Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Edgmond, Newport, Shropshire, TF10 8NB, United Kingdom.
Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Edgmond, Newport, Shropshire, TF10 8NB, United Kingdom.
J Dairy Sci. 2020 Oct;103(10):9024-9036. doi: 10.3168/jds.2020-18453. Epub 2020 Aug 6.
To test the hypothesis that Cu metabolism in dairy cows is affected by dietary starch concentration and additional sulfur S and Mo, 60 Holstein-Friesian dairy cows that were [mean ± standard error (SE)] 33 ± 2.5 days postcalving and yielding 41 ± 0.9 kg of milk/d were fed 1 of 4 diets in a 2 × 2 factorial design experiment over a 14-wk period. The 4 diets had a Cu concentration of approximately 15 mg/kg of dry matter (DM), a grass silage-to-corn silage ratio of 1:1, a dietary starch concentration of either 150 g/kg of DM (low starch, LS) or 220 g/kg of DM (high starch, HS), and were either unsupplemented (-) or supplemented (+) with an additional 0.8 g of S/kg of DM and 4.4 mg of Mo/kg of DM. We found an effect of dietary starch concentration on mean reticular pH, which was 0.15 pH units lower in cows fed the high starch diets. The addition of S and Mo decreased intake by 1.8 kg of DM/d, an effect that was evident beginning in wk 1 of the study. Mean milk and fat yields were 37.0 and 1.51 kg/d, respectively, and were not affected by dietary treatment. We found an effect of dietary starch concentration on milk protein concentration, protein yield, and urea nitrogen, which were increased by 2.8 g/kg, 0.09 kg/d, and 2.1 mg/dL, respectively, in cows fed the high starch diets. We found no effect of dietary treatment on either cow live weight or body condition. Mean plasma Cu, Fe, and Zn concentrations were 15.3, 42.1, and 14.4 µmol/L, respectively, and were not affected by dietary treatment. In contrast, we found an interaction between dietary starch concentration and Cu antagonists on plasma Mo, where feeding additional S and Mo increased plasma Mo to a greater extent when cows were offered the high versus low starch diet. We also found that increasing dietary starch concentration increased serum ceruloplasmin activity, but serum haptoglobin concentration was not affected by dietary treatment. The addition of S and Mo decreased hepatic Cu concentration, whereas in cows fed the higher dietary starch concentration, hepatic Cu concentration was increased over the period of our study. We concluded that increasing dietary starch concentration decreases rumen pH and increases milk protein yield and hepatic Cu concentration, whereas feeding additional S and Mo decreases intake and hepatic Cu concentration.
为了检验奶牛铜代谢是否受日粮淀粉浓度以及额外硫（S）和钼（Mo）影响的假设，选用 60 头泌乳期 33 ± 2.5 天、日产奶量 41 ± 0.9kg 的荷斯坦弗里生奶牛，在 14 周的试验期内进行 2×2 析因设计试验，日粮分为 4 种，每种日粮铜浓度约为 15mg/kg 干物质（DM），青贮玉米与青贮玉米的比例为 1:1，淀粉浓度分别为 150g/kg DM（低淀粉 LS）或 220g/kg DM（高淀粉 HS），并且分为不添加（-）或添加（+）额外 0.8g/kg DM 的 S 和 4.4mg/kg DM 的 Mo。我们发现日粮淀粉浓度对网胃 pH 平均值有影响，高淀粉日粮组的网胃 pH 平均值低 0.15 个单位。添加 S 和 Mo 使奶牛的干物质采食量减少 1.8kg/d，这一影响在研究的第 1 周就显现出来。奶牛的平均产奶量和乳脂率分别为 37.0kg/d 和 1.51kg/d，不受日粮处理的影响。我们发现日粮淀粉浓度对乳蛋白浓度、蛋白产量和尿素氮有影响，高淀粉日粮组的乳蛋白浓度、蛋白产量和尿素氮分别增加了 2.8g/kg、0.09kg/d 和 2.1mg/dL。我们发现日粮处理对奶牛活重或体况评分没有影响。血浆铜、铁和锌的浓度平均值分别为 15.3µmol/L、42.1µmol/L 和 14.4µmol/L，不受日粮处理的影响。相反，我们发现日粮淀粉浓度与铜拮抗剂对血浆钼有交互作用，当给奶牛提供高淀粉而非低淀粉日粮时，添加 S 和 Mo 会更大程度地增加血浆钼。我们还发现，增加日粮淀粉浓度会增加血清铜蓝蛋白活性，但血清结合珠蛋白浓度不受日粮处理的影响。添加 S 和 Mo 会降低肝脏铜浓度，而在高淀粉日粮组中，在研究期间肝脏铜浓度增加。我们的结论是，增加日粮淀粉浓度会降低瘤胃 pH 值，增加乳蛋白产量和肝脏铜浓度，而添加 S 和 Mo 则会降低采食量和肝脏铜浓度。
