Effects of roughage type on particle separation, rumination, fiber mat characteristics, in situ degradation, and ruminal fermentation parameters in beef steers.

Six ruminally cannulated steers (average BW = 791 ± 71 kg) were used in a replicated 3 × 3 Latin square experiment to determine the effects of roughage type on rumination, fiber mat characteristics, and rumen fermentation variables. Three roughages were included at 7% (DM basis) in a steam flaked corn-based diet: cotton burrs (CB), wheat silage (WS), or corn stalks (CS). Steers were fitted with a sensory collar to record rumination behaviors in 2-h intervals at the beginning of the experiment. Each 30-d period consisted of 7 d of recovery, 14 d of diet adaptation, 7 d of rumination data collection (daily and bi-hourly average rumination), 1 d of rumen fluid collection, and 1 d of rumen evacuations. In situ degradation of individual roughages was determined for 4 d after period 3 evacuations. During rumen evacuations, ruminal contents were removed; the rumen fiber mat (RF) was separated from the liquid portion with a 2-mm sieve, weighed, and a subsample was dried. Data were analyzed using the MIXED procedure of SAS with steer as the experimental unit and roughage (CB, WS, and CS) as the main effect. Dry matter intake (DMI) was not different for CB and WS (P = 0.25) and greatest for steers consuming CS diet (P ≤ 0.01). Roughage type did not influence the weight of the RF dry matter (%; DM; P = 0.92), RF weight (P = 0.69), or RF:DMI ratio (P = 0.29). Daily rumination (min/d) did not differ among roughages (P = 0.40), but min of rumination/kg of DMI was greatest for CS (18.0 min), min/kg of NDF was greatest for WS (89.8 min; P = 0.02), and min/kg of peNDF was greatest for CS (132.4 min; P ≤ 0.01). Wheat silage had the greatest percentage of soluble and degradable DM. Rumen fiber mat did not differ for roughages, although rumination min/kg of DMI and peNDF was greatest for steers consuming CS and WS. In situ degradation determined that CB-R and CS-R had the greatest percentage of ruminal undegraded DM. Based on the objective of the experiment, roughage type did not influence daily rumination or fiber mat characteristics.

Comparison of monensin sodium sources for finishing beef cattle.

The objective of this study was to evaluate the ruminal fermentation characteristics of ruminally fistulated beef steers consuming a steam-flaked corn (SFC) or dry-rolled corn (DRC) based diet containing either Rumensin 90 (RUM; Elanco, Greenfield, IN), or Monovet 90 (MV; Huvepharma, Peachtree City, GA). Six ruminally fistulated steers (657.7 kg ± 72.6) housed individually were used in a 6 × 6 Latin square design with 2 × 3 factorial treatment arrangement. Each of the 6 periods were 15 d with 14 d for diet adaptation and 1 d of rumen fluid collections. Dietary treatments were DRC without monensin sodium (DRC-C), SFC without monensin sodium (SFC-C), DRC with Rumensin 90 (DRC-R), DRC with Monovet 90 (DRC-MV), SFC with Rumensin 90 (SFC-R), and SFC with Monovet 90 (SFC-MV). Rumen contents and fluid were collected through the fistula of each animal at 0, 3, 6, 12, and 24 h on d 15 of each period. Rumen fluid collected at 6 h post-feeding each period was used for in vitro analyses. Steer was the experimental unit and the model included fixed effects of grain processing, additive, and grain processing × additive. Total gas produced was composited from each in vitro bottle into a gas collection bag for the 48-h determination of methane concentration. No differences were detected for DMI (P = 0.81). Ruminal pH did not differ for the control or additive treatments (P = 0.33). However, ruminal pH was lower (P < 0.01) with SFC compared to DRC. There was a significant difference in acetate to propionate ratio for grain type (P = 0.01) and a tendency for additive inclusion (P = 0.06). Additive inclusion reduced methane proportion of total gas compared to control treatments (P ≤ 0.01). Overall, monensin sodium reduced methane concentration though source had no effect on DMI or ruminal pH.

Impact of increasing levels of fumonisin on performance, liver toxicity, and tissue histopathology of finishing beef steers.

To address the gaps in current scientific knowledge, the objective of the present study was to investigate the impact of fumonisin exposure on feedlot cattle intake and performance. Fifty steers were received (day 0; 361 ± 6.4 kg), housed individually and fed once daily at 0800 hours. All steers were transitioned to a dry-rolled corn-based finishing diet from days 0 to 21 and then were fed the control finishing diet until day 50. Treatment diets were formulated to achieve ≤5 (CON), 15 (15PPM), 30 (30PPM), 60 (60PPM), or 90 ppm (90PPM) of total dietary fumonisin. Steers were fed the fumonisin treatment diets from day 50 until harvest on day 160; individual animal body weights (BW) were measured on days 0, 50, 100, 150, 159, and 160. Liver, kidney, and skeletal muscle tissue samples were collected at harvest for histopathological analyses, and liver samples were further analyzed for sphinganine (SA) and sphingosine (SO) concentration. Animal performance, carcass data, and liver enzyme concentration were analyzed using a mixed model; categorical data were analyzed via nonparametric models. Contrasts were used to test for linear and quadratic responses. Throughout the study, there was no effect of treatment (P > 0.60), or a linear response (P > 0.16) from increasing fumonisin levels, on BW or dry matter intake (DMI). However, CON tended to have a lower average daily gain (ADG) than the fumonisin treatments during the fumonisin treatment period (P = 0.10), and there was a positive linear response (P = 0.02) of ADG to fumonisin during the treatment period. There were no treatment differences in hot carcass weight, dressing percentage, marbling score, ribeye area, or yield grade. There were no effects of treatment on either liver abscesses (P = 0.95) or telangiectasis (P = 0.13). We observed a treatment difference for SA and SA:SO (P < 0.01), as well as a quadratic response (P < 0.02); both SA and SA:SO increased as dietary fumonisin increased. There were no observed differences between treatments for histopathology scores of kidney (P = 0.16), liver (P = 0.25), or skeletal muscle (P = 0.59) tissue. No adverse effects were observed in steers fed increasing dietary levels of fumonisin for 110 d prior to harvest. While elevated liver amino alcohol concentration did occur, negative effects on growth and carcass characters were not observed.

Associations of mucosal disaccharidase kinetics and expression in the jejunum of steers with divergent average daily gain.

The objective of this study was to quantify the differences in the activity of jejunal maltase and isomaltase between two groups of steers with average dry matter intake (DMI) and differing average daily gain (ADG). DMI and ADG were measured in crossbred steers (n = 69; initial body weight = 456 ± 5.0 kg) consuming a finishing diet containing 67.8% dry-rolled corn, 20.0% wet distillers grains with solubles, 8.0% alfalfa hay, and 4.2% vitamin/mineral supplement on a dry matter basis for 84 d. Jejunal mucosal samples were collected from eight steers with the greatest (high) or least (low) ADG and average DMI (± 0.55 standard deviation). Homogenates of jejunal mucosa were incubated with increasing amounts of maltose and isomaltose to determine the disaccharidase kinetics. Total mucosal protein concentration (mg protein/g tissue; P = 0.45) of the mucosa and small intestinal weights (P = 0.69) did not differ between the groups. Neither the Michaelis-Menten constant (Km) of isomaltase (P = 0.15) nor maltase (P = 0.21) differed between groups. The isomaltase maximum velocity (Vmax) expressed per gram of protein tended to differ (P = 0.10) between groups of steers but did not differ (P = 0.13) when expressed on a tissue basis. Similarly, neither the maltase Vmax expressed per gram of protein (P = 0.31) nor tissue (P = 0.32) differed between groups. While previous studies have indicated that disaccharidase expression is associated with differences in ADG, data presented here indicate that differences in enzyme activity at the end of the finishing period are minimal.