Search

We used systems thinking (ST) to identify the critical components of beef cattle production through the lens of ecosystem services (ES), offering a holistic approach to address its adverse externalities. We identified eight critical feedback loops in beef production systems: (i) grazing and soil health, (ii) manure management and soil fertility, (iii) feed efficiency and meat production, (iv) water use and soil moisture, (v) cultural services and community engagement, (vi) energy use, (vii) carbon sequestration and climate regulation, and (viii) environmental impact. Our analysis reveals how these interconnected loops influence each other, demonstrating the complex nature of beef production systems. The dynamic hypothesis identified through the loops indicated that improved grazing and manure management practices enhance soil health, leading to better vegetation growth and cattle nutrition, which, in turn, have a positive impact on economic returns to producers and society, all of which encourage the continuation of interlinked beef and ecosystem stewardship practices. The management of beef production ES using ST might help cattle systems across the globe to contribute to 9 of the 17 different United Nations' Sustainable Development Goals, including the "zero hunger" and "climate action" goals. We discussed the evaluation framework for agrifood systems developed by the economics of ecosystems and biodiversity to illustrate how ST in beef cattle systems could be harnessed to simultaneously achieve the intended environmental, economic, social, and health impacts of beef cattle systems. Our analysis of the literature for modeling and empirical case studies indicates that ST can reveal hidden feedback loops and interactions overlooked by traditional practices, leading to more sustainable beef cattle production outcomes. ST offers a robust framework for enhancing ES in beef cattle production by recognizing the interconnectedness of ecological and agricultural systems, enabling policymakers and managers to develop more effective and sustainable strategies that ensure the long-term health and resilience of humans and ES. [ABSTRACT FROM AUTHOR]

The inclusion of the coproduct dry distil- lers grains plus soluble (DDGS) in the diet of finishing cattle can lead to changes in the nutritional profile of the diets, causing an increase in protein content and a reduction in starch. It is necessary to understand how changes in rumen substrates affect rumen metabolic activity, acids, and enteric methane (CH4) production. Five treatments were used, considering levels of DDGS inclusion in the dry matter (DM) of 1) 0 g/kg of DDGS, 2) 150 g/kg of DDGS, 3) 300 g/kg of DDGS, 4) 450 g/kg DDGS, or 5) 600 g/kg DDGS in finishing diets. The metabolism experiment was conducted with rumen-cannulated Nellore bulls (n = 20) with initial body weight (BW) of 401.8 ± 27.0 kg. The production of short-chain fatty acids (SCFA) and CH4 were determined using the ex-situ ruminal fermentation technique. Rumen content was manually collected from 0, 4, 8 and 12 h post-feeding. The liquid and solid fractions of rumen content were used in four 50 mL penicillin-type flasks per animal. Of the four flasks prepared, two are called “blank” and inactivated in boiling water to stop fermentation, and the other two (microrumen) are incubated in a thermostatic bath, simulating the conditions existing in the rumen of animals (presence of microorganisms, anaerobes, temperature of 39ºC, natural animal saliva, physiological pH) for 30 min. After 30 min, incubated flasks were also inactivated in boiling water to stop fermentation. Subsequently, measurements of the final products of rumen fermentation (SCFA and CH4) were carried out in each bottle. Total rumen emptying was performed to determine the rumen pool of DM. The data will be analyzed in the SAS software, the mean of the treatments will be compared using test of mean and orthogonal contrasts. The declared significance is P ≤ 0.05. The inclusion or levels of DDGS did not affect CH4 production of gּ·kg DM-1ּ·d-1ּ and gּ·kg DM-1ּ d-1ּ (P > 0.05). There was an effect of the treatments on the production of propionate (gּ·kg DM-1ּ d-1ּ; P = 0.0448), with a decreasing linear effect (P = 0.0087) with the increase in the inclusion of DDGS in diet (0; 150; 300; 450; 600 g/kg of DDGS; means 137.20; 160.32; 117.60; 87.09; 91.52 gּ·kg DM-1ּ d-1ּ propionate, respectively). There was no effect of DDGS levels on the production of Acetate, Butyrate, or total SCFAs (gּ·kg DM-1ּ d-1ּ). In summary, DDGS inclusion affects rumen metabolic activity, decreasing propionate production, but does not affect the production of other SCFAs nor CH4 production. [ABSTRACT FROM AUTHOR]

Integrating tannin extracts (TE) into the diet of growing and finishing beef cattle has shown promise in optimizing protein utilization while potentially mitigating methane emissions. Despite these potential benefits, there is a notable gap in a comprehensive analysis of the influence of TE on growth rate. This study addressed this gap by collecting data on the supplementation of a blend of condensed (from Schinopsis spp.) and hydrolyzable (from Castanea spp.) tannins, which has about 70% total tannins, and its impact on critical metrics, such as average daily gain (ADG, kg/d), dry matter intake (DMI, kg/d), and feed efficiency ratio (FER, g/kg). Our objective was to conduct meta-regression analyses to understand better the nuanced effects of condensed tannin supplementation on the overall performance of beef cattle during the critical stages of growth and finishing. The dataset was constructed by collecting published studies that reported in vivo experimental data on growing and finishing beef cattle supplemented with different levels of TE. It contained 132 observations from 35 publications. The meta-analysis was conducted by linear regression with a mixed-effects model fitted by the restricted maximum likelihood method using the nlme package of R software (ver. 4.3.1). Studies were assumed as random variables, and their interaction with the intercept and slope were included in the regression. The number of animals per treatment was used as a study-specific weight. Studies accounted for 32%, 35%, or 27% of the total variance when regressing ADG, DMI, or FER, respectively, on TE (% DM). After adjusting for random effects, the ADG increased (P < 0.001) with increasing levels of dietary TE (P < 0.001): 1.344 (± 0.0071) + 0.240 (±0.0298) × TE (n = 99, r2 = 0.40). It was observed that as the dietary TE level increased, its impact on the ADG tended to decrease from 0.33 kg d-1 % TE-1 when fed up to 0.5% TE to 0.24 kg d-1 % TE-1 when fed up to 1.5% TE, suggesting a possible nonlinear relationship between these two variables. Similarly, DMI decreased slightly (P < 0.001) at 0.61 kg/d/% TE, but with a lower precision (n = 115, r² = 0.14). Consequently, FER increased (P < 0.001) at 17 kg d-1 % TE-1 (n = 93, r² = 0.34). Initial findings suggest that incorporating TE into the diet of growing and finishing cattle, up to a concentration of 0.5% DM, positively influences the growth rate and enhances FER while minimally affecting DMI. Subsequent research endeavors should delve into a more intricate examination of optimal TE inclusion levels and explore additional performance indicators for a comprehensive understanding of its impact. [ABSTRACT FROM AUTHOR]

The environmental impact of the livestock industry, particularly concerning greenhouse gas (GHG) emissions, has become a growing concern. Addressing this challenge requires accurate and efficient measurement methods for monitoring and mitigating gas emissions. One noteworthy method is the GreenFeed (GF), developed by C-Lock Inc., designed to measure methane (CH4 ) emissions and carbon dioxide (CO2 ) concentrations in ruminants through a real-time non-invasive monitoring device with reduced labor intensity and a high level of precision. The GF is the most used equipment to measure GHG in cattle; however, there is still considerable variability that is not explained due to the variation among animals. Thus, the objective of this work is to analyze other environmental factors influencing GF measurements in cattle to explain the variability observed. For this, a total of 127 yearling Angus steers were evaluated for GHG emissions through 6 GF units placed in 6 different pastures (n = 21 to 22 animals/pasture). Animals were evaluated from June to August (2023) at the South Dakota State University Cottonwood Field Station (Cottonwood, SD). The mean values of GHG evaluated were 174g CH4 /d and 5,885 g CO2 /d, showing a coefficient of variation (CV%) of 41% and 27%, respectively. To evaluate GHG variation, we used ANOVA type III (package car in R) for the following variables measured by the GF: temperature, wind speed, wind direction, variance influenced by the GF unit by itself, and animal factors as the number of visits and the duration per visit. Table 1 shows the percentage of variance explained by all these factors on the variation of CH4 and CO2 ; betweenanimal variation (13 and 15.5%), the GF unit (7.2 and 6.3%), duration of visits (2.7 and 2.8%), wind speed (1.7 and 1.3%), temperature (1.3 and 0.0%), wind direction (0.1 and 0.1%) and number of visits (0.3 and 0.0%). The residual error of the model represented 73.7% for CH4 and 73.9% for CO2, indicating the vast percentage of non-explained variance in these two gases, which, in this case, could be associated with different grazing systems or stocking density of animals in the different pastures. Results of this study demonstrate how other factors, non-related to the animal or the type of feed, may contribute to explaining the variation observed in CH4 and CO2 emissions. In future experiments, these factors should be considered to improve the accuracy of measurements and establish smaller differences between groups/individuals. [ABSTRACT FROM AUTHOR]

Monensin and virginiamycin are included in beef cattle finishing diets as prophylaxis to minimize the incidence of ruminal acidosis and liver abscesses. Due to different and probably complementary modes of action, this study aimed to determine the effects of a combination of monensin and virginiamycin, both included in the diet at recommended doses, on ruminal health, the occurrence of liver abscesses, and growth performance of feedlot-finished cattle. One hundred and forty-four steers (6 animals/pen) were fed 1 of 3 corn-based finishing diets containing 30 mg of monensin (MN), 25 mg of virginiamycin (VM), or 30 and 25 mg of monensin and virginiamycin (MN + VM), respectively, per kilogram of dry matter. Ruminal pH probes were inserted into two animals per pen and set to record pH every 10 min. On d 100, animals were slaughtered, and rumens and livers were recovered, on which occurrence and degree of ruminal damage, prevalence and number of liver abscesses, and liver scores (A−: livers with no more than two small abscesses; A+: livers with at least one large abscess or more than four medium abscesses; A: any other abscessed liver) were determined. Simultaneous inclusion of monensin and virginiamycin resulted in a 4.3% decrease (P < 0.04) in dry matter intake (DMI ; 8.8, 9.2, and 9.2 ± 0.19 kg/d for MN + VM, MN, and VM-fed animals, respectively) and similar (P > 0.13) average daily body weight gain (ADG ; 1.49 ± 0.021 kg/d) and hot carcass weight (HCW ; 269 ± 1.7 kg), compared with feeding diets containing one additive or the other. Therefore, in terms of ADG, a 9.4% improvement (P < 0.01) in feed efficiency was observed in MN + VM-fed animals. Backfat thickness (5.6 ± 0.08 mm) and ribeye area (69.9 ± 0.53 cm2) remained unaffected (P ≥ 0.74), as well as the minimum (4.98 ± 0.047), mean (6.11 ± 0.037), and maximum ruminal pH (7.23 ± 0.033) values and the time (125 ± 22.3 min/d), area (57.67 ± 12.383 pH × h), and episodes (22 ± 3.8 bouts) of pH below 5.6 (P ≥ 0.12). Overall, prevalence (24 ± 3.4%) and the number of liver abscesses (1.6 ± 0.14 abscesses/abscessed liver), liver scores (20 ± 3.1% of A− and 4 ± 1.8% of A livers), and prevalence (67 ± 3.5%) and degree of damage to the ruminal epithelium (2.5 ± 0.22% affected surface) were similar (P ≥ 0.18) across treatments; however, the occurrence of ruminal lesions tended (P ≤ 0.07) to be associated with that of liver abscesses and reduced ADG when feeding monensin alone. [ABSTRACT FROM AUTHOR]

Reliable predictions of metabolizable energy (ME) from digestible energy (DE) are necessary to prescribe nutrient requirements of beef cattle accurately. A previously developed database that included 87 treatment means from 23 respiration calorimetry studies has been updated to evaluate the efficiency of converting DE to ME by adding 47 treatment means from 11 additional studies. Diets were fed to growing-finishing cattle under individual feeding conditions. A citation-adjusted linear regression equation was developed where dietary ME concentration (Mcal/kg of dry matter [ DM ]) was the dependent variable and dietary DE concentration (Mcal/kg) was the independent variable: ME = 1.0001 × DE – 0.3926; r 2 = 0.99, root mean square prediction error [ RMSPE ] = 0.04, and P < 0.01 for the intercept and slope. The slope did not differ from unity (95% CI = 0.936 to 1.065); therefore, the intercept (95% CI = −0.567 to −0.218) defines the value of ME predicted from DE. For practical use, we recommend ME = DE – 0.39. Based on the relationship between DE and ME, we calculated the citation-adjusted loss of methane, which yielded a value of 0.2433 Mcal/kg of dry matter intake (DMI ; SE = 0.0134). This value was also adjusted for the effects of DMI above maintenance, yielding a citation-adjusted relationship: CH4, Mcal/kg = 0.3344 – 0.05639 × multiple of maintenance; r 2 = 0.536, RMSPE = 0.0245, and P < 0.01 for the intercept and slope. Both the 0.2433 value and the result of the intake-adjusted equation can be multiplied by DMI to yield an estimate of methane production. These two approaches were evaluated using a second, independent database comprising 129 data points from 29 published studies. Four equations in the literature that used DMI or intake energy to predict methane production also were evaluated with the second database. The mean bias was substantially greater for the two new equations, but slope bias was substantially less than noted for the other DMI-based equations. Our results suggest that ME for growing and finishing cattle can be predicted from DE across a wide range of diets, cattle types, and intake levels by simply subtracting a constant from DE. Mean bias associated with our two new methane emission equations suggests that further research is needed to determine whether coefficients to predict methane from DMI could be developed for specific diet types, levels of DMI relative to body weight, or other variables that affect the emission of methane. [ABSTRACT FROM AUTHOR]

The addition of natural plant secondary compounds to ruminant feed has been extensively studied because of their ability to modify digestive and metabolic functions, resulting in a potential reduction in greenhouse gas emissions, among other benefits. Condensed tannin (CT) supplementation may alter ruminal fermentation and mitigate methane (CH4 ) emissions. This study’s objective was to determine the effect of quebracho CT extract [QT; Schinopsis quebracho-colorado (Schltdl.) F.A. Barkley & T. Meyer] within a roughage-based diet on ruminal digestibility and kinetic parameters by using the in situ and in vitro gas production techniques, in addition to blood urea nitrogen (BUN) and ruminal (volatile fatty acid [VFA], NH3 -N, and protozoa count) parameters. Twenty rumen-cannulated steers were randomly assigned to four dietary treatments: QT at 0%, 1%, 2%, and 3% of dry matter (DM; QT0: 0% CT, QT1: 0.70% CT, QT2: 1.41% CT, and QT3: 2.13% CT). The in situ DM digestibility increased linearly (P = 0.048) as QT inclusion increased, whereas in situ neutral detergent fiber digestibility (NDFD) was not altered among treatments (P = 0.980). Neither total VFA concentration nor acetate-to-propionate ratio differed among dietary treatments (P = 0.470 and P = 0.873, respectively). However, QT3 had lower isovalerate and isobutyrate concentrations compared with QT0 (P ≤ 0.025). Ruminal NH3 and BUN tended to decline (P ≤ 0.075) in a linear fashion as QT inclusion increased, suggesting decreased deamination of feed protein. Ruminal protozoa count was reduced in quadratic fashion (P = 0.005) as QT inclusion increased, where QT1 and QT2 were lower compared with QT0 and QT3. Urinary N excretion tended to reduce in a linear fashion (P = 0.080) as QT increased. There was a treatment (TRT) × Day interaction for in vitro total gas production and fractional rate of gas production (P = 0.013 and P = 0.007, respectively), and in vitro NDFD tended to be greater for QT treatments compared with no QT inclusion (P = 0.077). There was a TRT × Day interaction (P = 0.001) on CH4 production, with QT3 having less CH4 production relative to QT0 on day 0 and QT2 on days 7 and 28. Feeding QT up to 3% of the dietary DM in a roughage-based diet did not sacrifice the overall DM digestibility and ruminal parameters over time. Still, it is unclear why QT2 did not follow the same pattern as in vitro gas parameters. Detailed evaluations of amino acid degradation might be required to fully define CT influences on ruminal fermentation parameters and CH4 production. [ABSTRACT FROM AUTHOR]

Sub-acute rumen acidosis (SARA) is a ruminal digestive disorder with a prevalence of 24 to 30% in United States-based feedlots and is responsible for a lost economic opportunity of approximately $1 billion annually. Our objective for this study was to develop a decision tool which feedlot decision-makers could use to make routine managemental interventions that can mitigate the prevalence of SARA. The continuous reduction in rumen pH (pH < 5.6) is the primary causative factor that triggers its onset. However, this prolonged lower rumen pH results from the interaction between multiple other etiological factors. We developed a random forest-based decision tree prediction tool which used seventeen plausible etiological factors, which we broadly classified under four categories, namely 1) animal factors, 2) nutritional factors, 3) environmental factors, and 4) management factors (Table 1), to predict the probability of SARA in a typical US feedlot. A synthetic dataset of 100 observations was created based on a survey conducted among subject matter experts, including ruminant nutritionists, epidemiologists, and decision modelers to chart out the alleged relationship between the above seventeen etiological factors and the probability of a beef cattle population contracting SARA. The random forest model (R, 2021) was used to train as well as test the boot-strapped (80:20 split) synthetic dataset. Ability of random forest to limit overfitting without substantially increasing error due to bias contributed to the high positive predictive value (84%) of the model. Our results indicated that beef yearling cattle with mild temperament, with a rumen pH maintained above 5.6, while being fed three or more times a day, for more than 150 days on concentrate feed, with a stocking density greater than 7 m2, with excellent preconditioning, fed either sorghum or oats which are tempered with a physically effective fiber of 15% and above, under ambient temperature and humidity, along with the feeding of prebiotics, probiotics and ionophores had the least probability to contract SARA. In conclusion, our model can be used by feedlot decision modelers to test different permutations and combinations of these seventeen etiological factors customized to their respective operations to predict the probability of SARA in their herd. Future studies will improve the accuracy of the model by training it on more robust epidemiological datasets sourced from beef herds located in multiple geographic regions. [ABSTRACT FROM AUTHOR]

Leveraging computer vision (CV) methods to study pen-fed cattle feeding behavior presents several advantages, including monitoring animal health and identifying feed efficient animals. This research employed a region-based convolutional neural network (RCNN) combined with the common objects in context (COCO) dataset for automatic livestock recognition using CV techniques in experimental feedlot pens. Thirty Angus-influenced steers were allocated in one pen with four automated feed intake systems (AFIS; Vytelle SENSE). CV data were recorded during daylight hours using a webcam (Microsoft LifeCam Cinema) with a resolution of 1280x720 pixels at ten frames per second connected to a video surveillance camera software (Contaware, Switzerland). The CV dataset obtained by the cameras, Figure 1, was benchmarked with feeding behavior data obtained from observed annotations (OA) and AFIS. The CV model utilized was a Mask-RCNN with pre-trained weights on the COCO dataset. The Mask RCNN algorithm can identify and locate multiple objects, objects of different scales, and overlapping objects within an image. The COCO dataset is a large and diverse set of annotated images that can be used for training and evaluating object detection models. The fully trained Mask-RCNN model takes each video frame as input and outputs the pixel segmentation of each object detected. For the CV analyses, each animal bounding box was associated with a score threshold, and each pixel within was assigned a probability threshold; both ranging from 0 to 100. The higher the score and probability thresholds are, the fewer the boxes and pixels will be marked as the animal boxing shape, resulting in less feeding detection from the CV system. In contrast, a low score and probability thresholds produce many predictions, including false detections, which might be misleading. Therefore, a dataset analysis was conducted to optimize the best threshold combination. We evaluated the accuracy and precision of the CV model compared with OA and AFIS by analyzing a dataset section of feeding events of one feed bunk using a 0.5 score and 0.5 probability thresholds. We obtained the values for the true positive (TP), false positive (FP), true negative (TN), and false negative (FN) to calculate the accuracy = [TP+TN]/[TP+TN+FP+FN], and precision = [TP]/[TP+FP], Table 1. As a result, the CV model achieved 95.39% and 99.82% accuracy and 93.60% and 99.90%precision when compared with OA and AFIS, respectively. Our findings showcase the promising capabilities of employing the Mask-RCNN algorithm and COCO datasets for detecting beef cattle feeding behavior in feedlot pens. This approach holds significant value for the cattle industry by enabling precise monitoring and analysis of individual animal behavior within feedlot pens, facilitating early detection of behavioral abnormalities. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the differences in feeding behavior patterns of steers with divergent phenotypes for residual feed intake (RFI). Three trials were conducted with 508 Angus-based composite crossbred steers (body weight [BW] = 309 ± 57 kg) fed a high-concentrate diet in pens equipped with electronic feed bunks (GrowSafe System). Initial and final carcass ultrasound measurements (intra-muscular fat, backfat depth, and rib-eye area) were collected on days 0 and 70, and BW measured at 14-d intervals. Individual dry matter intake (DMI) and feeding behavior traits were collected for 70 d, and RFI calculated as the residual from the regression of DMI on average daily gain (ADG) and mid-test BW0.75. Steers were ranked by RFI and assigned to low-, medium-, and high-RFI classes based on ± 0.5 SD from the mean RFI within the trial. The feeding behavior traits evaluated in this study included frequency and duration of bunk visit (BV) and meal events, head-down (HD) duration, mean meal length, time-to-bunk interval, the maximum nonfeeding interval, and the day-to-day variation of these traits, defined as the root mean squared error (RMSE) from linear regression of each trait on the day of trial. Additionally, three ratio traits were evaluated: BV events per meal, HD duration per BV event, and HD duration per meal event. Low-RFI (feed-efficient) steers consumed 16% less (P < 0.01) DMI, while BW and ADG were not different compared with high-RFI steers. Low-RFI steers had 18% fewer and 21% shorter (P < 0.01) BV events, and 11% fewer and 13% shorter (P < 0.01) meal events per day compared with high-RFI steers. Furthermore, low-RFI steers exhibited less (P < 0.05) day-to-day variance in DMI, as well as in frequency and duration of BV and meal events and HD duration compared with high-RFI steers. Differences in feeding behavior traits due to RFI were minimally affected by covariate adjustment for DMI, indicating that steers with divergent RFI have distinct feeding behavior patterns that are largely independent of differences in DMI. These results suggest that feeding behavior traits may be useful biomarkers for the prediction of feed efficiency in beef cattle. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of supplementing dry live yeast (LY ; Saccharomyces cerevisiae) on in vitro gas production (IVGP) fermentation dynamics, pH, and CH4 concentration at 48 h, and in situ rumen parameters and digestibility of DM (DMD) and NDF (NDFD) of growing cattle during 3 feeding phases: grower (GRW) for 17 d (38% steamed-flaked corn; SFC), transition (TRANS) for 15 d (55.5% SFC: 1.2 Mcal/kg NEg), and finisher (FIN) for 13 d (73% SFC: 1.23 Mcal/kg NEg). Twenty British-crossbred, ruminally cannulated steers (183 kg ± 44 kg) 6 mo of age were blocked by weight into 5 pens containing Calan gate feeders and received a control (CON) diet (17.2% CP, 35.8% NDF, 86.7% DM) without LY on days −12 to 0. After that, animals were randomly assigned to treatments (TRT), 5 animals per TRT: CON or LY at inclusion rates of 5 g/d (LY1), 10 g/d (LY2), or 15 g/d (LY3) top dressed every morning at 0800 for 45 d. The DMD and NDFD were assessed during 7 separate collection days using in situ nylon bags containing 5 g of GRW, TRANS, or FIN diets, incubated at 1200 for 48 h. Protozoa counts (PC) were determined during 5 collection periods. Data were analyzed as a repeated measure within a randomized complete block design, assuming a random effect of the pen. For GRW, TRT altered the total gas production of the nonfiber carbohydrate (NFC ; P = 0.045) and the fractional rate of degradation (kd) of the fiber carbohydrate (FC) pool (P = 0.001) in a cubic pattern (P ≤ 0.05): LY2 had the most gas production and fastest kd. TRT also influenced DMD (P = 0.035) and NDFD (P = 0.012) with LY2 providing the greatest digestibility. For TRANS, TRT tended to affect the NFC kd (P = 0.078) and influenced pH (P = 0.04) and DMD (P < 0.001) in which LY2 yielded the fastest kd, highest pH, and greatest DMD. For FIN, there was an effect of TRT on total gas production (P < 0.001) and kd (P = 0.004) of the NFC pool, FC kd (P = 0.012), in vitro CH4 concentration (P < 0.001), PC (P < 0.001), DMD (P = 0.039), and NDFD (P = 0.008). LY1 had the highest PC and provided the greatest DMD and NDFD. LY2 had the fastest kd of both the NFC and FC pools and had the least CH4 concentration. LY3 had the greatest NFC gas production. No specific dose–response pattern was observed, but 10 g/d provided the most beneficial result for all diets. We concluded that supplementation with LY affected IVGP as well as ruminal parameters and digestibilities. [ABSTRACT FROM AUTHOR]

The objectives of this study were to examine the relationship between residual feed intake (RFI) and DM and nutrient digestibility, in vitro methane production, and volatile fatty acid (VFA) concentrations in growing beef cattle. Residual feed intake was measured in growing Santa Gertrudis steers (Study 1; n = 57; initial BW = 291.1 ± 33.8 kg) and Brangus heifers (Study 2; n = 468; initial BW = 271.4 ± 26.1 kg) fed a high-roughage-based diet (ME = 2.1 Mcal/kg DM) for 70 d in a Calan-gate feeding barn. Animals were ranked by RFI based on performance and feed intake measured from day 0 to 70 (Study 1) or day 56 (Study 2) of the trial, and 20 animals with the lowest and highest RFI were identified for subsequent collections of fecal and feed refusal samples for DM and nutrient digestibility analysis. In Study 2, rumen fluid and feces were collected for in vitro methane-producing activity (MPA) and VFA analysis in trials 2, 3, and 4. Residual feed intake classification did not affect BW or BW gain (P > 0.05), but low-RFI steers and heifers both consumed 19% less (P < 0.01) DMI compared with high-RFI animals. Steers with low RFI tended (P < 0.1) to have higher DM digestibility (DMD) compared with high-RFI steers (70.3 vs. 66.5 ± 1.6% DM). Heifers with low RFI had 4% higher DMD (76.3 vs. 73.3 ± 1.0% DM) and 4 to 5% higher (P < 0.01) CP, NDF, and ADF digestibility compared with heifers with high RFI. Low-RFI heifers emitted 14% less (P < 0.01) methane (% GE intake; GEI) calculated according to Blaxter and Clapperton (1965) as modified by Wilkerson et al. (1995) , and tended (P = 0.09) to have a higher rumen acetate:propionate ratio than heifers with high RFI (GEI = 5.58 vs. 6.51 ± 0.08%; A:P ratio = 5.02 vs. 4.82 ± 0.14%). Stepwise regression analysis revealed that apparent nutrient digestibilities (DMD and NDF digestibility) for Study 1 and Study 2 accounted for an additional 8 and 6%, respectively, of the variation in intake unaccounted for by ADG and mid-test BW0.75. When DMD, NDF digestibility, and total ruminal VFA were added to the base model for Study 2, trials 2, 3, and 4, the R 2 increased from 0.33 to 0.47, explaining an additional 15% of the variation in DMI unrelated to growth and body size. On the basis of the results of these studies, differences in observed phenotypic RFI in growing beef animals may be a result of inter-animal variation in apparent nutrient digestibility and ruminal VFA concentrations. [ABSTRACT FROM AUTHOR]

The use of active dried yeast (ADY) in the diets of feedlot steers may improve feed efficiency, growth performance, and reduce days on feed. Strategic timing of ADY inclusion in the diet may increase feed conversion or aid in the dietary transition from growing to finishing diets. One hundred twenty steers, blocked by weight, were fed four diets for 164 d: grower (70 d), first transition diet (7 d), second transition diet for (7 d), and finisher (80 d) in a GrowSafe System. Four treatment sequences of ADY inclusion were evaluated in a Balaam's design where steers were fed a control diet before and after the grower phase (CC), control before and ADY after the grower phase (CY), ADY before and control after the grower phase (YC), and ADY before and after the grower phase (YY). A random coefficients model was used to evaluate the following variables of interest: feeding performance and growth traits, including biometric measurements and carcass ultrasound measurements, and carcass characteristics. Treatment was a fixed effect and block was a random effect. Treatment did not affect feeding performance or behavior (P ≥ 0.14). The rate of change of biometric measurements were not different (P ≥ 0.16) across treatment groups except for rib girth circumference, which was greater for the YY and CY groups intermediate for the CC group and least for the YC group (0.828 and 0.809 vs. 0.751 vs. 0.666 cm/d, respectively; P < 0.01). Faster growth rates of rib girth circumference resulted in larger final measurements for steers that were finished on ADY (P < 0.01). Ultrasound measurements (backfat, LM area, intra-muscular fat, and rump fat) were not different across treatments (P ≥ 0.15). However, there was a tendency for the YC group to have a slower rate of back fat deposition than other treatment groups (P = 0.09). Steers' final shrunk BWs did not differ (P = 0.61), but shrink percentage was greater for CC than for YY groups (3.7% vs. 2.7%, respectively; P = 0.05). Carcass characteristics were not different across treatments (P ≥ 0.20). Crude fat, CP, ash and moisture analyses of the 9th to 11th rib section were not different across treatments, and there was no difference in adjusted final shrunk BW (P ≥ 0.45). Feeding the ADY strain used in this study to growing and finishing feedlot steers increased rib girth circumference development rate and reduced shrink loss without affecting feeding behavior, feeding performance, or carcass characteristics. [ABSTRACT FROM AUTHOR]

Ruminal acidosis is a common metabolic disorder that affects feedlot and dairy cattle and occurs when the supply of organic acids from fermentation exceeds its absorption, accumulating acid content in the rumen. Virginiamycin (VM) has inhibitory effects on primary liver abscess-causing bacteria. In feedlot animals, dietary VM has been shown to reduce rumen acidosis and improve feed conversion actively. This study evaluated ruminal pH over 150 days on feed (DOF) of growing and finishing beef cattle and investigated the relationships between ruminal pH and growth and development outcomes and the effectiveness of the continuous or intermittent provision of VM in 120 Angus-crossbred steers. Steers received VM (240 mg/d) as follows: no VM (T000); VM in the last 50 d (T001); VM for the last 100 d (T011); VM in the first 50 d (T100); VM in the first 100 d (T110); and VM for 150 d (T111). Animals were fed a grower-type diet (metabolizable energy [ME]: 2.45 Mcal/kg; crude protein [CP]: 12.2 % dry matter basis [DM]) for 50 d before the adaptation of a finisher-type diet (ME: 2.60 Mcal/kg; CP: 10.6% DM) over a 17-d period. The finishertype diet was fed for the remaining 84 days. On d -1 and d 82 each animal received an indwelling pH bolus to record ruminal pH at 10-min intervals. Acidosis bout event was categorized as if the pH stayed below 5.6 for 3 hours. Data were analyzed using a random coefficient statistical model, binary data was analyzed using the logit link function and correlations were analyzed using PROC CORR in SAS (Table 1). Duration under pH 5.8 and 5.6 tended to have a negative correlation with gain to feed (G/F; P = 0.080), and % of the time that pH remained below 5.6 when under 5.8 was negatively correlated with G/F (P = 0.007) and tended to have a negative correlation with average daily gain (ADG; P = 0.081). Similarly, acidosis bouts event and duration of bout event (DURB) tended (P = 0.074) to have a negative correlation with G/F, while ADG was negatively correlated (P = 0.035). The number of acidosis bout events and probability of acidosis bout events to occur increase linearly (R2 = 0.89, P < 0.001, and R2 = 0.77; P < 0.001, respectively) as DOF progressed. The probability of an acidosis bout event decreased by 46% for the T111 treatment compared with T000 (35.43% vs. 18.82%; P = 0.049). Acidosis bout event seems to affect the growth and development of beef steers negatively, and it appears to be more critical as DOF progress. Administration of VM at 240 mg/d throughout the whole feeding period seems to reduce the incidence of acidosis bout events. [ABSTRACT FROM AUTHOR]

The judicious use of commercial products in livestock operations can be part of a sustainable and environmentally friendly production scenario. This study was designed to gather published data of virginiamycin (VM) used in feedlot conditions of the United States and analyze its effectiveness and optimum dosage in reducing the liver abscess incidence (LAI). The dataset contained 26 studies that evaluated more than 7,156 animals of diverse breeds fed in several regions in the United States under different management. Statistical analyses included contingency tables to assess the nonparametric independence of the LAI, meta regression analysis to remove study effects and to evaluate LAI and animal performance, broken-line analysis to determine thresholds of VM dosage on LAI, and residual-based shading mosaic plots to illustrate the contingency analysis. There were 1,391 of 5,430 animals with LAI scores 1, 2, or 3 (LAI1–3) and 651 of 4,690 animals with LAI A+ (score 3). Our analyses suggested that there was a significant dependency (χ2P-value < 0.001) and significant asymmetry (McNemar’s test P-value < 0.001) between LAI and VM treatment for both LAI1–3 and LAI A+. For the LAI1–3 group, only 22.5% of the treated animals had liver abscesses compared with 31.7% of the control animals. The metaregression analysis indicated that LAI1–3 was linearly reduced (P < 0.001) by about 0.42% per mg/kg of DM of VM. The lower 95% confidence interval of the intercept for LAI1–3 and LAI A+ obtained with a generalized nonlinear mixed regression was 18.7 and 20.3 mg/kg of DM, respectively. The broken-line regression analysis identified 2 thresholds for LAI (23.9 and 12.3 mg/kg of DM) at which the reduction in total LAI1–3 and LAI A+, respectively, would decrease faster as VM dosage increases (from 2.14% to 6% and from 1.91% to 4.33% per mg of VM per kg of DM, respectively). Additionally, our analyses indicated that after accounting for the study effects, VM significantly increased ADG at 2.08 g BW/d per mg/kg DM compared with 0.92 g BW/d per mg/kg DM for monensin (P < 0.001), suggesting that VM was about 2.3 times more effective in increasing ADG for the same dosage and feeding period length. All analyses yielded consistent results that led us to conclude that VM is effective in reducing LAI when fed between approximately 12 and 24 mg/kg of DM, and the maximum reduction might occur at approximately 24 mg/kg of DM or higher. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the effects of two feeding times and two sources of energy supplementation on pH, short-chain fatty acids (SCFA), and in vitro gas production (IVGP) of beef cattle reared in Urochloa brizantha cv. Marandu pastures. We used eight rumen-cannulated ½ Aberdeen Angus x ½ Nellore young bulls (280±7 kg) distributed in a double 4x4 Latin square design. Treatments consisted of supplementation at 0.3% of body weight with corn or citrus pulp, supplied at 0900 or 1700. Ruminal fluid pH was measured with a digital pH analyzer and SCFA was analyzed on a Shimadzu HPLC. The IVGP was determined using a transducer and a data logger for 48 h after incubation of samples combining forage and supplement in real intake proportion (88% forage, 12% supplement). Considering the rapid fermentation of sugars, animals supplemented with pectin maintained higher pH (P = 0.021) due to changes in bacterial populations to digest the pectic substances (Table 1). Lactate production after starch digestion caused lower pH. Despite the differences in evaluated energy substrates, there was no effect on the primary SCFA concentration (P > 0.05). Citrus pulp provided greater formic (P = 0.005) and valeric (P = 0.042) acids concentrations compared with corn, but there was no influence of formic acid in lactic acid production (Table 1). The greater IVGP by citrus pulp (P = 0.0140; Figure 1) may be related to its greater carbohydrate fraction A, soluble with a rapid rate of rumen degradation, and also because its ruminal fermentation results in greater acetic acid production, which provides more ruminal H2 and CO2, favoring the CH4 production. The citrus pulp can be used as an alternative source to corn because it might prevent acidosis, does not affect the main SCFA production, and is a non-human edible feed. [ABSTRACT FROM AUTHOR]

Intelligent societies are built through education. Wisdom gained through scientific knowledge and discourse is necessary for spreading reliable information and building consensus among citizens of the six continents on earth. Internationalization empowers the fostering and discovery of novel techniques and resources that could solve contemporary issues assailing humankind's prosperity, including sustainability, environmental pollution, and hunger. A community might have found solutions to problems other communities face; however, our failures of globalization postpone their resolution. Animal science is not immune to these failures. Livestock production could incorporate know-how from other communities, borrowing from experiences of student and faculty exchange and study abroad programs. The tremendous evolutionary aspects of ruminants' digestive system allow them to thrive in diverse and sometimes inhospitable ecosystems and convert human-inedible resources into high-quality animal products for human consumption. Humankind relies on ruminants for energy and protein consumption, wool, and draft power. This symbiotic relationship has led to extreme production systems due to economy-of-scale factors and the availability of resources in some countries. But, other countries have relied on rustic, low-intrusive production systems that are more amenable to the environment and more conducive to sustainability. Therefore, breaking the boundaries across nations through international partnership programs will lead to sharing scientific knowledge and enhancing management programs essential to the long-term continuation of this human-ruminant symbiotic relationship within responsible animal welfare programs. Besides improving the communication among societies and spreading scientific advancements, such internationalization programs will shape students, i.e., the workforce of the future, into citizens of the world with accurate and helpful information about the language, culture, problems, and needs of other civilizations and how to enrich our likelihood and theirs. As a result, leaders of the many different nations worldwide can, once again, expand the frontiers of scientific knowledge in seeking sustainable, responsible, and affordable animal agriculture activities. [ABSTRACT FROM AUTHOR]

The effects of a nutritional packet offered to beef yearling-steers during the feedlot-finishing phase on feeding behavior were evaluated. Crossbred-Angus steers (n = 30; initial BW = 542 ± 8 kg) were assigned to pens (15 steers/pen; animal = experimental unit) in a randomized complete block design. Steers were offered a steam-flaked corn-based finishing diet ad libitum, and treatments as follows: 1) control and 2) 30 g/steer-daily (DM-basis) of a nutritional packet (live yeast [Saccharomyces cerevisiae; 8.7 Log CFU/g], vitamin C [5.4 g/kg], vitamin B1 [13.33 g/kg], NaCl [80 g/kg], and KCl [80 g/kg]). Ground corn was used as a carrier and included at 1% of diet DM. Orts were subtracted from the dietary DM offered to calculate DM intake. Feeding behavior (meal frequency, meal size, bunk visit duration, and meal criterion) were continuously recorded using the Smartfeed system (individual animals). Three periods during the last 60 days before cattle harvest were assessed: 1) d7-11; 2) d28 -32; and 3) d49-53. Periods were used to compute meal criteria for each animal using the Meal Criterion Calculation (v. 1.9) software. Data were analyzed using the GLIMMIX procedure of SAS. No treatment × period interactions were observed (P ≥ 0.32) for meal frequency, duration (min/meal), and intake (kg/meal). Steers offered the nutritional packet had greater overall meal duration during periods 1 and 3 (75 and 77 min/d; P < 0.01), but did not differ (68 min/d; P = 0.09) for period 2 (Control AVR = 55 min/d). Steers offered the nutritional packet had greater (P ≤ 0.01) meal frequency (20 vs. 16 meals/d), while individual meal duration (3.85 min/meal) and meal intake (0.46 kg/meal) were not affected by treatments (P > 0.86). Improved meal frequency and overall time spent eating, without affecting intake, may induce a more desirable daily distribution of nutrients. [ABSTRACT FROM AUTHOR]

Virginiamycin (VM) is an antibiotic that possesses antimicrobial properties due to its ability to block protein synthase in Gram-positive bacteria. It reduces lactic acidosis and the incidence of liver abscesses. Animal growth and development is brought about because of improved ruminal health, and animal health and welfare. This study evaluated the continuous or intermittent provision of VM during the growing and finishing phases on 120 Angus-crossbred steers (291 ± 28 kg) in 20 pens equipped with a Calan gate feed system from which animals received VM (240 mg/d) as follow: no VM (T000); VM in the last 50 d (T001); VM for the last 100 d (T011); VM in the first 50 d (T100); VM in the first 100 d (T110); and VM for 150 d (T111). Data were analyzed using a random coefficients model with the pen as a random effect and animals within treatment as the subject. The T011 tended (0.075 ≥ P ≥ 0.052) to have a greater carcass, final shrunk body weight compared with T110. Empty body fat (EBF; %) tended (0.080 = P = 0.050) to be less for animals that consumed VM regardless of the period or length of feeding. Dry matter intake (DMI) was lesser for T111 compared with T000, and greater for T011 compared with T110 (P = 0.028), which resulted in greater average daily gain (ADG) with no difference in feed efficiency (P = 0.015 and 0.225, respectively). ADG-adjusted metabolizable energy (aME) content increased by 3.08% for T111 compared with T000. This study indicated that daily supplementation of 240 mg VM during the whole feeding phase increased feed efficiency and paME, whereas when withdrawn during the end of the finishing phase (T110) can impair DMI and ADG. [ABSTRACT FROM AUTHOR]

Nutritional grouping (NG) strategies have been proposed mainly in dairy cattle to improve economic efficiency (30-60$/cow per year) of dairy farmers. In dairy cattle, NG is made according to net energy (NE) requirements estimated from some animal variables (i.e., milk yield and dairy merit). However, NG has not been evaluated for beef cattle, likely because data are not readily available and existing protocols have been fixed for decades by the beef industry, such as allotting by body weight (BW): growing diet for 180 to 400-kg animals, and finishing diet for 400 to 550-kg animals. Therefore, we investigated an unsupervised machine learning (ML) technique in R to sort animals at the arrival according to their DM intake (DMI), NE and metabolizable protein (MP) requirements, estimated through INRA from BW and average daily gain. We utilized data from 77 growing Friesian steers allotted conventionally by BW (139±21.6 kg) in 4 pens, weighed every 3 weeks (n=9 weighings) during 190 days, and fed a high-energy diet (1.59 Mcal NE/kg DM and 89 g MP/kg DM). Results identified that estimated performances were significantly (P< 0.002) different between 3 groups made from ML and between 4 pens made from BW; however, ML groups presented a minor within-group variability of NE and MP requirements (-25%CV) than pens. We also regressed energy and protein intake minus their respective requirements by the duration of the experiment observing a better fitting (R2= 0.93 vs 0.80) when allotting animals by groups than by pens, which implicates better feed efficiency if diets were formulated according to requirements established by ML groups. We demonstrated that ML techniques could help the decision-making of beef farmers to better sort animals according to their requirements and not only by BW. The next step is to formulate rations according to animal requirements to improve efficiency. [ABSTRACT FROM AUTHOR]

Plant secondary metabolites (PSM) and yeast supplemented in growing cattle have been reported as improving dry matter digestibility (DMD) and reducing enteric methane emissions. This study aimed to evaluate the effect of combined supplementation with condensed tannin (CT; Schinopsis balansae) extract and active dry yeast (ADY; Saccharomyces cerevisiae) on fermentation dynamics, utilizing in vitro gas production (IVGP) technique. A 2 × 2 Latin square design was used to study fermentation patterns of four dietary treatments (CON-no CT and no ADY, ADY alone, CT alone or combined CT + ADY). Animals received daily CT at 1% DM and 10 g of ADY, respectively. On d 0, 7, 14, 21, 28, and 35 rumen inoculum was collected from 23 fistulated steers (284.3 ± 4.1 kg) four hours post-feeding. Samples were incubated under anaerobic conditions at 39oC for 48 h with 200 mg of a grower diet (14.8% CP, 40.6% NDF, 88.5% DM). Gas parameters were analyzed using a mixed linear statistical model. There was a day effect for total gas production (TGP; P < 0.001), non-fiber carbohydrate degradation (P = 0.031) and fractional degradation assuming an asymptote model (P = 0.015). Both asymptote and non-fiber fractional degradation rate estimates had an interaction between Day × TRT (P = 0.001 and 0.0104, respectively). Data were analyzed using polynomial contrasts showed a difference in non-fiber fractional rate of fermentation for CON × CT and CT × ADY (P = 0.052 and 0.054, respectively). This was also true if an asymptote model was assumed (P = 0.0 34 and 0.034, respectively). We concluded that combined supplementation of CT and ADY exhibited similar IVGP trends over time, this may be because animals only received a grower diet at 1.5% shrunk BW. Future studies should investigate the impact of combined supplementation on varying levels of concentrate diets. [ABSTRACT FROM AUTHOR]

We aimed to assess whether predicting the metabolizable energy (ME) to digestible energy (DE) ratio (MDR), rather than a prediction of ME with DE, is feasible and to develop a model equation to predict MDR in beef cattle. For this, we constructed a literature database based on published data. A metaanalysis was conducted with 306 means from 69 studies containing both dietary DE and ME concentrations measured by calorimetry to test whether the exclusion of the y-intercept is adequate in the linear relationship between DE and ME. A random coefficient model with study as the random variable was used to develop equations to predict MDR in growing and finishing beef cattle. The developed equations were evaluated with other published equations. The no-intercept linear equation represented the relationship between DE and ME more appropriately than the equation with a y-intercept. Within our growing and finishing cattle data, the animal's physiological stage was not a significant variable affecting MDR after accounting for the study effect (P = 0.213). The mean (± SE) of MDR was 0.849 (± 0.0063). Two linear equations with the dry matter intake and content of several dietary nutrients were developed to predict MDR. When using these equations, the observed ME was predicted with high precision (R2 = 0.92). The model accuracy was also high, as shown by the high concordance correlation coefficient (> 0.95) and small root mean square error of prediction (RMSEP), less than 5% of the observed mean. Moreover, a significant portion of the RMSEP was due to random bias (> 93%), without mean or slope bias (P > 0.05). We concluded that dietary ME in beef cattle could be accurately estimated from dietary DE and its conversion factor, MDR, using the two equations developed in this study. [ABSTRACT FROM AUTHOR]

Livestock water use sustainability is a growing concern in the beef cattle sector. The Water Footprint Assessment (WFA) method has been used to quantify the water footprint (WF) of beef products but does not suggest any specific management strategies to decrease the WF of beef cattle (WFB) within and across the beef supply chain. The WFB is primarily influenced by forage and grain production water uses (m3/t), which are directly linked to dry matter (kg/d) and water intake (L/d) and cattle growth (kg/d). Therefore, the objective of this study was to assess the alteration of forage quality and above-ground biomass production (t/ha) of annual ryegrass (Lolium multiflorum) and bermudagrass (Cynodon dactylon), in addition to published WF estimates for corn (Zea mays) and soybean (Glycine max) production (m3/t) on the daily Texas WFB. A dynamic Texas Beef Water Footprint Model (TXWFB) was developed to predict WFB, using the System Dynamic methodology and equations from the Ruminant Nutrition System (RNS) and Beef Nutrient Requirements (NASEM) models. Results indicated that forage and crop biomass production is a high-leverage solution to offset the daily Texas WFB (%∆ = -55 to 130). The alteration of forage TDN had less of an impact on the Texas WFB (%∆ = -39 to 17). An ANOVA with a Tukey Posthoc test indicated that all WFB scenarios were significantly different (P < 0.05) except for the low versus base TDN under low water use conditions scenario. The variability in the use of green and blue waters for grains indicated that the final WFB, in the feedlot phase, may be lower than the WFB in the cow-calf or stocker stages under certain efficiency conditions. Identification of high and low-leverage solutions may help Texas cattle stakeholders implement systemic strategies that aid in the efforts for sustainable beef water use. [ABSTRACT FROM AUTHOR]

Methods have been developed to measure the effectiveness of many roughages, but few evaluations have been conducted with tropical feeds. The objectives of this research were to determine the effectiveness of roughage sources based on bioassay and laboratory methods and identify the biological attributes of the diets that correlate with these methods. Six ruminally cannulated Nellore steers (408 ± 12 kg of BW) were randomly assigned to a 6 × 6 Latin square design within six diets: negative control diet (NC) with aNDF as 10% from corn silage (CS); positive control diet (PC) with aNDF as 20% from CS; and four diets containing 10% aNDF from CS and 10% aNDF from each of the following sources: sugarcane (SC), sugarcane bagasse (SCB), soybean hulls (SH), or low oil cottonseed hulls (LOCH). Physical effectiveness factor (pef , related to the physical characteristics of aNDF) and effectiveness factor (ef , related to the ruminal pH) were determined based on a linear model approach that uses a bioassay method in which CS aNDF was assumed to be the standard fiber source. Laboratory methods to estimate pef of roughage sources were based on the proportion of DM of roughage retained on a 1.18-mm sieve pef(>1.18 mm) or retained on the 8.0-mm Penn State Particle Separator screen pef(>8.0 mm). The pef calculated by the bioassay method (total chewing time and ruminal mat resistance) for CS, SCB, and SC were higher values (P < 0.05) compared with SH and LOCH. The pef(rumen mat) of SC and SCB were higher (P < 0.05) than that of CS, SH, and LOCH. The pef(rumen mat) of LOCH was 61% higher than SH. The ef(rumen pH) of SC and LOCH was higher (P < 0.05) than CS and SH. The pef(chewing, min/d), pef(chewing, min/kg of DM), pef(rumen mat), and ef(rumen pH) positively correlated with rumination time, total chewing time, and ruminal mat resistance (values from transit time in seconds). No correlation was observed (P > 0.05) between pef(>8.0 mm) and rumination time, chewing time, and ruminal pH. The pef calculated using the bioassay method as well as pef (>8.0 mm) were negatively correlated with rumen pH (P > 0.05). The values of the effectiveness of fiber sources obtained in this research can be used as a guideline for nutritionists aiming to replace roughage sources from tropical regions in beef cattle finishing diets. Under our conditions, the pef using the bioassay method or laboratory methods were not adequate in predicting ruminal pH. [ABSTRACT FROM AUTHOR]

The objectives of this research were to evaluate the effects of source and concentration of α-amylase-treated neutral detergent fiber (aNDF) from roughage on feed intake, ingestive behavior, and ruminal kinetics in beef cattle receiving high-concentrate diets. Six ruminally cannulated Nellore steers (408 ± 12 kg of body weight) were randomly assigned to a 6 × 6 Latin square design with six diets: 10% aNDF from corn silage (10CS); 20% aNDF from corn silage (20CS); or four diets containing 10% aNDF from corn silage and 10% aNDF from one of the following sources: sugarcane (SC), sugarcane bagasse (SCB), soybean hulls (SH), or low oil cottonseed hulls (LOCH). The parameters of passage and degradation kinetics were estimated based on a two-compartmental model with gamma- and exponential-distributed residence times. The nonlinear models were fitted by nonlinear least squares, and a linear mixed-effects model was fitted to all variables measured from the Latin square design that were related to intake, digestibility, digestion kinetic parameters, and residence times. Mean particle size (MPS) between roughage sources (CS, SCB, and SC) and coproducts (SH and LOCH) was affected (P < 0.05). Dry matter intake (DMI) was not affected (P > 0.05) by 20CS, SC, SH, or LOCH. Steers fed 20CS or LOCH diets had 16% and 20% greater DMI, respectively, (P < 0.05) than steers fed 10CS diet. Steers fed SCB consumed the least dry matter (DM). The SH and LOCH diets had lower MPS values (about 8.77 mm) in comparison to 20CS, SCB, and SC diets (about 13.08 mm) and, consequently, affected (P < 0.05) rumen content, ruminal in situ disappearance, nutrient digestibility, and solid fractional passage rate. Chewing time was affected (P < 0.05) by roughage sources and concentration. Lower values of distance travel inside the rumen (min/cm) were observed (P < 0.05) for the SCB and SC diets in comparison with any other diet. Except for SCB, there was no difference (P > 0.05) in rumen fill, among other treatments. Mean daily ruminal pH was not affected (P > 0.05) by 20CS, SCB, SC, and LOCH diets, and it ranged from 6.1 to 6.23. Total short-chain fatty acids concentration was affected (P < 0.05) by roughage source and concentration. Based on our results, we recommend that under Brazilian finishing diets, replacing roughage sources, except for SCB, based on aNDF concentration of the roughage in high-concentrate diets containing finely ground flint corn does not affect DMI. [ABSTRACT FROM AUTHOR]

Condensed tannins (CT) might improve animal and system-level efficiency due to enhanced protein efficiency and reduced CH4. This study evaluated the impact of quebracho tannin (QT) extract fed at 0%, 1.5%, 3%, and 4.5% of dry matter (DM), within a roughage-based diet on apparent digestibility of DM, organic matter (OM), fibrous fractions, and N retention and energy partitioning of growing steers (236 ± 16 kg BW). A Latin rectangle design with eight animals and four periods was used to determine the whole-animal exchange of CO2, O2, and CH4 as well as the collection of total feces and urine over a 48-h period, using two open-circuit, indirect calorimetry respiration chambers. Following the removal of steers from respiration chambers, rumen inoculum was collected to determine ruminal parameter, including volatile fatty acids (VFA) and ammonia. Animals were fed a 56.5% roughage diet at 1.7% BW (dry matter basis). Dry matter and gross energy intakes were influenced by the level of QT inclusion (P ≤ 0.036). Digestibility of DM, OM, and N was reduced with QT inclusion (P < 0.001), and fiber digestibility was slightly impacted (P > 0.123). QTs altered the N excretion route, average fecal N-to-total N ratio excreted increased 14%, and fecal N-to-urinary N ratio increased 38% (P < 0.001) without altering the retained N. Increased fecal energy with QT provision resulted in reduced dietary digestible energy (DE) concentration (Mcal/kg DM; P = 0.024). There were no differences in urinary energy (P = 0.491), but CH4 energy decreased drastically (P = 0.007) as QT inclusion increased. Total ruminal VFA concentration did not differ across treatments, but VFA concentration increased linearly with QT inclusion (P = 0.049). Metabolizable energy (ME) was not affected by the QT rate, and the conversion efficiency of DE-to-ME did not differ. Heat energy decreased (P = 0.013) with increased QT provision likely due to changes in the DE intake, but there was no difference in retained energy. There were no differences for retained energy or N per CO2 equivalent emission produced (P = 0.774 and 0.962, respectively), but improved efficiency for energy retention occurred for 3% QT. We concluded that QT provided up to 4.5% of dry matter intake (about 3.51% of CT, dry matter basis) does not affect N and energy retention within the current setting. Feeding QT reduced energy losses in the form of CH4 and heat, but the route of energy loss appears to be influenced by the rate of QT inclusion. [ABSTRACT FROM AUTHOR]

Beef production needs to increase from 60 million to 130 million tons by 2050 to feed a growing world population, and 70% of this production increase is expected from beef industries located in subtropical and tropical regions of the world. Bos indicus -influenced cattle predominate in these regions but are often managed using practices developed for Bos taurus breeds reared in temperate climates. Hence, a fundamental step to meet the increasing global demand for beef is to develop specific management for B. indicus -influenced cattle in tropical or subtropical environments. Bos taurus and B. indicus are different subspecies, and diverge in social and biological functions due to selection pressure caused by complex evolutionary and domestication processes. Bos indicus cattle display different social responses compared with B. taurus counterparts, which must be taken into account by management planning as these traits directly impact cattle performance and welfare. In tropical and subtropical regions, warm-season perennial C4 grasses are the dominant forages, and their availability has a significant influence on the productivity of beef cattle systems. The resilience of C4 grasses under adverse conditions is one of their most important characteristics, even though these forages have reduced nutritive value compared with forages from temperate climates. Accordingly, nutritional planning in tropical and subtropical conditions must include management to optimize the quantity and quality of C4 forages. Nutritional requirements of cattle raised within these conditions also require special attention, including inherent metabolic compromises to cope with environmental constraints and altered energy requirements due to body composition and heat tolerance. Nutritional interventions to enhance beef production need to be specifically tailored and validated in B. indicus- influenced cattle. As an example, supplementation programs during gestation or early life to elicit fetal programming or metabolic imprinting effects, respectively, yield discrepant outcomes between subspecies. Bos indicus- influenced cattle produce carcasses with less marbling than B. taurus cattle, despite recent genetic and management advances. This outcome is mostly related to reduced intramuscular adipocyte volume in B. indicus breeds, suggesting a lesser need for energy stored intramuscularly as a mechanism to improve thermotolerance in tropical and subtropical climates. [ABSTRACT FROM AUTHOR]

The objectives of this study were to examine the relationship between residual feed intake (RFI) and DM and nutrient digestibility, in vitro methane production, and volatile fatty acid (VFA) concentrations in growing beef cattle. Residual feed intake was measured in growing Santa Gertrudis steers (Study 1; n = 57; initial BW = 291.1 ± 33.8 kg) and Brangus heifers (Study 2; n = 468; initial BW = 271.4 ± 26.1 kg) fed a high-roughage-based diet (ME = 2.1 Mcal/kg DM) for 70 d in a Calan-gate feeding barn. Animals were ranked by RFI based on performance and feed intake measured from day 0 to 70 (Study 1) or day 56 (Study 2) of the trial, and 20 animals with the lowest and highest RFI were identified for subsequent collections of fecal and feed refusal samples for DM and nutrient digestibility analysis. In Study 2, rumen fluid and feces were collected for in vitro methane-producing activity (MPA) and VFA analysis in trials 2, 3, and 4. Residual feed intake classification did not affect BW or BW gain (P > 0.05), but low-RFI steers and heifers both consumed 19% less (P < 0.01) DMI compared with high-RFI animals. Steers with low RFI tended (P < 0.1) to have higher DM digestibility (DMD) compared with high-RFI steers (70.3 vs. 66.5 ± 1.6% DM). Heifers with low RFI had 4% higher DMD (76.3 vs. 73.3 ± 1.0% DM) and 4 to 5% higher (P < 0.01) CP, NDF, and ADF digestibility compared with heifers with high RFI. Low-RFI heifers emitted 14% less (P < 0.01) methane (% GE intake; GEI) calculated according to Blaxter and Clapperton (1965) as modified by Wilkerson et al. (1995) , and tended (P = 0.09) to have a higher rumen acetate:propionate ratio than heifers with high RFI (GEI = 5.58 vs. 6.51 ± 0.08%; A:P ratio = 5.02 vs. 4.82 ± 0.14%). Stepwise regression analysis revealed that apparent nutrient digestibilities (DMD and NDF digestibility) for Study 1 and Study 2 accounted for an additional 8 and 6%, respectively, of the variation in intake unaccounted for by ADG and mid-test BW0.75. When DMD, NDF digestibility, and total ruminal VFA were added to the base model for Study 2, trials 2, 3, and 4, the R 2 increased from 0.33 to 0.47, explaining an additional 15% of the variation in DMI unrelated to growth and body size. On the basis of the results of these studies, differences in observed phenotypic RFI in growing beef animals may be a result of inter-animal variation in apparent nutrient digestibility and ruminal VFA concentrations. [ABSTRACT FROM AUTHOR]

• Consumer perception of antibiotic use in the beef cattle industry has changed overtime. • Alternative management strategies to prevent liver abscesses have been an important research topic for beef cattle. • To reduce prevalence of liver abscesses in finishing beef steers, we must evaluate the possibility of pathogens originating from the hind gut as well as the rumen. • Increased roughage had no impact on ruminal papillary morphology or presence of bacterial species associated with liver abscesses within the ruminal, ileal, or colonic tissues. • Overall, increasing roughage in finishing diets to replace tylosin does not seem applicable for finishing cattle. • The potential for pathogens from the lower gastrointestinal tract to cause liver abscesses warrants further investigation in finishing beef cattle. To reduce prevalence of liver abscesses in finishing beef steers, we must evaluate the possibility of pathogens originating from the hind gut as well as the rumen. We hypothesized that pathogens promoting liver abscess formation are located throughout the gut, and increased dietary roughage levels could improve gut integrity over time. Two hundred sixty-three crossbred beef steers (BW = 258 ± 29 kg) were used in a randomized complete block design with 7-8 hd/pen (8 pens/treatment) using a 2 × 2 factorial treatment structure. Steers received steam-flaked corn-based diets with 5 or 15% corn stalk (CS) inclusion (dry matter basis, DMB) and with (TYL) or without (NTYL) tylosin (7.9 g/T; DMB). Half of the pens in each treatment remained on feed for the entire experiment duration (Exp 1) whereas the remaining half were designated for serial slaughter (Exp 2). Steers were fed each day at 0700 h for an average of 220 d (heavy block = 175 d, light block = 233 d). For Exp 2, eight steers were slaughtered on d 0 to obtain initial tissue samples and thereafter one pen/treatment was slaughtered every 56 d. During serial slaughter, dorsal and ventral sac rumen tissue samples were collected for histopathological evaluation along with ruminal, ileal, and colonic tissues for bacterial isolation. Data were analyzed using mixed models; pen was the experimental unit for performance outcomes and individual animal was the experimental unit for bacterial isolation and histopathological data. No interaction (P ≥ 0.40) between tylosin and CS inclusion was detected for ADG or final BW. Interactions were detected for DMI and G:F; both outcomes were similar when tylosin was included in the diet, however both outcomes differed notably without tylosin. Perimeter and length of ventral rumen papillae decreased (P ≤ 0.01) as DOF increased. In contrast, dorsal rumen papillae perimeter and length increased through d112 and then decreased through d231. Corn stalk inclusion rate did not affect the incidence of bacterial species isolated from the ruminal (P = 0.38), ileal (P > 0.15), or colonic (P > 0.37) epithelial tissues. Cattle consuming the TYL diets tended to have decreased (P = 0.06) presence of ileal Fusobacterium necrophorum subsp. necorphorum and increased (P = 0.07) rates of ruminal Salmonella enterica compared to NTYL. Prolonged consumption of a finishing diet, regardless of CS or TYL inclusion, seemed to be the major source of change in rumen epithelial tissue morphology. [ABSTRACT FROM AUTHOR]