Feeding Behavior of Yorkshire Pigs Selected for Residual Feed Intake

Feeding behavior traits were evaluated in Yorkshire gilts from the fourth generation of the ISU residual feed intake (RFI) selection experiment. Gilts were fed using FIRE feeders. Compared to the randomly selected control line, pigs from the line selected for lower RFI, had lower residual feed intake, ate less per day, spent less time eating per day, and ate faster per visit, regardless of whether analysis was over the whole test period, the first half of test period, or the second half of test period. In conclusion, selection for lower RFI has significantly changed feeding behavior, which could be part of the reason why they are more efficient

Differentially Expressed Genes in Blood from Young Pigs between Two Swine Lines Divergently Selected for Feed Efficiency: Potential Biomarkers for Improving Feed Efficiency

The goal of this study was to find potential gene expression biomarkers in blood of piglets that can be used to predict pigs’ future feed efficiency. Using RNA-seq technology, we found 453 genes were differentially expressed (false discovery rate (FDR) ≤ 0.05) in the blood of two Yorkshire lines of pigs divergently selected for feed efficiency (FE) based on residual feed intake (RFI). Genes involved in several biosynthetic processes were overrepresented among genes more highly expressed in the low RFI line compared to the high RFI line. Weighted gene co-expression network analysis (WGCNA) also revealed genes involved in some of these biosynthesis processes and having similar patterns of expression formed clusters. The average expression in the clusters was highly associated with lines (p \u3c 3.9E-07, R2 \u3e 0.59). Current findings implied these biosynthesis pathways might be more active in the high RFI line. After further stringent validation, some of the differentially expressed genes (DEGs) will be selected for validation as biomarkers for feed efficiency

Performance and Carcass Composition of Yorkshire Pigs Selected for Low Residual Feed Intake under Ad Libitum and Restricted Feeding

Growth performance and carcass composition of 40 Yorkshire pigs (74.8±9.9 kg or 164.9±21.8 lbs), 20 pigs from a line selected for low residual feed intake for 5 generations and 20 pigs from a control line, was observed while fed on either an ad libitum or NRC maintenance (weight-stasis) basis over a 6 week period. The aim of the latter diet treatment was to keep pigs at a constant weight for six weeks. In the ad libitum treatment, there was no difference in initial (p \u3c 0.49) or final body weights (p \u3c 0.65) but the low residual feed intake line consumed 9% less feed compared to the control (p \u3c 0.08). Similarly, there was no difference in LEA (p \u3c 0.57) but the low residual feed intake line had slightly less backfat compared to the control (p \u3c 0.21). These same results were found from chemical analysis of the carcass, as there was no difference in protein percentage (p \u3c 0.60), but the ad libitum low residual feed intake pigs had a slightly lower fat percentage (p \u3c 0.21). For the weight stasis treatment, the low residual feed intake pigs weighed 3.5% more than the control (p \u3c 0.08), despite attempts to maintain a static body weight, and consumed 7.6% less feed overall (p \u3c 0.09). Both lines had a decrease in backfat; however, the low residual feed intake line had an increase in loin eye area while the control line had a decrease. No differences were observed in chemical carcass composition between the two lines on the weight stasis treatment. These data show that the low residual feed intake line is more efficient, with only slight differences in carcass composition

Transcriptional Profiling of the Caloric Restriction in Key Metabolic Tissues of Pigs Differing in Feed Efficiency

Residual feed intake is a measure of feed efficiency, where low RFI denotes high feed efficiency. Caloric restriction (CR) is associated with feed efficiency in livestock species and to human health benefits such as longevity and cancer prevention. We have developed pig lines that differ in RFI and we are interested in identifying the genes and pathways that underlie feed efficiency. Prepubertal Yorkshire gilts with low RFI (n=10) or high RFI (n=10) were fed ad libitum or at 80% of maintenance for 8 days. We measured serum metabolites and generated transcriptional profiles of liver and subcutaneous adipose tissue on these animals. Overall, 6,114 genes in fat and 305 genes in liver were differentially expressed (DE) in response to CR, and 311 genes in fat and 147 genes in liver were DE due to RFI differences. Pathway analyses of CR-induced DE genes indicated a dramatic switch to a conservation mode of energy usage by down-regulating lipogenesis and steroidogenesis in both liver and fat. Interestingly, CR altered expression of genes in immune and cell cycle/apoptotic pathways in fat, which may explain part of the CR-driven lifespan enhancement. In-silico analysis of transcription factors revealed ESR1 as a putative regulator of the adaptive response to CR, as several targets of ESR1 in our DE fat genes were annotated as cell cycle/apoptosis genes. The lipid metabolic pathway was overrepresented by down-regulated genes due to both CR and low RFI. We propose a common energy conservation mechanism, which may be controlled by PPARA, PPARG, and/or CREB in both CR and feed efficient pigs