Barajas R, Zinn R A
Department of Animal Science, Desert Research and Extension Center, University of California, El Centro 92243, USA.
J Anim Sci. 1998 Jul;76(7):1744-52. doi: 10.2527/1998.7671744x.
We used 80 medium-framed yearling crossbred heifers (357 kg) in a 110-d trial to evaluate the influence of dietary protein level (11 vs 14%) on the feeding value of dry-rolled (DRC) and steam-flaked corn (SFC). All diets contained 1% urea; cottonseed meal (CSM) was the source of supplemental undegradable intake protein (UIP). Steam flaking corn reduced DMI (9%, P < .10) and increased (P < .01) feed efficiency (14%), dietary NEm (13%), and NEg (15%). Steam flaking increased the NEm by 17% and NEg by 19%. Supplemental CSM decreased (P < .10) feed efficiency (7%) and dietary NEm (4%) and NEg (6%). There were no treatment effects (P > .10) on carcass characteristics. Steam flaking corn increased (P < .05) fecal pH and reduced (P < .01) fecal starch. Supplemental CSM increased (P < .01) fecal pH and reduced (P < .01) fecal starch. Four Holstein steers (413 kg) were used in a 4 x 4 Latin square experiment to evaluate treatment effects on digestive function. Steam flaking corn increased (P < .05) flow of nonammonia N (11%, P < .05) and microbial N (15%, P < .01) to the duodenum. Supplemental CSM increased the flow of microbial N (6%, P < .01), feed N (21%, P < .10), and nonammonia N (12%, P < .05) to the duodenum. The UIP value of CSM was 28% for the DRC diet and 52% for the SFC diet. Steam flaking corn increased (P < .01) ruminal starch digestion (26%) and total tract digestibility of OM (17%), N (15%), starch (19%), and GE (17%). Steam flaking increased the DE value of corn by 21%. Supplemental CSM did not influence (P > .10) postruminal or total tract starch digestion. Supplemental CSM decreased (7%, P < .10) the DE value of the diet. We conclude that increasing the postruminal protein supply of a corn-based finishing diet beyond that provided by urea supplementation, alone, will not enhance starch digestion or the energy value of the diet.
我们在一项为期110天的试验中使用了80头中等体格的一岁杂交小母牛（体重357千克），以评估日粮蛋白质水平（11%对14%）对干碾压玉米（DRC）和蒸汽压片玉米（SFC）饲喂价值的影响。所有日粮均含有1%的尿素；棉籽粕（CSM）是补充不可降解摄入蛋白（UIP）的来源。蒸汽压片玉米降低了干物质采食量（9%，P < 0.10）并提高了（P < 0.01）饲料效率（14%）、日粮净能（NEm，13%）和净能（NEg，15%）。蒸汽压片使NEm提高了17%，NEg提高了19%。补充CSM降低了（P < 0.10）饲料效率（7%）、日粮NEm（4%）和NEg（6%）。对胴体特征没有处理效应（P > 0.10）。蒸汽压片玉米提高了（P < 0.05）粪便pH值并降低了（P < 0.01）粪便淀粉含量。补充CSM提高了（P < 0.01）粪便pH值并降低了（P < 0.01）粪便淀粉含量。使用4头荷斯坦公牛（体重413千克）进行了4×4拉丁方试验，以评估处理对消化功能的影响。蒸汽压片玉米增加了（P < 0.05）非氨氮（11%，P < 0.05）和微生物氮（15%，P < 0.01）向十二指肠的流量。补充CSM增加了微生物氮（6%，P < 0.01）、饲料氮（21%，P < 0.10）和非氨氮（12%，P < 0.05）向十二指肠的流量。对于DRC日粮，CSM的UIP值为28%，对于SFC日粮为52%。蒸汽压片玉米提高了（P < 0.01）瘤胃淀粉消化率（26%）以及有机物（OM，17%）、氮（15%）、淀粉（19%）和总能（GE，17%）的全肠道消化率。蒸汽压片使玉米的消化能（DE）值提高了21%。补充CSM对瘤胃后或全肠道淀粉消化没有影响（P > 0.10）。补充CSM降低了（7%，P < 0.10）日粮的DE值。我们得出结论，在基于玉米的育肥日粮中，仅靠增加瘤胃后蛋白质供应超过尿素补充所提供的量，不会提高淀粉消化率或日粮的能量值。
