This study aimed to evaluate the effects of plane of nutrition and advancing days of pregnancy (DP) on maternal body composition and fetal development. Differing planes of nutrition were established by 2 feeding regimens (FR): ad libitum (AL) or maintenance (MA). Sixty-two nonlactating multiparous Holstein × Gyr cows with average body weight of 480 ± 10.1 kg and an age of 5 ± 0.5 yr were used. Cows were divided into 3 groups: pregnant (n = 44), nonpregnant (n = 12), and baseline reference cows (n = 6). The 56 pregnant and nonpregnant cows were randomly allocated into 2 different FR: AL or MA. Cows fed at MA received 1.15% of their body weight on a dry matter (DM) basis, receiving corn silage and a concentrate-based diet at a ratio of 93:7 on a DM basis. Reference group cows were slaughtered at the beginning of the experimental period to estimate body composition and empty body weight. To evaluate the effects of DP, pregnant and nonpregnant animals were slaughtered at d 140, 200, 240, and 270 of gestation. Feeding regimen affected maternal tissue composition. Days of pregnancy affected fresh weight (FW), DM, and energy content, but no differences were observed for crude protein (CP) and ether extract (EE) because of DP. Feeding regimen affected mammary gland components (CP, EE, and energy content), but not fresh or dry weights. Days of pregnancy influenced almost all mammary gland components except energy content. Regarding the uterus, FR affected only fresh and dry weights; however, DP affected every uterus component measured. The only interaction between FR and DP in this study was observed for placental FW. Cows fed AL on d 270 presented the same placental FW as cows at MA and AL on d 200 and 240. Further, pregnant cows fed at MA on d 270 had greater placental FW than cows fed AL at this day. Days of pregnancy, but not FR, influenced the composition of fetal fluids in pregnant cows. Finally, cows fed at MA had greater FW for the fetus than cows fed AL; however, fetus composition changed over DP. The FW, DM, EE, and energy content increased until d 270, but CP decreased. In conclusion, the novelty of our data presents how changes due to FR and DP occur in maternal tissues and the conceptus.

中文翻译：

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杂交荷斯坦奶牛和吉尔牛在怀孕期间的身体成分变化。

这项研究旨在评估营养平面和怀孕日数（DP）对孕产妇身体组成和胎儿发育的影响。不同的营养面是通过2种喂养方案（FR）建立的：随意采食（AL）或维持（MA）。使用六十二只非泌乳的荷斯坦奶牛和吉尔牛，它们的平均体重为480±10.1 kg，年龄为5±0.5岁。母牛分为3组：怀孕（n = 44），未怀孕（n = 12）和基线参考母牛（n = 6）。将56头怀孕和未怀孕的母牛随机分为2个不同的FR：AL或MA。以MA喂养的母牛以干物质（DM）为基础的体重占其体重的1.15％，以DM为基础以93：7的比例接受玉米青贮饲料和浓缩饲料。在实验期开始时将参考组母牛屠宰，以估计体重和空体重。为了评估DP的效果，在妊娠第140、200、240和270天宰杀了怀孕和未怀孕的动物。喂养方式会影响母体组织组成。怀孕天数影响了鲜重（FW），干物质和能量含量，但由于DP，未观察到粗蛋白（CP）和醚提取物（EE）的差异。喂养方式影响乳腺成分（CP，EE和能量含量），但不影响鲜重或干重。怀孕天数几乎影响了除能量含量以外的所有乳腺成分。关于子宫，FR仅影响鲜重和干重。然而，DP影响了所测量的每个子宫成分。在本研究中，观察到胎盘FW的FR和DP之间仅有的相互作用。在第270天饲喂AL的母牛的胎盘FW与在200和240天在MA和AL饲喂的母牛相同。此外，在今天的270天在MA饲喂的怀孕母牛的胎盘FW比当天饲喂AL的母牛更大。怀孕天数（而不是FR）影响怀孕母牛胎液的成分。最后，在MA喂养的母牛的胎儿体重要比在AL喂养的母牛高。但是，胎儿组成在DP上发生了变化。直到d 270，FW，DM，EE和能量含量增加，而CP降低。总而言之，我们数据的新颖性提出了因FR和DP引起的变化如何在母体组织和概念中发生。于第270天在MA喂养的怀孕母牛的胎盘FW比今天AL喂养的母牛更高。怀孕天数（而不是FR）影响怀孕母牛胎液的成分。最后，在MA喂养的母牛的胎儿体重要比在AL喂养的母牛高。但是，胎儿组成在DP上发生了变化。直到d 270，FW，DM，EE和能量含量增加，而CP降低。总而言之，我们数据的新颖性提出了因FR和DP引起的变化如何在母体组织和概念中发生。于第270天在MA喂养的怀孕母牛的胎盘FW比今天AL喂养的母牛更高。怀孕天数（而不是FR）影响怀孕母牛胎液的成分。最后，在MA喂养的母牛的胎儿体重要比在AL喂养的母牛高。但是，胎儿组成在DP上发生了变化。直到d 270，FW，DM，EE和能量含量增加，而CP降低。总而言之，我们数据的新颖性提出了因FR和DP引起的变化如何在母体组织和概念中发生。