Transition cow nutrition and management strategies of large dairy herds in the northeastern United States: Part I–Herd description and performance characteristics

Our objective was to describe management and herd characteristics of the transition period on freestall dairy herds in the Northeastern United States using an on-farm survey and prospective cohort design. Enrolled herds (n = 72) had a median of 900 milking cows (range: 345 to 2,900), a rolling herd average of 12,674 kg (standard deviation ± 1,220 kg), and 87.2% (n= 82/94) of fresh pens were milked at least 3×/d. The prevalence of herds with ≥ 15% of sampled cows with elevated concentrations of non-esterified fatty acids (NEFA) prepartum (≥ 0.27 mmol/L, 2 to 14 d prior to parturition) and postpartum [primiparous: ≥ 0.60 mmol/L, multiparous: ≥ 0.70 mmol/L, 3 to 14 d in milk (DIM)], postpartum β-hydroxybutyrate (≥ 1.2 mmol/L, 3 to 14 DIM), and postpartum haptoglobin (≥ 1 g/L, 0 to 12 DIM) was 51%, 51%, 51%, and 57%, respectively. In most herds, cows were moved to a calving pen when showing signs of labor (73.6%; n = 53/72) instead of 0 to 3 d prior to expected calving (26.4%, n = 19/72). Cows remained in the calving or maternity pen for a median (range) time of 2 (0 – 24) h after parturition before moving to the next pen. Primiparous cows remained in the first pen moved to after parturition for a longer period than multiparous cows [median (range) d: 12 (1.5 – 25) vs. 6 (1.5 - 22). Nearly 20% of herds administered routine vaccinations in the maternity or calving pen, first pen after parturition, or both. Almost all herds (n = 69/72) performed fresh cow health checks; however, only 53% (n = 38/72) locked up all fresh cows daily. More herds housed primiparous and multiparous cows in separate pens during the far-off dry (65.3%; n = 47/72) and high lactation (81.9%; n = 59/72) periods compared to the close-up dry (31.9%; n = 23/72) and fresh periods (27.8%; n = 20/72). At least half of the pens observed during the far-off dry, close-up dry, and fresh periods had a stocking density <100%. Approximately 1/3 of pens observed during the far-off dry period had feed pushed up ≤4×/d compared to approximately 15 to 20% of pens observed during the close-up dry, fresh, and high lactating periods. More than half of the total mixed ration samples acquired from the far-off and close-up dry period visits had greater than the recommended proportion of particles in the 19-mm screen of the Penn State Particle Separator. The results of this observational study illustrate the range of management practices used in freestall herds in this region and lay the groundwork for future hypothesis-driven studies using this sampled population.

本研究旨在通过农场现场调查与前瞻性队列研究设计，描述美国东北部散栏式奶牛场（freestall dairy herds）过渡期的管理与牛群特征。纳入本研究的牛群共72群，泌乳牛中位数为900头（范围：345~2900头）；牛群滚动平均产奶量中位数为12674 kg（标准差±1220 kg）；87.2%（82/94）的新产牛栏舍每日至少挤奶3次。本研究中，产前（分娩前2~14 d）血中非酯化脂肪酸（non-esterified fatty acids, NEFA）浓度≥0.27 mmol/L的抽样奶牛占比≥15%的牛群占比为51%；产后泌乳天数（days in milk, DIM）3~14 d时，初产奶牛血中NEFA浓度≥0.60 mmol/L、经产奶牛≥0.70 mmol/L的抽样奶牛占比≥15%的牛群占比同样为51%；产后DIM 3~14 d时血β-羟丁酸浓度≥1.2 mmol/L的抽样奶牛占比≥15%的牛群占比为51%；产后DIM 0~12 d时血触珠蛋白浓度≥1 g/L的抽样奶牛占比≥15%的牛群占比为57%。多数牛群在奶牛出现分娩征兆时将其转移至产房（73.6%，53/72），而非在预计分娩前0~3 d转入（26.4%，19/72）。奶牛在分娩后会留在产房或待产栏舍，停留时长中位数为2 h（范围：0~24 h），随后转移至下一栏舍。初产奶牛在分娩后转入的首个栏舍中停留的时长显著长于经产奶牛[中位数（范围）：12 d（1.5~25 d） vs. 6 d（1.5~22 d）]。近20%的牛群会在待产/产房、分娩后首个栏舍，或两处均开展常规疫苗接种。几乎所有牛群（69/72）都会对新产奶牛开展健康检查，但仅53%（38/72）的牛群每日会将所有新产奶牛固定圈养。相较于干奶后期（31.9%，23/72）与新产牛期（27.8%，20/72），更多牛群在干奶前期（65.3%，47/72）与高产泌乳期（81.9%，59/72）将初产与经产奶牛分栏饲养。在干奶前期、干奶后期与新产牛期的观测栏舍中，至少有一半的栏舍饲养密度低于100%。干奶前期约有1/3的观测栏舍每日推料次数≤4次，而干奶后期、新产牛期与高产泌乳期的该比例仅为15%~20%。在干奶前期与干奶后期的调研中采集的全混合日粮（total mixed ration, TMR）样本中，超过半数样本的19 mm筛层颗粒占比高于宾夕法尼亚州立大学颗粒分离器（Penn State Particle Separator）推荐的标准占比。本观察性研究的结果阐明了美国东北部散栏式奶牛场的各类管理实践现状，并为后续基于该研究群体开展假说驱动型研究奠定了基础。