The objective was to determine if Zn retention improved with supplemental Zn above recommended concentrations with increasing growth rate. Angus steers (n = 32; 309 ± 4.2 kg BW) with Genemax gain scores of 3, 4, or 5 were utilized in a 2 × 2 factorial arrangement (8 steers/treatment). Steers were blocked by BW within growing diets to one of two Zn strategies (ZNTRT) 1) no supplemental Zn (analyzed 36 mg Zn/kg DM; CON) or 2) supranutritional Zn (analyzed 153 mg Zn/kg DM; SUPZN), fed for 60-d and then assigned to a dietary energy strategy (ENERGY) to emulate two different growth rates representing ~1.5 kg ADG (LOW) or ~2 kg ADG (HI). Beginning on d-60, HI steers were transitioned to HI for 14-d. On d 74, steers (4 groups; 8 steers/group; 2 steers/treatment) moved to metabolism crates and adapted for 10-d, followed by 5-d of total fecal and urine collection. Data were analyzed as a 2 × 2 factorial in Proc Mixed of SAS with ZNTRT×ENERGY×group as random; steer was experimental unit. No ZNTRT and ENERGY interactions were detected ( 0.12). Dry matter digestibility tended to increase due to SUPZN ( 0.10). Water intake was lesser ( 0.03) in SUPZN vs. CON and LOW vs. HI; urine output tended ( 0.08) to decrease in LOW vs. HI. Copper apparent absorption was unaffected by ZNTRT ( 0.28), but Cu apparent absorption increased in LOW (22.1%) vs. HI (15.3%; 0.04). SUPZN increased ( 0.01) intake and retention of Zn (377 vs. 100 mg/d) and decreased Zn apparent absorption vs. CON (30.9 vs. 25.5%; 0.04). Zinc apparent absorption (32.3 vs. 24.1%) increased in LOW vs. HI ( 0.01). Zinc absorption and retention appear to be influenced by diet energy concentration and more positively impacted by LOW energy diet.
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机译：目的是确定随着生长速率的增加，锌的保留量是否超过建议的浓度，锌的保留量是否会提高。 Genemax增益得分分别为3、4或5的安格斯牛（n = 32； 309±4.2 kg BW）采用2×2因子布置（8牛/次）。生长日粮中的体重限制了对两种锌策略（ZNTRT）中的一种的ers牛皮：1）无补充锌（分析为36 mg Zn / kg DM； CON）或2）超营养锌（分析为153 mg Zn / kg DM； SUPZN），喂食60天，然后分配到饮食能量策略（ENERGY）以模拟两种不同的生长速率，分别代表〜1.5 kg ADG（LOW）或〜2 kg ADG（HI）。从d-60开始，HI转向转向HI，持续14天。在第74天，将ers牛皮（4组；每组8个ers牛皮；每处理2个ers牛皮）移至新陈代谢箱，并适应10天，然后收集5天的粪便和尿液。在SAS的Proc Mixed中，以ZNTRT×ENERGY×group为随机变量，以2×2析因分析数据。转向是实验单位。未检测到ZNTRT和能量相互作用（0.12）。由于SUPZN（0.10），干物质消化率趋于增加。 SUPZN与CON和LOW与HI相比，进水量更少（0.03）； LOW与HI相比，尿量倾向于降低（0.08）。铜的表观吸收率不受ZNTRT（0.28）的影响，但Cu的表观吸收率在LOW（22.1％）与HI（15.3％; 0.04）相比增加。 SUPZN增加（0.01）锌的摄入和保留（377 vs. 100 mg / d），而锌的表观吸收相对于CON降低（30.9 vs. 25.5％； 0.04）。 LOW与HI（0.01）相比，锌的表观吸收率提高了（32.3 vs. 24.1％）。锌的吸收和滞留似乎受饮食能量浓度的影响，而受低能量饮食的影响更大。
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