Ruminal acidosis challenge impact on ruminal temperature in feedlot cattle

The objective of this experiment was to determine if ruminal temperature rise coincides with pH reduction using an acidosis challenge model. Twelve ruminally cannulated steers (518 ± 28 kg BW) were administered ruminal temperature-monitoring devices that recorded temperature every 2 min. Steers were fed a 63% concentrate diet at 1.6% BW for 20 d before being randomly assigned to 1 of 3 acidosis challenge treatments: no dietary change (CON), one-half of daily DMI replaced with cracked corn (HALF), or all of daily DMI replaced with cracked corn (CORN). The challenge was initiated by ruminally dosing steers with their treatment diets. Ruminal pH and rectal temperatures (T(rec)) were recorded every 3 h for 72 h. All steers were offered CON diets at 24 and 48 h after challenge. Ruminal pH showed a treatment × day effect (P = 0.01). Ruminal pH of CORN steers was lower (P = 0.03) than that of HALF steers on d 1, was lower (P ≤ 0.004) than that of HALF and CON steers on d 2, and tended to be lower (P ≤ 0.10) than that of HALF and CON steers on d 3. Treatment did not affect (P ≥ 0.42) RecT. Ruminal temperature (T(rum)) showed a treatment · d(-1) · h(-1) after feeding interaction (P < 0.01). At 3 h after challenge, T(rum) of CORN and HALF steers was higher (P ≤ 0.01) than that of CON steers. On d 2, T(rum) of CORN steers was higher (P ≤ 0.03) than that of CON between 6 and 12 h after feeding. From 15 to 21 h after feeding on d 2, T(rum) of HALF steers was higher (P < 0.01) than that of CORN and CON steers. On d 3, at the time of feeding until 3 h later, T(rum) of CORN steers was lower (P ≤ 0.04) than that of all other steers. Rectal temperature was correlated (P ≤ 0.01) with T(rum) on all days for CON and CORN steers. Ruminal pH was negatively correlated (P ≤ 0.04) with T(rec) on d 2 and T(rum) on d 1 in CORN steers, and T(rum) was negatively correlated (P ≤ 0.02) with ruminal pH in HALF and CON steers on d 1 and 3, respectively. The amount of time above T(rum) of 39.0°C or 39.45°C was correlated (P ≤ 0.05) with the time spent below a ruminal pH of 5.5 in CORN steers; however, time above T(rum) of 39.0°C did not differ (P = 0.87) among treatments. Results indicate that there is a negative relationship between T(rum) and ruminal pH during an acidotic episode; therefore, T(rum) monitoring can detect a potential acidotic episode.     

Relationship of ruminal temperature with parturition and estrus of beef cows

Spring-calving Angus cows (n = 30) were used to evaluate changes in ruminal temperature (RuT) related to parturition and estrus. Cows were synchronized and artificially inseminated with semen from a single sire. Temperature boluses were placed in the rumen at 7.0 ± 0.2 mo of gestation. Boluses were programmed to transmit RuT every 15 min. Cows (BW = 623 ± 44 kg, BCS = 4.9 ± 0.4) calved during 3 wk, and estrus was synchronized at 77 ± 7 d after calving with PGF(2α). Cows were observed every 12 h to detect estrus. Daily average ambient temperatures ranged from 2 to 22 °C during parturition (February to March) and 17 to 25 °C during estrus (May to June). Ruminal temperature from 7 d before to 3 d after parturition and 2 d before to 2 d after visual detection of estrus was analyzed using the MIXED procedure. Ruminal temperatures <37.72 °C were attributed to water consumption and excluded from analyses. Day did not influence (P = 0.36) RuT from d -2 to -7 before parturition (38.94 ± 0.05 °C). Ruminal temperature decreased (P < 0.001) from d -2 to d -1 before parturition (38.88 ± 0.05 to 38.55 ± 0.05 °C, respectively). Ruminal temperature was not influenced (P = 0.23) by day from 1 d before to 3 d after parturition (38.49 ± 0.05 °C). Ruminal temperature at 0 to 8 h after detection of estrus (38.98 ± 0.09 °C) was greater (P < 0.001) compared with RuT at the same daily hour of the day before (38.37 ± 0.11 °C) or the day after estrus (38.30 ± 0.09 °C). Ambient temperature did not influence (P > 0.30) RuT at parturition or estrus. Ruminal temperature decreased the day before parturition and increased at estrus in spring-calving beef cows and has potential use as a predictor of parturition and estrus.     

Effects of diet type and metabolizable energy intake on tympanic temperature of steers fed during summer and winter seasons

A summer study and a winter study were conducted using an incomplete factorial structure in a complete randomized design. Within season, the factors studied were 1) type of diet, which included 2 levels of ME, classified as either concentrate (3.04 Mcal of ME/kg) or roughage (2.63 Mcal of ME/kg) diets, and 2) daily ME intakes (MEI) of 11, 18, and 25 Mcal of ME/d for the roughage diets and 18, 25, and 32 Mcal of ME/d for the concentrate diets. In Exp. 1 (summer study), 30 steers (5 steers/treatment combination) were used to collect tympanic temperatures (TT). In Exp. 2 (winter study), 24 steers (4 steers/treatment combination) were used to collect TT. Mean TT was 0.3°C greater for summer than winter (38.9 vs. 38.6°C, respectively; P < 0.05). Steers fed diets based on concentrate tended to display greater TT than steers fed diets based on roughage. Season × diet × hour interactions were found for TT (P = 0.01). In the winter, greater TT (P < 0.05) were found from 0900 to 1400 h when an equal amount of MEI was derived from a concentrate-based vs. roughage-based diet. In cattle fed roughage-based diets during the summer, TT = 38.63 + 0.0114?MEI, whereas for cattle fed concentrate-based diets, TT = 38.69 + 0.0114?MEI. During the winter, for cattle fed a roughage-based diet, TT = 37.65 + 0.0856?MEI - 0.0018?MEI(2), whereas for cattle fed a concentrate-based diet, TT = 35.37 + 0.2635?MEI - 0.0051?MEI(2). In summary, results demonstrate that increases in the energy of the diet resulted in increases in TT. However, the response was dependent on season of the year, with a linear response in TT for summer and a quadratic response during winter.     

Differential haptoglobin responsiveness to a Mannheimia haemolytica challenge altered immunologic,physiologic, and behavior responses in beef steers

Indicator traits associated with disease resiliency would be useful to improve the health and welfare of feedlot cattle. A post hoc analysis of data collected previously (Kayser et al., 2019a) was conducted to investigate differences in immunologic, physiologic, and behavioral responses of steers (N = 36, initial BW = 386 ± 24 kg) that had differential haptoglobin (HPT) responses to an experimentally induced challenge with Mannheimia haemolytica (MH). Rumen temperature, DMI, and feeding behavior data were collected continuously, and serial blood samples were collected following the MH challenge. Retrospectively, it was determined that 9 of the 18 MH-challenged steers mounted a minimal HPT response, despite having similar leukocyte and temperature responses to other MH-challenged steers with a greater HPT response. Our objective was to examine differences in behavioral and physiological responses between MH-challenged HPT responsive (RES; n = 9), MH-challenged HPT nonresponsive (NON; n = 9), and phosphate-buffered saline-inoculated controls (CON; n = 18). Additionally, ¹H NMR analysis was conducted to determine whether the HPT-responsive phenotype affected serum metabolite profiles. The RES steers had lesser (P < 0.05) cortisol concentrations than NON and CON steers. The magnitude of the increases in neutrophil concentrations and rumen temperature, and the reduction in DMI following the MH challenge were greatest (P < 0.05) in RES steers. Univariate analysis of serum metabolites indicated differences between RES, NON, and CON steers following the MH challenge; however, multivariate analysis revealed no difference between HPT-responsive phenotypes. Prior to the MH challenge, RES steers had longer (P < 0.05) head down and bunk visit durations, slower eating rates (P < 0.01) and greater (P < 0.05) daily variances in bunk visit frequency and head down duration compared with NON steers, suggesting that feeding behavior patterns were associated with the HPT-responsive phenotype. During the 28-d postchallenge period, RES steers had decreased (P < 0.05) final BW, tended (P = 0.06) to have lesser DMI, and had greater (P < 0.05) daily variances in head down and bunk visit durations compared with NON steers, which may have been attributed to their greater acute-phase protein response to the MH challenge. These results indicate that the HPT-responsive phenotype affected feeding behavior patterns and may be associated with disease resiliency in beef cattle.     

The effect of environmental temperature on concentrations of thyroxine and triiodothyronine after thyrotropin releasing hormone in steers

Twenty-four Angus X Hereford steers (155 +/- 4 kg) were used to examine thyroid function during exposure to ambient temperatures of 4, 18 and 32 C. Jugular cannulae were inserted after steers were acclimated to individual stalls in environmentally controlled chambers at 18 C for 3 d. The day following cannulation, ambient temperatures were changed 2 C/h for 7 h and serum samples were collected hourly. After steers were exposed to either 4, 18 or 32 C for 1 and 72 h, thyrotropin releasing hormone (TRH; 50 micrograms, iv) was rapidly infused. Serum samples were collected hourly for 8 h after each treatment with TRH and every 8 h for 3 d between treatments. Rectal temperatures and respiratory were greater (P less than .05) in steers exposed to 32 C compared with steers at 4 C. During the change in environmental temperature, the concentrations of thyroxine (T4) and triiodothyronine (T3) over time tended (P less than .10) to decrease in steers exposed to 32 C compared with those at 4 C. Concentrations of T4 and T3 after the second treatment with TRH were significantly less in steers exposed to 32 C compared with those at 4 C. The response of T4 to TRH was reduced (P less than .01) after the second treatment with TRH compared with the first for steers exposed to all three temperatures, whereas, the response of T3 was reduced (P less than .05) after the second treatment with TRH only in steers exposed to 32 C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neutral detergent fiber concentration of corn silage and rumen inert bulk influences dry matter intake and ruminal digesta kinetics of growing steers

Corn silage with high NDF concentration has the potential to reduce DMI because it has a greater filling effect in the rumen than low-NDF corn silage. Our objective was to determine whether ruminal fill influences DMI to the same extent with low- or high-NDF corn silage-based diets. Eight ruminally cannulated Holstein steers (198 +/- 13 kg) were randomly assigned to a 2 x 2 factorial arrangement of treatments in a replicated 4 x 4 Latin square design with 16-d periods. Treatments were diets containing corn silage from a normal hybrid (low-fiber; LF) or its male-sterile isogenic counterpart (high-fiber; HF), offered for ad libitum consumption to steers with or without rumen inert bulk (RIB). The LF and HF diets contained 33.8 and 50.8% dietary NDF, respectively. Rumen inert bulk was added at 25% of pretrial ruminal volume in the form of plastic-coated tennis balls filled with sand to achieve a specific gravity of 1.1 and a total volume of 7.5 L. No fiber level x inert bulk interactions were detected for DMI or NDF intake (P > 0.10), suggesting that DMI was limited to the same extent by physical fill at both levels of dietary fiber. Addition of RIB decreased DMI by an average of 10.7%, which was 65.5 g/L of added bulk. The HF diet depressed DMI by an average of 15.5%, increased NDF intake 27.1%, and reduced ruminal NDF turnover time by 21.0% compared to the LF diet (P < 0.01), with no effect on ruminal volume or amount of NDF in the rumen (P > 0.10). Addition of RIB also reduced ruminal NDF turnover time and amount of NDF in the rumen (11.8% and 20.7%, respectively; P < 0.01), with no change in ruminal digesta volume (P > 0.10). The HF treatment decreased digestibility of DM and GE (5.5 and 5.7%, respectively; P < 0.01) but increased NDF digestibility (10.4%; P < 0.01) compared to LF. Rumen inert bulk had no effect on digestibility of DM, NDF, or GE (P > 0.10). The lack of reduction in digesta volume with addition of inert fill suggests that DMI of light-weight steers receiving corn silage-based diets within a wide range of NDF concentrations was not regulated by ruminal distension alone.     

Bovine acute-phase response after different doses of corticotropin-releasing hormone challenge

The objective was to compare the acute-phase response of steers receiving different doses of bovine corticotropin-releasing hormone (CRH). Fourteen weaned Angus steers (BW = 191 ± 2.1 kg, age = 167 ± 4.7 d) fitted with an indwelling jugular catheter and a rectal temperature (RT) monitoring device were assigned to receive 1 of 3 treatments (intravenous infusion): 1) 0.1 μg of CRH/kg of BW (CRH1; n = 5), 2) 0.5 μg of CRH/kg of BW (CRH5; n = 5), and 3) 10 mL of saline (0.9%; n = 4). Blood samples were collected via catheters, relative to treatment infusion (0 h), hourly from -2 to 0 h and 4 to 8 h and every 30 min from 0 to 4 h. Rectal temperatures were recorded every 30 min from -2 to 8 h. Blood samples were also collected via jugular venipuncture and rectal temperatures assessed using a digital thermometer every 6 h from 12 to 72 h and every 24 h from 96 to 168 h. All plasma samples collected during the study were analyzed for concentrations of haptoglobin. All plasma samples collected from -2 to 8 h were analyzed for cortisol concentrations. Serum samples collected hourly from -2 to 8 h were analyzed for concentrations of NEFA, IL-6, tumor necrosis factor (TNF)-α, and interferon-γ. Cortisol peaked at 0.5 h for CRH1 steers but returned to baseline concentrations at 1 h relative to infusion (time effect; P < 0.01). In CRH5 steers, cortisol peaked at 0.5 h and returned to baseline concentrations 3.5 h relative to infusion (time effect; P < 0.01). Cortisol concentrations did not change after treatment infusion for saline steers (time effect; P = 0.42). In CRH1 steers, NEFA concentrations peaked 5 h after treatment infusion (time effect; P = 0.01). Conversely, serum NEFA concentrations did not change for CRH5 and saline steers after treatment infusion (time effect; P > 0.37). Mean serum TNF-α concentrations in CRH1 steers after treatment infusion were greater compared with saline (P = 0.02), tended to be greater (P = 0.08) compared with CRH5, and were similar (P = 0.40) between CRH5 and saline steers. Mean RT in CRH1 steers after treatment infusion were greater (P < 0.04) compared with saline and CRH5 and similar (P = 0.50) between CRH5 and saline steers. Haptoglobin increased and peaked 72 h after treatment infusion for CRH1 steers (time effect; P = 0.01) but did not change for CRH5 and saline steers (time effect; P > 0.45). In conclusion, the bovine acute-phase response stimulated by CRH infusion is dependent on the CRH dose and the subsequent response in circulating cortisol.     

Effects of polyunsaturated fatty acid supplementation on ruminal in situ forage degradability, performance, and physiological responses of feeder cattle

Two experiments were conducted to compare ruminal, physiological, and performance responses of forage-fed cattle consuming grain-based supplements without (NF) or with the inclusion (10%; DM basis) of a rumen-protected PUFA (PF) or SFA source (SF). Supplements were offered and consumed at 0.6% of BW/animal daily (DM basis). In Exp. 1, DMI and ruminal in situ forage degradability were evaluated in 3 Angus × Hereford cows fitted with ruminal cannulas and allocated to a 3 × 3 Latin square design. Within each experimental period, hay was offered in amounts to ensure ad libitum access from d 1 to 13, DMI was recorded from d 8 to 13, and cows were limited to receive 90% of their average hay DMI (d 1 to 13) from d 14 to 21. On d 16, polyester bags containing 4 g of ground hay (DM basis) were incubated within the rumen of each cow for 0, 4, 8, 12, 24, 36, 48, 72, and 96 h. Hay and total DMI were reduced (P < 0.05) in cows receiving PF compared with cows receiving SF and NF. No treatment effects were detected (P > 0.48) for ruminal disappearance rate and effective ruminal degradability of hay DM and NDF. In Exp. 2, preconditioning DMI, ADG, carcass traits, and plasma concentrations of cortisol, fatty acids, acute-phase proteins, and proinflammatory cytokines were assessed in 72 Angus × Hereford steers receiving supplement treatments during a 28-d preconditioning period. All steers were transported to a commercial growing lot after preconditioning (d 1) and were later moved to an adjacent commercial finishing yard (d 144), where they remained until slaughter. No treatment effects were detected (P ≥ 0.52) for preconditioning ADG and G:F, but DMI tended (P = 0.09) to be reduced in steers receiving PF compared with those receiving NF and SF. Plasma PUFA concentrations were greater in steers receiving PF compared with those receiving NF and SF (P = 0.01). After transportation, concentration of tumor necrosis factor-α increased for steers receiving NF, did not change for steers receiving SF, but decreased for steers receiving PF (treatment × day interaction, P < 0.01). Steers fed PF had greater (P = 0.02) ADG compared with those fed NF during the growing phase. Carcass yield grade and marbling were greater (P < 0.05) for steers fed PF compared with those fed NF. In conclusion, PUFA supplementation did not affect ruminal forage degradability but did impair DMI in beef cows. Further, PUFA supplementation to steers during preconditioning reduced plasma concentrations of tumor necrosis factor-α after transportation, and benefited growing lot ADG and carcass marbling.     

Weaning management of newly received beef calves with or without continuous exposure to a persistently infected bovine viral diarrhea virus pen mate: effects on health, performance, bovine viral diarrhea virus titers, and peripheral blood leukocytes

Exposure to animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) results in immunomodulation of cohorts that may have health and growth consequences; however, effects may differ in low-risk, preconditioned (PC) vs. high-risk, auction market (AM) beef cattle. Our objective was to compare health and performance of PC or AM management systems with (PI) or without (CON) presence of a PI-BVDV pen mate using a 2 × 2 factorial arrangement. Four shipment blocks of crossbred PC steers (n = 236) from 3 ranch-origins were weaned, dewormed, vaccinated, tested for PI-BVDV, and kept on the ranch for ≥42 d. Subsequently, PC steers were transported to a stocker receiving unit (RU), weighed (251 ± 2 kg), blood sampled, stratified by d -1 BW, and assigned randomly to treatment (PCPI or PCCON) with no additional processing. Simultaneously, 4 blocks of crossbred AM calves (n = 292) were assembled from regional auction markets and transported to the RU ± 36 h from PC arrival. The AM calves were weighed (245 ± 1.3 kg), stratified by gender and d -1 BW, processed under the same regimen used for PC steers at their origin ranch except bull calves were castrated, and then assigned randomly to treatment (AMPI or AMCON). Treatment pens (0.45 ha) were arranged spatially such that PI did not have fence-line or water source contact with CON. Calves were fed identically and followed the same antibiotic treatment protocol. Daily BW gain for the entire 42-d receiving trial was greater (P < 0.001) for PC (1.2 kg) compared with AM (0.85 kg). There was an exposure effect (P = 0.002) on ADG from d 28 to 42; CON gained 1.12 kg vs. 0.90 kg BW for PI cohort. Morbidity was markedly greater (P < 0.001) in AM (70%) vs. PC (7%), resulting in (P < 0.001) an antibiotic treatment cost of $20.52 and $2.48/animal, respectively. Treatment with a third antibiotic occurred more often (P = 0.04) for PI cohort, and the percentage of chronically ill cattle was greatest (P = 0.06) for AMPI. Upon arrival, BVDV type 1a, 1b, and 2a titers were greater for PC (treatment × day, P < 0.001), and the percentage seropositive to BVDV type 1a on d 0 was 100% for PC vs. 23% in AM. Platelets increased transiently (P < 0.001) with greater platelets observed in AM (P < 0.001). Results indicate that PC calves gain faster and require fewer antibiotic treatments during the receiving period. Exposure to PI reduced BW gain from d 28 to 42, increased the number of calves treated thrice, and increased chronically ill cattle for AM.     

Comparative study on the aflatoxin B1 degradation ability of rumen fluid from Holstein steers and Korean native goats

The aflatoxin B1 degrading abilities of two different ruminants were compared in this study. One set of experiments evaluated the aflatoxin B1 degradation ability of different rumen fluid donors (steers vs. goats) as well as the rumen fluid filtration method (cheese cloth filtered vs. 0.45 µm Millipore) in a 2 × 2 factorial arrangement. Additional studies examined aflatoxin B1 degradation by collecting rumen fluid at different times (0, 3, 6, 9 and 12 h) after feeding. Cannulated Holstein steers (740 ± 10 kg bw) and Korean native goats (26 ± 3 kg bw) were fed a 60% timothy and 40% commercial diet with free access to water. Rumen fluid from Korean native goats demonstrated higher (p < 0.01) aflatoxin B1 degradability than Holstein steers. However, filtration method had no significant influence on degradability. In addition, aflatoxin degradation did not depend upon rumen fluid collection time after feeding, as no significant differences were observed. Finally, a comparison of two types of diet high in roughage found aflatoxin degradability in goats was higher with timothy hay opposed to rice straw, although individual variation existed. Thus, our findings showed the aflatoxin degradability is comparatively higher in goats compared to steers.     

Locomotor activity, core body temperature, and circadian rhythms in mice selected for high or low heat loss

Daily locomotor activity, core body temperature, and their circadian rhythms were measured in lines of mice selected for high (MH) or low (ML) heat loss and unselected controls (MC). Lines were created by selecting for 16 generations in each of three replicates. Collection of locomotor activity and core temperature data spanned Generations 20 and 21 for a total of 352 mice. Physical activity and core body temperature data were accumulated using implanted transmitters and continuous automated collection. Measurement for each animal was for 3 d. Activity was recorded for each half hour and then averaged for the day; temperature was averaged daily; circadian rhythm was expressed in 12-h (light vs dark) or 6-h periods as well as by fitting cyclic models. Activity means were transformed to log base 2 to lessen heterogeneity of variance within lines. Heat loss for a 15-h period beginning at 1630 and feed intake for 7 d were measured on 74 additional mice in order to estimate the relationship between locomotor activity and heat loss or feed intake. Selection lines were different (P < 0.01) for both locomotor activity and core body temperature. Differences were due to selection (MH-ML, P < 0.01), and there was no evidence of asymmetry of response (P > 0.38). Retransformed from log base 2 to the scale of measurement, mean activity counts were 308, 210, and 150 for MH, MC, and ML, respectively. Mean core temperatures were 37.2, 36.9, and 36.7 degrees C for MH, MC, and ML (P < 0.01), respectively. Females had greater physical activity (P < 0.01) and body temperature (P < 0.01) than males. There was no evidence of a sex x selection criterion interaction for either activity or temperature (P > 0.20). Overall phenotypic correlation between body temperature and log base 2 activity was 0.43 (P < 0.01). Periods during the day were different for both 12- and 6-h analyses (P < 0.01), but there were no period x selection criterion interactions (P > 0.1) for physical activity or body temperature. More sensitive cyclic models revealed significant (P < 0.01) 24-, 12-, 8-, and 6-h cycles that differed (P < 0.01) among lines. Estimated differences between MH and ML mice in feed intake and heat loss due to locomotor activity were 36 and 11.5%, respectively. Variation in activity thus contributed to variation in feed intake.     

Protective effects against abortion and fetal infection following exposure to bovine viral diarrhea virus and bovine herpesvirus 1 during pregnancy in beef heifers that received two doses of a multivalent modified-live virus vaccine prior to breeding

Objective-To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection. Design-Randomized controlled clinical trial. Animals-33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves. Procedures-20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days. Results-After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers. Conclusions and Clinical Relevance-Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.     

Fetal protection following exposure to calves persistently infected with bovine viral diarrhea virus type 2 sixteen months after primary vaccination of the dams

This study demonstrated that the bovine viral diarrhea virus (BVDV; types 1 and 2) fractions of a multivalent vaccine protected pregnant heifers and their fetuses at 149 to 217 days of gestation against exposure to calves persistently infected with BVDV type 2a. Eighty percent (eight of 10) of the control heifers were viremic at least 1 day following challenge, whereas all (20 of 20) BVDV-vaccinated heifers were virus isolation-negative on all postchallenge assessment days. Ninety percent (nine of 10) of the calves born to control heifers but only 5% (one of 20) of calves born to BVDV-vaccinated heifers seroconverted to BVDV type 2 before ingesting colostrum. One calf born to a control heifer was persistently infected. No calves from BVDV-vaccinated heifers were persistently infected.     

青贮玉米和混合干草对山羊胃肠内环境参数的影响

以8只装有永久性瘤胃瘘管和十二指肠近端T型瘘管的徐淮白山羊为试验动物,分为2组,分别饲喂青贮玉米和混合干草,研究山羊瘤胃和十二指肠内环境的昼夜动态变化。结果表明:①混合干草组瘤胃和十二指肠的pH值均极显著(P<0.01)高于青贮玉米组,其日内动态变化都表现出采食后先下降后上升的趋势;②混合干草组瘤胃液氨态氮浓度极显著(P<0.01)高于青贮玉米组,而十二指肠食糜的氨态氮浓度极显著(P<0.01)低于青贮玉米组;③混合干草组瘤胃乙酸浓度显著(P<0.05)高于青贮玉米组,丙酸浓度差异不显著(P>0.05),青贮玉米组丁酸浓度极显著(P<0.01)高于混合干草组;十二指肠液乙酸、丙酸、丁酸浓度青贮玉米组均极显著(P<0.01)高于混合干草组。     

Protein supplementation of ruminants consuming low-quality cool- or warm-season forage: differences in intake and digestibility

An in situ study (Exp. 1) using 4 ruminally cannulated steers (343 ± 11 kg of BW) in a completely randomized design was used to compare ruminal degradation characteristics of low-quality cool-season (C3; Kentucky bluegrass straw; Poa pratensis; 6.3% CP; DM basis) and warm-season (C4; tallgrass prairie; 5.7% CP; DM basis) forage. Four ruminally cannulated steers (252 ± 8 kg of BW; Exp. 2) and 4 wethers (38 ± 1 kg of BW; Exp. 3) were used in two 2 × 2 factorial arrangements of treatments to determine the influence of supplemental CP (CPSupp; soybean meal; 0.09 and 0.19% of BW, CP basis, for steers and lambs, respectively) on nutrient intake and digestion of C3 and C4 forages. Steers and wethers were allotted to separate 4 × 4 Latin squares that ran simultaneously with 20-d periods. In Exp. 1, C3 had a greater A fraction (fraction of total pool disappearing at a rate too rapid to measure) and effective degradability of DM and NDF compared with C4 (P < 0.01). In addition, C3 had a greater (P < 0.01) A fraction and effective degradability of N, whereas the C fraction (fraction of total pool unavailable in the rumen) was less (P < 0.01) than those for C4. Consequently, RDP accounted for 84.7% of total CP in C3 as compared with 66% for C4 (P < 0.01). In Exp. 2, a CPSupp × forage interaction (P < 0.01) was noted for forage and total DMI, with CPSupp increasing intake of C4 by 47% and intake of C3 forage by only 7%. Dry matter digestibility responded similarly, with a CPSupp × forage interaction (P = 0.05; CPSupp increased digestibility by 21% with C4 and by 9% with C3 forage). In addition, CPSupp × forage interactions were noted for ruminal liquid retention time (P = 0.02; CPSupp decreased retention by 3.6 h with C4 and by only 0.6 h with C3 forage) and particulate passage rate (P = 0.02; CPSupp increased passage by 46% with C4 and by 10% with C3 forage). As in Exp. 2, a CPSupp × forage interaction (P = 0.01; CPSupp increased digestibility by 18% with C4 and by 7% with C3 forage) was observed with DM digestibility in Exp. 3. In contrast, only N balance (P < 0.01) and N digestibility (P < 0.01) were affected by CPSupp. These data suggest that intake and digestion of low-quality C3 and C4 forages by ruminants are not similar and, more important, that the physiological response of ruminants to protein supplementation of low-quality forage is dependent on forage type.     

Effects of haylage and monensin supplementation on performance, carcass characteristics, and ruminal metabolism of feedlot cattle fed diets containing 60% dried distillers grains

The objectives of this research were to determine the interaction of monensin and haylage supplementation for steers fed 60% dried distillers grains (DDGS) on 1) mineral status, performance, and carcass characteristics, and on 2) ruminal pH, H(2)S, and short-chain fatty acid concentrations. In Exp. 1, Angus-cross steers (n=168; BW=277 ± 67 kg) were blocked by BW and allotted in a 2 × 2 factorial arrangement of treatments to 24 pens. Dietary treatments were 1) 0 mg of monensin/kg of diet + 0% haylage, 2) 33 mg of monensin/kg of diet + 0% haylage, 3) 0 mg of monensin/kg of diet + 10% haylage, and 4) 33 mg of monensin/kg of diet + 10% haylage. The remainder of the diet was 60% DDGS, 10% corn silage, 15% supplement, and corn (either 5 or 15%) on a DM basis. When supplemented with 0 mg of monensin/kg of diet, added haylage increased ADG by 5.7%, whereas when supplemented with 33 mg of monensin/kg of diet, added haylage increased ADG by 13% (P < 0.01). No interactions of monensin and haylage were observed for DMI or G:F (P ≥ 0.36). Haylage inclusion increased (P < 0.01) DMI and decreased (P < 0.01) G:F. No interactions (P > 0.05) on plasma mineral concentrations were observed; however, over time, plasma Cu concentrations decreased (P < 0.01), whereas plasma ceruloplasmin and S concentrations increased (P < 0.01). There were no treatment effects (P ≥ 0.08) on carcass characteristics. Cattle fed the 60% DDGS diets benefitted from increased dietary forage, and the effects of monensin and forage were additive for ADG and final BW. In Exp. 2, ruminally fistulated steers (n=8; BW = 346 ± 34 kg) were used in a replicated 4 × 4 Latin square design and were randomly assigned to the diets used in Exp. 1. Haylage inclusion increased ruminal pH from 1.5 through 12 h postfeeding, and the effects of monensin supplementation were additive (P < 0.05). From 1.5 through 9 h postfeeding, steers fed 33 mg of monensin/kg of diet tended to have reduced (P ≤ 0.10) concentrations of H(2)S when compared with steers fed 0 mg of monensin/kg of diet. Acetate:propionate ratios at 6 h postfeeding were 0.94, 0.93, 1.29, and 1.35 for diets 1 to 4, respectively (P < 0.01); total lactate was decreased regardless of treatment (range: 0.94 to 1.42 μmol/mL). Sulfuric acid in DDGS, not ruminal short-chain fatty acids, may be responsible for the low rumen pH observed and may influence the maximum inclusion of DDGS in cattle diets. Monensin supplementation decreased H(2)S concentration and may decrease the risk of polioencephalomalacia for cattle fed high-DDGS diets.     

Comparison of wheat or corn dried distillers grains with solubles on rumen fermentation and nutrient digestibility by feedlot heifers

A 5 × 5 Latin square design trial was conducted to evaluate rumen fermentation and apparent nutrient digestibility in 5 rumen-cannulated heifers (420 ± 6 kg) fed a barley-based finishing diet supplemented with 20 or 40% wheat or corn dried distillers grains with solubles (DDGS). The composition of the control diet was 88.7% rolled barley grain, 5.5% supplement, and 5.8% barley silage (DM basis). Increasing the quantity of corn DDGS in the ration resulted in a quadratic decrease in DMI (P = 0.04) and OM intake (P = 0.05). Rumen pH, pH duration, and area under rumen pH thresholds of 5.8 or 5.5 were not affected (P > 0.05) by treatment. Inclusion of wheat DDGS resulted in a quadratic increase (P = 0.05) in pH area below the cutoff value of 5.2, with the most pronounced effect at 20% inclusion. Wheat DDGS linearly increased (P = 0.01) rumen NH(3)-N concentrations. Increasing the inclusion rate of wheat and corn DDGS resulted in quadratic (P = 0.05) and linear (P = 0.04) decreases in rumen propionate, whereas butyrate increased quadratically (P < 0.01) and linearly (P < 0.01), respectively. Feeding wheat DDGS linearly decreased (P < 0.01) DM and OM digestibility values. Inclusion of corn DDGS increased the digestibility values of ether extract (P = 0.05; quadratic response) and CP (P < 0.01; linear response). Neutral detergent fiber digestibility increased in a linear fashion (P = 0.01) as both wheat and corn DDGS inclusion increased, whereas ADF digestibility increased linearly (P = 0.03) for wheat and quadratically (P = 0.02) for corn DDGS. Increased inclusion of wheat DDGS resulted in a linear decrease in GE digestibility (P = 0.01), whereas increasing corn DDGS inclusion linearly increased (P < 0.01) the DE content of the diet. Feeding both wheat and corn DDGS linearly increased (P = 0.01) the excretion of N and P. In summary, replacement of barley grain with up to 40% wheat or corn DDGS did not mitigate rumen pH conditions associated with mild to moderate acidosis in heifers fed a barley-based finishing diet. Supplementing corn DDGS increased nutrient digestibility of all nutrients and, as a result, led to greater DE content. Supplementation of wheat DDGS reduced DM and OM digestibility values, with no effect on DE content. Increased N and P excretion by heifers fed DDGS at 20 or 40% of dietary DM presents a challenge for cattle feeders with respect to nutrient management.     

Ruminal and host adaptations to changes in frequency of protein supplementation

The effect of altering supplementation frequency on host N balance and key N transactions in the ruminal ecosystem were monitored. Four ruminally fistulated beef steers (BW = 513 kg; SEM = 6.5) were used in a 2 x 2 crossover design with two periods and two supplementation frequency treatments. Supplementation frequencies were 2 and 7 d/wk. Steers were fed tallgrass prairie hay (73.1% NDF, 5.3% CP) ad libitum. Supplement (42% CP; DM basis) was fed at 0.36% BW/d to steers supplemented 7 d/wk. Steers supplemented 2 d/wk received the same amount of supplement per week, but it was equally split among the two supplementation events. Steers supplemented 7 d/wk had higher forage (P < 0.02) and total digestible OM intake (P < 0.06), total N intake, fecal N excretion, and N retention. Although both supplementation frequencies were characterized by positive N balance, the decrease in N retention in the steers supplemented 2 d/wk was due to higher (P < 0.01) urinary N loss. Ruminal fluid was sampled at 0, 2, 4, 6, 12, 24, 48, and 72 h after supplementation beginning on a day when both treatments were supplemented. Frequency x hour interactions (P < 0.02) were observed for ruminal N metabolism criteria. Counts of peptide- and AA-fermenting bacteria peaked at 2 h and returned to nadir by 12 h for steers supplemented 7 d/wk. Steers supplemented 2 d/wk peaked at 6 h with a greater population and returned to nadir at 48 h. Ruminal ammonia concentrations followed a similar trend. Specific activity of ammonia production was lower (P < or = 0.05) immediately after supplementation for steers supplemented 2 d/wk, but by 12 h was the same as for 7 d/wk steers. Ruminal peptides and free AA peaked at 2 h for steers supplemented 2 d/wk and were generally higher (P < or = 0.05) during the first 6 h compared with steers supplemented 7 d/wk. Total VFA concentration was not different (P = 0.35) due to supplementation frequency. Frequency x hour interactions (P < 0.01) were observed for all molar proportions of VFA. The molar proportion of acetate and acetate:propionate ratio were lower (P < 0.01) and the molar proportions of propionate and butyrate were higher for steers supplemented 2 d/wk from 4 h to 24 h. In conclusion, forage use and N balance improved with supplementation 7 d/wk, but supplementation 2 d/wk was associated with some desirable shifts in select ruminal events that may contribute to moderating potential negative impacts of supplementing infrequently.     

Effects of live yeast on differential genetic and functional attributes of rumen microbiota in beef cattle

Several studies have evaluated the effects of live yeast supplementation on rumen microbial population; however,its effect on differential microbial genes and their functional potential has not been described. Thus, this study applied shotgun metagenomic sequencing to evaluate the effects of live yeast supplementation on genetic and functional potential of the rumen microbiota in beef cattle. Eight rumen-cannulated Holstein steers were randomly assigned to two treatments in a cross-over design with two 25-day experimental periods and a 10-day wash-out between the two periods. The steers were housed in individual pens and fed 50% concentrate-mix and 50% red clover/orchard hay ad libitum. Treatments were(1) control(CON; basal diet without additive) and(2) yeast(YEA;basal diet plus 15 g/d of live yeast product). Rumen fluid samples were collected at 3, 6, and 9 h after feeding on the last d of each period. Sequencing was done on an Illumina Hi Seq 2500 platform. Dietary yeast supplementation increased the relative abundance of carbohydrate-fermenting bacteria(such as Ruminococcus albus, R.champanellensis, R. bromii, and R. obeum) and lactate-utilizing bacteria(such as Megasphaera elsdenii, Desulfovibrio desulfuricans, and D. vulgaris). A total of 154 differentially abundant genes(DEGs) were obtained(false discovery rate 0.01). Kyoto Encyclopedia of Genes and Genomes(KEGG) annotation analysis of the DEGs revealed that 10 pathways, including amino sugar and nucleotide sugar metabolism, oxidative phosphorylation, lipopolysaccharide biosynthesis, pantothenate and coenzyme A biosynthesis, glutathione metabolism, beta-alanine metabolism,polyketide sugar unit biosynthesis, protein export, ribosome, and bacterial secretory system, were enriched in steers fed YEA. Annotation analysis of the DEGs in the carbohydrate-active enzymes(CAZy) database revealed that the abundance of genes coding for enzymes belonging to glycoside hydrolases, glycosyltransferases, and carbohydrate binding modules were enriched in steers fed YEA. These results confirm the effectiveness of a live S. cerevisiae product for improving rumen function in beef steers by increasing the abundance of cellulolytic bacteria, lactic acid-utilizing bacteria, and carbohydrate-active enzymes in the rumen.     

Prevention of persistent infection in calves by vaccination of dams with noncytopathic type-1 modified-live bovine viral diarrhea virus prior to breeding

OBJECTIVE: To determine the ability of a modified-live virus (MLV) bovine viral diarrhea virus (BVDV) type 1 (BVDV1) vaccine administered to heifers prior to breeding to stimulate protective immunity that would block transmission of virulent heterologous BVDV during gestation, thus preventing persistent infection of a fetus. ANIMAL: 40 crossbred Angus heifers that were 15 to 18 months old and seronegative for BVDV and 36 calves born to those heifers. PROCEDURE: Heifers were randomly assigned to control (n = 13) or vaccinated (27) groups. The control group was administered a multivalent vaccine where-in the BVDV component had been omitted. The vaccinated heifers were administered a single dose of vaccine (IM or SC) containing MLV BVDV1 (WRL strain). All vaccinated and control heifers were maintained in pastures and exposed to BVDV-negative bulls 21 days later. Thirty-five heifers were confirmed pregnant and were challenge exposed at 55 to 100 days of gestation by IV administration of virulent BVDV1 (7443 strain). RESULTS: All control heifers were viremic following challenge exposure, and calves born to control heifers were persistently infected with BVDV. Viremia was not detected in the vaccinated heifers, and 92% of calves born to vaccinated heifers were not persistently infected with BVDV. CONCLUSIONS AND CLINICAL RELEVANCE: These results document that vaccination with BVDV1 strain WRL protects fetuses from infection with heterologous virulent BVDV1.