Genetic and phenotypic relationships of serum leptin concentration with performance, feed efficiency, and carcass merit of feedlot cattle

¹ Igenity Livestock Production Business Unit, Merial Ltd.; Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada
² Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta, T1J 4B1 Canada
³ Alberta Agriculture, Food and Rural Development, Lacombe Research Centre, 6000 C&E Trail, Lacombe, AB, Canada, T4L 1W1
⁴ Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada
⁵ Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada; Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta, T1J 4B1 Canada

^* To whom correspondence should be addressed. E-mail: stephen.moore{at}ualberta.ca.

	Abstract

Leptin is the hormone product of the obese gene that is synthesized and predominantly expressed by adipocytes. This study estimated the genetic variation in serum leptin and evaluated the genetic and phenotypic relationships of serum leptin concentration with performance, feed efficiency, and carcass merit. There were 464 animals with records for serum leptin concentration, performance, and feed efficiency and 381 animals with records for carcass traits. The analyses included a total of 813 animals, including those without phenotypic records. Phenotypic and genetic parameter estimates were obtained using SAS and ASREML, respectively. Serum leptin concentration was moderately heritable (h² = 0.34 ± 0.13) and averaged 13.91 (SD = 5.74) ng/mL. Sire breed differences in serum leptin concentration correlated well with breed differences in body composition. Specifically, serum leptin concentration was 20% greater in Angus-sired steers compared with Charolais-sired steers (P < 0.001). Consequently, ultrasound backfat (27%), carcass gradefat (31%), ultrasound marbling (14%), and carcass marbling (15%) were less in Charolais- than Angus-sired steers (P < 0.001). Conversely, carcass LM area (P = 0.05) and carcass lean meat yield (P < 0.001) were greater in Charolais- compared with Angus-sired steers. Animals with greater serum leptin concentration also had greater DMI (P < 0.001), greater residual feed intake (P = 0.04), and partial efficiency of growth (P = 0.01), but did not differ in feed conversion ratio (P > 0.10). Serum leptin concentration was correlated phenotypically with ultrasound backfat (r = 0.41; P < 0.001), gradefat (r = 0.42; P < 0.001), ultrasound marbling (r = 0.25; P < 0.01), carcass marbling (r = 0.28; P < 0.01), ultrasound LM area (r = - 0.19; P < 0.01), carcass LM area (r = -0.17; P < 0.05), lean meat yield (r = -0.38; P < 0.001), and yield grade (r = 0.32; P < 0.001). The corresponding genetic correlations were generally greater than the phenotypic correlations and included ultrasound backfat (r = 0.76 ± 0.19), gradefat (r = 0.54 ± 0.23), ultrasound marbling (r = 0.27 ± 0.22), carcass marbling (r = 0.76 ± 0.21), ultrasound LM area (r = -0.71 ± 0.19), carcass LM area ( r = -0.75 ± 0.20), lean meat yield (r = -0.59 ± 0.22) and yield grade (r = 0.39 ± 0.26). Serum leptin concentration can be a valuable tool that can be incorporated into appropriate selection programs to favorably improve the carcass merit of cattle.

Key Words: Beef catlle, carcass merit, feed efficiency, performance, serum leptin

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