Table_1_Periconception and First Trimester Diet Modifies Appetite, Hypothalamic Gene Expression, and Carcass Traits in Bulls.DOCX

Nulliparous yearling beef heifers (n=360) were used to evaluate the effects of maternal dietary protein during the periconception and first trimester periods of gestation on postnatal growth, feedlot performance, carcass characteristics, and the expression of genes associated with appetite in the arcuate nucleus of their male progeny. Heifers were individually fed a diet of 1.18g crude protein (CP)/day High protein (HPeri) or 0.62g CP/day Low protein (LPeri) beginning 60days before conception. From 24 to 98days post-conception (dpc), half of each treatment group changed to the alternative post-conception diet and were fed 1.49g CP/day (HPost) or 0.88g CP/day (LPost) yielding four treatment groups in a 2×2 factorial design. From day 98 of gestation, heifers received a common diet until parturition. Calves were weaned at 183days and developed on pasture before feedlot entry. Bulls underwent a 70-day Residual Feed Intake (RFI) feedlot test commencing at 528days of age. Feedlot entry and final body weight (BW), feedlot average daily gain (ADG) and RFI were not different (p>0.05). Progeny of dams that had a change in diet (LPeri/HPost and HPeri/LPost) had 9% higher daily dry matter intake (DMI) during the RFI test (p<0.05) than progeny of dams that received low diet throughout both the peri-conception period and first trimester (LPeri/LPost). Further, mRNA expression of the appetite-stimulating agouti-related protein (AGRP) was increased in the arcuate nucleus of High Peri/LPost bulls (p<0.05). Longissimus dorsi muscle cross sectional area, carcass dressing percentage, and estimated retail beef yield (RBY) were all higher (p<0.05), and rump (P8) fat tended to be lower (p=0.07), for bulls from HPost dams despite no difference in carcass weight (p<0.05). This study is of commercial importance to the livestock industry as specific periods of maternal dietary supplementation may increase feed intake, enhance progeny muscling, and alter fat deposition leading to improvement in efficiency of meat production in beef cattle.

本研究选取360头未产过犊的周岁肉牛母牛（Nulliparous yearling beef heifers），旨在评估妊娠围受孕阶段与妊娠早期母体日粮蛋白水平对其子代公犊的产后生长性能、育肥表现、胴体性状，以及下丘脑弓状核内食欲相关基因表达的影响。受试母牛于配种前60天起开始单栏饲喂，分别每日供给1.18g粗蛋白（crude protein, CP）的高蛋白日粮（High protein, HPeri）或0.62g CP的低蛋白日粮（Low protein, LPeri）。在配种后24至98天（days post-conception, dpc），每个处理组的半数母牛更换为对应的替代妊娠后日粮，分别饲喂1.49g CP（HPost）或0.88g CP（LPost），最终通过2×2析因设计得到4个处理组。妊娠第98天起，所有受试母牛统一饲喂相同日粮直至分娩。犊牛于183日龄断奶，在牧场完成育成饲养后进入育肥场。受试公犊于528日龄启动为期70天的剩余采食量（Residual Feed Intake, RFI）育肥试验。各组公犊的育肥入栏体重、终末体重（body weight, BW）、育肥平均日增重（average daily gain, ADG）以及剩余采食量（RFI）均无显著差异（p>0.05）。相较于全程在围受孕与妊娠早期均饲喂低蛋白日粮的母牛子代（LPeri/LPost组），日粮变更组（LPeri/HPost与HPeri/LPost组）的母牛子代在RFI试验期间的每日干物质采食量（dry matter intake, DMI）高出9%（p<0.05）。此外，HPeri/LPost组公犊下丘脑弓状核内促食欲基因刺鼠相关蛋白（agouti-related protein, AGRP）的mRNA表达量显著上调（p<0.05）。HPost组母牛的子代公犊，其背最长肌横截面积、胴体屠宰率以及估算零售牛肉产量（retail beef yield, RBY）均显著升高（p<0.05），而臀部P8脂肪厚度呈降低趋势（p=0.07），尽管各组胴体重无显著差异（p<0.05）。本研究对畜牧产业具备商业应用价值，因为母体日粮蛋白补充的特定阶段可提升子代采食量、增强肌肉发育，并改变脂肪沉积模式，从而改善肉牛的肉用生产效率。