Daniel Jean-Baptiste, Brugger Daniel, van der Drift Saskia, van der Merwe Deon, Kendall Nigel, Windisch Wilhelm, Doelman John, Martín-Tereso Javier
Trouw Nutrition R&D, Amersfoort, the Netherlands.
Institute of Animal Nutrition and Dietetics, Vetsuisse-Faculty, University of Zurich, Zurich, Switzerland.
J Nutr. 2023 Apr;153(4):1008-1018. doi: 10.1016/j.tjnut.2023.02.022. Epub 2023 Feb 21.
Trace metals are supplemented in cattle to prevent nutrient deficiencies. Levels supplemented to mitigate worst-case basal supply and availability scenarios can, however, result in trace metal intakes far above the nutritional requirements of dairy cows with high feed intakes.
We evaluated Zn, Mn, and Cu balance in dairy cows from late lactation through the subsequent mid-lactation, a period of 24 wk characterized by large changes in dry matter intake.
Twelve Holstein dairy cows were housed in a tie-stall from 10 wk before to 16 wk after parturition and fed 1 unique lactation diet when lactating and a dry cow diet otherwise. After 2 wk of adaptation to the facility and diet, Zn, Mn, and Cu balances were determined at weekly intervals, by calculating the difference between total intakes and complete fecal, urinary, and milk outputs, with the latter 3 fluxes quantified over a 48-h period. Repeated measure mixed models were used to evaluate the effects on trace mineral balances over time.
The Mn and Cu balances of cows were not significantly different from 0 mg/d between 8 wk prepartum and calving (P ≥ 0.54), when dietary intake was the lowest of the period evaluated. However, when dietary intake was highest, between wk 6 and 16 postpartum, positive Mn and Cu balances were observed (80 and 20 mg/d, respectively, P ≤ 0.05). Cows were in positive Zn balance throughout the study except during the first 3 wk after calving during which the Zn balance was negative.
Large adaptations occur in trace metal homeostasis in transition cows in response to changes in dietary intake. High dry matter intakes, associated with high milk production of dairy cows, combined with current Zn, Mn, and Cu supplementation practices may exceed regulatory homeostatic mechanisms resulting in potential body accumulation of Zn, Mn, and Cu.
在牛的饲养中添加微量金属以预防营养缺乏。然而，为缓解最坏情况下的基础供应和可利用性情况而添加的水平，可能导致采食量高的奶牛微量金属摄入量远高于营养需求。
我们评估了从泌乳后期到随后的泌乳中期（为期24周，其特征是干物质摄入量有很大变化）的奶牛锌、锰和铜平衡情况。
12头荷斯坦奶牛在分娩前10周开始至分娩后16周被关在栓系牛舍中，泌乳期饲喂1种独特的泌乳日粮，其他时间饲喂干奶牛日粮。在适应设施和日粮2周后，通过计算总摄入量与粪便、尿液和牛奶总排出量之间的差值来确定锌、锰和铜的平衡，后3种排出量在48小时内进行定量。使用重复测量混合模型来评估随时间对微量矿物质平衡的影响。
在产前8周和产犊期间，日粮摄入量是评估期间最低的时候，奶牛的锰和铜平衡与0毫克/天无显著差异（P≥0.54）。然而，当产后第6周至16周日粮摄入量最高时，观察到锰和铜呈正平衡（分别为80和20毫克/天，P≤0.05）。除产犊后的前3周锌平衡为负外，在整个研究过程中奶牛的锌平衡均为正。
围产期奶牛的微量金属稳态会随着日粮摄入量的变化而发生很大的适应性变化。与奶牛高产奶量相关的高干物质摄入量，再加上目前锌、锰和铜的补充方式，可能会超出调节性稳态机制，导致锌、锰和铜在体内潜在蓄积。
