At the start of lactation, a severe energy deficiency can have negative impacts on dairy cows’ performance and health. The objective of this 3 × 2 factorial study was to compare the effects of three concentrate (C) build-up strategies during transition period (C-21; C1; C+21) and two milking frequencies (M) during 1^st week of lactation (once vs. twice-daily milking; M1 vs. M2) on feed intake, milk yield, energy supply, body weight, body condition score, metabolic status, health, and fertility parameters.

During the three years of study, data were collected for 66 transition periods (N) from 37 individual animals (21 Holstein Friesian (HF) and 16 Austrian dual purpose Simmental animals (SI); 8 primiparous cows in each breed). Four weeks (1^st Nov., ±57.2 days) before expected calving date the animals were allocated randomly (balanced for parity, breed, calving date, insemination index in the previous breeding season and genetic merit) to one of three concentrate supplementation strategies (C) during the transition period (C-21; C+1; C+21; N=22 group⁻¹). Within these three C groups, half of the cows were either milked once (M1) or twice (M2) during 1^st week of lactation, and from 8 DIM onwards all cows were milked twice a day. All animals were offered a high-quality forage basal diet comprising hay and grass silage from four weeks before expected calving date until 98^th days in milk (DIM). In group C-21 the concentrate supplementation started 21 days (-21 days) before expected calving date and was increased (DIM -21 to -15) from 1.8 kg dry matter (DM) to 2.6 kg DM (DIM -14 to 1) until parturition; during the first 14 DIM concentrate supplementation was daily increased by 0.26 kg DM cattle⁻¹ from 2.6 to 5.9 kg DM and from 15 DIM onwards concentrate supply depended on actual milk yield of the individual cow. In group C+1 no concentrate was fed pre-partum, and from lactation day 1 onwards the same concentrate building up strategy and allocation was made as described for group C-21. In group C+21 the concentrate supplementation did not start until 21 DIM and from this point on the same concentrate build-up-strategy was implemented as described for group C+1, but with each phase delayed by 21 days.

Pre-calving feed and net energy intake (NEL) as well as net energy balance (EB) was significantly higher in C-21 compared to groups C+1 and C+21. During the first seven weeks of lactation C+21 groups (P<0.001) showed the significant lowest NEL intake, and for energy-corrected-milk (ECM) yield a tendency (P=0,067) for an interaction between C and M was found. In C-21 and C+1, cows in M1 had significantly lower ECM yields compared to cows in groups M2 (C-21: 22.5 and 25.0 kg/d; C+1: 20.3 and 26.1 kg/d in M1 und M2, respectively); in C+21, ECM yield differed only numerically between M1 (22.1 kg/d) and M2 (23.9 kg/d). Cows in M1 showed in all C groups higher milk protein contents and higher somatic cell counts compared to M2; no significant C x M interactions were found. Within all concentrate supplementation strategies, cows in M1 showed higher EB during lactation weeks 1 to 7, within C groups the differences between M1 and M2 were significant in C-21 (C-21M1 +4.8 and -4.2 MJ NEL/d) and C+1 (C+1M1 +7.8 and -4.7 MJ NEL/d), in C+21 groups only numerical differences were found (C+21M1 -2.1 and C+21M2 -8.1 MJ NEL/d). During the first six weeks of lactation, the lowest blood glucose concentrations were detected in C+21 (2.80 in C+21M1 and 2.68 mmol/l in C+21M2). For nonesterified fatty acids concentration (NEFA) a significant interaction between C and M treatment was found (P_CxM<0.001), within C-21 and C+1 groups cows in M1 showed significantly lower NEFA concentrations compared to M2 groups, in C+21 NEFA concentration were higher in M1. The significant highest ß-hydroxybutyric acid concentrations (BHBA) were found in C+21 groups with 0.80 and 0.92 mmol/l in M1 and M2, respectively, between C-21 and C+1 no significant BHBA concentration differences were found in both milking groups. Cows in M1 require fewer veterinary treatments, were significantly earlier inseminated, but the first service conception rate and the total number of services per conception varied not significantly between groups. In conclusion, a delayed concentrate supplementation to 21 DIM (C+21) reduced energy intake and showed negative effects on EB and metabolic parameters. Once a day milking up to 7 DIM (M1) had no effect on energy intake, reduced ECM yield and improved EB and metabolic parameters in the first seven weeks of lactation. Also M1 reduced total number of veterinary treatments, led to earlier inseminations, had no effects on the other measured reproduction parameter, and increased somatic cell counts (SCC).

在泌乳开始时，严重的能量缺乏会对奶牛的生产性能和健康产生负面影响。这项 3 × 2 析因研究的目的是比较过渡期（C-21；C1；C+21）和两种挤奶频率（M）在过渡期（C-21；C1；C+21）和第二周^第1哺乳期（一次与每天两次挤奶；M1 与 M2）对采食量、产奶量、能量供应、体重、身体状况评分、代谢状态、健康和生育参数的影响。

在三年的研究期间，从 37 只个体动物（21 只荷斯坦弗里斯兰 (HF) 和 16 只奥地利双重用途西门塔尔动物 (SI)；每个品种 8 头初产奶牛）收集了 66 个过渡期 (N) 的数据。在预计产犊日期前4 周（11 月1^日，±57.2天），将动物随机分配（平衡胎次、品种、产犊日期、前一个繁殖季节的授精指数和遗传价值）到三种浓缩补充策略之一（ C)在过渡期(C-21；C+1；C+21；N=22组^-1 )。在这三个C三组，奶牛的一半或者在1个挤奶一次（M1）或两次（M2）^ST泌乳周，从 8 点开始，所有奶牛每天挤奶两次。从预计产犊日期前 4 周到牛奶中的^第98天（DIM），向所有动物提供包括干草和青贮青贮饲料的高质量草料基础日粮。在 C-21 组中，在预计产犊日期前 21 天（-21 天）开始补充浓缩物，并从 1.8 kg 干物质（DM）增加（DIM -21 至 -15）至 2.6 kg DM（DIM -14 至 1）直到分娩；在前 14 天，每天添加 0.26 kg DM 牛^-1从 2.6 到 5.9 kg DM 以及从 15 DIM 开始的浓缩供应取决于每头奶牛的实际产奶量。在 C+1 组中，没有在产前喂食浓缩物，并且从泌乳第 1 天开始，按照 C-21 组所述的相同的浓缩物建立策略和分配进行。在 C+21 组中，直到 21 DIM 才开始补充浓缩物，从这一点开始，按照 C+1 组所述实施相同的浓缩物积累策略，但每个阶段都延迟了 21 天。

与 C+1 和 C+21 组相比，C-21 组的产犊前饲料和净能量摄入量 (NEL) 以及净能量平衡 (EB) 显着更高。在哺乳的前七周，C+21 组 (P<0.001) 显示出显着最低的 NEL 摄入量，并且对于能量校正奶 (ECM) 产量而言，发现 C 和 M 之间存在相互作用的趋势 (P=0,067) . 在 C-21 和 C+1 中，与 M2 组的奶牛相比，M1 中的奶牛的 ECM 产量显着降低（C-21：22.5 和 25.0 kg/d；C+1：M1 和 M2 中的奶牛为 20.3 和 26.1 kg/d，分别）; 在 C+21 中，ECM 产量在 M1 (22.1 kg/d) 和 M2 (23.9 kg/d) 之间仅在数值上有所不同。与 M2 相比，M1 中的奶牛在所有 C 组中都表现出更高的乳蛋白含量和更高的体细胞计数；没有发现显着的 C x M 相互作用。在所有浓缩补充剂策略中，M1 奶牛在泌乳第 1 至 7 周期间表现出较高的 EB，在 C 组中，M1 和 M2 之间的差异在 C-21（C-21M1 +4.8 和 -4.2 MJ NEL/d）和 C+1（C+1M1 +7.8 和 -4.7 MJ NEL/d），在 C+21 组中仅发现数值差异（C+21M1 -2.1 和 C+21M2 -8.1 MJ NEL/d）。在哺乳的前六周，在 C+21 中检测到最低的血糖浓度（在 C+21M1 中为 2.80，在 C+21M2 中为 2.68 mmol/l）。对于非酯化脂肪酸浓度 (NEFA)，发现 C 和 M 处理之间存在显着的相互作用（P 在哺乳的前六周，在 C+21 中检测到最低的血糖浓度（在 C+21M1 中为 2.80，在 C+21M2 中为 2.68 mmol/l）。对于非酯化脂肪酸浓度 (NEFA)，发现 C 和 M 处理之间存在显着的相互作用（P 在哺乳的前六周，在 C+21 中检测到最低的血糖浓度（在 C+21M1 中为 2.80，在 C+21M2 中为 2.68 mmol/l）。对于非酯化脂肪酸浓度 (NEFA)，发现 C 和 M 处理之间存在显着的相互作用（P_坐标系<0.001)，在 C-21 和 C+1 组中，与 M2 组相比，M1 中的奶牛显示出显着较低的 NEFA 浓度，M1 中 C+21 中的 NEFA 浓度较高。在 C+21 组中发现了显着最高的 ß-羟基丁酸浓度 (BHBA)，M1 和 M2 中分别为 0.80 和 0.92 mmol/l，在 C-21 和 C+1 之间没有发现显着的 BHBA 浓度差异。组。M1 中的奶牛需要较少的兽医治疗，受精时间明显更早，但首次受孕率和每次受孕的服务总数在各组之间没有显着差异。总之，延迟补充 21 DIM (C+21) 的浓缩物会减少能量摄入，并对 EB 和代谢参数产生负面影响。一天一次挤奶至 7 DIM (M1) 对能量摄入没有影响，在泌乳的前七周，ECM 产量降低，EB 和代谢参数改善。此外，M1 减少了兽医治疗的总数，导致早期受精，对其他测量的繁殖参数没有影响，并增加了体细胞计数 (SCC)。