| Leptin is produced and secreted from adipose tissue in response to changes in metabolic energy balance within the animal. Factors such as pregnancy status, lactation, sex, breed, stress, and age may all influence leptin production and secretion.; In our first study, our objective was to determine concentrations of leptin in the blood and milk serum of ewes and to determine if there were any associations between lamb blood serum leptin concentrations and ewe serum leptin concentrations. In ewes, blood serum leptin increased 12 hours after birth, but then declined to pre-delivery concentrations. Concentration of leptin in milk serum was highest in the colostrum but declined within the first 24 hours after parturition. Leptin concentrations in lambs was lowest at birth then increased to day 5 only to then decrease and remain stable throughout the remainder of the trial.; Our next series of experiments consisted of four trials in which our objective was to determine if circulating concentrations of leptin were correlated with carcass quality and composition. In three groups of market cattle, blood samples were obtained prior to exsanguination and carcass quality was evaluated by trained personal approximately 24 hours post-harvest. In a fourth trial, 6 genetic lines of pigs entered into the 2000 National Barrow Show were used to determine the relationship between serum concentrations of leptin and carcass merit. In all four trials, leptin concentrations were significantly correlated to subcutaneous fat depth and visual marbling score. In one of the cattle trials and the swine trial, leptin was negatively associated with longissimus dorsi area. In two of the beef studies, leptin concentrations were associated with kidney, pelvic and heart fat. Differences in findings among the four trials may be due to differences in species, breed, sex, or management prior to exsanguination. We concluded that leptin concentrations measured shortly prior to harvest were associated with body composition. |
