Circulating ghrelin and leptin concentrations and growth hormone secretagogue receptor abundance in liver, muscle, and adipose tissue of beef cattle exhibiting differences in composition of gain

Abstract

Data from species other than cattle indicate that ghrelin and GH secretagogue receptor (GHS-R) could play a key role in fat deposition, energy homeostasis, or glucose metabolism by directly affecting liver and adipose tissue metabolism. Beef steers (n = 72) were used to test the hypothesis that plasma ghrelin and leptin concentrations and abundance of the GHS-R in liver, muscle, and adipose tissues differ in steers exhibiting differences in composition of gain. At trial initiation (d 0), 8 steers were slaughtered for initial carcass composition. The remaining 64 steers were stratified by BW, allotted to pen, and treatment was assigned randomly to pen. Steers were not implanted with anabolic steroids. Treatments were 1) a low-energy (LE) diet fed during the growing period (0 to 111 d) followed by a high-energy (HE) diet during the finishing period (112 to 209 d; LE-HE) or 2) the HE diet for the duration of the trial (1 to 209 d; HE-HE). Eight steers per treatment were slaughtered on d 88, 111, 160, and 209. Carcass ninth, tenth, and eleventh rib sections were dissected for chemical composition and regression equations were developed to predict compositional gain. Liver, muscle, and subcutaneous adipose tissues were frozen in liquid nitrogen for subsequent Western blotting for GHS-R. Replicate blood samples collected before each slaughter were assayed for ghrelin and leptin concentrations. When compared at a common compositional fat end-point, the rate of carcass fat accretion (g·kg of shrunk BW(-1)) was greater (P < 0.001) in HE-HE steers whereas the rate of carcass protein accretion (g·kg of shrunk BW(-1)) was less (P < 0.001) compared with LE-HE steers. When compared at a common compositional fat end-point, plasma leptin, ghrelin, and insulin concentrations were greater (P < 0.05) for HE-HE compared with LE-HE steers. Abundance of the GHS-R, to which ghrelin binds, increased over time in liver and adipose tissue but did not differ as a result of treatment. Plasma ghrelin concentrations were increased for cattle continuously fed the HE diet as they became increasingly fatter; however, abundance of the GHS-R in liver, muscle, and subcutaneous adipose tissue was not different between treatment groups. The role of ghrelin in cattle metabolism warrants further investigation as it could have a significant effect on composition of BW gain, feed efficiency, and metabolic disorders such as ketosis and fatty liver.

Review: Biological determinants of between-animal variation in feed efficiency of growing beef cattle

“…Ghrelin concentration has been associated with energy intake/partitioning in ruminants (Jennings et al, 2011). However, current data does not discern whether ghrelin is a true regulator of DM intake.…”

“…However, this was dependent on the time when plasma was sampled in relation to the feeding process, because this association was not found in studies with multiple samplings (Foote et al, 2016). Moreover, if ghrelin affects feed intake and animal growth, it may depend on the physiological state and type of diet (Jennings et al, 2011;Foote et al, 2014). The role of glucose-dependent insulinotropic polypeptide on beef cattle has not been studied in detail with no available data evaluating its role on feed efficiency.…”

Association of circulating active and total ghrelin concentrations with dry matter intake, growth, and carcass characteristics of finishing beef cattle1

“…However, pulses of ghrelin release are not evident in ad libitum fed sheep (Sugino et al, 2002b); therefore, a single measure of ghrelin concentrations are likely sufficient to determine associations with DMI and efficiency. Additionally, Jennings et al (2011) have shown that ghrelin concentrations can change over the feeding period and are affected by composition of BW gain. Future research may warrant further investigation of changes of ghrelin concentrations over the finishing period and association with DMI and efficiency.…”

Changes in acyl and total ghrelin concentrations and their association with dry matter intake, average daily gain, and feed efficiency of finishing beef steers and heifers

“…It is still unclear, however, if acyl ghrelin is associated with body composition, or composition of BW gain. Foote, et al [8] showed no correlation of acyl ghrelin with carcass composition; however, Jennings, et al [16] showed that cattle accreting fat at a greater rate also had greater acyl ghrelin concentrations, which would concur with rodent literature [3,6,23].…”

“…In the Foote, et al [8] study, ghrelin was measured after the completion of the DMI measurement period, indicating the association of ghrelin with DMI could be reflective of previous feed intake; however it is unclear how ghrelin concentrations change over time. Jennings, et al [16] showed that acyl-ghrelin concentrations increase with age and/or body fatness in beef steers, but the change was dependent on composition of growth, where cattle accreting more fat had greater acyl-ghrelin concentrations.…”