Effects of adding ruminal propionate on dry matter intake and glucose metabolism in steers fed a finishing ration

Authors: RATHERT-WILLIAMS, ABIGAIL - Oklahoma State University; MCCONNELL, HUNTER - Oklahoma State University; SALISBURY, CARLEE - Oklahoma State University; Lindholm-Perry, Amanda; LALMAN, DAVID - Oklahoma State University; PEZESHKI, ADEL - Oklahoma State University; FOOTE, ANDREW - Oklahoma State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2023
Publication Date: 4/13/2023
Citation: Rathert-Williams, A.R., McConnell, H.L., Salisbury, C.M., Lindholm-Perry, A.K., Lalman, D.L., Pezeshki, A., Foote, A.P. 2023. Effects of adding ruminal propionate on dry matter intake and glucose metabolism in steers fed a finishing ration. Journal of Animal Science. 101. Article skad072. https://doi.org/10.1093/jas/skad072.
DOI: https://doi.org/10.1093/jas/skad072

Interpretive Summary: Propionate metabolism by the liver is thought to be a key regulator of appetite and feed intake of animals, including cattle. Previous research has shown that providing propionate to the rumen of cattle decreases feed intake. Propionate is also a major contributor to glucose for cattle to use as an energy source for growth and maintenance. In this experiment, it was hypothesized that increasing ruminal propionate would depress feed intake and decrease insulin sensitivity. Results showed that supplying 300 grams of propionate a day decreased feed intake and increased the proportion of propionate in the rumen fluid of steers. However, when propionate production was calculated based on feed intake, there was no difference in propionate supply to the animal. The lack of increase in propionate could explain the lack of effect on glucose metabolism, insulin sensitivity, and liver gene expression. The lack of an increase in propionate also indicates that the effect of propionate on feed intake could be due to alternative mechanisms than liver metabolism of propionate.

Technical Abstract: The objective of this experiment was to determine if supplying additional propionate to the rumen alters dry matter intake (DMI), feeding behavior, glucose metabolism, and rumen fluid metabolites in steers fed a finishing diet. Ruminally cannulated steers (n = 6) were fed a finishing diet ad libitum. Steers were randomly assigned to one of three treatments in a 3×6 Latin rectangle design with three 15 d periods. Treatments of no Ca propionate (Control), 100 g/d (Low), or 300 g/d (High) were ruminally dosed twice daily. Individual intake was measured using an Insentec feeding system. Pre-feeding blood samples were collected on day 7 and rumen fluid samples were collected on day 13. An intravenous glucose tolerance test (IVGTT) was conducted on day 14 and liver biopsies were collected on day 15. Liver samples were analyzed for expression of genes involved in gluconeogenesis. Data were analyzed using a mixed model with period, treatment, day, and their interaction included, with day and minute within period as a repeated measure and steer as a random effect. Meal size (P = 0.049), meal frequency (P = 0.046), and DMI (P < 0.001) were decreased in High steers. Day 7 plasma glucose (P = 0.23) and lactate (P = 0.47) were not affected by treatment, but insulin was decreased (P = 0.008) and non-esterified fatty acids were increased (P = 0.044) in the High treatment compared with the Control. Rumen fluid lactate was decreased (P = 0.015) in the High treatment compared with the Low treatment. Total VFA concentrations did not differ (P = 0.88) between treatments. There was treatment × time interaction for proportions of acetate and propionate (P < 0.001) and the acetate:propionate ratio (P = 0.005). The effect on acetate was due to a decrease in the High treatment 2 h after dosing the treatment. Propionate proportions were greater in the High treatment than the Control at all time points and differed from the Low except at 0 h. Propionate treatments had no major effects on the glucose and insulin parameters observed in the IVGTT other than a tendency (P = 0.09) for an increased insulin time to peak. These data indicate that exogenous propionate decreases DMI but the decrease in propionate from fermentation due to reduced DMI might negate the supply of exogenous propionate in VFA supply to the animal. Mechanisms other than hepatic oxidation of propionate are responsible for DMI regulation.