This study aimed to quantify the effects of physiological status (PS) and potential interaction of this factor with days of pregnancy (DOP) on beef heifers’ weight variation, intake, and digestion kinetics. Twelve rumen-cannulated zebu beef heifers (n = 7 pregnant; n = 5 non-pregnant) were used. Heifers were placed in individual pens and fed medium-quality corn silage plus a protein-based supplement. Heifers’ body weight was assessed at the beginning and end of each collection period. The feed intake was measured daily. Target outcomes were evaluated at 107, 170, 208, 240, 267, and 286 days of pregnancy. The apparent total-tract digestibility was determined considering the fecal spot collection, during five days within each collection period. Omasal and ruminal digesta samples were collected at 107, 208, and 267 days of pregnancy for determination of partial digestibilities and diet component outflow. For these purposes, Co-EDTA and indigestible neutral detergent fiber (iNDF) were used as indicators. All data were analyzed using a mixed model framework, considering the PS and DOP as fixed effects and the animal as a random effect. Significant differences were declared when P ≤ 0.05. Pregnant heifers showed an increase in body reserves (+35 kg) from 107 to 240 days of pregnancy, but experienced a decrease in shrunk body weight (-36 kg) from 240 to 286 days of pregnancy. The intake of dry matter (DM), organic matter (OM), crude protein (CP), and ash- and protein-free neutral detergent fiber (apNDF) increased as pregnancy progressed (P < 0.04). The apparent total-tract digestibility of DM tended to be lower (P = 0.09), and the apparent total-tract digestibility of apNDF was reduced (P < 0.01) in pregnant heifers. The digestibility of CP was higher (P < 0.01) on days 267 and 286 in pregnant cows compared to non-pregnant heifers. The ruminal digestibility of OM tended to be lower (P = 0.09) in pregnant beef heifers, while the ruminal digestibility of apNDF was lower (P = 0.02) in pregnant heifers compared to non-pregnant ones. The ruminal pool of wet matter and DM was lower (P ≤ 0.01) in pregnant heifers at 267 days of pregnancy. In all periods, the outflow tended to be greater (P = 0.06) in pregnant heifers compared to non-pregnant heifers. Pregnant beef heifers exhibited a faster (P = 0.01) digesta passage rate during late gestation. In conclusion, late-gestating beef heifers are less efficient in extracting energy from feed compared to non-pregnant animals.

中文翻译：

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怀孕会影响肉牛母猪的产妇生产性能、采食量和消化动力学参数


本研究旨在量化生理状态 （PS） 以及该因素与怀孕天数 （DOP） 的潜在相互作用对小母牛体重变化、摄入量和消化动力学的影响。使用了 12 头瘤胃空心瘤牛小母牛 （n = 7 妊娠;n = 5 非妊娠）。将小母牛放在单独的围栏中，并喂食中等质量的玉米青贮饲料和基于蛋白质的补充剂。在每个采集期的开始和结束时评估小母牛的体重。每天测量采食量。在怀孕 107 、 170 、 208 、 240 、 267 和 286 天评估目标结局。在每个收集期的 5 天内，根据粪便斑点收集确定表观总消化率。在怀孕 107 、 208 和 267 天收集 omasal 和 ruminal digesta 样本，以确定部分消化率和饮食成分流出。为此，使用 Co-EDTA 和不可消化的中性洗涤纤维 （iNDF） 作为指示剂。使用混合模型框架分析所有数据，将 PS 和 DOP 视为固定效应，将动物视为随机效应。当 P ≤ 0.05 时，宣布存在显著差异。怀孕的小母牛在怀孕 35 天到 107 天期间身体储备（+240 公斤）有所增加，但在怀孕 240 天到 286 天期间体重减少（-36 公斤）。随着妊娠的进展，干物质 （DM） 、有机质 （OM） 、粗蛋白 （CP） 和无灰分和无蛋白的中性洗涤纤维 （apNDF） 的摄入量增加 （P < 0.04）。DM 的表观全消化率趋于较低 （P = 0.09），而怀孕小母牛 apNDF 的表观全消化率降低 （P < 0.01）。CP 的消化率较高 （P < 0.01） 与未怀孕的小母牛相比，怀孕奶牛在第 267 天和第 286 天。怀孕肉小母牛的 OM 瘤胃消化率往往较低 （P = 0.09），而与未怀孕的小母牛相比，怀孕小母牛的 apNDF 瘤胃消化率较低 （P = 0.02）。怀孕小母牛在怀孕 267 天时瘤胃湿物质和 DM 池较低 （P ≤ 0.01）。在所有时期，与未怀孕的小母牛相比，怀孕小母牛的流出量往往更大 （P = 0.06）。怀孕的肉牛小母牛在妊娠晚期表现出更快的 （P = 0.01） 消化通过率。总之，与未怀孕的动物相比，妊娠晚期的肉牛小母牛从饲料中提取能量的效率较低。