Apparent zinc absorption: a comparison between Ayrshire and Holstein lactating cows - Raw data

There is a lack of data about potential differences in trace mineral absorption within dairy cow breeds. The objective of this study was to evaluate if apparent zinc absorption between Ayrshire and Holstein lactating cows differs. A total of 12 multiparous cows (6 Ayrshire and 6 Holstein) were used in a replicated 3 × 3 Latin square design with periods of 35-d duration (26 d of diet adaptation followed by data collection). Daily intake and total faeces collection were performed on 7 consecutive days. Daily samples of total mixed ration, refusals, and faeces were composited by week and analysed for zinc concentration by atomic absorption spectrometry. Apparent absorption was calculated as daily dietary intake minus excretion in faeces over dietary intake. The percentage of inclusion of the mineral and vitamin supplement was 1.56% and 1.47% for Ayrshire and Holstein cows, respectively, accounting for different milk production, body weight, and dry matter intake between the 2 breeds. Dry matter intake of Ayrshire cows averaged 20.5 (SE: 0.8) kg/d and 25.8 (SE: 0.8) kg/d for Holstein cows resulting in a tendency for Holstein cows to ingest greater quantity of zinc. Zinc excretion was significantly greater for Holstein cows compared to Ayrshire cows but this was not translated into different retention or apparent absorption. Averaged apparent zinc absorption did not differ between breeds and was 21% and 16% for Ayrshire and Holstein, respectively, with a variation from -15 to 31%, regardless of the breed. In summary, averaged apparent zinc absorption was similar to the values reported in the literature. However, under the current experimental conditions, the technique using dietary intake minus faecal output to measure apparent zinc absorption led to an important variation between animals.

关于不同奶牛品种间微量元素吸收差异的数据匮乏。本研究旨在评估艾尔夏和荷斯坦泌乳奶牛之间锌的表观吸收是否存在差异。研究采用了一个重复的3×3拉丁方设计，周期为35天（包括26天的饮食适应期和随后的数据收集），共使用了12头经产奶牛（6头艾尔夏和6头荷斯坦）。在连续7天内，对每日的饲料摄入量和总粪便进行了收集。每周对全混合日粮、拒食物和粪便样本进行复合，并利用原子吸收光谱法分析锌浓度。表观吸收计算为每日饲料摄入量减去粪便排泄量。矿物质和维生素补充剂的添加比例分别为艾尔夏和荷斯坦奶牛的1.56%和1.47%，这一比例考虑到了两个品种间的不同产奶量、体重和干物质摄入量。艾尔夏奶牛的干物质摄入量平均为20.5（标准误：0.8）千克/日，而荷斯坦奶牛为25.8（标准误：0.8）千克/日，这导致荷斯坦奶牛摄入的锌量更多。与艾尔夏奶牛相比，荷斯坦奶牛的锌排泄量显著增加，但这并未转化为不同的保留或表观吸收。平均表观锌吸收在两个品种间无显著差异，分别为艾尔夏和荷斯坦奶牛的21%和16%，变化范围为-15%至31%，不受品种影响。总之，平均表观锌吸收与文献报道的值相似。然而，在当前实验条件下，使用饲料摄入量减去粪便输出量来测量表观锌吸收的技术在动物之间导致了重要的变异。