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An experiment was conducted to evaluate: (1) the effects of ensiling maize or sorghum grains after reconstitution on readily soluble fraction (a), potentially degradable fraction in the rumen (b) and rate constant for degradation of b (c) of dry matter (DM), organic matter (OM) and starch (STA); and (2) an appropriate incubation time for in situ or in vitro procedures to estimate in vivo digestibility. Four rumen-cannulated Nellore bulls (body weight = 262 ± 19.6 kg) distributed in a 4 × 4 Latin square were used. Diets were based on dry ground maize (DGM); or dry ground sorghum (DGS); or reconstituted ground maize silage; or reconstituted ground sorghum silage. In vitro and in situ incubations of the individual grains and diets were simultaneously performed with in vivo digestibility. In general, reconstituted grains and diets based on reconstituted grains presented greater (P < 0.05) fraction a and lower (P < 0.05) fraction b of DM, OM and STA compared to dry grains and diets based on dry grain. However, the magnitude of response of the reconstitution and ensiling process on DM and OM degradability parameter was greater for maize than that for sorghum. Moreover, no differences (P > 0.05) were observed between DGM- and DGS-based diets for c estimates. The results suggest that the reconstitution process promotes grains protein matrix breakdown increasing STA availability. The incubation times required for in vivo digestibility estimations of DM, OM and STA are 24 h for in situ and 36 h for in vitro procedures.

The objective of this meta-analysis study was to develop and validate equations estimated from in situ and in vitro methods to predict in vivo ruminal digestibility of organic matter (OM) of beef cattle diets. The database was composed of individual data of 23 diets from six experiments. Information collected from these studies was: in vivo digestibility and degradation parameters of OM calculated from in situ and in vitro incubations. The values of estimated times for the in situ and in vitro incubations to access in vivo digestibility of OM, and differences between degradation at 24, 48 and 72 h (in situ and in vitro) and in vivo digestibility were analysed in a model that included the fixed effects of forage neutral detergent fibre level. Thereafter, a multiple stepwise regression was carried out using OM digestibility as a dependent variable and degradation parameters (A = water-soluble fraction; B = potentially degradable water-insoluble fraction; and kd = degradation rate of fraction B) as independent variables. Equation validation was performed using data from a seventh experiment that have the same methods than previous studies. Stepwise regression results showed that the kd contributed significantly in most of the algorithms derived to predict in vivo digestibility. Validation analysis showed that equations developed from both in vitro and in situ incubations accurately estimated the in vivo digestibility of OM (P > 0.05). Our results suggest that equations developed to estimate OM digestibility showed both precision and accuracy; however, in situ method presented better results than in vitro.

Effects of dietary crude protein (CP) supply on intake, digestibility, performance, and N balance were evaluated in young Nellore bulls consuming static or oscillating CP concentrations. Forty-two young bulls (initial BW of 260 ± 8.1 kg; age of 7 ± 1.0 mo) were fed ad libitum and were randomly assigned to receive one of six diets with different CP concentrations for 140 d: 105 (LO), 125 (MD), or 145 g CP /kg DM (HI), and LO to HI (LH), LO to MD (LM), or MD to HI (MH) oscillating CP at a 48-h interval for each feed. At the end of the experiment, bulls were slaughtered to evaluate carcass characteristics. Linear and quadratic effects were used to compare LO, MD, and HI, and specific contrasts were applied to compare oscillating dietary CP treatments vs. MD (125 g CP/kg DM) static treatment. Dry matter intake (DMI) was not affected (P > 0.26) by increasing or oscillating dietary CP. As dietary N concentration increased, there was a subsequent increase in apparent N compounds digestibility (P = 0.02), and no significant difference (P = 0.38) was observed between oscillating LH and MD. Daily total urinary and fecal N increased (P < 0.01) in response to increasing dietary CP. Significant differences were observed between oscillating LM and MH vs. MD, where bulls receiving the LM diet excreted less (P < 0.01; 71.21 g/d) and bulls fed MH excreted more (P < 0.01) urinary N (90.70 g/d) than those fed MD (85.52 g/d). A quadratic effect was observed (P < 0.01) for retained N as a percentage of N intake, where the bulls fed LO had greater N retention than those fed HI, 16.20% and 13.78%, respectively. Both LH and LM had greater (P < 0.01) daily retained N when compared with MD. Performance and carcass characteristics were not affected (P > 0.05) by increasing or oscillating dietary CP. Therefore, these data indicate that although there is no alteration in the performance of growing Nellore bulls fed with oscillating CP diets vs. a static level of 125 g CP/kg DM, nor static low (105 g CP/kg DM) and high (145 g CP/kg DM) levels; there may be undesirable increases in environmental N excretion when the average dietary CP content is increased. The results suggest that dietary CP concentrations of 105, 125 g/kg DM, or within this range can be indicated for finishing young Nellore bulls, since it reaches the requirements, reduces the environmental footprint related to N excretion, and may save on costs of high-priced protein feeds.

Water is the most important nutrient in animal nutrition; however, water intake is rarely measured. The objective of this study was to determine whether previously published water intake (WI) equations for beef cattle would accurately predict WI from four experiments conducted under tropical conditions. The experiments were conducted from 2013 to 2015. Nellore (Bos indicus) growing bulls (Exps. 1, 2, and 3) and heifers (Exp. 4) were used in the feedlot trials. In all experiments, animals were fed for ad libitum DMI. The WI, animal performance, diet composition, and environmental data were collected. The prediction of WI using the current published WI equations was evaluated by regressing predicted and measured WI values. The regression was evaluated using the two-hypothesis test: H0: β0 = 0 and H0: β1 = 1 and Ha: not H0. If both null hypotheses were not rejected, it was concluded that the tested equation accurately estimated WI. To develop a WI prediction equation based on the input variables, a leave-one-out cross-validation method was proposed. The proposed equation was evaluated using similar methodology described above. All previously published eight equations overestimated WI of cattle used in the four experiments conducted in southeast Brazil. A possible explanation for the overestimate of WI is that previously published WI equations were generated from data collected from predominantly Bos taurus cattle raised under temperate climates. From the data collected from experiments conducted with Nellore cattle in southeast Brazil, the proposed equation (WI = 9.449 + 0.190 × MBW + 0.271 × T(MAX) −0.259 × HU + 0.489 × DMI, where the MBW is the metabolic BW (kg(0.75)), T(MAX) is the maximum temperature (°C), HU is the humidity (%) and DMI in kg/d), more accurately to predicts WI of cattle raised under tropical conditions.

Background: Rehydration of grains, such as corn and sorghum, is used to increase nutrient absorption. However, the effect of this practice on meat quality is poorly understood. Objective: To evaluate the effects of type of grain and processing on the meat quality of Nellore steers in a feedlot. Methods: Twenty-four non-castrated Nellore steers (270 ± 53 kg initial body weight) were distributed in a completely randomized 2×2 factorial design, with six replicates. The first factor was cereal type (corn or sorghum), and the second was the grain processing (dry or rehydrated and ensiled). The diets were composed of 30% corn silage and 70% concentrate. Sixty days before the beginning of the experiment, corn and sorghum grains were rehydrated and ensiled. The animals were slaughtered after 140 days of confinement. Meat quality analyses were determined in samples of fresh and aged meat (7 days) from the Longissimus lumborum muscle. Results: no difference between treatments was observed for carcass pH and L* (lightness), a* (redness), and b* (yellowness) values, shear force, thawing and cooking losses, and chemical composition of meat (p>0.05). The b* (yellowness) value of subcutaneous fat was higher in steers fed corn, regardless of grain processing (p=0.03). Sarcomere length was higher in aged meat of steers fed sorghum, regardless of processing method (p=0.01). Conclusions: the grain processing method does not affect beef quality; however, grain type can affect subcutaneous fat color and sarcomere length of aged beef. Resumen Antecedentes: La rehidratación de granos, tales como maíz y sorgo, se usa para aprovechar mejor sus nutrientes. Sin embargo, es poco conocido el efecto de esta práctica sobre la calidad de la carne. Objetivo: Evaluar los efectos del tipo de cereal y su procesamiento sobre la calidad de carne de toretes Nelore en confinamiento. Métodos: Veinticuatro novillos Nelore enteros con un peso promedio inicial de 270 ± 53 kg, se distribuyeron en un diseño factorial 2×2 completamente aleatorizado (n=6). El primer factor fue el tipo de cereal (maíz o sorgo) y el segundo fue su procesamiento (seco o rehidratado y ensilado). Las dietas estuvieron compuestas por 28,44% de ensilaje de maíz y 71,56% de concentrado. Sesenta días antes de iniciar el experimento, los granos de maíz y sorgo se rehidrataron y ensilaron. Los animales se sacrificaron después de 140 días de confinamiento. La calidad de la carne se determinó en muestras de carne fresca y madurada (7 días) obtenidas del músculo Longissimus lumborum. Resultados: No hubo diferencias entre tratamientos para el pH de las canales, ni para los valores de color (L* “luminosidad”, a* “intensidad de rojo” y b* “intensidad de amarillo”), fuerza de corte, composición química, o pérdidas de agua por descongelamiento o cocción (p>0,05). El valor de b* de la grasa subcutánea fue mayor en los novillos alimentados con maíz, independientemente del tipo de procesamiento (p=0,03). La longitud de sarcómero fue más alto en la carne madurada de novillos alimentados con sorgo, sin importar el método de procesamiento (p=0,01). Conclusiones: El método de procesamiento del grano no afecta la calidad de la carne; sin embargo, el tipo de cereal afecta el color de la grasa subcutánea y la longitud del sarcómero de la carne madurada. Resumo Antecedentes: A reidratação de grãos, como milho e sorgo, tem sido usada para aumentar a utilização de seus nutrientes. Contudo, o efeito dessa prática na qualidade da carne é pouco compreendido. Objetivo: Avaliar os efeitos do tipo de grão de cereais e seu processamento sobre a qualidade da carne de bovinos confinados. Métodos: Vinte e quatro bovinos Nelore não castrados, com peso corporal médio inicial de 270 ± 53 kg foram distribuídos em delineamento inteiramente casualizado, fatorial 2×2, com seis repetições. O primeiro fator foi o tipo de grão de cereal no concentrado (milho ou sorgo), e o segundo foi o processamento destes grãos (seco ou reidratado e ensilado). As dietas foram compostas por 28,44% de silagem de milho e 71,56% de concentrado. Sessenta dias antes do início do experimento, os grãos de milho e sorgo foram reidratados e ensilados. Os animais foram abatidos após 140 dias de confinamento. As análises de qualidade da carne foram determinadas em amostras não maturadas e maturadas (7 dias) obtidas do músculo Longissimus lumborum. Resultados: Não houve diferenças significativas (p>0,05) entre os tratamentos para pH da carcaça e L* (luminosidade), a* (intensidade de vermelho), b* (intensidade de amarelo), força de cisalhamento, perdas por descongelamento, perdas por cocção, perdas totais e composição química da carne. O valor de b* da gordura subcutânea foi maior (p=0,03) em bovinos alimentados com dietas contendo grãos de milho, independentemente do tipo de processamento. O comprimento de sarcômero foi maior na carne maturada de novilhos alimentados com sorgo, independente do método de processamento (p=0,01). Conclusões: O método de processamento dos grãos não afetou a qualidade da carne bovina, no entanto, a cor da gordura subcutânea e o comprimento de sarcômero da carne maturada foram afetados pelo tipo de grão.

An experiment was conducted to evaluate the feed intake, nutrient digestibility and selected rumen parameters in feedlot bulls fed diets containing different feed additives. Six rumen-cannulated Nellore bulls (age = 8 ± 1.0 months; initial BW = 225 ± 13.2 kg) were distributed in a 6 × 6 Latin square design. Six experimental diets based on 30% corn silage and 70% concentrate on a dry matter (DM) basis were evaluated. Diets differed in feed additive on a DM basis, as follows: 1.4% bicarbonate and magnesium oxide in 3:1 ratio (BOX); 36 ppm lasalocid sodium (LAS); 30 ppm monensin sodium (MON); 25 ppm virginiamycin (VIR); 30 ppm monensin sodium plus 25 ppm virginiamycin (MV); and 3.15% commercial mineral supplement containing D-limonene and exogenous α-amylase (EOA). The experiment lasted 144 d, with six periods of 24 d. Each period consisted of 14 d for dietary adaptation, 3 d for feces and urine collection, and 7 d for omasal and ruminal digesta collection. Bulls fed the BOX diet showed greater (P < 0.05) intake of DM, organic matter (OM), neutral detergent fiber (apNDF), crude protein (CP), and starch compared to the other diets. Diets with LAS, MON, VIR, MV, or EOA did not influence (P > 0.05) the DM, OM, apNDF, CP, or starch intake of feedlot bulls. Bulls fed the EOA diet showed greater (trend; P = 0.09) ruminal digestibility of starch compared to the other diets. The feed additives did not affect (P > 0.05) the intestinal or total tract digestibility of starch, rumen pH, microbial efficiency, total rumen fluid, dilution rate, rate of intake, rate of degradation, or passage rate of the DM, OM, apNDF, and starch. In conclusion, LAS, MON, VIR, MV, and EOA diets reduced nutrient intake compared to BOX. Although all feed additives presented similar effects on rumen pH, temperature, and kinetics the presence of exogenous α-amylase in the EOA diet may increase ruminal starch digestibility and apparent total tract digestibility of DM and OM.

This study aimed to estimate energy requirements of pregnant Holstein × Gyr cows. Different planes of nutrition were established by two feeding regimens: Ad libitum or maintenance. Sixty-two nonlactating cows with average body weight of 480 ± 10.1 kg and an age of 5 ± 0.5 years were used. Cows were divided into three groups: Pregnant (n = 44), non-pregnant (n = 12), and baseline reference (n = 6). The 56 pregnant and non-pregnant cows were randomly allocated into a feeding regimen: Ad libitum or maintenance. To evaluate the effects of days of pregnancy, pregnant and non-pregnant animals were slaughtered at 140, 200, 240, and 270 days of pregnancy. Energy requirements for maintenance differed between pregnant and non-pregnant cows, thus two equations were developed. Net energy and metabolizable energy requirements for maintenance of non-pregnant cows were 82 kcal/kg empty body weight0.75/day and 132 kcal/kg empty body weight0.75/day, respectively. The efficiency of use of metabolizable energy for maintenance of non-pregnant cows was 62.4%. Net energy and metabolizable energy for maintenance of pregnant cows were 86 kcal/kg empty body weight0.75/day and 137 kcal/kg empty body weight0.75/day, respectively. Efficiency of use of metabolizable energy for maintenance of pregnant cows was 62.5%. The efficiency of use of metabolizable energy for gain was 41.9%. The efficiency of use of metabolizable energy for pregnancy was 14.1%. Furthermore, net energy requirement for pregnancy was different from zero from day 70 of pregnancy onwards. In conclusion, net energy and metabolizable energy requirements for maintenance of non-pregnant cows are different from pregnant cows. Furthermore, we believe that the proposed non-linear equations to estimate net energy requirements for pregnancy are more adequate than current NRC equation, and should be recommended for Holstein × Gyr cows.

The aim of this study was to investigate the effect of sex and levels of dietary crude protein (CP) on the recovery of 15N in microbial protein as well as to evaluate nitrogen balance compounds and variables related to urea renal handling in Nellore cattle. Four Nellore bulls and four Nellore heifers, fitted with rumen cannulas, were distributed in a two 4 × 4 Latin square design. The four experimental diets differed in levels of CP: 90.0, 110.0, 130.0, and 150.0 g/kg on a dry matter basis. Continuous intravenous infusion of ^15N^15N-urea solution was provided at a rate of 0.30 mmol urea/h followed by determination of ^15N in ruminal bacteria, ammonia (NH3), and feces to determine the incorporation of recycled N in rumen bacteria. The increased dietary CP revealed a linear increase (P < 0.05) in total digestible nutrients (TDN), total digestibility of CP and neutral detergent fiber (NDF), retained nitrogen, urinary excretion of urea-N, amount of filtered and absorbed urea (g/day), and plasmatic concentrations of urea-N. Fecal excretion of N presented a linear increase (P < 0.05) in relation to dietary CP. Rumen NH3 concentration increased in a linear fashion (P < 0.05), and rumen ^15N-NH3 contents and fecal ^15N contents decreased in a linear fashion (P < 0.05) with increasing dietary CP. The regressions NH3 = 23.6183 × e^(0.0104×NI) and ^15N-NH3 = −0.00062 × NI + 0.1219 were obtained in order to calculate rumen NH3 concentrations (mg/l) and ^15N-NH3 (atom percent excess), respectively, as a function of N intake (NI, g/day). The contents of total-N and ^15N did not differ between liquid-associated bacteria (LAB) and particle-associated bacteria (PAB). There was no effect of sex (P > 0.05) on the percentage of infused ^15N that was recovered from feces and bacteria. There was no effect of dietary CP level on the percentage of ^15N infused in plasma that was recovered from feces. However, there was a decreasing linear effect of the level of dietary CP (P < 0.05) on the percentage of ^15N infused in the jugular vein recovered from bacteria. We concluded that microbial protein synthesis was not affected by sex. The LAB and PAB had the same total-N content and recovery of infused ^15N-urea. The greater recovery of infused intravenous ^15N-urea on microbial protein synthesis in a low CP diet suggests greater urea recycling in association with this diet.

This study evaluated intake, microbial efficiency, and ruminal, small and large intestinal, and total digestibility of DM, OM, CP, and NDF, as well as availability of Ca, P, Mg, Na, K, Cu, Mn, and Zn in Zebu cattle fed with or without supplemental sources of Ca and P or a micromineral premix. Five rumen- and ileum-cannulated Nellore bulls (BW = 200 ± 10.5 kg; 9 mo) were used in the experiment, distributed in a 5 × 5 Latin square design. The experiment was developed in a 2 × 2 + 1 factorial design to measure the effects of mineral supplementation on intake, digestibility, and site of nutrient absorption. The factors consisted of 2 Ca and P levels (macromineral factor; CaP+ or CaP-) and 2 microminerals levels (micromineral factor; CuMnZn+ or CuMnZn-). In addition, a treatment with alimentary restriction (REST) was evaluated at 1.7% of BW. Nutrient fluxes were measured in the omasum and ileum, in addition to intake and fecal excretion. Microbial efficiency was estimated using purine derivative excretion. Dry matter, OM, NDF, CP intake, and total digestibility were not affected ( ≥ 0.058) by the absence of Ca, P, Cu, Mn, and Zn supplementation. Intake of Ca, P, and Mg were reduced ( 0.05) of OM, NDF, and CP digestion sites and coefficients, we assume that omitting supplemental sources of Ca, P, Cu, Mn, and Zn may be an option in raising cattle on feedlots. If supplementation is viable, knowledge about the specific absorption site of each mineral could positively impact choices about the supplemental source.

Weaned Nellore bulls ( = 36; 274 ± 34 kg) were used in a randomized block design with a 2 × 2 factorial arrangement of treatments to evaluate intake, fecal excretion, and performance with different concentrations of minerals. Experimental diets were formulated with 2 concentrations of Ca and P (macromineral factor; diet supplying 100% of Ca and P according to BR-CORTE () [CaP+] or diet without limestone and dicalcium phosphate [CaP-]) and 2 concentrations of microminerals (micromineral factor; diet with supplementation of microminerals [Zn, Mn, and Cu; CuMnZn+] or diet without supplementation of microminerals [Zn, Mn, and Cu; CuMnZn-]). The factor CaP- was formulated without the addition of limestone and dicalcium phosphate, and the factor CuMnZn- was formulated without inorganic supplementation of microminerals (premix). The diets were isonitrogenous (13.3% CP). Intake was individually monitored every day. Indigestible NDF was used as an internal marker for digestibility estimates. The bulls were slaughtered (84 or 147 d on feed), and then carcass characteristics were measured and liver and rib samples were collected. Feed, feces, rib bones, and liver samples were analyzed for DM, ash, CP, ether extract (EE), Ca, P, Zn, Mn, and Cu. There were no significant interactions ( ≥ 0.06) between macro- and micromineral supplementation for any variables in the study. Calcium, P, and micromineral concentrations did not affect ( ≥ 0.20) intake of DM, OM, NDF, EE, CP, TDN, and nonfiber carbohydrates (NFC). Calcium and P intake were affected ( < 0.01) by macromineral factor. Animals fed without Ca and P supplementation consumed less of these minerals. Dry matter and nutrient fecal excretion (OM, NDF, EE, CP, and NFC) were similar ( ≥ 0.23) among all factors. Performance and carcass characteristics were similar ( ≥ 0.09) among diets. The content of ash in rib bones was not affected by diets ( ≥ 0.06). Plasma P and phosphatase alkaline concentrations were similar ( ≥ 0.52) among diets. Supplementation of microminerals decreased ( < 0.01) plasma Ca concentration; nevertheless, all analyzed blood metabolites were within the reference values. Supplementation of Ca and P increased ( < 0.01) fecal excretion of these minerals. These results indicate that mineral supplementation (Ca, P, Zn, Mn, and Cu) of conventional feedlot diets for Nellore bulls may be not necessary. Dietary reductions in these minerals would represent a decrease in the cost of feedlot diets. Dietary reduction in Ca and P content cause a decrease in fecal excretion of these minerals, which, in turn, represents an opportunity to reduce the environmental impact of feedlot operations.

The objectives of this study were to quantify the mineral balance of Nellore cattle fed with and without Ca, P, and micromineral (MM) supplementation and to estimate the net and dietary mineral requirement for cattle. Nellore cattle ( = 51; 270.4 ± 36.6 kg initial BW and 8 mo age) were assigned to 1 of 3 groups: reference ( = 5), maintenance ( = 4), and performance ( = 42). The reference group was slaughtered prior to the experiment to estimate initial body composition. The maintenance group was used to collect values of animals at low gain and reduced mineral intake. The performance group was assigned to 1 of 6 treatments: sugarcane as the roughage source with a concentrate supplement composed of soybean meal and soybean hulls with and without Ca, P, and MM supplementation; sugarcane as the roughage source with a concentrate supplement composed of soybean meal and ground corn with and without Ca, P, and MM supplementation; and corn silage as the roughage source with a concentrate supplement composed of soybean meal and ground corn with and without Ca, P, and MM supplementation. Orthogonal contrasts were adopted to compare mineral intake, fecal and urinary excretion, and apparent retention among treatments. Maintenance requirements and true retention coefficients were generated with the aid of linear regression between mineral intake and mineral retention. Mineral composition of the body and gain requirements was assessed using nonlinear regression between body mineral content and mineral intake. Mineral intake and fecal and urinary excretion were measured. Intakes of Ca, P, S, Cu, Zn, Mn, Co, and Fe were reduced in the absence of Ca, P, and MM supplementation ( < 0.05). Fecal excretion of Ca, Cu, Zn, Mn, and Co was also reduced in treatments without supplementation ( < 0.01). Overall, excretion and apparent absorption and retention coefficients were reduced when minerals were not supplied ( < 0.05). The use of the true retention coefficient instead of the true absorption coefficient provided a better estimate of mineral requirements. Dietary mineral requirements were lower for P, Cu, and Zn and greater for Fe compared with previously published recommendations. This study provides useful information about mineral requirements and mineral supplementation to obtain adequate dietary mineral supply of Nellore cattle in tropical conditions.

The objective of this study was to evaluate the inclusion of physically effective fiber (peNDF) from sugarcane in feedlot diets containing whole corn grain on ingestive, digestive, and ruminal parameters. Five rumen-cannulated Nellore bulls (BW = 393 ± 9 kg) distributed in an incomplete 5 × 5 Latin square received diets containing 5% (D5), 15% (D15), 25% (D25), or 35% (D35) sugarcane. All diets included a mineral-protein supplement. Omasal digesta collection and fecal spot collection were carried out to estimate ruminal and total digestibility. The ruminal contents were emptied to calculate ingestion (ki), passage (kp), and digestion (kd) rates. The linear, quadratic, and cubic effects of including sugarcane (i.e., different peNDF contents) were evaluated using orthogonal contrasts. The intake of total digestible nutrients (TDN, P = 0.06), dry matter (DM, P = 0.03), and organic matter (OM, P = 0.03) showed a quadratic pattern, with the highest estimated values occurring between 6.14 and 10.2% of peNDF. Ruminal digestibility [%, (P = 0.01) and kg/d, (P =

This study aims to (1) verify the influence of flint corn processing methods on intake; rumen digestion kinetics; microbial efficiency; rumen pH; and ruminal, intestinal, and total tract digestibilities in Nellore bulls; and (2) determine whether snaplage (SNAP) plus a mineral–protein supplement could be used successfully to supply energy, fiber, and protein in a finishing diet without causing ruminal acidosis. Five rumen-cannulated Nellore bulls (265 ± 18.2 kg, 8 ± 1.0 mo old) were distributed in a 5 × 5 Latin square design. Five different diets were evaluated. Three experimental diets [dry matter (DM) basis] comprised 600 g/kg dry ground corn grain (DCG), high–moisture corn (HMC), or reconstituted corn grain silage (RCG) plus 300 g/kg whole-plant corn silage and 100 g/kg mineral–protein supplement. SNAP was included in two experimental diets, namely 900 g/kg SNAP (SNAP-90) or 800 g/kg SNAP +100 g/kg stalklage (SNAP-80) plus 100 g/kg mineral–protein supplement. The experiment lasted 115 d, with five periods of 23 d. These periods were divided into two subperiods of 14 d for dietary adaptation and 9 d for ruminal emptying, omasal, urinary, and fecal sample collection. Statistical analyses were performed using the MIXED procedure in SAS 9.4. DCG-based diet tended (P = 0.07) to increase DM and organic matter (OM) intake. Diets based on HMC, RCG, SNAP-80, and SNAP-90 increased (P

It is expensive and laborious to evaluate carcass composition in beef cattle. The objective of this study was to evaluate a method to predict the 9th to 11th rib section (rib) composition through empirical equations using dual energy X-ray absorptiometry (DXA). Dual energy X-ray absorptiometry is a validated method used to describe tissue composition in humans and other animals, but few studies have evaluated this technique in beef cattle, and especially in the Zebu genotype. A total of 116 rib were used to evaluate published prediction equations for rib composition and to develop new regression models using a cross-validation procedure. For the proposed models, 93 ribs were randomly selected to calculate the new regression equations, and 23 different ribs were randomly selected to validate the regressions. The rib from left carcasses were taken from Nellore and Nellore × Angus bulls from 3 different studies and scanned using DXA equipment (GE Healthcare, Madison, WI) in the Health Division at Universidade Federal de Vicosa (Vicosa, Brazil). The outputs of the DXA report were DXA lean (g), DXA fat free mass (g), DXA fat mass (g), and DXA bone mineral content (BMC; g). After being scanned, the rib were dissected, ground, and chemically analyzed for total ether extract (EE), CP, water, and ash content. The predictions of rib fat and protein from previous published equations were different ( 0.05), respectively, then the equation correctly estimated the rib composition. Comparing observed and predicted values using the new equations, Mayer's test was not significant for lean mass ( = 0.26), fat free mass ( = 0.67), EE mass ( = 0.054), and ash mass ( = 0.14). We concluded that the rib composition of Nellore and Nellore × Angus bulls can be estimated from DXA using the proposed equations.

Restricted-feeding may be a useful management tool available to reduce environmental impact in feedlots. Therefore, the objectives of the present study were to determine the effects of the duration of restricted-feeding on nitrogen (N) and phosphorus (P) excretion, growth performance and carcass characteristics of finishing steers. Twenty-five Holstein × Zebu steers (average initial bodyweight (BW) = 319 ± 16.2 kg; age = 19 ± 1 months) were used. Five steers were slaughtered to provide baseline empty BW (EBW) and empty body composition at Day 0. The remaining steers were randomly allotted to four groups of five steers, which were restricted to 85% ad libitum feed intake for either 0 (R0), 28 (R28), 42 (R42) or 84 (R84) days of an 84-day finishing period. All steers were fed a diet of 40% corn silage and 60% concentrate (DM basis) for 84 days. Total excretion of faeces and urine were collected during two periods: Days 25 to 27 (period 1) and Days 73 to 75 (period 2). The DM intake, average daily gain (ADG) and gain-to-feed ratio (G:F) were evaluated in three blocks, Days 0 to 28, Days 28 to 42 and Days 42 to 84. As expected, DM, N and P intakes were greater (P < 0.05) for R0 steers than R28, R42 and R84 steers when steers in R28, R42 and R84 treatments were restricted. When transitioned to ad libitum feeding, R28 and R42 steers had similar (P > 0.05) DM, N and P intakes compared with R0 steers. Faecal N and urinary P excretions did not differ (P ≥ 0.40) among restricted and ad libitum-fed steers in either period evaluated. However, greater (P < 0.05) faecal P excretions were observed in steers fed ad libitum intake in period 2 (R0). Phosphorus retention in period 2, and whole-body N retention were greatest (P < 0.05) in steers fed R28 and least (P < 0.05) in steers fed R84, steers fed R0 and steers fed R42 were intermediate and not different (P > 0.05). Final BW, overall ADG, G:F and carcass characteristics were not affected (P ≥ 0.11) by treatments. Restricted-feeding Holstein × Zebu steers to 85% of ad libitum intake for 84 days in the feedlot reduced DM intake and P excretion, without impairing steer growth performance or carcass characteristics. Nevertheless, it is important to highlight that the small sample size was one limitation of this present experiment.

Bos indicus cattle are susceptible to metabolic disorders associated to the use of diets without roughage. Therefore, our objective was to obtain the physically effective fiber content from forage (pefNDF) necessary to improve the intake and digestibility of dry matter (DM), potentially degraded NDF (pdNDF) and starch. Five Nellore bulls rumen cannulated (BW = 393 ± 9 kg) were used in a 5 x 5 Latin square design. The treatments were:1) whole grain (850 g/kg) plus pelleted concentrate, and no forage inclusion (control); and 2 to 5) inclusion of 50, 150, 250 and 350 g/kg of sugarcane, respectively, and no inclusion of pelleted concentrate. A Pen State Particle Separator was used to determine the dietary pefNDF. Ruminal digestibilities were estimated through omasal flux using double marker system. Total digestibilities were estimated by fecal spot collection (using iNDF as a marker). Ruminal pH was measured each 9-h in three consecutive days. The digestion (kd) and passage (kp) rates of pdNDF were obtained from ruminal emptying during two sampling days (one before and other after the feeding). The pefNDF inclusion was evaluated for the linear, quadratic and cubic effects, and were compared with the control using the Dunnett test (α=0.05).The measured pefNDF in the treatments 2 to 5 were, respectively, 20.5, 61.4, 102.4 and 143.3 g/kg DM. Intake and digestibilities of DM and starch were linearly decreased (P Intake and digestibilities of pdNDF were linearly increased) P20.5 g of pefNDF/kg DM maximized kd and kp of pdNDF (P2= 0.82). From our results, it is recommended to use 20.5 g/kg pefNDF from sugarcane on whole corn grain diets. [Image: see text] Key Words

Two experiments were carried out to evaluate the effects of corn and sorghum with different processing methods on the expression of genes involved in volatile fatty acids transport and pH regulation, and ruminal keratinization in rumen epithelium of finishing bulls. For Exp. 1, five rumen cannulated Nellore bulls were used in a 5x5 Latin square arrangement, with 14 d for adaptation and 9 d for sample collection. Treatments were: dry ground corn, dry ground sorghum, reconstituted corn, reconstituted sorghum, and control (forage-based diet). Samples of rumen epithelium from ventral sac were excised, rinsed, snap-frozen and stored at -80°C until total RNA isolation and quantitative real-time PCR analysis. In the Exp. 2, 24 Nellore bulls were assigned to a completely randomized design lasting 168 d. Experimental treatments were similar to those at Exp. 1, but without the control treatment. After the experimental period, bulls were slaughtered and rumen epithelium samples were rapidly excised for further histological analysis. Rumen epithelial tissue from animals fed reconstituted corn had lower expression of downregulated-in-adenoma (P = 0.03) and Na+/H+ exchanger 2 (trend; P = 0.09). The expression of Na+/ H+ exchanger 1 (P = 0.10) and putative anion transporter (P = 0.06) tended to be lower in rumen epithelium of bulls fed reconstituted grains. Ruminal concentration of valerate was greater for animals fed reconstituted grain (P = 0.01). Likewise, animals fed reconstituted corn tended to have greater butyrate ruminal concentration (P = 0.08). Keratinized layer thickness did not differ among treatments (P > 0.10). Therefore, reconstituted grains (especially corn) decrease the mRNA expression of genes involved in volatile fatty acids transport and pH control in the rumen epithelium.

The present experiment was designed to evaluate the use of microbial markers (MM), sampling sites (SS), and marker systems (MS) to estimate microbial nitrogen (MN) synthesis in bulls and to develop equations to correct MN estimates when only one of the aforementioned techniques was utilized. The MM systems evaluated were (1) purine bases (PB) and (2) 15 N labeling. The SS evaluated were: (1) reticulum, (2) omasum, and (3) abomasum, and the single, double and triple MS were evaluated. Eight crossbred (Holstein×Zebu) bulls (353±36.9 kg of BW; 24±1 mol) with ruminal and abomasal cannulas were utilized in this experiment. The following experimental diets were used: (1) 60% corn silage+40% concentrate, (2) 40% corn silage+60% concentrate, (3) 60% fresh sugarcane+40% concentrate, and (4) 40% fresh sugarcane+60% concentrate. Four experimental periods lasting 16 d each were completed with 10 d for adaptation to the experimental diet and 6 d for sampling. Bulls were randomly distributed into two 4×4 Latin squares balanced for residual effects. Data were analyzed in a Latin square design using PROC MIXED. Interactions were observed ( P P 15 N, the greatest ( P P 15 N from those estimated using abomasum and 15 N. Thus, the equation developed to correct MN value was: MN (g/d)=27.93±2.46+0.99±0.09×reticulum 15 N. The triple MS exhibited the greatest ( P P >0.05) were observed between MS and MM or SS; thus, the equation established to correct MN value used only the MS. In conclusion, we have demonstrated that there is no difference using 15 N to estimate MN yield if omasum or abomasum are used. Therefore, the omasum can be used as an accurate SS to predict MN. The triple MS presented higher values than the single and double MS. Thus, if single or double MS is used the value must be corrected by the equation obtained using the triple MS.

This study aimed to evaluate the ensiling time effects on grain nitrogen fractions and the effects of ensiling corn and sorghum grains rehydrated on ruminal, intestinal and total starch digestion. At the trial beginning, corn and sorghum samples were milled in a 3mm sieve, rehydrated until 35% moisture and ensiled in bag silo during 0, 7, 14, 28, 60, 90, 120, 180 and 360d with three repetitions per ensiling time. These samples were analyzed for dry matter, soluble nitrogen, insoluble nitrogen and non-protein nitrogen. To evaluate digestibility the grains were ensiled 60d before the experiment beginning. Five Nellore rumen-cannulated bulls, with 262 ± 18 kg average BW were used, following a 5 × 5 Latin square design with a 2 × 2 + 1 factorial arrangement. Five experimental diets were tested, where four were composed by 28.44% corn silage, 60.83% corn and sorghum grains rehydrated or dried and 10.73% protein and mineral supplement. The fifth diet was based in dry corn with 45:55 roughage:concentrate ratio. Each experimental period lasted 22d, with 14d adaptation, 5d of total feces collection and 3 days collection to obtain omasal flow using double marker system (iNDF and Co-EDTA as markers). Data were analyzed using MIXED-SAS. There was a reduction (P

Nutrient apparent digestibility, intake, performance, microbial efficiency, and energy and protein requirements for growing Nellore heifers and steers were evaluated, fifty animals were used, 32 Nellore heifers and 18 Nellore steers. Four animals of each gender used as baseline reference animals were slaughtered at the beginning of the experiment. Four animals from each gender were fed at MAIN receiving 11 g/kg BW, whereas 10 steers and 24 heifers were assigned to the ADLIB group. The ADLIB heifers were divided further into 4 groups according to the dietary treatment: (1) Ca and P fed at their proposed requirements (CaPR) with a 50:50 roughage:concentrate (R:C) diet, (2) CaPR with a 70:30 R:C diet, (3) 43% of their proposed requirements for Ca and 80% of their requirements for P (CaPL) with a 50:50 R:C diet, and (4) CaPL with a 70:30 R:C diet. The ADLIB and MAIN steers were fed CaPR with a 50:50 R:C diet. Half of the ADLIB steers and heifers were slaughtered at day 50; the other ADLIB animals were slaughtered after 100 days of the feeding period, whereas all MAIN animals were slaughtered at day 100. Total feces and urine were collected from all animals for 72 h prior to slaughter. After slaughter, EBW was measured. The NEm and MEm requirements were estimated by exponentially relating heat production with metabolizable energy intake; NEg was estimated from EBW and EBG. The NPg was estimated from EBG and RE. Dry matter digestibility and the apparent absorption and retention of Ca and P were similar across Ca and P treatments. Final body weight, and consequently ADG, was greater (P0.05) performance. The NEm and MEm requirements were 294 and 496 kJ/kg EBW0.75, respectively. Net protein for maintenance was 1.28 g/kg BW0.75 and NEg and NPg were estimated from the following equations: NEg=0.222×EBW0.75×EBG0.6263 and NPg=137.53×EBG−0.038×RE, respectively. Under the conditions of this experiment, reducing the dietary concentrations of Ca and P had no significant impact on intake, digestibility, or performance of growing Nellore heifers and steers.

The aim of this study was to evaluate the effect of diets containing corn silage (CS) or sugarcane (SC) with 300 or 500 g/kg of concentrate (on a DM basis) on energy conversion, enteric methane (CH4) production, and the animal performance of Holstein × Zebu heifers. An experiment was conducted while using comparative slaughter. Twenty Holstein × Zebu heifers with an average age of 12 ± 1.0 months and an average bodyweight of 218 ± 36.5 kg were used. Four heifers were assigned to a baseline group, whereas the remaining 16 heifers were distributed in a completely randomised design using a 2 × 2 factorial scheme (n = 4), with two types of roughage (CS or SC) and two levels of concentrate (300 or 500 g/kg) on a DM basis of the diet over the course of 112 days. For the evaluation of the apparent total-tract digestibility of diets and energy losses, a digestibility assay was performed by using the total collection of faeces and urine over three consecutive days. The enteric CH4 production was quantified by continuous analysis of regular samples of air excreted by the animals throughout the day. The greatest (P < 0.05) average daily gain was observed for heifers that were fed CS-based diets or with 500 g/kg of concentrate. Greater (P < 0.05) daily CH4 emissions were observed for heifers that were fed 500 g/kg of concentrate; CH4 production as a function of DM intake was greater (P < 0.05) for heifers that were fed SC-based diets. The efficiency of the conversion from digestible energy (DE) to metabolisable energy (ME) was not influenced (P > 0.05) by variables that were analysed in this study. However, the mean value that was observed in the present study was above those values proposed by the main evaluation systems of feedstuffs and nutrient requirements of ruminants. Therefore, we concluded that CS-based diets allow for better animal performance of Holstein × Zebu heifers in relation to SC-based diets. Also, the increased concentrate improves the performance of growing heifers. A greater inclusion of concentrate in SC-based diets can allow for a reduction of CH4 emissions per consumed unit and per gain unit. The mean suggested value for the ME : DE ratio based on this study is 0.86. However, more studies are necessary to validate this result.