Rumen temperature change monitored with remote rumen temperature boluses after challenges with bovine viral diarrhea virus and Mannheimia haemolytica.

Remote rumen temperature monitoring is a potential method for early disease detection in beef cattle. This experiment was conducted to determine if remotely monitored rumen temperature boluses could detect a temperature change in steers exposed to bovine viral diarrhea virus (BVDV) and challenged with a common bovine respiratory disease pathogen, Mannheimia haemolytica (MH). Twenty-four Angus crossbred steers (BW = 313 ± 31 kg) were allotted to 1 of 4 treatments: 1) no challenge (control); 2) challenge by a 72-h exposure to 2 steers persistently infected with BVDV; 3) bacterial challenge with MH; and 4) viral challenge by a 72-h exposure to 2 steers persistently infected with BVDV followed by bacterial challenge with MH (BVDV + MH). Remotely monitored rumen temperature boluses programmed to transmit temperature every minute were placed in the rumen before the time of exposure to steers persistently infected with BVDV. Rectal temperatures were taken before MH challenge (0) and at 2, 4, 6, 12, 18, 24, 36, 48, 72, and 96 h after MH challenge. Rumen temperatures were recorded 3 d before (-72 h; period of BVDV exposure) through 14 d after (336 h) MH challenge. Rumen temperatures were analyzed as a randomized complete block design with a 2 × 2 factorial arrangement of treatments and a first-order autoregressive covariance structure for repeated measures. A treatment × day interaction was observed for average daily rumen temperature (P < 0.01). A treatment difference (P < 0.01) was observed on d 0, when MH-challenged steers had greater rumen temperatures than steers not challenged with MH. There was no BVDV × day interaction (P > 0.01). Rumen temperatures averaged every 2 h resulted in a BVDV × hour interaction (P < 0.01) and an MH × hour interaction (P < 0.01). The BVDV × hour differences occurred at h -18 to -14, 40 to 46, 110, 122, and 144 to 146 (P < 0.01). The MH × hour difference occurred at h 4 to 24 (P < 0.01). Maximum rumen temperature was increased (P < 0.01) for BVDV (0.8 °C), MH (1.2 °C), and BVDV + MH (1.3 °C) compared with the control. On average, rumen temperatures measured by the boluses at the same time points as the rectal temperatures were 0.13 °C less than rectal temperatures, and the 2 body temperatures were highly correlated (r = 0.89). Rumen temperature boluses appear to have potential as a tool for detecting temperature changes associated with adverse health events such as exposure to bovine respiratory disease and BVDV.

In situ ruminal degradation characteristics of by-product feedstuffs for beef cattle consuming low-quality forage.

Eight ruminally cannulated steers (BW = 753 +/- 48 kg) were used to evaluate in situ N, NDF, and DM degradation characteristics of by-product feeds and their application for beef cows consuming low-quality forage. Experimental feedstuffs included (DM basis) 1) extruded-expelled cottonseed meal (ECSM; 33% CP and 55% NDF), 2) extruded-expelled cottonseed meal with linters (ECSML; 25% CP and 41% NDF), 3) dried distillers grains with solubles (DGS; 33% CP and 36% NDF), 4) solvent-extracted cottonseed meal (CSM; 43% CP and 29% NDF), and 5) a blend of 76% wheat middlings with 18% CSM (WMCSM; 23% CP and 40% NDF). Steers were fed chopped prairie hay (4.8% CP, 69% NDF; DM basis) ad libitum and received 0.38 kg/100 kg of BW of WMCSM daily. In situ degradation kinetics of N, NDF, and DM components included the following fractions: A (immediately soluble), B (potentially degradable), and C (undegradable). Calculated rumen degradable protein (RDP) for ECSM was the greatest among all feedstuffs (83.8%; P < 0.01), which was composed of a large A fraction of N (41%). Similar RDP values were observed for DGS and ECSML (50.7 and 50.9%, respectively, P = 0.93). The B fraction N for ECSML was large (88.9%); however, most of this was unavailable for ruminal degradation. The amount of RDP in CSM and WMCSM was similar (78.2 and 73.5%, respectively; P = 0.12) though the A fraction of N was greater for WMCSM compared with CSM (P < 0.01). Degradability of NDF was greatest (P < 0.01) for DGS (67.4%) and was similar (P = 0.48) for WMCSM and CSM (54.5 and 57.0%, respectively). The least degradability of NDF was calculated for ECSM (29.3%; P < 0.01), attributed to greater lignin content (13.3%, DM). Degradability of DM was greatest (P < 0.01) for CSM and WMCSM (63.7 and 59.4%, respectively) and least (P < 0.01) for ECSM (36.5%) and ECSML (40.6%). Ruminal N degradation characteristics of ECSM were similar to more traditional supplements containing CSM and WMCSM. The RDP for ECSML and DGS N was less compared with other feedstuffs, indicating these feeds may need to be blended with other ingredients containing greater concentrations of degradable N, particularly in situations in which forage RDP is low.