The competitiveness and sustainability of low input cost dairy production systems are generally supported by efficient use of pasture in the diets. Therefore, pasture intake directly affects overall efficiency of these systems. We aimed to assess feeding and grazing management main factors that affect pasture dry matter intake (DMI) in commercial dairy farms during the different seasons of the year. Fortnightly visits to 28 commercial dairies were carried out between June 2016 and May 2017 to record production and price, supplement offered and price, pasture access time (PAT), herbage mass (HM) and allowance (HA). Only farms with the most contrasting estimated pasture DMI per cow (eDMI) were compared as systems with high (HPI; N = 8) or low (LPI; N = 8) pasture DMI. Despite a lower individual milk production in HPI than LPI (19.0 v. 23.3 ± 0.7 l/cow, P < 0.01), daily margin over feeding cost was not different between groups (3.07 v. 2.93 ± 0.15 U$S/cow for HPI and LPI, respectively). During autumn and winter, HPI cows ingested more pasture than LPI cows (8.3 v. 4.6 and 5.9 v. 2.9 ± 0.55 kg DM/cow per day, respectively, P < 0.01) although PAT, HM and HA were similar between groups. Both groups offered high supplementation levels during these seasons, even though greater in LPI than HPI (14.7 v. 9.7 ± 0.7 kg DM supplement/cow per day, respectively, P < 0.01). On the other hand, differences between groups for both pasture and supplement DMI were more contrasting during spring and summer (13.1 v. 7.3 ± 0.5 and 4.0 v. 11.4 ± 0.4 kg DM/cow per day for HPI and LPI, respectively, P < 0.01), with higher PAT in both seasons (P < 0.05) and higher HA during summer in HPI than LPI (P < 0.01). Unlike LPI, during these seasons HPI adjusted offered supplement according to HA, achieving a higher pasture eDMI and making more efficient use of available pastoral resource than LPI. As there was no grazing limiting condition for pasture harvesting in either group, the main factor affecting pasture DMI was a pasture by supplement substitution effect. These results reinforce the importance of an efficient grazing management, and using supplements to nutritionally complement pasture intake rather than as a direct way to increase milk production.

中文翻译：

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在集约化乳制品生产系统中，每头母牛的牧场干物质摄入量：放牧和饲喂管理的影响。

低投入成本的乳制品生产系统的竞争力和可持续性通常受到牧场中饲料有效利用的支持。因此，牧草的摄入量直接影响这些系统的整体效率。我们旨在评估一年中不同季节影响商业奶场牧场干物质摄入量（DMI）的进食和放牧管理主要因素。在2016年6月至2017年5月期间，每两周对28个商业奶牛场进行了访问，以记录产量和价格，提供的补充品和价格，牧场使用时间（PAT），牧草质量（HM）和津贴（HA）。仅将每头牛的牧场DMI估计值差异最大的农场与具有高（HPI; N = 8）或低（LPI; N = 8）牧场DMI的系统进行比较。尽管HPI中的单乳产量低于LPI（19.0 v。23.3±0。7 l /牛，P <0.01），日均饲喂成本利润在两组之间没有差异（HPI和LPI分别为3.07 v。2.93±0.15 U / S）。在秋季和冬季，尽管两组之间的PAT，HM和HA相似，但HPI牛比LPI牛（分别为8.3 v。4.6和5.9 v。2.9±0.55 kg DM /牛/天，P <0.01）摄入更多的牧草。两组在这些季节均提供高水平的补充，即使LPI高于HPI（分别为每天14.7 v。9.7±0.7 kg DM补充/牛，P <0.01）。另一方面，春季和夏季，牧草和补充DMI的组间差异更大（HPI和LPI分别为每天13.1 v。7.3±0.5和4.0 v。11.4±0.4 kg DM /牛，P < 0.01），两个季节的PAT均较高（P <0。05）且HPI夏季的HA高于LPI（P <0.01）。与LPI不同，在这些季节中，HPI根据HA调整了提供的补品，与LPI相比，获得了更高的牧场eDMI并更有效地利用了可用的牧草资源。由于两组都没有放牧限制牧草的条件，因此影响牧草DMI的主要因素是补给替代效应的牧草。这些结果加强了有效放牧管理的重要性，并使用补品来补充牧草的营养，而不是直接增加牛奶产量。由于两组都没有放牧限制牧草的条件，因此影响牧草DMI的主要因素是补给替代效应的牧草。这些结果加强了有效放牧管理的重要性，并使用补品来补充牧草的营养，而不是直接增加牛奶产量。由于两组都没有放牧限制牧草的条件，因此影响牧草DMI的主要因素是补给替代效应的牧草。这些结果加强了有效放牧管理的重要性，并使用补品来补充牧草的营养，而不是直接增加牛奶产量。