Nutrient Requirements Of Cattle Research Articles

74 Ovulatory Follicle and Corpus Luteum Development ofBos Taurus Cows Under Nutrient Restriction

Abstract Establishment and maintenance of pregnancy is a central concern to the cattle industry, as it strongly impacts efficiency and profitability of beef cow-calf operations. The objective of this study was to determine if nutrient restriction impacts ovulatory follicle size and corpus luteum (CL) volume of Angus cows enrolled in estrous synchronization. A total of 26 Angus cows were housed at the Virginia Tech – Shenandoah Valley Agricultural Research and Education Center (SVAREC) equipped with a Calan gate system for individual animal intake, stratified by body weight (BW) and randomly assigned to one of two treatments: 1) a maintenance diet that provided 100% of nutrient requirements (MTN; n = 13) or 2) a diet providing 70% of nutrient requirements (REST; n = 13). Nutrient requirements were calculated and adjusted weekly based on BW using the 2016 NRC version of Beef Cattle Nutrient Requirements Model Software. Cattle underwent an acclimation period of4 days and were exposed to nutritional treatments for 30 days before estrous synchronization. Body weight was measured daily using an automated scale, and a conventional livestock scale at the beginning and end of the experiment. Cows were synchronized using a 7-day CO-synch + CIDR protocol beginning on day -10. An estrus alert patch was applied on day -3 and read on day 0 to assess expression of estrus. Ultrasonography of the ovaries was performed at each event of the estrous synchronization protocol. Data were analyzed using the MIXED procedure of SAS. Initial BW was similar between treatments (P = 0.07; 600 ± 32 kg), but MTN compared with REST cows had greater final BW (P < 0.01; 687 ± 24 and 556 ± 27 kg, respectively) and greater average daily gain (1.35 ± 0.18 and -0.72 ± 0.21 kg/d, respectively). Estrus expression was numerically greater (P = 0.185) MTN (84.62%) than REST (61.54%) cows. Diameter of the largest follicle was similar (P = 0.851) between treatments at the CIDR insertion (12.6 ± 0.6 mm) and CIDR removal (12.9 ± 0.4 mm), but were greater for MTN than REST cows at 60 hours after CIDR removal (14.01 ± 0.6 and 12.37 ± 0.5 mm, respectively). Volume of CL was similar (P > 0.01) at 5 (3211 ±13 mm3) and 7 (5280.3 ± 212 mm3) days after ovulation. In conclusion, nutrient restriction during estrous synchronization negatively affects diameter of the ovulatory follicle, but it did not affect subsequent CL volume in mature Angus cows.

Evaluating differences between formulated dietary net energy values and net energy values determined from growth performance in finishing beef steers.

Based on principles of the California Net Energy System, the dry matter intake (DMI) by feedlot cattle can be subdivided into DMI required for maintenance and DMI required for gain. Thus, if DMI along with body weight at a compositional endpoint and shrunk weight gain are known, dietary concentrations of net energy for maintenance and gain (NEm and NEg, respectively) can be calculated from growth performance data. Close agreement between growth performance-predicted and tabular NEm and NEg values implies the system can be used to accurately predict growth performance and be used to evaluate marketing and management decisions. We used 747 pen means from 21 research studies conducted at Texas Tech University and South Dakota State University to assess the agreement between growth performance-predicted NEm and NEg values and those calculated from tabular energy values for feeds reported by the 2016 National Academies of Science, Engineering, and Medicine publication on beef cattle nutrient requirements. Regression of growth performance-predicted values on tabular values with adjustment for random effects of study indicated that the intercepts of the two regressions did not differ from zero, and the slopes did not differ from one. Residuals (tabular minus growth performance-predicted values) for NEm and NEg averaged -0.003 and -0.005, respectively. Nonetheless, the precision of growth performance-predicted values was low, with approximately 40.3% of performance-predicted NEm values and 30.9% of NEg values falling within 2.5% of the corresponding tabular value. Residuals for NEm were divided into quintiles to evaluate dietary, growth performance, carcass, and energetics variables that might help explain lack of precision in growth performance-predicted values. Among the variables considered, gain:feed ratio was the most discriminating, with differences (P < 0.05) among each of the quintiles. Despite these differences, however, gain:feed ratio did not explain important percentages of variation in components of growth performance-predicted NEm values like maintenance energy requirements (r2 = 0.112) and retained energy (r2 = 0.003). Further research with large datasets that include dietary composition, growth performance and carcass data, and environmental variables, along with fundamental research on maintenance requirements and energy retention, will be required to identify ways to improve the precision of growth performance-predicted NE values.

Predicting microbial crude protein synthesis in cattle from intakes of dietary energy and crude protein.

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.

Tillage, sole and intercrop systems and soil amendment influence on sorghum grain and stover nutrient levels

Sorghum [Sorghum bicolor (L) Moench) is a major grain crop in Burkina Faso. A three-year experiment was conducted in the Sudanian zone to determine the combined effects of tillage methods (T) and cropping systems with different soil amendments (CS/SA) on plant nutrient concentrations and related this to human and cattle nutrient requirements. The analysis of variance indicated that tillage, soil amendment nor cropping system affected the stover nutrient concentration of grain sorghum. Nitrogen, P, K, S, Ca, Mg, Zn, Mn and Cu concentrations in grain were all influenced by the Y x T interaction largely due to increased nutrient concentrations for no-till in 2012 and tied ridges in 2013. As grain yield increased, grain N, Ca, Mg and Mn concentrations decreased while P and Zn increased. Grain N, P, Mg, S, Fe and Zn concentrations met human nutritional requirements, while K, Ca, Mn and Cu were deficient and merited supplementation. Nutrient gross means indicated that cattle nutrient requirements were met for N, P, Mg, Fe and Zn, but low for K, Ca, S, Mn and Cu. Tillage, CS/SA and Y had no or small effects on the nutrient concentrations of sorghum grain and stover. The agroecological zones in 2012 and 2013 indicated most nutrients to be adequate for human and cattle diets, but not for K, Ca, Mn and Cu.

Seasonal patterns of forage quality in six native forb species

The forage value of native forbs is rarely considered in pasture mixtures, even though such species can make up a substantial proportion of the diet of cattle on native rangelands. Incorporating non-leguminous forbs into pasture grazing systems can provide additional ecosystem services such as pollination habitat, and ideally those forbs would also provide some forage value. We therefore assessed the seasonal variation in protein and fiber [neutral detergent fiber (NDF) and acid detergent fiber (ADF)] content of six common western Canadian native forb and sub-shrub species: yarrow (Achillea millefolium), smooth aster (Symphyotricum laeve), prairie crocus (Pulsatilla patens), prairie rose (Rosa arkansana), Canada goldenrod (Solidago canadensis), and American vetch (Vicia americana). The legume V. americana displayed the highest protein followed by S. canadensis and S. laeve. V. americana also has the highest fiber concentration through the growing season. S. canadensis and S. laeve had lower fiber content; thus, making them a good choice for addition in seed mixes to meet the energy and nutrient requirements of cattle. Forb protein and fiber content showed opposite trends during the growing season. Crude protein decreased while NDF and ADF increased as a general pattern tied to physiological stage and degree of senescence. The promising nutritional profile of some forb species suggests that these species should be considered in pasture mixes.

77 Evaluation of Models Used to Predict Dry Matter Intake in Forage-Based Diets

Abstract Data from experiments conducted at the University of Nebraska-Lincoln were pooled to compare predicted and observed dry matter intake (DMI) of growing cattle consuming foraged-based diets (corn silage, grass, alfalfa, or sorghum-hay) to determine the accuracy of current modeling systems. Experiments (n = 22) were a minimum of 84 days and included individually fed calves using the Calan gate system with 8 to 12 calves per treatment mean or pen-fed calves with 8 to 12 head per pen. Average body weight (BW) of calves ranged from 235 to 397 kg with average daily gain (ADG) between 0.16 and 1.65 kg. Cattle were fed ad libitum and mid-point BW and ADG were entered into the Beef Cattle Nutrient Requirements Model (2016) to determine predicted DMI. Simple regression was used to compare predicted and observed DMI to determine the accuracy of the prediction model. Ninety-three treatment means were evaluated and were separated into three categories: hay-based diets (n = 24), hay-based diets with distillers grains (n = 31), and corn silage-based diets (n =38). The model for observed versus predicted DMI was significant (P &amp;lt; 0.05; R2 = 0.09) when comparing all means but had a poor R2. The model was the best at predicting DMI for forage-based diets (P &amp;lt; 0.08; R2 = 0.22). Observed and predicted DMI were regressed along TDN values, calculated using book values and digestion studies. As TDN increased, observed DMI increased linearly (P &amp;lt; 0.01) and predicted DMI had a quadratic response (P &amp;lt; 0.01), increasing up to 63% and then decreasing with increasing TDN. The model over predicted DMI intake for TDN &amp;lt; 63% and under predicted DMI in forage-based diets greater than 63% TDN. Further development of the current modeling system through addition of intake data from forage fed growing cattle is needed

207 Effects of increasing dietary metabolizable protein in lightweight beef calves

Abstract The objective was to assess the effect of increasing metabolizable protein (MP) supply to lightweight beef steers on total tract digestion, N balance, and performance. The 2016 Beef Cattle Nutrient Requirements Model (BCNRM) prediction of MP requirements in lightweight beef steers (less than 250 kg) is limited by available data. Spring-born Angus steers (n = 12; BW = 166 +/- 10.7 kg) were weaned at 97 ± 10 d of age, backgrounded 42 d, implanted with Component TE-IS, stratified by BW, and assigned to one of four treatments in a crossover design with two 19 day periods. Each period included a 12-day adaptation followed by a 6-day collection period of total orts, feces, and urine. Treatment diets were formulated to provide 0.62 (MP1), 0.76 (MP2), 0.89 (MP3), and 1.01 (MP4) kg MP per day. Metabolizable energy was similar across diets (2.14 Mcal/kg). Data were analyzed using the Mixed procedure of SAS. Dry matter intake was not affected by treatment (P = 0.92) and averaged 5.7 kg per d. Average daily gain (ADG) tended (P = 0.06) to increase quadratically with MP provision with 1.45, 1.72, 1.93, and 1.71 kg per day for MP1, MP2 MP3, and MP4, respectively. Feed efficiency (G:F) also increased quadratically (P = 0.05) at 0.27, 0.32, 0.35, and 0.31 for MP1, MP2 MP3, and MP4, respectively. Greater dietary MP linearly increased (P &amp;lt; 0.01) N intake, N absorption, and urinary N. Fecal N and retained N were not affected by treatment (P ≥ 0.56). Apparent organic matter digestibility increased linearly (P ≤ 0.01). Increasing MP resulted in a linear increase in N absorption but a quadratic response for ADG, suggesting MP greater than 0.89 kg per d may exceed MP requirements for steers weighing 166 kg and consuming a 2.14 Mcal/kg diet.

Development of an equation to predict net protein requirements for the growth of Zebu beef cattle

The accurate estimation of protein requirements for beef cattle is a key factor in increasing livestock profitability and decreasing the environmental impacts of excessive N excretion due to mismatching between assumed requirements and diet formulation. A meta-analysis was conducted to evaluate and validate a new equation to predict the net protein requirements for growth (NPg) of Zebu beef cattle. For the development of the new approach, a database of 552 observations comprised of bulls, steers, and heifers of different genetic groups (Zebu, beef crossbreed, and dairy crossbreed) was assembled. The new approach was evaluated and compared to current models devised by the international nutrient requirements system committees (Agricultural Research Council, 1980; Beef Cattle Nutrient Requirements Model, 2016; BR-CORTE, 2016) to predict NPg. The model evaluation was performed through the model evaluation system (version 3.1.16) using an independent data set (n = 177 observations). An equation was considered the best estimator of NPg if the following conditions were met: (1) the intercept and slope of the regression between ordinary residues and/or predicted NPg values must have been equal to zero and one, respectively; and (2) the greatest concordance correlation coefficient (CCC) and determination coefficient (R), and lowest mean squared error of prediction (MSEP) were attained. Based on the regression models of the observed v. predicted NPg of Zebu beef cattle, both the new approach and that of the ARC (1980) correctly estimated NPg, since the intercept and slope were not different (P > 0.05) from zero and one, respectively. Additionally, the new approach’s determination coefficient was the greatest and the closest to one. The fact that the new model achieved a higher CCC and lower MSEP than the existing models indicated its superior reproducibility and accuracy. The equations proposed by BR-CORTE (2016) and the BCNRM (2016) did not correctly estimate NPg in that the intercept and slope were different (P < 0.01) from zero and one, respectively. Thus, the equations proposed by the new approach and the ARC (1980) accurately and precisely estimated NPg and are recommended for Zebu cattle. Furthermore, the inclusion of equivalent empty BW (EQEBW) in the new approach improves the estimation of NPg. We suggest the use of the following equation to calculate NPg for Zebu beef cattle: NPg = 176.01 × EBG – 0.381 × EQEBW0.75 × EBG1.035 (R = 0.80 and CCC = 0.75); where NPg = net protein requirements for growth, EBG = empty body gain, and EQEBW = equivalent empty BW.

335 Metabolizable protein requirement of lightweight beef calves

Abstract The objective was to assess the metabolizable protein (MP) requirements of lightweight beef steers. The 2016 Beef Cattle Nutrient Requirements Model (BCNRM) prediction of MP requirements in lightweight beef steers (less than 250 kg) is limited by available performance data in beef calves. Fall born Angus × Simmental crossbred steers (n = 172; BW = 153 kg) were weaned at 70 d of age (± 26 d), backgrounded 73 d, implanted with Component TE-IS, blocked by BW as light (96–163 kg) or heavy (163–215 kg), and assigned to one of four treatments for 56 d. Treatment diets provided MP at: 0.59 (MP1), 0.69 (MP2), 0.85 (MP3), and 0.91 kg per d (MP4) based on observed DMI. Energy was similar across all treatments at 2.14 Mcal/kg ME. Shrunk body weights were collected on d 0 and 56 to estimate performance. Dry matter intake was affected (P &lt; 0.01) by treatment and increased (linear; P &lt; 0.01) with greater provision of MP. As a percent of shrunk body weight, DMI averaged 2.8% and tended (linear; P = 0.07) to increase with MP. Based on observed DMI, ADG for MP1, MP2, MP3, and MP4 was predicted using the BCNRM at 1.15, 1.55, 1.99, and 1.98 kg, respectively. Observed ADG increased quadratically (P = 0.01) with MP1, MP2, MP3, and MP4 gaining 1.86, 2.13, 2.3, and 2.3 kg, respectively. Final BW increased (quadratic; P = 0.02) with greater MP as MP1, MP2, MP3, and MP4 were 258, 273, 282, and 284 kg, respectively. Gain:feed increased quadratically (P = 0.04) with observed values for MP1, MP2, MP3, and MP4 being 0.323, 0.357, 0.359, and 0.360, respectively. Steer ADG response exceeded BCNRM predictions by 29%. Data suggest MP requirements of lightweight beef steers (BW = 213 kg) are 0.85 kg per d to achieve 2.3 kg ADG when fed a 2.14 Mcal/kg ME diet.

Impact of microbial efficiency to predict MP supply when estimating protein requirements of growing beef cattle from performance.

Data from 16 trials were compiled to calculate microbial CP (MCP) production and MP requirements of growing cattle on high-forage diets. All cattle were individually fed diets with 28% to 72% corn cobs in addition to either alfalfa, corn silage, or sorghum silage at 18% to 60% of the diet (DM basis). The remainder of the diet consisted of protein supplement. Source of protein within the supplement varied and included urea, blood meal, corn gluten meal, dry distillers grains, feather meal, meat and bone meal, poultry by-product meal, soybean meal, and wet distillers grains. All trials included a urea-only treatment. Intake of all cattle within an experiment was held constant, as a percentage of BW, established by the urea-supplemented group. In each trial the base diet (forage and urea supplement) was MP deficient. Treatments consisted of increasing amounts of test protein replacing the urea supplement. As protein in the diet increased, ADG plateaued. Among experiments, ADG ranged from 0.11 to 0.73 kg. Three methods of calculating microbial efficiency were used to determine MP supply. Gain was then regressed against calculated MP supply to determine MP requirement for maintenance and gain. Method 1 (based on a constant 13% microbial efficiency as used by the beef NRC model) predicted an MP maintenance requirement of 3.8 g/kg BW and 385 g MP/kg gain. Method 2 calculated microbial efficiency using low-quality forage diets and predicted MP requirements of 3.2 g/kg BW for maintenance and 448 g/kg for gain. Method 3 (based on an equation predicting MCP yield from TDN intake, proposed by the Beef Cattle Nutrient Requirements Model [BCNRM]) predicted MP requirements of 3.1 g/kg BW for maintenance and 342 g/kg for gain. The factorial method of calculating MP maintenance requirements accounts for scurf, endogenous urinary, and metabolic fecal protein losses and averaged 4.2 g/kg BW. Cattle performance data demonstrate formulating diets to meet the beef NRC model recommended MP maintenance requirement (3.8 g/kg S) works well when using 13% microbial efficiency. Therefore, a change in how microbial efficiency is calculated necessitates a change in the proposed MP maintenance requirement to not oversupply or undersupply RUP. Using the 2016 BCNRM to predict MCP production and formulate diets to meet MP requirements also requires changing the MP maintenance requirement to 3.1 g/kg BW.

Lifetime productivity of dairy cows in smallholder farming systems of the Central highlands of Kenya

Evaluation of lifetime productivity is sensible to target interventions for improving productivity of smallholder dairy systems in the highlands of East Africa, because cows are normally not disposed of based on productive reasons. Feeding strategies and involuntary culling may have long-term effects on productive (and therefore economic) performance of dairy systems. Because of the temporal scale needed to evaluate lifetime productivity, experimentation with feedstuffs in single lactations is not enough to assess improvements in productivity. A dynamic modelling approach was used to explore the effect of feeding strategies on the lifetime productivity of dairy cattle. We used LIVSIM (LIVestock SIMulator), an individual-based, dynamic model in which performance depends on genetic potential of the breed and feeding. We tested the model for the highlands of Central Kenya, and simulated individual animals throughout their lifetime using scenarios with different diets based on common feedstuffs used in these systems (Napier grass, maize stover and dairy concentrates), with and without imposing random mortality on different age classes. The simulations showed that it is possible to maximise lifetime productivity by supplementing concentrates to meet the nutrient requirements of cattle during lactation, and during early development to reduce age at first calving and extend productive life. Avoiding undernutrition during the dry period by supplementing the diet with 0.5 kg of concentrates per day helped to increase productivity and productive life, but in practice farmers may not perceive the immediate economic benefits because the results of this practice are manifested through a cumulative, long-term effect. Survival analyses indicated that unsupplemented diets prolong calving intervals and therefore, reduce lifetime productivity. The simulations with imposed random mortality showed a reduction of 43% to 65% in all productivity indicators. Milk production may be increased on average by 1400 kg per lactation by supplementing the diet with 5 kg of concentrates during early lactation and 1 kg during late lactation, although the optimal supplementation may change according to milk and concentrate prices. Reducing involuntary culling must be included as a key goal when designing interventions to improve productivity and sustainability of smallholder dairy systems, because increasing lifetime productivity may have a larger impact on smallholders’ income than interventions targeted to only improving daily milk yields through feeding strategies.

Effects of residual and reapplied biosolids on forage and soil concentrations over a grazing season in North Florida. I. Macrominerals, crude protein, and in vitro digestibility*

Effects of applications of exceptional quality biosolids (sludge) to bahiagrass (Paspalum notatum) pastures in successive years, or residual effects of applications the previous year, on macromineral crude protein (CP) and in vitro digestibility (IVOMD) status of forage and soils in north Florida were studied in relation to beef cattle nutrient requirements. Thirty 0.8 ha pastures were assigned one of 9 treatments representing two sources of biosolids. Biosolids (Baltimore and Tampa) were applied at an “agronomic rate” (X) and 2X. Four of the treatments represented residual applications of the Baltimore and Tampa biosolids which had been applied to pastures as in the previous year. The control plot received NH4NO3. Forages were analyzed for calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), sodium (Na), crude protein (CP), and in vitro organic matter digestibility (IVOMD), and soils were analyzed for Mehlichl extractable Ca, P, Mg, and K. Single (agronomic or twice this) applications, or reapplication of different biosolids slightly improved Ca, P, and K status of some forages. Both Tampa reapplied treatments resulted in forage Ca higher than the control. Although treatment effects were observed for each macromineral, the results were variable among treatments at various sampling times. Little or no difference (P > 0.05) was observed between pairs of residual and reapplied treatments. Forage CP concentrations were high and met beef cattle requirements for all treatments. Forage digestibility was similar for all treatments, with a general decline in digestibility evident at season's end. Soil extractable Ca, P, and Mg concentrations for all treatments were adequate to promote plant growth, while soil K concentrations were marginal or low, depending on treatment and sampling time. In relation to grazing beef cattle requirements, forages from all treatments contained adequate Ca, P, Mg, K, CP, and IVOMD, but were deficient in Na. Many biosolids treated pastures contained excess S, (>0.40%) and were greater (P > 0.05) than controls. In general, results were similar to those observed in the previous year, with reapplication of biosolids having no cumulative effects in most cases, although the soil P levels of some treatments did appear higher in year two. *Florida Agricultural Experiment Station Journal Series No. R-07561.

Effects of pasture‐applied biosolids on forage and soil concentrations over a grazing season in north Florida. I. macrominerals, crude protein, and in vitro digestibility1

The rationale for this experiment was to determine forage nutrient concentrations as affected by biosolids fertilization. We studied the effects of single applications of two exceptional quality biosolids to bahiagrass (Paspalum notatum) pasture with regard to satisfying beef cattle nutrient requirements. Twenty‐five 0.8‐ha pastures were divided into five blocks. Two biosolids were applied as normal and double agronomic rates. The control plot received NH4NO3. Forages were analyzed for calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), sodium (Na), crude protein (CP), and in vitro organic matter digestibility (IVOMD), and soils were analyzed for Mehlich I extractable Ca, P, Mg, and K. Single (agronomic or twice this) applications of biosolids to pastures had little effect on Ca, P, Na, and K forage concentrations, but forage Mg was elevated in several treatments late in the season. Crude protein concentrations were elevated above the control for all biosolids treatments late in the season, whereas only small differences were observed at early sampling times. Trends were similar for IVOMD. In general, all treatments were associated with soils with adequate Ca, P, and Mg concentrations, while soil K was uniformly low. In relation to grazing beef cattle requirements, all treatments resulted in generally adequate forage levels of Ca, P, Mg, K, CP, and IVOMD, however, Na (<0.06%) was deficient.