The objective of this study was to determine if increasing propionate alters dry matter intake (DMI), glucose clearance rate, blood metabolites, insulin concentrations and hepatic gene expression in steers fed a finishing diet. Holstein steers (n = 15; BW = 243 ± 3.6 kg) were individually fed a finishing diet ad-libitum. Steers were allocated by body weight (BW) to receive: no Ca propionate (Control), 100 g/d Ca propionate (Low), or 300 g/d Ca propionate (High) in the diet. Orts were collected and weighed daily to determine DMI. Blood samples were collected on d 0, 7, and 21, and BW recorded on d 0, 14, and 28. An intravenous glucose tolerance test (IVGTT) was conducted on d 14 and 28 of the trial. Liver biopsies were collected on d 33 for gene expression analysis. Blood samples were analyzed for whole blood glucose and lactate, plasma non-esterified fatty acids (NEFA) and insulin concentrations. Data were analyzed using a mixed model with treatment, day and their interaction included, with day and minute as a repeated measure. The control treatment had greater (P < 0.01) DMI than low and high steers. Body weight was increased in control steers on d 14 and 28 compared to the steers receiving the High treatment (P = 0.03 for the interaction). Blood glucose concentrations tended (P = 0.09) to be higher on d 21 than d 0 and 7 but was not affected by treatment (P = 0.58). Plasma NEFA concentrations were lower (P = 0.05) for control steers than other treatments, and greater (P = 0.002) on d 0 than d 7 and 21. Blood lactate concentrations were greater (P = 0.05) on d 7, than d 0 and 21, but not affected by treatment (P = 0.13). High steers had greater plasma insulin concentrations in response to the IVGTT than steers on the other treatments (P = 0.001). There was no treatment (P ≥ 0.16) or day effect (P ≥ 0.36) on glucose peak, plateau, or clearance rate. High steers had greater expression of solute carrier family 16 member 1 (SLC16A1; P = 0.05) and tended to have greater hepatic expression of solute carrier family 2 member 2 (SLC2A2; P = 0.07). These data indicate that increased propionate may decrease DMI and insulin sensitivity.

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 might be responsible for DMI regulation.

The objective of this experiment was to determine whether increasing ruminal propionate in various amounts will lead to an increased expression of genes in the liver related to glucose metabolism. Holstein (n = 15) steers were individually fed a finishing diet ad libitum, twice a day, with free access to water. Treatments consisted of no added calcium propionate (CON), 100 g/d (LOW), or 300 g/d (HIGH). Treatments were split in half and mixed in the diet twice daily. Liver biopsies were taken on day 33 of propionate treatment and immediately frozen on dry ice. Samples were extracted for RNA, reverse transcribed to produce cDNA, and then analyzed using quantitative real-time PCR. Five genes involved in gluconeogenesis were selected as target genes, including solute carrier family 16 member 1 (SLC16A1), phosphoenolpyruvate carboxykinase 1 (PCK1), phosphoenolpyruvate carboxykinase 2 (PCK2), glucose-6-phosphatase (G6PC), and solute carrier family 2 member 2 (SLC2A2). There was a treatment effect (P = 0.04) for SLC16A1 expression, which encodes the protein MCT1, with steers on the HIGH treatment displaying the greatest expression, CON the least, and LOW was intermediate. There was also a tendency for a treatment effect on SLC2A2 (P = 0.07), which encodes the protein GLUT1, with the HIGH treatment displaying the greatest expression and CON the lowest. There was no significant treatment effect on expression of PCK1 (P = 0.27), PCK2 (P = 0.93), or G6PC (P = 0.29). These data indicate that increasing ruminal propionate may increase the expression of MCT1, which is likely due to increased propionate supply to the liver and could lead to greater glucose output from the liver.

The objective of this experiment was to determine if supplementing propionate alters DMI, glucose clearance rate, and blood metabolite concentrations in steers fed a finishing diet. Holstein (n = 15) steers were individually fed a finishing diet ad-libitum. Steers were allocated by BW to receive: no Ca propionate (CON), 100 g/d (LOW), or 300 g/d (HIGH) in the diet. Orts were collected and weighed daily to determine DMI. Blood samples were collected on d 0, 7, and 21, and BW recorded on d 0, 14, and 28. A glucose tolerance test was conducted on d 14 and 28 of the trial. Samples were analyzed for whole blood glucose and lactate, and plasma NEFA. Data were analyzed using a mixed model with treatment, day and their interaction included, with day as a repeated measure. The CON treatment had greater (P < 0.01) DMI than LOW and HIGH. BW was greater for CON throughout the experiment and all treatments had an increased BW on day 28 (P = 0.03 for the interaction). Whole blood glucose concentrations tended (P = 0.09) to be higher on d 21 than d 0 and 7, but was not affected by treatment (P = 0.58). Plasma NEFA concentrations were lower (P = 0.05) for CON than other treatments, and greater (P = 0.002) on d 0 than d 7 and 21. Whole blood lactate concentrations were greater (P = 0.05) on d 7, than d 0 and 21, but was not effected by treatment (P = 0.13). There was no treatment (P ≥ 0.16) or day effect (P ≥ 0.36) on glucose peak, plateau, or clearance rate. These data indicate that supplemental propionate may decrease dry matter intake but might not alter glucose clearance rate.

The objective of this experiment was to determine the effects of diet type and sequence on average daily gain (ADG) and feed intake (DMI) in Angus bulls. Diets were concentrate (CONC; 58% dry-rolled corn, 18% Sweet Bran, 9% prairie hay, 5% alfalfa hay, and 10% supplement) and forage (FOR; 60% prairie hay, 30% alfalfa hay, and 10% supplement). Angus bulls (n=19; initial BW = 293 ± 10.3 kg) were placed in individual pens and assigned to receive FOR followed by CONC (FC; n=9) or CONC followed by FOR (CF; n=10). Cattle were transitioned to the respective diets over 21 days and acclimated to the treatment diet for 10 days. Each period was 56 days. BW was measured on consecutive days at the beginning and end and every 14 days during each period. Data were analyzed using a mixed model (SAS 9.4) including the fixed effects of diet, sequence, and the interaction. Diet was treated as a repeated measure. Pearson correlations were also performed within the treatment groups. There was a sequence × diet interaction (P < 0.01) for DMI, indicating that the difference in diet DMI was smaller when cattle consumed CONC before FOR. The correlation of diet DMI was only significant in the FC group (r = 0.72; P = 0.03). There was a sequence x diet interaction (P = 0.02) for ADG, indicating that while ADG was greater during CONC feeding, the difference between the diets was greater for the FC sequence. The ADG:DMI ratio was greater for CONC (P < 0.01) but was not affected by sequence (P = 0.96). These data indicate that estimates for DMI and ADG on forage or concentrate diets do not depend strongly on the sequence of feeding the diets, but the correlation of DMI and ADG between the two diets does.