矿物质补充剂时，放牧于施AS肥牧场奶牛的肝脏铜浓度低于放牧于施AN肥牧场的奶牛；从高硫牧场转移后，牛能够对铜补充做出反应。
