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SPECIAL TOPICS |
Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Key Words: beef cattle • feedlot • nutrient recommendation • nutritionist
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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; Galyean and Gleghorn, 2001). Galyean (1996) surveyed 6 consulting nutritionists regarding concentrations and sources of CP in feedlot finishing diets. The results indicated that recommended CP concentrations exceeded values calculated using standard values of the NRC (1984) factorial system; however, the concentrations being applied in practice were in close agreement with those suggested by the NRC (1996) MP system.
Galyean and Gleghorn (2001) conducted a more detailed survey in which 19 consulting nutritionists representing all the major cattle feeding areas of the United States provided data about industry nutrition and management practices. Their results verified the more limited survey of Galyean (1996) with respect to CP concentrations and expanded the knowledge base with respect to recommendations for other nutrients (e.g., minerals and vitamins) as well as management practices typically applied by practical nutritionists.
The objectives of the present survey were to update information contained in the Galyean and Gleghorn (2001) survey and to evaluate new nutritional and management information not obtained previously. These data should be useful for understanding industry practices and thereby facilitating the design of industry-oriented research as well as for development and evaluation of recommendations in future National Research Council (NRC) beef cattle nutritional requirement publications.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Nutritionists
Based on consultation with industry technical service professionals and personal knowledge, 42 nutritionists were selected to represent practices in all of the major cattle feeding areas of the United States (e.g., Midwest, High Plains, and Southwest) and were contacted by e-mail regarding their interest in participating in the survey. Four nutritionists chose not to participate, and 7 did not return our request. Thirty-one nutritionists agreed to participate, but only 29 completed the survey. Approval to conduct the survey was granted by the Texas Tech University Institutional Review Board.
Data Collection
The survey was conducted with the use of a Web-based survey tool (http://www.surveymonkey.com; last accessed 19 July 2007). Each of the 31 nutritionists who agreed to take part in the survey was sent an e-mail message describing how to access the survey and given an identification number to be used when taking the survey. Two nutritionists preferred to receive a paper copy of the survey, which was provided to them as a portable document format (.pdf) file (Adobe Systems Inc., San Jose, CA) via e-mail. These 2 nutritionists returned a completed paper copy of the survey to us by surface mail. All participants received a guarantee of anonymity and were requested to complete the survey at their earliest possible convenience. The 29 completed surveys were received within 1 mo.
Survey Questions
The survey contained 74 questions divided into several categories, including general information (n = 8 questions); general commodity information (n = 13); questions about the use of grain coproducts (n = 5); roughage sources and levels (n = 4); finishing diet adaptation methods (n = 3); supplements and micronutrients (n = 7); feed mixers (n = 2); feed mills (n = 1); feeding management (n = 1); cattle management (n = 5); liquid feeds (n = 7); formulation practices (n = 15); and information resources used for nutritional recommendations (n = 2). The final question in the survey asked for comments about other nutrients supplemented in finishing diets that were not listed in the survey.
Data Analyses
All data were tabulated in Microsoft Excel spreadsheet (Microsoft, Redmond, WA). The number of responses per question, mean, minimum value, maximum value, and mode were calculated for all questions using spreadsheet formulas.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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).
General Commodity Information
Grain.
Corn was the primary grain used by all 29 (100%) nutritionists who participated in this survey (Table 1). Corn also was the top grain choice of nutritionists surveyed by Galyean and Gleghorn (2001). The secondary grain most used was wheat, followed by sorghum and barley. Six nutritionists did not use a secondary grain in the feedlots served by their practices.
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. Dry-rolling was used as the primary processing method by 4 nutritionists; high-moisture harvesting and storage was used by another 4; and a combination of dry-rolling and high-moisture harvesting and storage was used as the primary processing method by 2. Nine nutritionists reported high-moisture harvesting and storage as the second most common processing method, 8 each reported steam-flaking and dry rolling was the secondary method, 1 nutritionist reported reconstitution, and 3 did not indicate use of a secondary processing method (Table 1
).
Source of Information on Feed Energy Values.
The NRC was the main source of information on energy values for 82.76% of the respondents (Table 1), with the remaining 5 nutritionists using the NRC values with modifications or adaptations based on their own data or other sources such as internal company models and personal data (Table 1). Three of these nutritionists indicated that they used NRC recommendations with additional information from their own data set and peer-reviewed journals, and 1 used only a model developed by the feed company for which this person worked. Most of the nutritionists did not specify which edition of the NRC they use.
Starch Availability Method.
In the US feedlot industry, grains are processed to increase energy (starch) availability. Given that steam-flaking is the most common grain processing method, one might expect considerable effort being devoted to assessment of the effects of processing on starch availability. Thus, we asked participants to identify the method they typically used to assess the success of the steam-flaking process (Table 1). The enzymatic method to determine starch availability was preferred by 44.83% of the nutritionists, whereas a gas production method was preferred by 13.79% and gelatinization by 6.90%. Five nutritionists (17.24%) used a combination of the enzymatic method with gas production, gelatinization, Flake Color Index System (FCIS; a proprietary color intensity measurement device marketed by Lextron Inc., Greeley, CO), or the Kansas State University refractometer method (Sindt et al., 2000). One nutritionist used another method not listed in the survey (3.45%), and 3 nutritionists did not use any method to assess starch availability. It should be noted that an important use of these methods is for quality control in standardizing the steam-flaking process to yield a consistent product from day to day.
Level of Inclusion of Grain in Finishing Diets.
As stated by Brown et al. (2006), the cost per megacalorie of NEm or NEg of dietary ingredients favors feeding high-concentrate diets based on cereal grains in finishing diets. In addition, handling characteristics of most dry forages also favor minimizing forage inclusion because of improved operational efficiency in feedlot mills (Brown et al., 2006). Thus, it is not surprising that results from the present survey showed that finishing diets formulated by our respondents contain high concentrations of grain. Two-thirds of our nutritionists formulated diets containing from 70 to 85% grain (80 to 85% = 34.48%; 70 to 80% = 31.03%). Six nutritionists formulated diets for 60 to 70% grain, 2 for 50 to 60%, and 2 for 85 to 90% grain. None reported formulation of diets with more than 90% grain. Given the high level of inclusion of grain coproducts (as noted in a subsequent section) in finishing diets, it is likely that some respondents included and some excluded grain coproducts in their response to this question.
Energy and Starch Recommendations
The average NEg concentration recommended for finishing diets was 1.50 Mcal/kg (29 responses) with a minimum value of 1.37, a maximum of 1.70, and a mode of 1.54 (Table 2). Dietary NEg concentrations of this magnitude reflect low roughage concentrations and extensive use of supplemental fat that will be discussed in subsequent sections. In terms of grain processing, the average bulk density recommended for steam-flaked corn was 0.35 kg/L, (27 pounds/bushel), whereas for sorghum, the average recommendation was 0.33 kg/ L (26 pounds/bushel; Table 2). The recommended starch availability (using the enzymatic method) was 60% for corn and 62% for sorghum, with values 4 to 5% less when gas production methods were used to assess starch availability. On average, 11.8% of clients used the FCIS. This system is not intended to provide a direct measure of starch availability but to allow a rapid measure of flake color that is presumably associated with starch availability. More importantly, the FCIS measure is potentially repeatable over time, thereby allowing it to be used for quality control in the steam-flaking process; however, because the system is proprietary, there is no published research on its use.
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). Our respondents seemed to recognize the greater energy value of steam-flaked corn and considered steam-flaked corn to increase in NEg concentration by an average of 10.9% compared with dry-rolled corn and 6.8% compared with high-moisture corn (Table 2). In contrast, NRC (1996) suggested an increase of only 4.5% for steam-flaked vs. dry-rolled corn, and no difference in the NEg concentration of high-moisture and steam-flaked corn. Thus, although most (82.76%) of our nutritionists used the NRC as their source of information on energy values, they deviated substantially from NRC estimates of NEg val- ues for processed grains.
Grain Coproduct Use in Finishing Diets
The increase in fuel ethanol demand has increased the milling of corn and sorghum for ethanol production and other uses of grain starch. As a result, grain coproducts from the dry and wet milling processes are being used extensively as protein and energy sources for ruminants. The average percentage of clients that use grain coproducts in finishing diets was 82.76%, with the primary grain coproducts used being wet distiller’s grains, dry distiller’s grains with solubles (corn, sorghum, or both), wet corn gluten feed, and dry corn gluten feed. These grain coproducts were included in finishing diets at concentrations (DM basis) ranging from 5 to 50% (average = 16.5%; mode = 20%). Responses to the question regarding the second most commonly used grain coproduct resulted in the same coproducts noted for the primary list, with the addition of wheat middlings. Secondary grain coproducts use, on average, was 14.2% of finishing diets (Table 3).
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, the question regarding roughage level was separated by season. During the summer, our respondents used slightly less (average = 8.30%) roughage than during the winter (average = 9.00%), with the primary roughage source being corn silage (41.38%), followed by alfalfa (31.03%; Table 4). Although roughage levels are similar to values noted by Galyean and Gleghorn (2001), our findings with roughage source contrast with theirs, in which alfalfa was considered the primary roughage source used by 68% of the nutritionists they surveyed, with corn silage considered the secondary roughage source by most nutritionists. The greater use of corn silage noted in the present survey likely reflects the broader geographical area covered by the respondents in the present survey compared with the survey of Galyean and Gleghorn (2001), in which fewer nutritionists participated who practiced extensively in Midwestern cattle feeding areas. Other primary roughage sources that were mentioned in the present survey included cottonseed hulls, cotton burrs, and Sudangrass hay, all of which also were included in the secondary roughage source list (Table 4).
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) was the crude fiber method (41.38%), followed closely by NDF (34.48%). Fewer of our respondents used ADF method, and 4 did not consider any method of fiber analysis in formulation. The use of crude fiber in formulation might reflect its common use in the feed industry, with many feed formulation programs automatically generating estimates of dietary crude fiber concentration. Galyean and Defoor (2003) suggested that NDF supplied by roughage was a reasonable method of formulating finishing diets with different roughage sources (e.g., effective for determining roughage substitution values). Whether NDF use will increase over time probably depends on the availability of rapid and reliable analytical estimates of NDF for concentrate diets.
Cattle Management
Sorting Systems.
Methods to sort cattle into more uniform outcome groups are becoming increasingly important in the feedlot industry (MacDonald et al., 2006). With our respondents’ clients (data not shown), those who sorted cattle into outcome groups were the majority (41.4%; 29 responses). The most common time of sorting was at arrival for 37.2% of the clients (26 responses); reimplant for 29.2% of clients (25 responses); and other times for 28.7% (23 responses). The sorting systems used were as follows: (1) BW (61.6%; 26 responses); (2) ultrasound (8.5%; 26 responses); and (3) other methods, which are used by 24.3% of the clients (25 responses).
All consulting nutritionists surveyed were responsible for their clients’ implant strategy (data not shown). The recommended maximum number of days on the terminal estrogen/trenbolone acetate implant was 110 d for almost half (14) the 29 nutritionists surveyed. Others recommended 120 (7), 130 (7), or 140 d (1).
Cattle Adaptation Methods.
The initial time spent adapting cattle to feedlot finishing diets is a critical period in which nutritional management practices can potentially promote or impair subsequent performance and health (Brown et al., 2006). Twenty-two of the 29 nutritionists surveyed recommend multiple step-up diets to adapt cattle to the finishing diet (diets with stepwise increases in the concentration of grain and corresponding decreases in roughage level). On average, 3.1 diets were fed before the finishing diet. The mode, however, was 2 diets (Table 5), with an average of 7.2 d per diet (mode = 7). The initial level of roughage during the adaptation process with this method varied from 27.5 to 46.0% (average = 39.9%; mode = 45.0%). Two-ration blending (feeding varying proportions of a higher- and a lower-roughage diet) was used by only 4 nutritionists, with an average and mode of 21 d to the final diet, and an average and mode for initial level of roughage of 40.0%. Two nutritionists used both multiple step-up diets and 2-ration blending, and 1 nutritionist used another adaptation method not listed in the survey. Most nutritionists recommended an average of 21 d for adaptation, regardless of the method used. According to Brown et al. (2006), performance studies indicate that when cattle are offered ad libitum access to feed, adapting feedlot cattle with incremental increases in dietary concentrate from approximately 55 to 90% of diet DM, in 14 d or less generally results in decreased performance during adaptation or over the entire feeding period compared with adapting cattle over longer periods of time (e.g., 21 d).
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) was 45.4%, and these supplements were included on average as 5.2% of the dietary DM. Similarly, the 38.6% of clients who used pelleted dry supplements had an average inclusion level of 5.0% (DM basis). Loose dry supplements are used by fewer clients (10.4%) at an average 5.0% inclusion rate, but the mode was 3.0%. Our respondents indicated that 49.0% of their clients used microingredient machines. A stationary mixer/delivery truck approach was used by an average of 30.1% of the clients served by our respondents, with 66.8% of the clients using truck-mounted mixers. Vertical mixers are used by only 3.7% of the clients serviced by our nutritionists, with most (96.0%) using horizontal mixers. When describing feed mill systems, nutritionists reported that 33% of their clients used batch systems, whereas only 4.9% used a continuous-flow system. Most clients (62.1%) used flat storage and a truck-mounted mixer (Table 6). Cattle in feedlots advised by our respondents were typically fed 2 (46.4%) or 3 (46.0%) times daily (Table 6). In 3.4 and 0.8% of the feedlots, cattle were fed once daily or more than 3 times daily, respectively.
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), with an average recommended level of non-fat liquids of 4.4% and a mode of 5.0%. The primary non-fat liquid used in finishing diets was condensed corn distiller’s solubles (CCDS), followed by molasses, molasses blends, and CCDS in combination with blends. On average, 71% of clients used added fat, with the primary fat source being tallow, followed by yellow grease, a combination of sources, or choice white grease (Table 7). The average recommended level of added fat was 3.1%, with a very similar mode of 3.0%. The maximum total fat (from basal ingredients plus added fat) recommended was 7.6% (mode = 8.0%). As noted previously, extensive use of added fat is an important factor associated with the high NEg concentration of finishing diets used by most respondents.
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and Galyean and Gleghorn (2001). The urea concentration in finishing diets recommended by our respondents was 1.01% (mode = 1.2%), with a maximum CP allowed from NPN of 2.83% (mode = 3.0%). Perhaps somewhat surprisingly, most of our nutritionists did not formulate for degradable intake protein (DIP; 20 respondents or 68.97%). Similarly, Galyean and Gleghorn (2001) reported that approximately 74% of their 19 respondents did not formulate for DIP. In the present survey, for the 9 respondents who use DIP, the recommended DIP level was 8.5% of the DM, with a mode of 7.0%. The primary sources of plant-based protein (data not shown) were either generally described as by-products (5) or specified as distiller’s grains (3), dried distiller’s grains (5), wet distiller’s grains (3), gluten feed (2), or wet corn gluten feed (1). Traditional sources of plant-based protein such as soybean meal and cottonseed meal were used by 5 and 4 nutritionists, respectively. The second most commonly used sources of plant-based protein included: none (6), cottonseed meal (4), dried distiller’s grains (4), soybean meal (2), canola (2), sunflower meal (2), distiller’s grains (1), wet distiller’s grains (1), mill run (1), corn gluten feed (1), wheat middlings (1), gluten feed (1), CCDS (1), oilseed meal (1), or by-products (1).
Mineral Availability.
As done previously by Galyean and Gleghorn (2001), the extent to which concentrations of minerals in basal dietary ingredients were considered in formulation was assessed. Sixteen (55.2%) of our nutritionists give full value in formulation to basal dietary ingredient mineral concentrations, and 11 (37.9%) give only partial value in formulation. Two (6.9%) nutritionists did not consider basal mineral concentrations in formulation (data not shown).
Major Minerals.
The average Ca concentration recommended for finishing diets was 0.70% (Table 8), and all 29 nutritionists used limestone as the source of Ca (data not shown). Phosphorus concentration recommended for finishing diets was 0.30%, and as expected, 24 of 29 nutritionists did not add P to the finishing diets, likely reflecting an appreciation that the requirement for P by feedlot cattle is less than P supplied by basal ingredients in feedlot diets (Vasconcelos et al., 2007). Thus, our data suggest that feedlot nutritionists have responded to environmental concerns by decreasing P supplementation to cattle. The recommended Mg concentration of finishing diets was 0.22% (mode = 0.25%). The sources of Mg used (data not shown) were MgO (16; 59.3% of 27 respondents), MIN-AD (a commercially available Ca-Mg carbonate; 9; 33.3% of 27 respondents), both MgO and MIN-AD (1; 3.7% of 27 respondents), and MgCl (1; 3.7% of 27 respondents). The average K concentration recommended for finishing diets was 0.70%, and the average S concentration recommended for finishing diets was 0.22%. Salt levels were, on average, 0.30% of the DM.
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. Except for Fe, which was not typically added (mode = 0), these recommendations are close to those of NRC (1996), especially in terms of the mode. Some nutritionists, however, recommended relatively high concentrations of certain minerals (e.g., Cu and Zn), which increased average values relative to NRC (1996) recommendations. Overall, the average concentrations of trace minerals recommended by the nutritionists in the present survey are greater than the concentration of trace minerals reported by nutritionists in the Galyean and Gleghorn (2001) survey.
Vitamins.
The average vitamin A concentration recommended by our respondents was 5,215.0 IU/kg, and the average vitamin E concentration was 25.7 IU/kg. The average vitamin D recommendation was 329.9 IU/ kg, but the mode was 0, indicating that most nutritionists do not commonly supplement vitamin D. As observed by Galyean and Gleghorn (2001), average vitamin A concentration was greater than the NRC (1996) recommendations; likewise, vitamin E levels were somewhat greater than the NRC (1996) recommendations.
Sources of Information
In terms of sources of information used by our respondents (data not shown), a surprisingly high number (20.7%) used the NRC (1984) as their sole source of information. Seven nutritionists used the NRC (1996) as their only source of information (24.1%), whereas another 7 used both the NRC (1984) and NRC (1996). One nutritionist (3.45%) used both the NRC (1996) and the Cornell Net Carbohydrate and Protein System (CNCPS); 1 used the NRC (1976) and the NRC (1984); 1 used the NRC (1976), NRC (1984), and the NRC (1996); and 1 used NRC (1984), NRC (1996), and the CNCPS. Finally, 1 nutritionist used the NRC (1996) plus other sources, and 1 used the NRC (1984) and NRC (1996) plus other sources, and 3 of the respondents used only other sources. The CNCPS was not mentioned in the Galyean and Gleghorn (2001) survey, suggesting that some practicing nutritionists have started to apply nutritional recommendations from published sources other than the NRC. Nonetheless, the importance of the NRC publications is evident in that 17 nutritionists used the NRC (1984) and 19 used the NRC (1996) as a reference source for formulation.
With respect to source of scientific or recent information, the Journal of Animal Science was mentioned by 27 of the 29 nutritionists. The Professional Animal Scientist was noted by 19, Feedstuffs by 17, Beef magazine by 6, Animal Feed Science and Technology by 2, Feedlot magazine by 3, and other sources (university reports, private or in-house research, and other peer-reviewed journals) by 7. When asked about nutrients not assessed in the survey, 6 respondents mentioned the use of thiamin in diets with grain coproducts. One nutritionist cited NPN (urea) levels, with reference to how NPN concentrations vary with grain processing method and concentration of grain coproducts in the diet.
The results of our survey provide a summary of nutritional recommendations currently being applied in the feedlot industry and also give some insight into management practices recommended by consultants. Generally, most major and trace mineral recommendations fell within a range from 1 to 2 times the NRC (1984, 1996) recommendations; however, a slight trend for oversupplying of nutrients was observed, perhaps reflecting some degree of a desire to err on the side of caution and provide a safety net for both the consultant and the producers they serve. Failure to apply concepts like the use of DIP in assessing protein adequacy is somewhat surprising, but it might reflect the absence of widely accepted laboratory methods for assessing DIP in feed ingredients and diets, as well as the typically low price of urea nitrogen. Overall, the variation noted among responses by these 29 nutritionists was not large, verifying commonality in the sources of information used by these professionals and further suggesting that the values reported herein could be used to describe real-world application of nutritional recommendations.
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Footnotes |
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2 Corresponding author: judson.vasconcelos{at}ttu.edu
Received for publication May 9, 2007. Accepted for publication June 14, 2007.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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