Division of Animal Sciences, University of Missouri, Columbia, MO 65211, USA.
USDA, ARS, Roman L Hruska US Meat Animal Research Center, Clay Center, NE 68933, USA.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad195.
Fall-calving primiparous crossbred beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were allocated by fetal sex and expected calving date to receive either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to calving. Heifers were individually-fed chopped poor quality hay and supplemented to meet targeted nutritional planes based on estimated hay intakes. Dam BW, BCS, backfat, and metabolic status were determined pre-treatment, every 21 d (BW and metabolic status) or 42 d (BCS and backfat) during gestation, and post-calving. At birth, calf BW and size were measured, and total colostrum from the most full rear quarter was collected pre-suckling. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Gestational metabolites included day and nutritional plane × day as repeated measures. During late gestation, CON dams gained (P < 0.01) maternal (non-gravid) BW and maintained (P ≥ 0.17) BCS and backfat, while NR dams lost (P < 0.01) maternal BW, BCS, and backfat. Circulating glucose, urea N, and triglycerides were less (P ≤ 0.05) in NR dams than CON at most late gestational timepoints after treatment initiation. Circulating non-esterified fatty acids were greater (P < 0.01) in NR dams than CON. Post-calving, NR dams weighed 63.6 kg less (P < 0.01) and were 2.0 BCS less (P < 0.01) than CON. At 1 h post-calving, NR dams had less (P = 0.01) plasma glucose and tended to have less (P = 0.08) plasma triglycerides than CON. Nutrient restriction did not affect (P ≥ 0.27) gestation length, calf birth weight, or calf size at birth. Colostrum yield was 40% less (P = 0.04) in NR dams than CON. Protein and immunoglobulin concentrations were greater (P ≤ 0.04), but free glucose and urea N concentrations were less (P ≤ 0.03), in colostrum of NR dams than CON. Colostrum total lactose, free glucose, and urea N were less (P ≤ 0.03) in NR dams than CON, but total protein, triglycerides, and immunoglobulins were not affected (P ≥ 0.55). In summary, beef heifers experiencing late gestational nutrient restriction prioritized partitioning nutrients to fetal growth and colostrum production over maternal growth. During undernutrition, fetal and colostral nutrient demands were largely compensated for by catabolism of maternal tissue stores.
从妊娠 160 天到分娩，按胎儿性别和预计分娩日期将体重为 451±28（SD）kg、体况评分为 5.4±0.7 的初产杂交肉牛母羊分为接受 100%（对照；CON；n=13）或 70%（营养受限；NR；n=13）维持、妊娠和生长所需可代谢能量和可代谢蛋白的母牛。根据估计的干草摄入量，每个小母牛单独喂食切碎的低质量干草，并进行补充以满足目标营养水平。在处理前、妊娠期间每 21 天（BW 和代谢状态）或每 42 天（BCS 和背膘）以及产后测定母羊 BW、BCS、背膘和代谢状况。在出生时，测量小牛 BW 和大小，并在吮吸前从最丰满的后四分体中收集总初乳。数据分析时考虑了营养水平、处理开始日期和小牛性别（当 P＜0.25 时）作为固定效应。妊娠代谢物包括日和营养水平×日作为重复测量。在妊娠后期，CON 母羊增加（P＜0.01）母体（非妊娠）BW 并维持（P≥0.17）BCS 和背膘，而 NR 母羊则失去（P＜0.01）母体 BW、BCS 和背膘。与 CON 相比，NR 母羊在处理开始后的大多数妊娠后期时间点上的循环葡萄糖、尿素氮和甘油三酯都较少（P≤0.05）。NR 母羊的非酯化脂肪酸循环量大于 CON（P＜0.01）。产后，NR 母羊比 CON 轻 63.6 公斤（P＜0.01），BCS 低 2.0（P＜0.01）。产后 1 小时，NR 母羊的血浆葡萄糖水平较低（P=0.01），血浆甘油三酯水平较低（P=0.08），与 CON 相比，NR 母羊的血浆葡萄糖水平较低（P=0.01），血浆甘油三酯水平较低（P=0.08）。营养限制不影响（P≥0.27）妊娠时间、小牛出生体重或小牛出生时的大小。NR 母羊的初乳产量比 CON 少 40%（P=0.04）。NR 母羊的蛋白质和免疫球蛋白浓度较高（P≤0.04），但游离葡萄糖和尿素氮浓度较低（P≤0.03），NR 母羊的初乳中，与 CON 相比，NR 母羊的初乳总乳糖、游离葡萄糖和尿素氮较少（P≤0.03），但总蛋白、甘油三酯和免疫球蛋白不受影响（P≥0.55）。总之，经历妊娠后期营养限制的肉牛小母牛优先将营养物质分配给胎儿生长和初乳生产，而不是母体生长。在营养不良的情况下，胎儿和初乳的营养需求主要通过母体组织储存的分解代谢来补偿。
