Carroll A L, Hanford K J, Abney-Schulte C, Kononoff P J
Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68583.
Department of Statistics, University of Nebraska-Lincoln, Lincoln, NE 68503.
JDS Commun. 2024 Apr 20;5(6):548-552. doi: 10.3168/jdsc.2024-0564. eCollection 2024 Nov.
Diets formulated for dairy cattle are designed to supply nutrients, but rations delivered to the animal may deviate from original formulations, resulting in implications for milk production, composition, and even pregnancy rate. The objective of this study was to evaluate retrospective feed mixing records collected from 8 commercial dairy farms over 52 wk. Farms ranged from 2,982 to 29,783 animals, producing 31.8 ± 5.93 (±SD) kg of milk with 4.14 ± 0.461% fat and 3.26 ± 0.218% protein. Data collected included daily TMR nutrient deviation, calculated as diet nutrient content minus the observed divided by the formulated diet concentrations of CP, fat, NDF, and starch. Data were analyzed with fixed effects of time (modeled as 28-d periods) and days of positive nutrient deviation in fat, CP, NDF, and starch with each nutrient alone and in combination with the other nutrients, random effects of herd, and repeated measure of time within herd. The nutrient deviation by farm averaged (±SD) 1.68 ± 2.655, 2.28 ± 4.473, 1.75 ± 2.621, and 1.47 ± 2.147% for CP, fat, NDF, and starch, respectively. Days of positive nutrient deviation per period averaged (±SD) 25.5 ± 3.47, 25.5 ± 3.72, 25.6 ± 3.49, and 25.9 ± 2.61, respectively. Dry matter intake (DMI; 17.2 ± 1.78 kg/d) decreased with increasing positive deviation days in starch (-0.0483 ± 0.01265) and increased with increasing positive deviation days in CP (0.0211 ± 0.00942). Milk yield (31.4 ± 2.50 kg/d) increased with positive deviation days in starch (0.0486 ± 0.02110) and decreased with increased positive deviation days in NDF (-0.0298 ± 0.02202). Finally, pregnancy rate (21.7 ± 4.34) increased with increasing positive deviation days in fat (0.385 ± 0.1635) and decreased with increasing positive deviation days in CP (-0.420 ± 0.1879). For these models, period significantly affected milk yield but was not observed to affect pregnancy rate and DMI. Results suggest farm and nutrient type were significant sources of variation, and overall, farms overfeed nutrients CP, fat, NDF, and starch 92% of the days of a 28-d period.
为奶牛配制的日粮旨在提供营养，但输送给动物的日粮可能会偏离原始配方，从而对产奶量、奶成分甚至妊娠率产生影响。本研究的目的是评估从8个商业奶牛场收集的52周回顾性饲料混合记录。各农场奶牛数量从2982头到29783头不等，产奶量为31.8±5.93（±标准差）千克，乳脂率为4.14±0.461%，乳蛋白率为3.26±0.218%。收集的数据包括每日全混合日粮（TMR）营养偏差，计算方法为日粮营养成分含量减去观察值，再除以配方日粮中粗蛋白（CP）、脂肪、中性洗涤纤维（NDF）和淀粉的浓度。数据采用时间（建模为28天周期）、脂肪、CP、NDF和淀粉正营养偏差天数（各营养素单独及与其他营养素组合）的固定效应、牛群的随机效应以及牛群内时间的重复测量进行分析。各农场CP、脂肪、NDF和淀粉的营养偏差平均（±标准差）分别为1.68±2.655%、2.28±4.473%、1.75±2.621%和1.47±2.147%。每个周期正营养偏差天数平均（±标准差）分别为25.5±3.47、25.5±3.72、25.6±3.49和25.9±2.61。干物质采食量（DMI；17.2±1.78千克/天）随着淀粉正偏差天数的增加而降低（-0.0483±0.01265），随着CP正偏差天数的增加而增加（0.0211±0.00942）。产奶量（31.4±2.50千克/天）随着淀粉正偏差天数的增加而增加（0.0486±0.02110），随着NDF正偏差天数的增加而降低（-0.0298±0.02202）。最后，妊娠率（21.7±4.34）随着脂肪正偏差天数的增加而增加（0.385±0.1635），随着CP正偏差天数的增加而降低（-0.420±0.1879）。对于这些模型，周期对产奶量有显著影响，但未观察到对妊娠率和DMI有影响。结果表明，农场和营养类型是显著的变异来源，总体而言，在28天周期中，92%的天数里农场对CP、脂肪、NDF和淀粉营养成分供应过量。
