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Residual feed intake (RFI) is a popular measure of feed efficiency in livestock animals. The functionality of mitochondrial metabolism has been shown to be associated with variation in feed efficiency. In this study, mitochondrial biogenesis was determined by measuring the mitochondrial DNA (mtDNA) copy number in skeletal muscle of two groups of fat-tailed lambs divergently ranked on phenotypic expression of RFI (high- and low-RFI). A quantitative real-time PCR was performed to determine the relative mRNA levels of peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α) and NAD+-depended deacetylase sirtuin1 (SIRT1), as two major genes involved in the regulation of mitochondrial biogenesis. The level of mtDNA in skeletal muscle of low-RFI lambs was higher than those ranked as high-RFI. Higher mRNA level of PGC-1α was also detected in low-RFI lambs in compared with the high-RFI group. However, no significant difference was observed between the RFI groups for mRNA expression of SIRT1. The results showed a negative relationship between phenotypic expression of RFI with mitochondrial biogenesis and PGC-1α mRNA level in skeletal muscle of fat-tailed lambs. Overally, our results suggest that the increased mitochondrial dynamics has a potential to regulates bioenergetic efficiency and energy expenditure in low-RFI lambs. [ABSTRACT FROM AUTHOR]

In cells with fluctuating energy demand (e.g., skeletal muscle), a transfer system of proteins across the inner and outer mitochondrial membranes links mitochondrial oxidative phosphorylation to cytosolic phosphorylated creatine (PCr) that serves as a phosphate reservoir for rapid repletion of cytosolic adenosine triphosphate (ATP). Crucial proteins of this energy transfer system include several creatine kinase (CK) isoforms found in the cytosol and mitochondria. In a recent proteomic study (Kong et al., 2016), several components of this system were up-regulated in high feed efficiency (FE) compared to low FE breast muscle; notably adenine nucleotide translocase (ANT), voltage dependent activated channel (VDAC), the brain isoform of creatine kinase (CK-B), and several proteins of the electron transport chain. Reexamination of the original proteomic dataset revealed that the expression of two mitochondrial CK isoforms (CKMT1A and CKMT2) had been detected but were not recognized by the bioinformatics program used by Kong et al. (2016a). The CKMT1A isoform was up-regulated (7.8-fold, P = 0.05) in the high FE phenotype but there was no difference in CKMT2 expression (1.1-fold, P = 0.59). From these findings, we hypothesize that enhanced expression of the energy production and transfer system in breast muscle of the high FE pedigree broiler male could be fundamentally important in the phenotypic expression of feed efficiency. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to evaluate the effect of moderate feed restriction on productivity of lambs classified on the basis of phenotypic expression of residual feed intake (RFI). In Exp. 1, 58 fat-tailed Kurdi ram lambs (32.1 ± 4.2 kg BW) were individually fed, ad libitum, a pelleted diet (35% alfalfa hay and 65% concentrate). Feed intake and ADG were determined for a 6-wk period and 3 feed efficiency measures including RFI, G:F, and partial efficiency of maintenance (PEM) were calculated. The lambs were sorted based on RFI and the 16 highest RFI (RFI ≥ mean + 0.5 SD) and 16 lowest RFI (RFI ≤ mean - 0.5 SD) lambs were subjected to body composition (BC) and DM digestibility (DMD) analysis. Feeding behavior traits (FB) were also evaluated for 24 h using a regular 5-min interval observation method. The high- and low-RFI lambs (14 lambs/RFI group) so classified in Exp. 1 were used in Exp. 2. Half of the lambs in each RFI group were randomly selected to be fed ad libitum or 85% of ad libitum (restricted feeding), which resulted in 4 experimental groups: 1) ad libitum high-RFI, 2) feed restricted high- RFI, 3) ad libitum low-RFI, and 4) feed restricted low- RFI. The lambs were fed the same diet as Exp. 1, and growth efficiency during a 6-wk test period as well as BC, DMD, and FB were also determined in Exp. 2. In Exp. 1, the low-RFI lambs consumed 14% (P < 0.01) less feed than high-RFI lambs. Differences were also observed between high- and low-RFI groups for G:F (P = 0.01), RFI (P < 0.01), and PEM (P < 0.01) in Exp. 1, but no differences were detected between high- and low-RFI lambs for ADG (P = 0.79), DMD (P = 0.42), BC (P > 0.72), and FB (P > 0.24). In Exp.2, the restriction feeding regime negatively affected ADG (P < 0.01) and G:F (P = 0.02) in low-RFI lambs, whereas G:F (P = 0.02) and PEM (P < 0.01) were improved in high-RFI lambs under the feed restriction condition. No effects of feed restriction on DMD (P = 0.87) and BC (P > 0.05) were observed. The lambs fed at the restricted level of intake presented a greater time (P < 0.01) and rate (P = 0.01) of eating than those fed ad libitum. Although bunk visits and feeding events were decreased (P < 0.01) with feed restriction, no interaction (P > 0.05) was detected between RFI phenotype and feeding regime for FB. In summary, feeding high- RFI lambs at 85% of ad libitum level improved G:F with no effect on ADG, whereas growth performance was reduced by feeding low-RFI lambs at 85% of ad libitum. However, these changes in feed efficiency were not related to DMD, BC, or FB. [ABSTRACT FROM AUTHOR]

Global RNA expression in breast muscle obtained from a male broiler line phenotyped for high or low feed efficiency (FE) was investigated using microarray analysis. Microarray procedures and validation were reported previously. By using an overlay function of a software program (Ingenuity Pathway Analysis, IPA) in which canonical pathways are projected onto a set of genes, a subset of 27 differentially expressed focus genes were identified. Focus genes that were up-regulated in the high FE phenotype were associated with important signal transduction pathways (Jnk, G- coupled, and retinoic acid) or in sensing cell energy status and stimulating energy production that would likely enhance growth and development of muscle tissue. In contrast, focus genes that were upregulated in the low FE muscle phenotype were associated with cytoskeletal architecture (e.g., actinmyosin filaments), fatty acid oxidation, growth factors, or ones that would likely be induced in response to oxidative stress. The results of this study provide additional information on gene expression and the cellular basis of feed efficiency in broilers. [ABSTRACT FROM AUTHOR]

Because avian uncoupling protein (avUCP), melanocortin 3 receptor (MC3R), melanocortin 4 receptor (MC4R), and pro-opiomelanocortin (POMC) genes may be associated with production traits [e.g., BW, weight gain (WG), and feed conversion ratio (FCR)], male and female broilers from an elite broiler line were screened for polymorphisms in these genes. The PCR-restriction fragment length polymorphism (RFLP) tests were developed to type the missense polymorphisms UCPAla 11 8Val, MC4RSer76Leu, MC3R-Met54Leu, and Gly104Ser and POMCPro61Leu. Of 39 single nucleotide polymorphisms identified in all 4 genes, 24/39 were transitions with 11 having a C to T change. Of the 23 polymorphisms in UCP, 17 represented at least 7 haplotypes in this pedigreed broiler line. The UCP Ala-118Val allele was associated with a) high feed efficiency (FE; P = 0.03) and WG (P = 0.053) in selected males, and b) high BW in selected females (P = 0.07) and unselected males (P = 0.015). The UCPVal118Val allele was found in approximately 10% of the birds that were screened. Five silent substitutions, 3 in MC3R and 2 in MC4R, were also identified. Thirteen polymorphisms were identified in the POMC gene representing at least 3 different alleles. A missense Pro61Leu heterozygote was associated with greater BW in females. The heterozygote MC3R Gly104Ser polymorphism was associated with greater FE in selected males (P = 0.03) and greater BW in unselected males (P = 0.007). The MC4R Ser76Leu heterozygote polymorphism was associated with greater BW than the Leu76 homozygote in females (P = 0.05). From these findings, we hypothesize that UCP, MC3R, MC4R and POMC genes may play important roles and could be candidate loci for production traits such as feed conversion and BW in commercial broiler breeding stock. [ABSTRACT FROM AUTHOR]

Vitamin E(VE) is known for its antioxidant properties and has been shown to modulate immune system functions in various species. This study examined the influence of different levels of dietary VE (α-tocopherol acetate) on phagocytic functions of macrophages (abdominal exudate cells) in broiler chickens at 3, 5, and 7 wk. Birds were fed commercial diets containing 16 (control), 110, or 220 mg of VE/kg of feed. Macrophages were elicited into the abdominal cavity by injecting a 3% Sephadex solution prepared in PBS (G50-50, 1 mL/100 g of BW) 42 h prior to harvest. The percentage of phagocytically active macrophages and the number of SRBC phagocytosed per macrophage for unopsonized and antibody-opsonized SRBC were determined. These aspects of macrophage function were assessed based on 900 macrophages per sample. When unopsonized SRBC were used, dietary VE supplementation above control level did not affect phagocytic function of macrophages at wk 3, 5, or 7. With antibody-opsonized SRBC, the percentage of phagocytically active macrophages and the number of SRBC phagocytosed per macrophage were higher (P = 0.08 and P = 0.01, respectively) in 3-wk-old birds fed 110 and 220 mg of VE/kg of feed compared with age-matched controls. This enhancing effect of VE supplementation on macrophage function was not observed in 5- and 7-wk- old broilers. It appears from this study that supplemental VE enhances Fc-receptor-mediated macrophage phagocytic activity at early stages of broiler growth. [ABSTRACT FROM AUTHOR]

Abstract Background Infectious laryngotracheitis virus (ILTV; gallid herpesvirus 1) infection causes high mortality and huge economic losses in the poultry industry. To protect chickens against ILTV infection, chicken-embryo origin (CEO) and tissue-culture origin (TCO) vaccines have been used. However, the transmission of vaccine ILTV from vaccinated- to unvaccinated chickens can cause severe respiratory disease. Previously, host cell responses against virulent ILTV infections were determined by microarray analysis. In this study, a microarray analysis was performed to understand host-vaccine ILTV interactions at the host gene transcription level. Results The 44 K chicken oligo microarrays were used, and the results were compared to those found in virulent ILTV infection. Total RNAs extracted from vaccine ILTV infected chicken embryo lung cells at 1, 2, 3 and 4 days post infection (dpi), compared to 0 dpi, were subjected to microarray assay using the two color hybridization method. Data analysis using JMP Genomics 5.0 and the Ingenuity Pathway Analysis (IPA) program showed that 213 differentially expressed genes could be grouped into a number of functional categories including tissue development, cellular growth and proliferation, cellular movement, and inflammatory responses. Moreover, 10 possible gene networks were created by the IPA program to show intermolecular connections. Interestingly, of 213 differentially expressed genes, BMP2, C8orf79, F10, and NPY were expressed distinctly in vaccine ILTV infection when compared to virulent ILTV infection. Conclusions Comprehensive knowledge of gene expression and biological functionalities of host factors during vaccine ILTV infection can provide insight into host cellular defense mechanisms compared to those of virulent ILTV.