Relationship of plasma leptin concentration to intramuscular fat content in beef from crossbred Wagyu cattle. Can. J. Anim. Sci. 81: 451-457. Plasma leptin concentrations and beef cattle carcass characteristics in eight Continental Crossbred steers [0% Wagyu Cattle (WC)] were compared to crossbred cattle with 50 and 75% WC (eight steers each) genetic makeup to determine if a relationship exists between plasma leptin concentrations and intramuscular fat content (marbling) in beef cattle. Plasma leptin concentrations were measured at two stages of cattle growth, 16 and 4 wk prior to slaughter (WPS). Beef cattle characteristics including marbling score, ribeye area, i.m. total lipid content, and backfat depth were determined, and correlation coefficients obtained between these traits and leptin concentration at both sampling dates. Plasma leptin concentrations increased relative to the lipid content in the 24 steers based on the significant positive correlation observed between plasma leptin and total lipids (% wet weight) from both pars costalis diaphragmatis (p.c. Key words: Wagyu crossbred cattle, meat quality, intramuscular fat, marbling, leptin Wegner, J., Huff, P., Xie, C. P., Schneider, F., Teuscher, F., Mir, P. S., Mir, Z., Kazala, E. C., Weselake, R. et Ender, K. 2001. La relation du niveau de leptin de plasma à la teneur en graisse intramusculaire en bovins croisés de Wagyu. Can. J. Anim. Sci. 81: 451-457. Des niveaux de leptin de plasma et les caractéristiques de carcasse de bovins dans le métis continental (0% Wagyu (WC), 8 bouvillons) ont été comparés aux bovins croisés avec 50 ou 75% Wagyu (8 bouvillons chacun) pour déterminer si un rapport existe entre les concentrations de leptin de plasma et la teneur en graisse intramusculaire (marbrer) dans la viande bovins. Des niveaux de leptin de plasma ont été mesurés à deux étapes de croissance de bétail 16 et 4 semaines avant l'abattage (WPS). Des caractéristiques de bovins comprenant l'indice de marbrure, la zone de ribeye, le contenu total de lipide, et la profondeur de gras du dos ont été déterminées et des calculs de corrélation ont été exécutés. Les concentrations de leptin de plasma ont augmenté relativement au contenu de lipide car il y avait des corrélations positives significatives observées entre les lipides totaux (% de poids humide) et le leptin de plasma pour les pars costalis diaphragmatis (16 WPS: r = 0.69, P = 0.0004; 4 WPS: r = 0.35, P = 0.104) et les muscles longissimus (16 WPS: r = 0.59, P = 0.002; 4 WPS: r = 0.51, P = 0.011). On observe une tendance variable à 4 WPS quand les différentes croix sont comparées. Le leptin de plasma est franchement corrélé pour le 0% Wagyu (longissimus: r = 0.62, P = 0.103; p.c.d.: r = 0.40, P = 0.410), est presque zéro pour les bovins de 50% Wagyu (longissimus: r = 0.11, P = 0.797; p.c.d.: r = 0.005, P = 0.990), et démontre une corrélation négative pour les 75% WC (longissimus: r = -0.60, P = 0.120; p.c.d.: r = -0.65, P = 0.164). Les résultats suggèrent que cela la génétique croissante de Wagyu viole n'impo...

SummaryLeptin is a hormone involved in the regulation of feed intake and energy balance in animals. The expression and secretion of leptin is highly correlated with body fat mass and adipocyte size. The regulation of leptin is integrated into a broad regulatory network including other hormones and cytokines. Leptin's effects on food intake and energy expenditure is thought to be mediated centrally via various neurotransmitters. Peripheral hormones, including insulin and glucocorticoids, stimulate the expression of leptin. While leptin action has been well studied in rodents and humans, its role in farm animals remains to be determined in relation to feed intake and energy metabolism. Leptin may play a role in the regulation of regional fat distribution. The deposition of intramuscular fat (marbling) is positively correlated with the palatability of beef and, therefore, investigations into the mechanisms underlying fat aecretion in this depot are underway. Studying the relationship between leptin and lipid metabolizing enzymes may provide us with clues on the mechanisms governing site-speeifie fat aecretion in farm animals.

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