Supplementation of grazing beef cows during gestation as a strategy to improve skeletal muscle development of the offspring.

The appropriate supply of nutrients in pregnant cows has been associated with the optimal development of foetal tissues, performance of their progeny and their meat quality. The aim of this study was to evaluate supplementation effects of grazing cows in different stages of gestation on skeletal muscle development and performance of the progeny. Thereby, 27 Nellore cows were divided into three groups (n=9 for each group) and their progeny as follows: UNS, unsupplemented during gestation; MID, supplemented from 30 to 180 days of gestation; LATE, supplemented from 181 to 281 days of gestation. The percentage composition of the supplement provided for the matrices was the following: ground corn (26.25%), wheat bran (26.25%) and soya bean meal (47.5%). The supplement was formulated to contain 30% CP. Supplemented matrices received 150 kg of supplement (1 and 1.5 kg/day for cows in the MID and LATE groups, respectively). After birth, a biopsy was performed to obtain samples of skeletal muscle tissue from calves to determine number and size of muscle fibres and for messenger RNA (mRNA) expression analysis. The percentage composition of the supplement provided for the progeny was the following: ground corn grain (30%), wheat bran (30%), soya bean meal (35%) and molasses (5%). The supplement was formulated to contain 25% CP and offered in an amount of 6 g/kg BW. Performance of the progeny was monitored throughout the suckling period. Means were submitted to ANOVA and regression, and UNS, MID and LATE periods of supplementation were compared. Differences were considered at P0.10). Similarly, no differences were observed between calves for nutrient intake (P>0.10). However, greater subcutaneous fat thickness (P=0.006) was observed in the calves of LATE group. The ribeye area (P=0.077) was greater in calves born from supplemented compared with UNS cows. The supplementation of pregnant cows did not affect the muscle fibre size of their progeny (P=0.208). On the other hand, calves born from dams supplemented at mid-gestation had greater muscle fibre number (P=0.093) compared with calves from UNS group. Greater mRNA expression of peroxysome proliferator-activated receptor α (P=0.073) and fibroblast growth factor 2 (P=0.003) was observed in the calves born from MID cows. Although strategic supplementation did not affect the BW of offspring, it did cause changes in carcass traits, number of myofibres, and mRNA expression of a muscle hypertrophy and lipid oxidation markers in skeletal muscle of the offspring.

FE and experimental study on how the cortex material properties of synthetic femurs affect strain levels.

The primary aim of this work was to validate the "numerical" cortex material properties (transversely isotropic) of synthetic femurs and to evaluate how the strain level of the cancellous bone can be affected by the FE modeling of the material's behavior. Sensitivity analysis was performed to find out if the parameters of the cortex material affect global strain results more than the Polyurethane (PU) foam used to simulate cancellous bone. Standard 4th generation composite femurs were made with 0.32g/cm3 solid PU foam to model healthy cancellous bone, while 0.2g/cm3 cellular PU was used to model unhealthy cancellous bone. Longitudinal and transversal Young's moduli of cortical bone were defined according the manufacturer data, while shear modulus and Poisson's ratios were defined from the literature. All femurs were instrumented with rosette strain gauges and loaded according to ISO7206 standards, simulating a one-legged stance. The experimental results were then compared with those from finite element analysis. When cortical bone was modelled as transversely isotropic, an overall FE/experimental error of 11% was obtained. However, with isotropic material the error rose to 20%. Strain field distributions predicted inside the two bone models were similar, but the strain state of a healthy cancellous bone was much more a compression state than that of unhealthy bone, the compression state decreased about 90%. Strain magnitudes show that average strain-levels of cancellous bone can be significantly affected by the properties of the cortical bone material and, therefore, simulations of femur-implanted systems must account for the composite behavior of the cortex, since small shear strains would develop near isotropic cancellous bone-implant interfaces. Moreover, the authors suggest that changing the volume fraction of glass fibers used to manufacture the cortical bone would allow a more realistic osteoporotic synthetic femurs to be produced.

Reducing mineral usage in feedlot diets for Nellore cattle: I. Impacts of calcium, phosphorus, copper, manganese, and zinc contents on microbial efficiency and ruminal, intestinal, and total digestibility of dietary constituents.

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 ( < 0.01) by CaP-. The absence of CuMnZn reduced ( < 0.01) Cu, Mn, and Zn intake. Ruminal recycling of P, Na, and K is significant for increasing the influx of these minerals to the digestive tract; however, influences of treatments were not observed. The small and large intestines contributed to mineral absorption in different proportions ( < 0.05), according to minerals and treatments. Because of the similarity ( > 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.

Effects of supplements containing different additives on nutritional and productive performance of beef cattle grazing tropical grass.

A grazing trial was carried out to evaluate the inclusion of three feed additives in supplements (crude protein, CP 230 g/kg dry matter, DM) on the performance, voluntary intake, and digestibility of beef heifers grazing Brachiaria decumbens (CP 81 and neutral detergent fiber, NDF 615 g/kg DM). Thirty-five Nellore heifers (21 months of age and 383 ± 6.29 kg of body weight, BW) were used in a completely randomized design. The treatments were as follows: no supplement (control); supplement fed at 1 kg/animal/day without additives (S); supplement with monensin (S + M); supplement with yeast culture (S + YC); and supplement with enzyme complex (S + EC). All of the supplemented heifers had greater (P < 0.1) average daily gain (∼0.186 kg/day) compared to the control treatment (0.014 kg/day). Average daily gain and final BW were similar (P > 0.1) among supplemented heifers. Monensin inclusion in the supplement decreased (P < 0.1) forage DM (expressed as g/kg BW) and NDF intake (expressed as kg/day and as g/kg BW). All of the feed additive inclusions decreased (P < 0.1) NDF digestibility. In conclusion, the heifers' performance was improved by concentrate supplementation. However, the inclusion of additives did not enhance this effect.

Effects of Supplements with Different Protein Contents on Nutritional Performance of Grazing Cattle During the Rainy Season.

The objective of this study was to evaluate the effects of supplements with different crude protein (CP) contents on grazing cattle intake, digestibility, ruminal fermentation pattern, and nitrogen (N) metabolism characteristics during the rainy season. Five ruminal and abomasal cannulated Holstein×Zebu steers (296 kg body weight, BW) were used in a 5×5 Latin square design. The animals grazed five signal grass paddocks (0.34 ha). The five treatments evaluated were: Control (no supplement) and 1.0 g of supplement/kg BW with 0, 330, 660, and 1,000 g of CP/kg as-fed. The supplement was composed of starch, soybean meal, urea, and ammonium sulphate. There was a positive linear effect (p≤0.033) of the CP content in the supplements on the organic matter (OM), CP, and digested OM intakes. The provision of supplements did not increase (p≥0.158), on average, total and ruminal digestibilities of OM and CP. However, the increase in CP content in the supplements caused a positive linear effect (p≤0.018) on ruminal digestibilities of OM and CP. Additionally, a quadratic effect of the CP contents of the supplements were observed (p = 0.041) for the ruminal digestibility of neutral detergent fiber corrected for ash and protein, with the highest estimate obtained with the CP content of 670 g/kg. The supply of supplements increased (p<0.001) the ruminal ammonia N concentration, which also changed linearly and positively (p<0.001) according to increase in CP content in the supplements. The apparent N balance and relative N balance (g/g N intake) were not, on average, changed (p≥0.164) by the supplements supply. However, both showed a tendency of a linear increase (p≤0.099) with increasing supplement CP content. The supplements increased (p = 0.007) microbial N production in the rumen, which also changed linearly and positively (p = 0.016) with increasing supplement CP content. In conclusion, protein supplementation in grazing cattle during the rainy season, while stimulating voluntary forage intake, results in higher efficiency of N utilization when compared to energy supplementation. This is a possible response to increased microbial protein synthesis in the rumen and improved N status in the animal body.

Effects of varying ruminally undegradable protein supplementation on forage digestion, nitrogen metabolism, and urea kinetics in Nellore cattle fed low-quality tropical forage.

Effects of supplemental RDP and RUP on nutrient digestion, N metabolism, urea kinetics, and muscle protein degradation were evaluated in Nellore heifers () consuming low-quality signal grass hay (5% CP and 80% NDF, DM basis). Five ruminally and abomasally cannulated Nellore heifers (248 ± 9 kg) were used in a 5 × 5 Latin square. Treatments were the control (no supplement) and RDP supplementation to meet 100% of the RDP requirement plus RUP provision to supply 0, 50, 100, or 150% of the RUP requirement. Supplemental RDP (casein plus NPN) was ruminally dosed twice daily, and RUP supply (casein) was continuously infused abomasally. Jugular infusion of [NN]-urea with measurement of enrichment in urine was used to evaluate urea kinetics. The ratio of urinary 3-methylhistidine to creatinine was used to estimate skeletal muscle protein degradation. Forage NDF intake (2.48 kg/d) was not affected ( ≥ 0.37) by supplementation, but supplementation did increase ruminal NDF digestion ( < 0.01). Total N intake (by design) and N retention increased ( < 0.001) with supplementation and also linearly increased with RUP provision. Urea entry rate and gastrointestinal entry rate of urea were increased by supplementation ( < 0.001). Supplementation with RUP linearly increased ( = 0.02) urea entry rate and tended ( = 0.07) to linearly increase gastrointestinal entry rate of urea. Urea use for anabolic purposes tended ( = 0.07) to be increased by supplementation, and RUP provision also tended ( = 0.08) to linearly increase the amount of urea used for anabolism. The fraction of recycled urea N incorporated into microbial N was greater ( < 0.001) for control (22%) than for supplemented (9%) heifers. Urinary 3-methylhistidine:creatinine of control heifers was more than double that of supplemented heifers ( < 0.001). Control heifers reabsorbed a greater ( < 0.001) fraction of urea from the renal tubule than did supplemented heifers. Overall, unsupplemented heifers had greater mobilization of AA from myofibrillar protein, which provided N for urea synthesis and subsequent recycling. Supplemental RUP, when RDP was supplied, not only increased N retention but also supported increased urea N recycling and increased ruminal microbial protein synthesis.

Nutritional evaluation of young bulls on tropical pasture receiving supplements with different protein:carbohydrate ratios.

The objective of this work was to evaluate the nutritional parameters of young bulls supplemented with different ratios of protein: carbohydrate on tropical pastures from 4 until 18 months old. Fifty-five non-castrated beef calves (138.3±3.4 kg, 90 to 150 d of age) were used. The calves (young bulls) were subjected to a 430-d experimental period encompassing 4 seasons. The treatments were as follows: control, only mineral mixture; HPHC, high protein and high carbohydrate supplement; HPLC, high protein and low carbohydrate supplement; LPHC, low protein and high carbohydrate supplement; and LPLC, low protein and low carbohydrate supplement. The amount of supplement was adjusted every 28 d. Dry matter (DM) intake was higher in the dry-to-rainy transition and rainy seasons for all nutritional plans. Non-supplemented animals had lower intakes of DM and total digestible nutrients (TDN) than supplemented young bulls in all seasons. Although differences in DM intake were not observed between supplemented animals, the supplements with high carbohydrate (HPHC and LPHC) had lower forage intake during suckling (rainy-to-dry transition season) and in the rainy season. However, the HPHC treatment animals had higher intake and digestibility of neutral detergent fiber. It can be concluded that supplementation with high protein levels (supplying 50% of the crude protein requirement) provide the best nutritional parameters for grazing young bulls in most seasons, increasing intake and digestibility of diet, and these effects are more intense when associated with high carbohydrate levels level (supplying 30% TDN requirement).

Digesta sampling sites and marker methods for estimation of ruminal outflow in bulls fed different proportions of corn silage or sugarcane.

The objective of this experiment was to assess ruminal outflow and apparent total-tract digestibility using digesta samples from 3 sites (reticulum, omasum, and abomasum) and 3 marker methods (single marker: indigestible NDF [iNDF; sample without separation]; double marker: iNDF + Co-EDTA [filtered sample]; and triple marker: iNDF + ytterbium [Yb] acetate + Co-EDTA [filtered and centrifuged]) in bulls fed corn silage and sugarcane-based diets. Eight crossbred (Holstein × Zebu) bulls (353 ± 37 kg of BW; 24 ± 1 mo of age) with ruminal and abomasal cannulas were randomly distributed into two 4 × 4 Latin squares that were balanced for residual effects. 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. Reticular, omasal, and abomasal digesta samples were collected at 9-h intervals over 3 d. At the end of the experiment, a composite sample was prepared for each bull, and these samples were subsequently assigned to the 3 marker methods. The concentrations of CP, NDF, and iNDF of reticular digesta differed (P < 0.01) from those of the omasum and abomasum. Use of omasal and abomasal samples led to similar estimates of ruminal outflow and ruminal digestibility for DM (P = 0.65), OM (P = 0.68), CP (P = 0.85), and NDF (P = 0.57). In contrast, the ruminal outflow of digesta based on reticular sampling appeared to be underestimated. We recommend sampling from the omasum because sampling from this region is less invasive than sampling from the abomasum. Although we did not observe differences in ruminal NDF digestibility among the different marker methods, we did observe that ruminal digestibility of CP was greater for the single marker method than for the double and triple marker methods; we therefore recommend the use of the double or triple marker method.

Predicting carcass and body fat composition using biometric measurements of grazing beef cattle.

This study was conducted to develop equations to predict carcass and body fat compositions using biometric measures (BM) and body postmortem measurements and to determine the relationships between BM and carcass fat and empty body fat compositions of 44 crossbred bulls under tropical grazing conditions. The bulls were serially slaughtered in 4 groups at approximately 0 d (n = 4), 84 d (n = 4), 168 d (n = 8), 235 d (n = 8), and 310 d (n = 20) of growth. The day before each slaughter, bulls were weighed, and BM were taken, including hook bone width, pin bone width, abdomen width, body length, rump height, height at withers, pelvic girdle length, rib depth, girth circumference, rump depth, body diagonal length, and thorax width. Others measurements included were total body surface (TBS), body volume (BV), subcutaneous fat (SF), internal fat (InF), intermuscular fat, carcass physical fat (CFp), empty body physical fat (EBFp), carcass chemical fat (CFch), empty body chemical fat (EBFch), fat thickness in the 12th rib (FT), and 9th- to 11th-rib section fat (HHF). The stepwise procedure was used to select the variables included in the model. The r(2) and the root-mean-square error (RMSE) were used to account for precision and variability. Our results indicated that lower rates of fat deposition can be attributed to young cattle and low concentration of dietary energy under grazing conditions. The BM improved estimates of TBS (r(2) = 0.999) and BV (r(2) = 0.997). The adequacy evaluation of the models developed to predict TBS and BV using theoretical equations indicated precision, but lower and intermediate accuracy (bias correction = 0.138 and 0.79), respectively, were observed. The data indicated that BM in association with shrunk BW (SBW) were precise in accounting for variability of SF (r(2) = 0.967 and RMSE = 0.94 kg), InF (r(2) = 0.984 and RMSE = 1.26 kg), CFp (r(2) = 0.981 and RMSE = 2.98 kg), EBFp (r(2) = 0.985 and RMSE = 3.99 kg), CFch (r(2) = 0.940 and RMSE = 2.34 kg), and EBFch (r(2) = 0.934 and RMSE = 3.91 kg). Results also suggested that approximately 70% of body fat was deposited as CFp and 30% as InF. Furthermore, the development of an equation using HHF as a predictor, in combination with SBW, was a better predictor of CFp and EBFp than using HHF by itself. We concluded that the prediction of physical and chemical CF and EBF composition of grazing cattle can be improved using BM as a predictor.

Grazing behavior and locomotion of young bulls receiving different nutritional plans in a tropical pasture.

The objectives of this study were to compare visual observation and an electronic grazing time method and to evaluate the effects of nutritional plans on intake, grazing behavior and horizontal and vertical locomotion of young bulls in a tropical pasture. Thirty-nine Nellore young bulls with an average body weight of 345±9.3 kg kept in pasture were used. The experimental treatments consisted of: restricted: animals kept in a plot with a low mass of forage receiving mineral mixture only; control: animals receiving mineral mixture only; HPHC: a high protein and high carbohydrate supplement; HPLC: a high protein and low carbohydrate supplement; LPHC: a low protein and high carbohydrate supplement; LPLC: a low protein and low carbohydrate supplement. GPS collars equipped with activity sensors were used. Information about head position, latitude, longitude and altitude were recorded. Daytime grazing behavioral patterns monitored by a continuous focal animal recording method was compared to behavior estimated by the activity sensor. Feed intake was estimated by a marker method. The Restricted group presented lower (p<0.05) intake of dry matter and TDN. However, difference in dry matter intake was not found (p>0.05) between non-supplemented and supplemented animals. Difference was not found (p>0.05) in daytime grazing time obtained by visual observation or the activity sensor method. The restricted group showed longer (p<0.05) grazing time (9.58 h/d) than other groups, but difference was not found (p>0.05) in the grazing time between Control (8.35 h/d) and supplemented animals (8.03 h/d). The Restricted group presented lower (p<0.05) horizontal locomotion distance (2,168 m/d) in comparison to other groups (2,580.6 m/d). It can be concluded that the use of activity sensor methods can be recommended due to their being similar to visual observation and able to record 24-h/d. While supplements with high carbohydrates reduce pasture intake, they do not change grazing behavior. Moderate supplementation (until 50% of protein requirement and 30% of energy requirement) of beef cattle on tropical pasture has no effect on daily locomotion.

Desempenho e exigências de energia e proteína de bovinos de corte em pasto suplementados / Performance, energy and protein requirements of beef cattle grazing supplemented

Avaliou-se o efeito dos níveis de suplementação sobre o desempenho, as características de carcaça, a composição corporal e as exigências de energia e proteína de bovinos de corte sob pastejo. A área experimental constituiu-se de cinco piquetes formados com Brachiaria decumbens. Utilizaram-se 22 bovinos não castrados, com peso corporal médio inicial de 320kg e idade de 18 meses. Três animais foram abatidos ao início do experimento para servirem como referência. Dos 19 animais restantes, três foram designados ao grupo mantença (MT), os outros 16 foram distribuídos em quatro tratamentos: controle ou mistura mineral (MM), 1kg, 2kg e 3kg de suplemento ao dia. Observou-se aumento linear no consumo de matéria seca (CMS), energia digestível (CED) e energia metabolizável (CEM); o consumo de nutrientes digestíveis totais (CNDT) foi máximo para o consumo de 2,88kg de suplemento. O ganho médio diário (GMD) máximo, 0,91kg/dia, foi observado para o consumo de suplemento de 2,69kg/dia. Verificou-se aumento linear no peso corporal em jejum (PCJ), no peso de corpo vazio (PCVZ) e no peso da carcaça para os animais suplementados. Não foi observado efeito da suplementação sobre o rendimento da carcaça. Verificou-se aumento sobre a área de olho de lombo (AOL) e a espessura de gordura subcutânea (EGS), quando os animais não suplementados foram comparados com os suplementados. Não foi observado efeito para o comprimento da carcaça (CCA), nem para os rendimentos dos cortes comerciais. As exigências líquidas de energia e proteína apresentaram, respectivamente, aumento e redução com o aumento do PC dos animais. As exigências de energia líquida para mantença (ELm) foram de 85 kcal/PCVZ0,75. As exigências de energia metabolizável para mantença foram estimadas em 130,08 kcal/PCVZ0,75. A suplementação de bovinos no período de transição águas-seca aumenta o consumo de MS e energia, promovendo aumento do ganho de peso dos animais.

This experiment aimed to evaluate the performance, carcass characteristics, body composition, and energy and protein requirements of beef cattle under grazing conditions. The experimental area constituted of 5 paddocks with Brachiaria decumbens as forage source. Twenty two steers (Zebu) with mean body weight and ages of 320kg and 18 months, respectively, were used. Three animals were slaughtered at the beginning of the experiment and used as standard. Of the nineteen remaining animals, three were designated for maintenance group and the others were randomly submitted to one of four treatments: mineral mixture (MM), 1, 2 or 3kg of supplement daily. There was a linear increase in dry matter intake (DMI), digestible energy (DEI) and metabolizable energy (MEI), and total digestible nutrients intake (TDNI) was maximum consumption of 2.88kg of supplement. The maximum average daily gain (ADG), 0.91kg/day, was observed for supplement intake of 2.69kg/day. Linear increase was observed in shrunk body weight (SBW), EBW and carcass weight. There was no effect on the carcass allowance, however, it was observed on the ribeye area and back fat thickness. No effect was observed on carcass length and commercial cuts. The requirement of net energy (NE) and net protein (NP) increased and decreased as the animals BW increased. The maintenance requirement for net (NEm) and metabolizable energy were 85 kcal/EBW0.75 and 130 kcal/EBW0.75. Supplementation of cattle in the period of transition between rainy and dry seasons increased the dry matter and energy intake, promoting an increase in animal weight gain.

Fontes proteicas em suplementos para novilhos no período de transição seca-águas: características nutricionais / Protein sources in supplements for bulls in the dry-rainy transition season: nutritional characteristics

Avaliaram-se fontes proteicas em suplementos para novilhos em pastagens de Brachiaria decumbens Stapf., durante a transição seca-águas, sobre as características nutricionais. Utilizaram-se quatro animais Holandês x Zebu, não castrados, com média de peso de 300kg, fistulados no esôfago, rúmen e abomaso, distribuídos em delineamento em quadrado latino 4x4. Avaliaram-se suplementos isoproteicos, balanceados para 38 por cento de proteína bruta (PB), sendo um tratamento controle mistura mineral (MM); e três suplementos à base de grãos de milho moído + ureia (MU); grãos de milho moído + farelo de soja (MFS) e farelo de algodão 38 por cento PB (FA), fornecidos na quantidade de 0,17 por cento do peso vivo (PV). O consumo de fibra em detergente neutro pelos animais do tratamento MU, de 12,1g/kg PV, foi maior em 19,9 por cento do que o observado para os dos tratamentos MM e MFS, 10,2g/kg PV, e semelhante ao observado para os do tratamento FA, 11,0g/kg PV. Foram observados valores mais altos de digestibilidade aparente total da matéria seca (MS) para os tratamentos MU e MFS em relação aos demais. Os valores de pH ruminal, produção de nitrogênio microbiano e eficiência de síntese microbiana não foram influenciados pelos tratamentos. A suplementação com MU proporciona maior consumo e digestibilidade aparente total da MS em relação ao tratamento MM.

This study was conducted to evaluate protein sources in supplements for bulls grazing Brachiaria decumbens Stap., in the dry-rainy transition season, regarding nutritional characteristics. Four Holstein x Zebu bulls (300kg of body weight - BW) fitted with esophageal, ruminal, and abomasal cannulas, allotted in a latin square experimental design 4x4. The treatments were protein supplements with 38 percent of crude protein (CP) based on grounded corn grain + urea (GCU); grounded corn grain + soybean meal (GCSB); and cotton seed meal (38 percent CP) (CSM), supplied at a level of 0.17 percent BW, and a mineral mix control treatment (MM). The animals fed diets of GCU treatment showed neutral detergent fiber (NDF) intake of 12.1g/kg of BW, 19.9 percent greater than the observed on animals fed diets of MM and GCSB, 10.2 g/kg of BW, and similar to the NDF intake found for animals fed CSM treatment, 11.0g/kg of BW. The dry matter (DM) total apparent digestibility (TAD) was higher for GCU and GCSB treatments. The ruminal pH, microbial nitrogen production (MNP), and microbial synthesis efficiency (MSE) were not influenced by the treatments. The supplementation with corn and urea provides greater DM intake and digestibility when compared to the mineral mix.

Consumo, digestibilidade total, produção de proteína microbiana e balanço de nitrogênio em dietas para ruminantes de subprodutos / Intake, total digestibility, microbial protein production, and the nitrogen balance in ruminant diets based on agricultural and agro-industrial by-products

Avaliaram-se os efeitos da inclusão da fonte - subproduto do cacau, mandioca-casca, mandioca-caule e farelo de glúten de milho - e da proporção - 10 e 30 por cento - de subprodutos, em substituição parcial à silagem de milho sobre consumo, digestibilidade dos nutrientes, produção de proteína microbiana, balanço de nitrogênio, predição das frações digestíveis e nutrientes digestíveis totais. Os consumos de matéria seca e de fibra em detergente neutro foram influenciados pela fonte de subproduto. A fonte de subproduto influiu na digestibilidade do extrato etéreo e dos carboidratos não fibrosos. O subproduto farelo de glúten de milho apresentou valor energético 17 por cento maior do que a da silagem de milho, enquanto os da mandioca-casca, da mandioca-caule e do cacau apresentaram valores energéticos 10, 19 e 38 por cento menores do que o valor observado para silagem de milho. A fonte e o nível de subproduto não influíram na excreção urinária de derivados de purinas totais, de purinas absorvidas e de nitrogênio microbiano, e na eficiência microbiana. A fonte do subproduto influenciou a ingestão, a excreção nas fezes e na urina dos compostos nitrogenados e o balanço de nitrogênio. O farelo de glúten de milho e a mandioca-casca podem substituir, parcialmente, os concentrados energéticos, sem prejuízos para consumo, digestibilidade, eficiência microbiana e retenção de nitrogênio.

The effects of inclusion of by-products (cocoa, cassava peel, cassava stalk, and corn gluten meal) and their levels (10 and 30 percent), replacing part of corn silage on intake, digestibility of nutrients, microbial protein production, nitrogen balance, prediction of digestible fractions, and total digestible nutrients were evaluated. The intakes of dry matter and neutral detergent fiber were affected by source of by-product, which affected the digestibility of ether extract and non-fibrous carbohydrates. The energy corn gluten meal was 17 percent higher than that of corn silage, while the values for cassava peel, cocoa, and cassava stalk were 10, 19, and 38 percent lower than the value for corn silage. The source and the level of by-product did not affect the urinary excretion of total purine, purine absorbed, microbial nitrogen, and microbial efficiency. The source of by-product affected intake, nitrogen compounds, excretion in feces and urine, and nitrogen balance. The corn gluten meal and cassava peel are by-products with potential to partly replace the energhetic concentrates, with no influence on the intake, digestibility, microbial efficiency, and nitrogen retention.

Estimação por aproximação química dos teores de proteína indegradável insolúvel em detergente neutro em forragens tropicais / Estimation of undegradable neutral detergent insoluble protein in tropical forages by chemical approaching

A mathematical model was developed to predict the content of undegradable neutral detergent insoluble protein (UNDIP) from chemical characteristics of tropical forages. This study was based on a biological limitation of a previous model, which restricts the UNDIP estimates to values equals or higher than 1.34 percent of dry matter. The databank was formed by 540 samples of tropical forages used in cattle feeding (fresh forage and hay). The ratio of UNDIP on neutral detergent insoluble protein (NDIP) was chosen as response variable and the acid detergent insoluble protein (ADIP) as independent variable. The mathematical model was found to be exponential, assuming the formula: UNDIP = NDIP x e-(0,818+0.16764DIP) , in which all values are expressed on dry matter basis. It was observed that biological limitation of the previous model was eliminated, even though a low statistical improvement was obtained. The prediction of a biological parameter (UNDIP) from a chemical characteristic (ADIP) still have some restrictions and the estimates should be applied with caution in some situations. The main application of the model described above is estimate UNDIP contents when biological methods are not available.

Determination of carcass and body fat compositions of grazing crossbred bulls using body measurements.

The objectives of this study were to analyze body measurements of 40 crossbred bulls grazing low quality forage with different supplementation strategies, to estimate interrelationships among those measurements and carcass and body compositions, and to develop systems of equations to predict body fat using body and carcass measurements. Eight animals were slaughtered at the beginning of the experiment, and the remaining animals were slaughtered at 90 or 220 d. The biometric measures (BM) were obtained the day before the slaughter and included hook width, pin width, pelvic girdle length, rump depth, rump height, abdomen width, body length, height at withers, rib depth, girth, and body diagonal length. Other measurements included full, shrunk, and empty BW; internal physical and chemical fats; body volume; body area; carcass weight; 9th- to 11th-rib section weight and composition; fat thickness; subcutaneous fat; intermuscular fat; carcass chemical fat; and empty body physical and chemical fats. The relationships between BM and body components were evaluated, and equations to predict body area, body volume, subcutaneous fat, and carcass and body physical and chemical fat were developed. Biological interpretations of the parameter estimates of equations were similar to those found in the literature such as a ratio of 1 kg of subcutaneous fat to 1.6 kg of intermuscular fat and a deposit of 72 to 76% of body fat in the carcass. The first system used to predict carcass and empty body physical and chemical fat was devised using in vivo information, whereas the second system used BW and the 9th- to 11th-rib fat weight. Our results indicated the combination of BW, carcass traits, and BM was precise and accurate in estimating carcass and body fat composition of backgrounding bulls. The second system had better adequacy statistics [r(2) > 0.92, concordance correlation coefficient (CCC) > 0.957, and root mean square error (RMSE) < 14.4% of the average observed value] compared with the first system. The first system had acceptable adequacy statistics (r(2) > 0.767, CCC > 0.866, and RMSE varying from 15.8 to 22.3% of the average observed value). For both systems, the simultaneous F-test of the linear regression of observed on model-predicted values indicated intercepts were equal to zero, and slopes were equal to 1 (P > 0.246). We concluded that BM can improve the accuracy and precision of the predictions of body composition of grazing animals.

Dinâmicas de trânsito e degradação da fibra em detergente neutro em bovinos alimentados com forragem tropical de baixa qualidade e compostos nitrogenados / Transit and degradation dynamics of neutral detergent fiber in cattle fed low-quality tropical forage and nitrogenous compounds

Avaliaram-se as dinâmicas de trânsito e degradação da fibra em detergente neutro (FDN) em bovinos alimentados com forragem tropical de baixa qualidade e compostos nitrogenados. Foram utilizadas cinco novilhas Holandês x Zebu fistuladas no rúmen. A alimentação volumosa basal dos animais foi constituída por feno de capim-braquiária (Brachiaria decumbens Stapf.), com 5,08 por cento de proteína bruta (PB), com base na matéria seca (MS), fornecido ad libitum. Os cinco tratamentos avaliados foram definidos de acordo com o nível de suplementação proteica (0, 3, 5, 7 e 9 pontos percentuais acima do nível de PB da forragem). Como fonte de compostos nitrogenados, empregou-se mistura de ureia:sulfato de amônia:albumina (4,5:0,5:1,0). O experimento foi estruturado segundo delineamento em quadrado latino 5 x 5. Os níveis médios de PB nas dietas foram de 5,28; 8,08; 9,82; 11,87 e 13,63 por cento, com base na MS. Verificou-se elevação linear (P<0,05) da fração potencialmente degradável da FDN até o nível de 8,62 por cento de PB, com platô estimado de 47,92 por cento da FDN. Verificou-se efeito quadrático (P<0,05) sobre a taxa de degradação da fração potencialmente degradável da FDN em função dos níveis de PB da dieta, com máxima resposta estimada sobre 13,39 por cento de PB. O fluxo ruminal de partículas fibrosas apresentou relação linear-response-plateau em função do nível de PB na dieta (P<0,05), com ponto crítico para o início do platô sobre 7,59 por cento de PB.

Rumen transit and degradation dynamics of neutral detergent fiber (NDF) in cattle fed low-quality tropical forage and nitrogenous compounds were evaluated. Five crossbred heifers fitted with rumen cannulae were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay, which had crude protein (CP) content of 5.08 percent in dry matter (DM). The five treatments were defined according to the level of CP in the diet (0, 3, 5, 7, and 9 percentile points above the CP level of the roughage). The supplement was a mixture of urea, ammonium sulfate, and albumin (4.5:0.5:1.0, respectively). The experiment was carried out according to a 5 x 5 Latin square design. The average CP levels in the diets were: 5.28, 8.08, 9.82, 11.87, and 13.63 percent in DM basis. The potentially degradable fraction of NDF was linearly increased (P<0.05) by CP levels in diet until 8.62 percent CP. From this point, there was stabilization of estimates (47.92 percent of NDF). The degradation rate of potentially degradable NDF showed a quadratic response (P<0.05) to CP levels, with maximal response at 13.39 percent of CP. The ruminal rate of passage of fibrous particles showed a linear-response-plateau (P<0.05) according to CP levels in the diet, with plateau beginning at 7.59 percent of CP.

Frações dos compostos nitrogenados associados à parede celular em forragens tropicais / Fractions of cell wall nitrogenous compounds in tropical forages

The total and undegradable fractions of nitrogenous compounds associated to cell wall organic matrix in some tropical forages were evaluated. Samples of corn silage, elephantgrass silage and sugarcane were used. Neutral detergent insoluble nitrogenous compounds were divided in three different fractions associated with: hemicellulose (HN), cellulose (CN), and lignin (LN). The size of the different fractions varied among feeds. A portion of acid detergent insoluble nitrogen, which is the sum of CN and LN, was potentially degradable in the rumen. A portion of HN was not degradable in the rumen. The heterogeneous dimensions of degradable portion of all nitrogenous compounds among feeds can compromise the estimates of cell wall undegradable nitrogen by simple chemical approaches in tropical forages. The LN overestimated the lignin contents and the correction for those compounds on lignin has been suggested.

Contaminação salivar da extrusa em novilhos alimentados com diferentes volumosos, com e sem suplementação / Saliva contamination in the extrusa in steers fed with different forages, supplemented or not

Determinaram-se as alterações nos teores de proteína bruta (PB), compostos nitrogenados não protéicos (NNP), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), lignina (LIG), cinzas, cálcio (Ca), fósforo (P), magnésio (Mg), potássio (K) e sódio (Na) de alimentos usados para novilhos, provocadas pela contaminação da extrusa pela saliva. Foram utilizados cinco novilhos fistulados no rúmen e esôfago, cinco dietas e cinco períodos experimentais. Os tratamentos foram: capim-elefante picado (CE), capim-elefante obtido em pastejo simulado (CES), capim-braquiária obtido em pastejo simulado (CBS), pré-secado de capim-tifton 85 (PS), feno de capim-braquiária (FB1), feno de capim-tifton 85 (FT), feno de capim-braquiária e concentrado a 0,5 por cento PV (FB2) e feno de capim-braquiária e concentrado 1,0 por cento PV (FB3). A presença de saliva na extrusa não alterou (P>0,05) o teor de proteína bruta dos alimentos. Os teores de NNP foram superestimados (P<0,05) na extrusa em 135,0 por cento. Os níveis de FDN foram subestimados (P<0,05) em 3,4 por cento. Os níveis de FDA e LIG foram superestimados (P<0,05) em amostras de extrusa, em média 11,0 e 44,0 por cento, respectivamente. A contaminação por minerais foi significativa (P<0,05) para cinzas, P e Na, ocorrendo superestimativa em 31,2 por cento, 116,7 por cento e 3250,0 por cento, respectivamente. O Mg foi subestimado (P<0,05) em 15,4 por cento na extrusa.

Alterations on the levels of crude protein (CP), non-protein nitrogen compounds (NNP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (LIG), ash, calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K) and sodium (Na) of feeds used for steers, caused by the saliva contamination in the extrusa, were evaluated. Five steers, fistulated in the rumen and esophagus were fed five diets, in five experimental periods. The treatments were: chopped elephantgrass (CE), elephantgrass obtained by hand-plucked (CES), Brachiaria decumbens obtained by hand-plucked (CBS), Tifton-85 bermudagrass haylage (PS), Brachiaria decumbens hay (FB1), Brachiaria decumbens hay and concentrate at 0.5 percent LW (FB2), and Brachiaria decumbens hay and concentrate at 1.0 percent LW (FB3). The extrusa CP content was not affected (P>0.05) by saliva contamination. The NNP levels were overestimated (P<0.05) in the extrusa in 135.0 percent. The NDF levels were underestimated (P<0.05) in 3.4 percent. The ADF and LIG contents were overestimated (P<0.05) in extrusa samples, on average 11.0 and 44.0 percent, respectively. The mineral contamination was significant (P<0.05) for ash, P and Na, and the levels were overestimated in 31.2, 116.7 and 3250.0 percent, respectively. The Mg content was underestimated (P<0.05) in 15.4 percent in the extrusa.

Performance, digestibility and carcass characteristics of feedlot dairy steers fed diets with different urea levels

The effects of urea levels on feed intake, digestibility and carcass traits of 27 confined cross bred steers weighing 303.25 ± 60.8kg, were evaluated. After weighing, castrating, vaccinating and a period of seven days, three steers were slaughtered at the beginning of the experiment and the remaining 24 were allotted in a completely randomized design to four isonitogenous experimental diets (12 percent of crude protein) and increasing level of urea on the dry matter-basis (0.0; 0.65; 1.30 and 1.65 percent) to replace soybean meal, so that the final content of the experimental diets were approximately 22, 37, 50 and 63 percent of crude protein in the form of NPN. Corn and elephant grass silages were supplied at a 70:30 ratio and the total diet had a 65:35, forage: concentrate ratio on a DM-basis. The urea level did not affect nutrient intake, except for rumen degradable protein (RDP) and total digestible nutrients (TDN) linearly increased in function of diet urea level. The nutrient digestibilities linearly increased except for ether extract and non fiber carbohydrate (NFC). A quadratic effect of diet urea level on daily weight gain and no effect of urea level on carcass traits were observed. Urea can totally replace soybean meal in diets for confined crossed dairy steers allowing gains of 1kg/day. Urea can enhance nutrient digestibility of diets.

Foram avaliados os efeitos dos níveis de uréia sobre o consumo, digestibilidade e características da carcaça de 27 novilhos (303,25 ± 60,80) confinados. Três animais foram abatidos no início do experimento e os 24 restantes foram distribuídos em delineamento inteiramente ao acaso em quatro tratamentos: 0; 0,65; 1,30 e 1,95 por cento de uréia na MS total da dieta, em substituição ao farelo de soja. A dieta final continha em torno de 22, 37, 50 e 63 por cento da PB na forma de compostos nitrogenados não-protéicos. Como volumoso foi utilizada uma mistura de 65 por cento de silagem de milho e silagem de capim-elefante na proporção 70:30, respectivamente. O consumo dos nutrientes não foi afetado pelos tratamentos, com exceção para o consumo de PDR e NDT que aumentaram linearmente. As digestibilidades dos nutrientes apresentaram comportamento linear crescente com exceção das digestibilidades do EE e CNF. Com relação ao desempenho dos animais, houve efeito quadrático dos tratamentos sobre o GMD. Não foi verificado nenhum efeito sobre as características de carcaça avaliadas. A uréia pode substituir completamente o farelo de soja na dieta de novilhos mestiços leiteiros em confinamento, permitindo ganhos de peso próximos a 1kg/dia. O uso de uréia na dieta pode melhorar a digestibilidade dos nutrientes.

Consumo, digestibilidade e produção microbiana em novilhos alimentados com diferentes volumosos, com e sem suplementação / Intake, digestibility and microbial production in steers fed with different forages, supplemented or not

Determinaram-se os consumos e as digestibilidades aparentes totais da matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), carboidratos totais (CHO), fibra em detergente neutro (FDN), carboidratos não fibrosos (CNF), o consumo de nutrientes digestíveis totais (NDT), e estimou-se a produção microbiana (PMic) de dietas para novilhos. Avaliou-se, também, a degradabilidade in situ dos alimentos. Foram utilizados cinco novilhos, fistulados no rúmen, com peso vivo (PV) médio de 185,4kg, em delineamento inteiramente ao acaso, alimentados com: 1- capim-elefante picado (CE); 2- pré-secado de capim-tifton 85 (PS); 3- feno de capim-braquiária (FB); 4- feno de capim-braquiária e concentrado a 0,5 por cento PV (FB:C1); e 5- feno de capim-braquiária e concentrado a 1 por cento PV (FB:C2). O PS proporcionou maior ingestão de MS (6kg/novilho/dia) e de NDT (4,2kg/novilho/dia) em relação aos demais volumosos utilizados, mostrando ser boa alternativa na nutrição de bovinos. A adição de concentrado ao feno de capim-braquiária aumentou o consumo de MS do volumoso, que passou de 2,7kg/novilho/dia para 3,9kg/novilho/dia, constituindo estratégia para a utilização de volumosos de baixa qualidade. O maior consumo do concentrado C2 (1 por centoPV) resultou em aumento no consumo de MS (0,9kg/novilho/dia) e de NDT (1kg/novilho/dia) na dieta FB:C2, em relação à dieta FB:C1.

The intake and total apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), total carbohydrates (CHO), neutral detergent fiber (NDF) and non-fiber carbohydrates (NFC); the total digestible nutrients (TDN) intake and the microbial protein production (MicP) in diets of steers were determined. The in situ degradability of feeds was also evaluated. Five steers averaging 185.4kg live weight (LW) and fistulated in the rumen and esophagus were randomly, assigned in a completely randomized experimental design. They were fed on: 1- chopped elephantgrass (CE); 2- tifton-85 bermudagrass haylage (PS); 3- brachiaria decumbens hay (FB); 4- brachiaria decumbens hay plus concentrate at 0.5 percent LW (FB:C1); and 5- brachiaria decumbens hay plus concentrate at 1.0 percent LW (FB:C2). Tifton-85 bermudagrass haylage provided higher intake of DM (6.0kg/steer/day) and TDN (4.2kg/steer/day) related to other forages, showing that its use is a good alternative for bovine feeding. The addition of concentrate to the brachiaria decumbens hay increased the forage intake, from 2.7kg/steer/day to 3.9kg/steer/day, constituting a strategy for the poor quality forages use. The highest concentrate C2 intake (1.0 percent LW) increased DM (0.9kg/steer/day) and TDN (1.0kg/steer/day) intake of FB:C2 dietary, relative to FB:C1 dietary.