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It is well established that kisspeptin signaling is necessary for the onset of puberty in laboratory animals. However, the role that kisspeptin may have in regulating puberty in large domestic animals is unknown. We tested the hypothesis that either central or peripheral infusion of kisspeptin would stimulate gonadotropin and GH secretion in prepubertal gilts. In experiment 1, prepubertal gilts were fitted with i.c.v. cannula and indwelling jugular catheters. Animals were randomly assigned to receive 0, 10, or 100 mg kisspeptin in saline. In experiment 2, prepubertal gilts, fitted with indwelling jugular catheters, randomly received 0, 1, 2.5, or 5 mg kisspeptin in saline intravenously. Serial blood samples were collected every 15 min for 3 h before and 5 h after infusions, and serum concentrations of LH, FSH, and GH were determined. Mean concentrations of LH and FSH remained at basal levels for control animals but were increased (P!0.001) for animals receiving i.c.v. infusion of kisspeptin. Area under the LH and FSH curves following i.c.v. infusion of kisspeptin increased (P!0.001) in a dose-dependent manner. Concentrations of GH were unaffected by i.c.v. treatment. Peripheral administration of kisspeptin increased (P!0.05) serum concentrations of LH but not FSH or GH. Thus, kisspeptin can activate gonadotropic but not somatotropic hormone secretion in prepubertal gilts. The present data support the concept that kisspeptin plays a role in the mechanism involved in initiating puberty in swine.

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Residual feed intake (RFI) is a measure of feed efficiency, in which low RFI denotes improved 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 ϭ 10) or high RFI (n ϭ 10) were fed ad libitum or fed at restricted intake of 80% of maintenance energy requirements for 8 days. We measured serum metabolites and hormones 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. microarray; transcriptional profiling; ESR1; residual feed intake; peroxisome proliferator-activated receptor a; peroxisome proliferatoractivated receptor g; cAMP response element binding; protein GENETIC MECHANISMS THAT CONTROL feed intake (FI) and feed efficiency are not well understood. Differences in feed efficiency arise due to factors such as variations in body composition, feeding patterns, digestibility, activity, thermoregulation, and tissue metabolic rates (68). Residual feed intake (RFI) has been broadly accepted as a reliable method of measuring feed efficiency and is defined as the feed consumed above or below what is required for growth and maintenance (47, 54). Pigs with low RFI (LRFI) consume less food than the population average without a significant loss in growth parameters such as body weight and composition, and therefore, they are more feed efficient. Our group has successfully developed pig lines that differ in RFI up to 124 g/day without significant change in the body composition, with an estimated heritability for RFI of 0.33 (12). The physiology underlying RFI differences has been studied mainly in poultry and in beef cattle, in which whole-genome SNP analyses and microarray approaches have been undertaken (6, 9, 74). For example, transcriptomic analysis of liver biopsies from Angus bulls identified 163 differentially expressed genes...