Abstract：
The objective of this study was to describe the nutritional strategies used on Canadian dairy farms with automated milking systems (AMS), both at the feed bunk and the concentrate offered at the AMS, as well as to determine what dietary components and nutrients, as formulated, were associated with milk production and milking behaviors on those farms. Formulated diets (including ingredients and nutrient content) and AMS data were collected from April 1, 2019, until September 30, 2020, on 160 AMS farms (eastern Canada [East] = 8, Ontario [ON] = 76, Quebec [QC] = 22, and western Canada [West] = 54). Both partial mixed ration (PMR) and AMS concentrate samples were collected from May 1 to September 30, 2019, on 169 farms (East = 12, ON = 63, QC = 42, West = 52). We collected AMS milking data for 154 herds. For each farm (n = 161), milk recording data were collected and summarized by farm to calculate average milk yield and components. Multivariable regression models were used to associate herd-level formulated nutrient composition and feeding management practices with milk production and milking behavior. Milk yield (mean ± SD = 37.0 ± 0.3 kg/d) was positively associated with the PMR ether extract (EE) concentration (+0.97 kg/d per percentage point [p.p.] increase) and with farms that fed barley silage as their major forage source (n = 16; +2.18 kg/d) as compared with haylage (n = 42), whereas farms that fed corn silage (n = 96; +1.23 kg/d) tended to produce more milk than farms that fed haylage. Greater milk fat content (4.09 ± 0.28%) was associated with a greater PMR-to-AMS concentrate ratio (+0.02 p.p. per unit increase) and total diet net energy for lactation (+0.046 p.p. per 0.1 Mcal/kg increase), but a lesser percentage of NFC of the PMR (-0.016 p.p. per p.p. increase of NFC percentage). Milk protein content (3.38 ± 0.14%) was positively associated with the forage percentage of the PMR (+0.003 p.p. per p.p. increase of forage percentage) and the total diet starch percentage (+0.009 p.p. per p.p. increase of starch percentage), but was negatively associated with farms feeding corn silage (-0.1 p.p. compared with haylage) as their major forage. Greater milking frequency (2.77 ± 0.40 milkings/d) was observed on farms with free-flow cow traffic systems (+0.62 milkings/d) and was positively associated with feed push-up frequency (+0.013 milkings/d per additional feed push-up), but negatively associated with PMR NFC content and forage percentage of the total ration (-0.017 milkings/d per p.p. increase of forage percentage). Lastly, greater milking refusal frequency (1.49 ± 0.82 refusals/d) was observed on farms with free-flow cow traffic systems (+0.84 refusals/d) and farms feeding barley silage (+0.58 refusals/d) than with guided flow and farms feeding either corn silage or haylage, respectively. These data give insight into the ingredients, nutrient formulations and type of diets fed on AMS dairy farms across Canada and the association of those factors with milk production and milking behaviors.
摘要：
这项研究的目的是描述加拿大奶牛场使用自动挤奶系统（AMS）的营养策略，在饲料铺位和AMS提供的浓缩物上，以及确定哪些膳食成分和营养素，如制定的那样，与这些农场的牛奶产量和挤奶行为有关。配方饮食，包括成分和营养成分，从2019年4月1日至2020年9月30日，在160个AMS农场（加拿大东部[东部]=8，安大略省[ON]=76，魁北克[QC]=22，加拿大西部[西部]=54）收集了AMS数据。从2019年5月1日至9月30日，在169个农场（East=12，ON=63，QC=42，West=52）收集了部分混合日粮（PMR）和AMS浓缩样品。收集了154个畜群的AMS挤奶数据。对于每个农场(n=160)，收集牛奶记录数据并按农场汇总，以计算平均牛奶产量和成分。使用多变量回归模型将牛群水平的配方营养成分和喂养管理实践与牛奶生产和挤奶行为相关联。产奶量（37.0±0.3kg/d）与PMR醚提取物（EE）浓度（PMR％EE；每增加一个百分点（p.p.）0.97kg/d）呈正相关，并且与饲喂大麦青贮饲料作为其主要饲料来源的农场（n=16；2.18kg/d）相比，与干草（n=42）相比，而饲喂玉米青贮饲料的农场（n=96；1.23kg/d）往往比饲喂黑麦草的农场生产更多的牛奶。更高的乳脂含量（4.09±0.28％）与更高的PMR与AMS浓缩物比（每单位增加0.02pp.p.）和哺乳期总日粮净能量（每0.1Mcal/kg增加0.046p.p.）相关，但PMR的非纤维碳水化合物(NFC)%较低(-0.016p.p.每p.p.增加%NFC)。牛奶蛋白质含量（3.38±0.14％）与PMR的草料百分比（每p.p增加的草料百分比0.003p.p.）和总饮食淀粉百分比（每p.p.增加的淀粉百分比0.009p.但与饲喂玉米青贮饲料的农场呈负相关（与干草相比为-0.1p.p.）。在具有自由流动奶牛交通系统（0.62挤奶/d）的农场中观察到更高的挤奶频率（2.77±0.40挤奶/d），并且与饲料推进频率呈正相关（每次额外的饲料推进增加0.013挤奶/d），同时与PMRNFC含量和总日粮的草料百分比呈负相关（每p.p.增加-0.017次挤奶/d饲料百分比）。最后,在具有自由流动奶牛交通系统(+0.84拒绝/d)和饲喂大麦青贮饲料(+0.58拒绝/d)的农场中观察到更高的挤奶拒绝频率(1.49±0.82拒绝/d),分别。这些数据可以深入了解成分，加拿大AMS奶牛场的营养配方和饮食类型，以及这些因素与牛奶产量和挤奶行为的关系。
