The 2015 feedlot consulting nutritionist survey is a collaborative project between New Mexico State University and Texas Tech University that focuses on summarizing the professional practices of ...consulting feedlot nutritionists and updates a 2007 survey. Forty-nine consulting feedlot nutritionists were asked to participate, of which 24 completed the survey. The nutritionists surveyed service over 14,000,000 cattle annually and were representatives from individual consulting practices (54.2%), corporate cattle feeding companies (20.8%), corporate feed manufacturing companies (20.8%), or a combination of consulting practices (4.2%). The survey was completed using a web-based survey tool and contained 101 questions that were divided into sections regarding general information about the consulting practice; general cattle management; receiving cattle management, diet adaption; mixers, feed mills, and feeding management; grains and grain processing; grain by-product use; roughage use; information about supplements and microingredients; liquid feed use; nutrient formulation; feed additive use; and information used as a basis for nutritional recommendations. In most cases, the results of the current survey were similar to those reported for the 2007 survey, with a few notable exceptions such as shifts in cattle numbers and preferences for specific feedstuffs. The present study introduced a number of new questions not included in the 2007 survey that focused on management strategies used in the receiving period. Data from this survey provide insight into current nutritional and management practices of consulting nutritionists and, as in past surveys, should be useful for informing national committees that make nutritional recommendations for cattle, as well as nutrition and management strategies employed within university research settings.
Morbidity and mortality from bovine respiratory disease (BRD) and associated losses in performance and carcass merit continue to plague the beef cattle industry. Several viral/bacterial agents are ...responsible for BRD, and interactions occur among the agents. Viral agents often predispose animals to bacterial infections, and Mannheimia haemolytica is the most frequently isolated organism in cattle with BRD. Laboratory tests are available to characterize organisms causing BRD using easily obtained nasal swab samples. Testing for persistent infection with bovine viral diarrhea virus can be done by a 2-stage technique using PCR and immunohistochemistry. Preconditioning programs that include preweaning viral vaccination programs along with castration could have a significant influence on decreasing BRD in the cattle feeding industry. Metaphylactic antibiotic programs continue to be effective; however, antibiotic resistance is a public concern, and additional management options (e.g., direct-fed microbials or other compounds with antimicrobial properties) deserve attention. Diets with an increased energy concentration achieved by decreasing the dietary roughage concentration may slightly increase the rate of BRD morbidity; however, these diets also increase ADG, DMI, and G:F compared with lower-energy, greater-roughage diets. The extent to which performance and BRD morbidity are affected by dietary protein concentration needs further study, but low and high protein concentrations should probably be avoided. Several trace minerals (e.g., Cu, Se, and Zn) affect immune function, but the effects of supplementation on performance and immune function in model challenge systems and in field studies are equivocal. Adding vitamin E to receiving diets at pharmacological levels (e.g., >1,000 IU·animal⁻¹·day⁻¹) seems beneficial for decreasing BRD morbidity, but it has little effect on performance. Given the limited ability to consistently modify immune function and BRD morbidity through dietary manipulations, we recommend that the diets for newly received cattle be formulated to adjust nutrient concentrations for low feed intake and to provide optimal performance during the receiving period.
Forty-two consulting feedlot nutritionists were asked to participate in a survey regarding nutritional recommendations for feedlot cattle. Eleven nutritionists chose not to participate or did not ...reply to our request. Thirty-one nutritionists agreed to participate, and 29 completed the survey. Their practices were located in the following states: Texas, Kansas, and Oklahoma (46.43%); Iowa, Nebraska, Colorado, and South Dakota (31.25%); Washington and Idaho (8.93%); Arizona and California (6.25%); and other states (7.14%). The survey was conducted using a Web-based system and included 74 questions divided into sections that covered general information about the nutritionist's practice (n = 8 questions); commodity information (n = 13); use of grain coproducts (n = 5); information regarding roughage sources and levels (n = 4); methods used to adapt cattle to finishing diets (n = 3); information about supplements and micronutrients (n = 7); types of feed mixers (n = 2) and feed mills (n = 1) used by clients; feeding (n = 1) and cattle management (n = 5); liquid feeds (n = 7); recommendations for nutrient formulation (n = 15); information resources used as the basis for nutritional recommendations (n = 2); and perceived needs for additional information on items or nutrients not addressed in the survey. With respect to nutrient formulation practices, the results indicated that the recommended concentrations of major nutrients and trace minerals typically fell within a range of 1 to 2 times the NRC (2000) recommendations for beef cattle; however, some important aspects of the NRC models (e.g., formulation for degradable intake protein) were not applied by the majority of respondents. Data from this survey provide a snapshot of practices used by feedlot nutritionists and should aid in development of future National Research Council models and recommendations.
Abstract
Accurate predictions of microbial crude protein (MCP) synthesis are needed to predict metabolizable protein supply in ruminants. Since 1996, the National Academies of Sciences, Engineering, ...and Medicine series on beef cattle nutrient requirements has used the intake of total digestible nutrients (TDN) to predict ruminal MCP synthesis. Because various tabular energy values for feeds are highly correlated, our objective was to determine whether intakes of digestible energy (DE), metabolizable energy (ME), and net energy for maintenance (NEm) could be used as predictors of MCP synthesis in beef cattle. A published database of 285 treatment means from experiments that evaluated MCP synthesis was updated with 50 additional treatment mean observations. When intakes of TDN, fat-free TDN, DE, ME, NEm, dry matter, organic matter, crude protein (CP), ether extract, neutral detergent fiber, and starch were used in a stepwise regression analysis to predict MCP, only intakes of DE and CP met the P < 0.10 criterion for entry into the model. Mixed-model regression analyses were used to adjust for random intercept and slope effects of citations to evaluate intake of DE alone or in combination with CP intake as predictors of MCP synthesis, and the intakes of TDN, ME, and NEm as alternatives to DE intake. Similar precisions in predicting MCP synthesis were obtained with all measures of energy intake (CV = root mean square error RMSE as a percentage of the overall mean MCP varied from 9% to 9.67%), and adding CP intake to statistical models increased precision (CV ranged from 8.43% to 9.39%). Resampling analyses were used to evaluate observed vs. predicted values for the various energy intake models with or without CP intake, as well as the TDN-based equation used in the current beef cattle nutrient requirements calculations. The coefficient of determination, concordance correlation coefficient, and RMSE of prediction as a percentage of the mean averaged 0.595%, 0.730%, and 28.6% for the four measures of energy intake, with average values of 0.630%, 0.757%, and 27.4%, respectively, for equations that included CP intake. The TDN equation adopted by the 2016 beef cattle nutrient requirements system yielded similar results to newly developed equations but had a slightly greater mean bias. We concluded that any of the measures of energy intake we evaluated can be used to predict MCP synthesis by beef cattle and that adding CP intake improves model precision.
Intake of total digestible nutrients has been used extensively to predict rumen microbial protein synthesis by beef cattle. We found that other measures of energy intake, like digestible energy, metabolizable energy, and net energy for maintenance, are equally effective in predicting microbial protein synthesis and that adding crude protein intake to models improved the precision of predictions.
Lay Summary
The ability to accurately and precisely predict microbial protein synthesis is crucial in predicting the supply of metabolizable protein in beef cattle. We updated a database previously used to predict microbial crude protein (CP) supply in beef cattle. Then we evaluated the utility of using total digestible nutrients (TDN) and different measures of energy intake to predict ruminal microbial protein synthesis. Using regression analyses, we found that intakes of digestible and metabolizable energy and intake of net energy for maintenance were as effective as the intake of TDN as independent variables to predict microbial protein synthesis. Adding the intake of CP to the models improved the precision of predictions, and all models performed as well or better than the regression model adopted by the 2016 nutrient requirement system for beef cattle.
Feedlot consulting nutritionists were invited to participate in a survey of feedlot nutritional and management practices in Brazil. Thirty-one nutritionists completed the survey on a Web site that ...was designed for collection of survey data. The survey consisted of 94 questions that included general information (n = 10); commodity information (n = 12); and questions about the use of coproducts (n = 5), roughage source and levels (n = 5), finishing diet adaptation methods (n = 7), supplements and micronutrients (n = 8), feed mixers (n = 6), feeding management (n = 3), cattle management and type of cattle fed (n = 16), formulation practices (n = 17), information resources used for nutritional recommendations (n = 2), and 2 additional questions. One final question addressed the primary challenges associated with applying nutritional recommendations in practice. The number of animals serviced yearly by each nutritionist averaged 121,682 (minimum = 2,000; maximum = 1,500,000; mode = 120,000; total = 3,163,750). Twenty-two respondents (71%) worked with feedlots that feed less than 5,000 animals/yr. Labor, along with availability and precision of equipment, seemed to be the main challenges for the nutritionists surveyed. Most of the nutritionists surveyed used TDN as the primary energy unit for formulation. More than 50% of the clients serviced by the 31 nutritionists did not manage feed bunks to control the quantity of feed offered per pen, and 36.6% fed cattle more than 4 times daily. The NRC (1996) and Journal of Animal Science were the most used sources of information by these nutritionists. Overall, general practices and nutritional recommendations provided by the 31 nutritionists surveyed were fairly consistent. Present data should aid in development of new research, future National Research Council models, and recommendations for Brazilian feeding systems in which Bos indicus cattle predominate.
Fecal shedding of Escherichia coli O157:H7, the prevalence of Escherichia coli O157:H7 in pens and on carcasses and hides, and cattle performance as a result of daily dietary supplementation with ...Lactobacillus-based direct-fed microbials (DFMs) were evaluated in a feeding trial involving 180 beef steers. Steers were evaluated for shedding of E. coli O157:H7 by an immunomagnetic separation technique on arrival at the feedlot, just before treatment with the DFMs, and every 14 days thereafter until slaughter. Composite pen fecal samples were collected every 14 days (alternating weeks with animal testing), and prevalence on hides and carcasses at slaughter was also evaluated. Feedlot performance (body weight gain and feed intake) was measured for the period during which the DFMs were fed. Gain efficiency was calculated as the ratio of weight gain to feed intake. Lactobacillus acidophilus NPC 747 decreased (P < 0.01) the shedding of E. coli O157:H7 in the feces of individual cattle during the feeding period. E. coli O157:H7 was approximately twice as likely to be detected in control animal samples as in samples from animals receiving L. acidophilus NPC 747. In addition, DFM supplementation decreased (P < 0.05) the number of E. coli O157:H7-positive hide samples at harvest and the number of pens testing positive for the pathogen. Body weight gains (on a live or carcass basis) and feed intakes during the DFM supplementation period did not differ among treatments. Gain efficiencies on a live-weight basis did not differ among treatments, but carcass-based gain/feed ratios tended (P < 0.06) to be better for animals receiving the two DFM treatments than for control animals. The results of this study suggest that the feeding of a Lactobacillus-based DFM to cattle will decrease, but not eliminate, fecal shedding of E. coli O157:H7, as well as contamination on hides, without detrimental effects on performance.
Prediction of microbial CP (MCP) synthesis in the rumen is an integral part of the MP system. For the NRC beef model, MCP is calculated as 0.13 multiplied by TDN intake (TDNI), with adjustment for ...physically effective NDF (peNDF) concentrations less than 20%. Despite its application for nearly 2 decades, MCP predictions using this approach have not been extensively evaluated. We assembled a database of 285 treatment means from 66 published papers using beef cattle and dairy or dairy × beef crossbred steers, fed diets with a wide range of TDN, CP, and ether extract (EE) concentrations, in which MCP synthesis was measured. Fat-free TDN (FFTDN) concentration was calculated by subtracting 2.25 × percent EE from the TDN concentration. Based on initial model selection procedures indicating that DMI and concentrations of TDN, FFTDN, and CP were significantly (P < 0.04) related to MCP synthesis, linear and quadratic effects of TDNI and FFTDN intake (FFTDNI) and CP intake (CPI) were considered as potential independent variables. Mixed model regression methods were used to fit 1-, 2-, and 3-independent-variable models based on either TDNI or FFTDNI (e.g., TDNI only, TDNI and CPI, and TDNI, CPI, and the quadratic effect of TDNI; or FFTDNI only, FFTDNI and CPI, and FFTDNI, CPI, and the quadratic effect of FFTDNI). True ruminal OM digested (TROMD; g/d) was highly related (r(2) = 0.84 using citation-adjusted data) to MCP synthesis. Similarly, both TDNI and FFTDNI were highly related to citation-adjusted TROMD (r(2) > 0.96) and MCP synthesis (r(2) > 0.89). Models with FFTDNI were slightly more precise with slightly smaller prediction errors than those with TDNI. Randomly dividing the citations into Development (60%) and Evaluation (40%) data sets indicated that models such as those derived from the overall database accounted for 46 to 56% of the variation in MCP synthesis, with neither mean nor linear bias (P ≥ 0.26). In contrast, calculating MCP as 0.13 × TDNI, with or without adjustment for peNDF concentration, resulted in overprediction of MCP (P < 0.001 for both mean and linear bias). Cross-validation using 5,000 randomly drawn training and testing data sets yielded results similar to the Development/Evaluation approach. Recommended equations are provided, but the errors of prediction associated with these empirical regression equations were on the order of 25 to 30% of the mean MCP.
Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E₂) implants and feeding of zilpaterol hydrochloride (ZH) on performance and carcass ...characteristics of finishing beef steers. A randomized complete block design was used with a 3 x 2 factorial arrangement of treatments. British x Continental steers (n = 168; initial BW = 362 kg) were blocked by BW and allotted randomly to 42 pens (7 pens/treatment; 6 pens/block; 4 steers/pen). The main effects of treatment were implant no implant (NI); Revalor-S (REV-S; 120 mg of TBA + 24 mg of E₂); and Revalor-XS (REV-X; 200 mg of TBA + 40 mg of E₂) and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before slaughter). Blocks were split into 2 groups, and block groups were fed for either 153 or 174 d. No implant x ZH interactions were noted for cumulative performance data. Overall, shrunk final BW (567, 606, and 624 kg for NI, REV-S, and REV-X, respectively), ADG (1.25, 1.51, and 1.60 kg), and G:F (0.14, 0.16, and 0.17) increased (P < 0.05) as TBA and E₂ dose increased. Implanting increased (P < 0.05) DMI, but DMI did not differ (P > 0.10) between REV-S and REV-X (8.8 for NI vs. 9.4 kg/d for the 2 implants). From d 1 to 112 of the feeding period, implanting increased (P < 0.05) ADG and G:F, but REV-S and REV-X did not differ (P > 0.10). From d 112 to end, ADG increased by 19% (P < 0.05) and G:F was 18% greater (P < 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (29-kg difference), ADG (0.2-kg/d difference), and G:F (0.02 difference) were increased (P < 0.05) by ZH, but daily DMI was not affected by feeding ZH. Hot carcass weight was increased (P < 0.05) by ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 kg for REV-S and REV-X, respectively; P < 0.05). An implant x ZH interaction (P = 0.05) occurred for dressing percent (DP). Without ZH, implanting increased DP, but DP did not differ (P > 0.10) between REV-X and REV-S. With ZH, REV-X increased (1.7%; P < 0.05) DP vs. NI and REV-S. Marbling score, 12th-rib fat, and KPH were not affected (P > 0.10) by implant or ZH. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA + E₂ and extended payout improved steer performance and HCW.
British and British x Continental steers (n = 560; initial BW = 339.4 ± 1.76 kg) were used in a serial slaughter study with a completely random design to evaluate effects of zilpaterol hydrochloride ...(ZH; 8.33 mg/kg of dietary DM basis) on performance and carcass characteristics. Treatments were arranged in a 4 x 4 factorial (112 pens; 7 pens/treatment; 5 steers/pen) and included duration of ZH feeding (0, 20, 30, or 40 d before slaughter plus a 3-d ZH withdrawal period) and days on feed (DOF) before slaughter (136, 157, 177, and 198 d). No duration of ZH feeding x slaughter group interactions were detected for the performance measurements (P > 0.10). Final BW did not differ (P = 0.15) between the 0-d group and the average of the 3 ZH groups, but ADG was greater for the average of the 3 ZH groups during the period in which ZH diets were fed (P < 0.01) and for the overall feeding period (P = 0.05). As duration of ZH feeding increased, DMI decreased (P = 0.01) and G:F increased linearly (P < 0.01). With the exception of KPH (P = 0.022), no duration of ZH feeding x slaughter group interactions (P > 0.10) were detected for carcass characteristics. Regardless of the duration of ZH feeding, cattle fed ZH had greater HCW (P < 0.01), greater dressing percent (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.03), and lower yield grade (P < 0.01) than the 0-d cattle. The 0-d group had greater marbling scores (P < 0.01) than cattle fed ZH diets, with a tendency for a linear decrease in marbling score (P = 0.10) as duration of ZH feeding was extended. A greater percentage of carcasses in the 0-d group graded USDA Choice or greater (P < 0.01) than in the 3 ZH groups, whereas the percentage of Select carcasses was greater (P = 0.01) for the 3 ZH groups. From d 0 to end (P = 0.04) and during the last 43 d on feed (P < 0.01), ADG responded quadratically to DOF before slaughter. No differences were detected among slaughter groups for DMI for the entire trial period; however, a quadratic response (P = 0.02) was observed for the final 43 d before slaughter. A quadratic response was also detected for the final 43 d before slaughter (P < 0.01) and from d 0 to end (P = 0.02) for G:F. Final BW, HCW, dressing percent, and 12th-rib fat increased linearly (P < 0.01) as DOF before slaughter increased. Our results indicate that no substantial effects on performance and carcass measurements were observed when ZH was fed for 30 or 40 d as opposed to 20 d, and that effects of ZH generally did not interact with DOF before slaughter.
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