Impact of maternal protein restriction in first-calf heifers during mid- to late- gestation on gene expression, feedlot performance, and carcass characteristics of progeny

Abstract Text: Maternal nutrient restriction in beef cows impacts developmental processes in the fetus that may influence postnatal performance.  This study investigated impacts of MP restriction in mid- and late-gestation on the transcriptome of neonatal muscle tissue and subsequent feedlot performance and carcass characteristics of progeny. One hundred eight Angus × Simmental heifers were blocked by BW and method of conception (AI or natural service, based on fetal age at ultrasound) and allocated to 12 pens in a randomized complete block design with a 2 ´ 2 factorial treatment structure including 2 stages of gestation (mid- and late-) and 2 levels of dietary protein (control [CON]; approximately 102% of MP requirements and restricted [R]; approximately 80% of MP requirements).  Pens were randomly assigned to CON or R treatments within blocks during mid- and/or late-gestation.  Heifers were removed from treatments after calving and managed as a common group.  Within 48 h of birth, LM biopsy samples were collected from a subset of 3 male AI calves from each treatment combination for analysis of gene expression using RNA-Seq technology.  Following weaning, calves were backgrounded for two weeks then finished in a GrowSafe feeding system on a common finishing diet.  Individual carcass measurements were recorded.  Genes found in pathways associated with muscle tissue development were upregulated (P ≤ 0.02) in calves born to dams on the CON treatment throughout mid- and late- gestation. Genes involved in adipogenesis were upregulated in calves born to dams on the R-R treatment (P = 0.05). No differences were observed for calf BW, DMI, ADG, G:F, or residual feed intake (RFI) due to maternal nutritional treatments across the entire feeding period (P > 0.10).  Hot carcass weight, adjusted 12^th rib fat thickness, KPH, marbling score, and proportion of carcasses in each USDA quality grade were not influenced (P > 0.10) by maternal diet during gestation. Progeny of dams on the R treatment in late gestation had greater LM area (P = 0.05) vs. progeny from CON dams. There was a tendency (P = 0.06) for a mid- by late-gestation treatment interaction for yield grade, with lower yield grades in progeny from dams on CON-R or R-CON treatments vs. CON-CON.   Differences in gene expression, animal performance, and carcass characteristics indicate MP restriction during mid- and late-gestation may impact developmental programming.

Keywords: Beef cattle, MP restriction, gene expression