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The objective was to evaluate the effect of including low-fat dried distillers grains (DDG) in finishing diets on protein and energy intake and retention and to estimate the protein and energy requirement of young Nellore bulls. Thirty-five animals were used: baseline (n = 4), maintenance (n = 4), and ad libitum intake (n = 27). Ad libitum animals were divided into four groups: diets with the inclusion of DDG at the levels of 0, 150, 300, and 450 g/kg (dry matter basis). At the end of the experiment, all animals were slaughtered. There was a linear reduction with increasing DDG levels in the total digestible nutrients intake (p = 0.008), metabolizable energy (ME) intake (p < 0.010), in total retained energy (p = 0.065), and in heat production (p < 0.001). Metabolizable protein (MP) intake increased linearly (p < 0.010) but retained protein did not differ (p = 0.499). Daily net energy and ME requirement for maintenance were 75.9 and 122 kcal/kg0.75 EBW, respectively. Daily MP for maintenance was 3.6 g/kg0.75 shrunk body weight. DDG inclusion in finishing diets reduces energy intake and deposition, and we recommend the equations of this study to estimate the requirements of young Nellore bulls. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of including low-fat dried distillers grains (DDG) on young Nellore bulls performance, nutritional parameters, and nitrogen metabolism. Thirty-five Nellore cattle were randomly divided into four diets: without dried distillers grains (D0) or with the inclusion of DDG at 150 g/kg (D150), 300 g/kg (D300), or 450 g/kg (D450). The evaluation period lasted 126 days, and three periods of collection of feces and urine were carried out. Final body weight (P = 0.099) and average daily gain (P = 0.097) tended to decrease linearly; the digestibility of dry matter (P < 0.001), organic matter (P < 0.001), ether extract (P < 0.001) and nonfiber carbohydrates (P < 0.001), and intakes of total digestible nutrients (TDN, P < 0.001) decreased linearly. The increase in crude protein intake (P < 0.001) did not result in an increase in the amount of nitrogen retained (P = 0.540). We concluded that the inclusion of low-fat DDG in finishing diets up to the level of 450 g/kg tends to reduce animal performance and the intake of TDN. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate whole body chemical composition and energy and protein nutrient requirements for maintenance and gain of Nellore bulls. Fifty young bulls, with an average age of 7 ± 1 mo and initial body weight (BW) of 260.0 ± 8.1 kg, were used in this experiment. Four bulls were used as baseline reference animals and were slaughtered at the beginning of the experiment. Four bulls were fed at maintenance (12 g dry matter [DM]/kg of BW), whereas 42 bulls were divided into six groups (n = 7/group) and were randomly assigned to the following dietary treatments 105 (low [LO]), 125 (medium [MD]), or 145 (high [HI]) g crude protein (CP)/kg DM, LO to HI (LH), LO to MD (LM), or MD to HI (MH) oscillating CP at a 48-h interval for 140 d. At the end of the experiment, bulls were slaughtered and samples of the whole body were collected. All samples were lyophilized, ground, and composed as percentage of component of empty body weight (EBW) from each bull. A power model was used to estimate carcass, non-carcass components, and gastrointestinal content of the shrunk body weight (SBW), and CP and water present in the empty body, whereas an exponential model was used to estimate adipose tissue and ether extract (EE) present in the EBW. Nonlinear regression equations were developed to predict heat production from metabolizable energy (ME) intake and retained energy (RE). The net energy requirements for maintenance and ME for maintenance were 77 and 122.75 kcal/EBW0.75/d, respectively. The efficiency of ME utilization for maintenance was 62.7%. The equation obtained for net energy for gain (NEg) was: NEg (Mcal/EBW0.75/d) = 0.0535 × EBW0.75 × EBG0.7131, where EBG is the empty body gain, and the efficiency was 24.25%. Net protein requirement for growth (NPg) was: NPg (g/d) = 227.372 × EBG – 19.479 × RE. There was a linear increase for carcass, CP, and water present in the EBW as the animal grew. The EE deposition exponentially increased as EBW increased. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Weaned Nellore bulls (n = 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 (Valadares Filho et al., 2010) [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 (P = 0.06) between macro- and micromineral supplementation for any variables in the study. Calcium, P, and micromineral concentrations did not affect (P ≥ 0.20) intake of DM, OM, NDF, EE, CP, TDN, and nonfiber carbohydrates (NFC). Calcium and P intake were affected (P < 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 (P ≥ 0.23) among all factors. Performance and carcass characteristics were similar (P ≥ 0.09) among diets. The content of ash in rib bones was not affected by diets (P ≥ 0.06). Plasma P and phosphatase alkaline concentrations were similar (P ≥ 0.52) among diets. Supplementation of microminerals decreased (P < 0.01) plasma Ca concentration; nevertheless, all analyzed blood metabolites were within the reference values. Supplementation of Ca and P increased (P < 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. [ABSTRACT FROM AUTHOR]

Our objective was to study the effect of different roughage sources produced in a tropical environment on intake, digestibility, and ruminal parameters of crossbred bulls. Five rumen-fistulated 30-mo-old Holstein × Bos indicus bulls (average BW = 459 ± 32.5 kg) were utilized in a 5 × 5 randomized Latin square design. The experiment consisted of five 19-d experimental periods (10 d for adaptation and 9 d for data collection) and 5 treatments. Experimental diets consisted of corn (Zea mays L.) silage (CS), Brachiaria grass (Brachiaria decumbens Stapf.) silage (BGS), elephant grass (Pennisetum purpureum Schumach.) silage (EGS), Tifton 85 (Cynodon spp.) hay (T85), and fresh sugarcane (Saccharum officinarum L.; SC). Diets were formulated to have approximately 11% CP (DM basis) using a mixture of urea and ammonium sulfate (9:1 ratio) that was diluted in water and then mixed with roughage. Intake, ruminal outflow, digestibility coefficients, ruminal pool, intake, passage (kp) and digestion rates, microbial parameters, and pH data were assessed. Dry matter intake was greater (P < 0.01) for CS compared with SC. Among treatments, lesser (P < 0.01) potentially digestible NDF, ash-and protein-free NDF (apNDF), and digestible ash-and protein-free NDF intake values were observed for SC. Ruminal outflows of DM and nonfibrous carbohydrates were lesser (P < 0.01) for SC compared with other treatments. Dry matter apparent digestibility and ruminal digestibility did not differ (P > 0.27) among treatments. No differences (P = 0.11) were observed for ruminal apNDF pool and ruminal kp of apNDF (P = 0.06) among treatments. No treatment effect (P > 0.28) was observed for DM and nitrogen of rumen-isolated bacteria, and microbial efficiency was greater (P = 0.02) for BGS among treatments. A treatment × time interaction (P < 0.01) was found for ruminal pH, with a quadratic pattern in terms of time for CS, BGS, EGS, and T85, whereas pH values for CA linearly decreased as a function of time. In summary, these roughages, when supplemented with an additional nitrogen sources, show similar overall apparent digestibility and ruminal pool values, but conversely, bulls fed sugarcane had less overall nutrient intake and lower ruminal outflow and digestion rate values. We conclude that fresh-cut sugarcane, when provided with urea, can affect digestion rate and, consequently, impact nutrient intake. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to assess ruminai 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 com silage and sugarcane-based diets. Eight crossbred (Holstein x Zebu) bulls (353 ± 37 kg of BW; 24 ± 1 mo of age) with ruminai 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% com 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 ruminai outflow and ruminai digestibility for DM (P = 0.65), OM (P = 0.68), CP (P = 0.85), and NDF (P = 0.57). In contrast, the ruminai 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 ruminai NDF digestibility among the different marker methods, we did observe that ruminai 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. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the influence of corn silage (CS) or sugarcane (SC) additions to finishing diets on voluntary intake, apparent digestibility, animal performance, and LM fatty acid (FA) composition in crossbred Holstein x Zebu bulls. Forty-two bulls (initial BW 328 ± 39.2 kg and an initial age of 23.5 mo) were used in this experiment. A completely randomized design was used to examine roughage source (CS vs. SC) and ratio of concentrate (CO) on nutrient utilization and production. The experimental diets consisted of 1 ) 60% CS and 40% CO on DM basis fed for 84 d (CS60:40), 2) 60% CS and 40% CO on DM basis fed for 42 d and 40% CS and 60% CO on DM basis fed for 42 d (CS reverse diet [CSR]), 3) 40% CS and 60% CO on DM basis fed for 84 d (CS40:60), 4) 60% SC and 40% CO on DM basis fed for 84 d (SC60:40), 5) 60% SC and 40% CO on DM basis fed for 42 d and 40% SC and 60% CO on DM basis fed for 42 d (SC reverse diet [SCR]), and 6) 40% SC and 60% CO on DM basis fed for 84 d (SC40:60). Dry matter and NDF intakes were greater (P < 0.01 ) in bulls fed CS-based diets than bulls fed SC-based diets. The greatest (P <0.01) DM and CP digestibility were observed in bulls fed SC-based diets. Bulls fed CSR and CS40:60 had greater {P < 0.01) ADG than bulls fed SC-based diets. However, ADG was similar (P = 0.52) in bulls fed CS60:40, CSR, and SC40:60 diets. The percentage of C 18:3 n-3 and C20:5 n-3 were greater (P <0.01) in LM of bulls fed SC-based diets. The percentage of CLA was greater (P <0.01) in LM of bulls fed SC60:40 than those fed CS-based diets. The findings of the present study indicate that SC40:60 can replace CS60:40 and CSR in finishing diets and, more-over, roughage source significantly altered the FA composition of crossbred Holstein x Zebu bulls LM. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Twenty-six comparative slaughter studies were used (n = 752 animals) and coded within each experiment by gender (431 bulls, 204 steers, and 117 heifers) and breed (447 Nellore and 305 Bos indicus and Bos taurus crossbreds) to develop equations to predict the efficiency of use of ME to NE for growth (kg) and ME to NE for maintenance (km). The retained energy (RE) was regressed on ME intake (MEI) available for gain using orthogonal regression to obtain the kg within each experiment. The estimated kg was regressed on RE as protein (REp) according to the following equation: kg = a/(b + REp). Gender and breed effects were not tested because of limited number of experiments. The km was estimated as the intercpt of the following equation: HP = β0 × e(β1 × MEI), in which HP is heat production, β0 and β1 are coefficients, and e is the natural logarithm. The ME for maintenance (MEm) was computed assuming MEI equals to HP at maintenance. The km was obtained using the stepwise procedure of a multiple regression including ADG, empty body gain (EBG), empty BW (EBW), EBW0.75, kg, and energy content in the EBW. A random coefficient model, assuming a random variation for study effects, was used to test breed and gender effects to identify the best model to estimate km. The overall equation to predict kg was 0.327 (±0.142)/[0.539 (±0.317) + REp], with an R² of 0.963. The equation to predict km was 0.513 (±0.024) + 0.173 (±0.061) × kg + a × EBG, R² = 0.92, in which a = 0.100 (±0.021) for B. indicus or a = 0.073 (±0.021) for crossbreds. Our results indicated that B. indicus were more efficient to use ME for maintenance. We concluded that km can be predicted from kg and EBG and that B. indicus × B. taurus crossbreds can affect km. Furthermore, kg can be predicted from REp and neither gender nor crossbreeding (B. indicus × B. taurus) affected kg. Because our database consisted of Nellore and B. indicus and B. taurus crossbreds, it is necessary to further evaluate differences between B. taurus and B. indicus regarding the kg. [ABSTRACT FROM AUTHOR]

The goal of this research was to develop empirical equations to predict chemical and physical compositions of the carcass and the body using the composition of the 9th- to 11th-rib section (rib9-11) and other measurements. A database (n = 246) from 6 studies was developed and comprised 37 bulls (BU), 115 steers (STR), and 94 heifers (HF), of which 132 were Nellore (NEL), 76 were NEL × Angus crossbreds (NA), and 38 were NEL × Simmental crossbreds (NS). The right half carcass and the rib9-11 from the left half carcass were analyzed for ether extract (EE), CP, and water. The remaining components were chemically analyzed to determine the composition of the body. A stepwise procedure was used to determine the variable inclusion in the regression models. The variables included were EE in the rib9-11 (EER; %), CP in the rib9-11 (CPR; %), water in the rib9-11 (WR; %), visceral fat (VF; %; KPH and mesenteric fats), organs plus viscera (OV; %), carcass dressing percentage (CD; %), cold carcass weight (kg), and empty BW (EBW; kg). No sex or breed effects were found on EE and CP compositions of the carcass (CEE and CCP, respectively; %); the equations were as follows: CEE = 4.31 + 0.31 × EER + 1.37 × VF [n = 241; R² = 0.83; mean square error (MSE) = 4.53] and CCP = 17.92 + 0.60 × CPR - 0.17 × CD (n = 238; R² = 0.50; MSE = 1.58). Breed affected water content in the carcass (CW, %); the equations were as follows: CW = 48.74 + 0.28 × WR - 0.017 × EBW for NEL; CW = 46.69 + 0.32 × WR - 0.017 × EBW for NA; and CW = 38.06 + 0.48 × WR - 0.017 × EBW for NS (n = 243; R² = 0.67; MSE = 5.17). A sex effect was found on body chemical EE composition (BWEE); the equations were as follows: BWEE = 2.75 + 0.33 × EER + 1.80 × VF for BU; BWEE = 1.84 + 0.33 × EER + 1.91 × VF for STR; and BWEE = 4.77 + 0.33 × EER + 1.28 × VF for HF (n = 243; R² = 0.89; MSE = 3.88). No sex or breed effects were found on CP composition in the body (BWCP); the equation was as follows: BWCP = 14.38 + 0.24 × CPR (n = 240; R² = 0.59; MSE = 1.06). A sex effect was found for body water content (BWW); the equations were as follows: BWW = 38.31 + 0.33 × WR - 1.09 × VF + 0.50 × OV for BU; BWW = 45.67 + 0.25 × WR - 1.89 × VF + 0.50 × OV for STR; and BWW = 31.61 + 0.47 × WR - 1.06 × VF + 0.50 × OV for HF (n = 241; R² = 0.81; MSE = 3.84). The physical carcass composition indicated a breed effect on all components and a sex effect for fat in the carcass. We conclude that body and carcass compositions can be estimated with rib9-11 for purebred and crossbred NEL animals, but specific equations have to be developed for different groups of animals. [ABSTRACT FROM AUTHOR]

A comparative slaughter trial was conducted with 36 F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg of BW, to assess the net requirements of protein and energy for growth and maintenance. Three cattle from each group (i.e., steers, bulls, and heifers) were slaughtered at the beginning of the trial to determine the initial body composition. The remaining calves were randomly assigned to 1 of 3 treatments: maintenance (diet containing 70% of DM as corn silage fed at 1.2% of BW daily) or concentrate at 0.75 or 1.5% of BW daily with corn silage available for ad libitum consumption. The diets were isonitrogenous (2% N, DM basis). The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict the maintenance requirements for NE and net protein (MRNE and MRNP, respectively) and the growth requirement for NE and net protein (GRNE and GRNP, respectively). After 84 d of growth, the cattle were slaughtered. The cleaned gastrointestinal tracts, organs, carcasses, heads, hides, tails, feet, blood, and tissues were weighed to measure empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. For each animal within a period, DMI was measured daily and samples of feces were collected to determine diet digestibility. There were no differences in MRNE (P = 0.06) among groups. The combined data indicated a MRNE of 71.2 kcal·kg-0.75 of EBW·d-1, with a partial efficiency of use of ME to NEm of 0.71. The partial efficiency of use of ME to NE for growth was 0.54 for bulls, 0.47 for steers, and 0.54 for heifers. The GRNE for steers and heifers were similar (P = 0.15) but were 18.7% greater (P = 0.03) for steers and heifers than for bulls. The MRNP did not differ among groups and averaged 2.53 g of CP·kg-0.75 of EBW·d-1. Likewise, GRNP was not different among groups. The percentage of retained energy deposited as protein (REp) increased as the content of retained energy in the gain (REC, Mcal/kg of empty body gain) decreased. The REp equation of the pooled data was 46.5 x e-0.2463 x REc. We conclude that the energy requirement of crossbred Bos indicus x Bos taurus for maintenance might be less than that of purebred Bos taurus and that REp is nonlinearly, negatively correlated with REc. The GRNE was less for bulls than for steers and heifers. However, we found no differences in MRNE, MRNP, and GRNP for bulls, steers, and heifers of Nellore x Red Angus crossbreds. [ABSTRACT FROM AUTHOR]

It is well established that the net energy required for maintenance of Bos taurus beef cattle is approximately 77 kcal.kg-0.75. However, for Bos indicus cattle, particularly the Nellore breed that comprises more than 85% of the Brazilian herd, the energy required for maintenance appears to be lower. The maintenance energy requirements of Nellore cattle have been estimated in Brazil, but little effort has been made to gather data from different studies and to analyze them as a whole to increase confidence in the estimates. Therefore, the objective in this study was to estimate the energy required for maintenance of Nellore cattle, using data obtained from the Brazilian literature. Individual observations were collected from seven different trials comprising 135 intact Nellore males that averaged 303 kg (SD = 62.0 kg) empty body weight. Retained energy (RE) was obtained by comparative slaughter, metabolizable energy (ME) intake (MEI) was measured directly, and heat production was calculated as the difference between MEI and RE. Metabolizable energy intake ranged from 122 kcal.kg-0.75 (maintenance level) to 352.02 kcal.kg-0.75(high energy intake). The ME required for maintenance (MEm) was estimated using traditional and orthogonal regressions. The orthogonal regression equation obtained for RE on MEI was: RE = - 0.0457 + 0.398 * MEI (r2 = 0.67). Rearranging and solving for RE = 0, MEm = 0.114 Mcal.kg-0.75.d-1. Considering efficiency of utilization of ME for maintenance as 0.64 (the mode of the 7 experiments), a value of NEm = 0.73 Mcal.kg-0.75.d-1 was obtained, which is 18% lower than the NRC (2000) recommendation for intact males (0.77 x 1.15 = 0.89 Mcal.kg-0.75.d-1.). It can be concluded that Nellore cattle indeed have lower endogenous energy expenditures than Bos taurus cattle. [ABSTRACT FROM AUTHOR]

A comparative slaughter trial was conducted at the Federal University of Vicosa in Brazil aiming to determine the net requirements of Ca, P, Na, K and Mg. Thirty-six F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg BW, were utilized. At the beginning of the trial, three animals from each gender were slaughtered to determine the initial body composition. Three animals of each gender were randomly assigned to two treatments in which diets were offered at 0.75 or 1.5% of BW of concentrate. The diets were based on corn silage and were isonitrogenous (12.5% CP, DM basis). After three growing periods of 28 d, all animals were slaughtered. The cleaned gastrointestinal tract, organs, carcass, head, hide, tail, feet, blood, and tissues were weighed to determine the empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. The log of the contents of each mineral in the empty body was regressed on the log of the EBW to estimate the net requirement for each mineral per kg of empty body gain (EBG). There were no differences (P>0.05) in the net requirements for growth of all macrominerals among genders. The equations of the pooled data of the net requirements for growth (g/kg EBG) were: 0.33256×EBW-0.63666 for Ca, 0.11214×EBW-0.56146 for P, 0.01085×EBW-0.39924 for Na, 0.00401×EBW-0.15304 for K, and 0.00359×EBW-0.46205 for Mg. The mean EBW was 0.9244×BW. Our flndings indicated that an animal of 250 kg BW would require 9.342, 4.804, 1.155, 1.698, and 0.269 g/kg EBG of Ca, P, Na, K, and Mg, respectively, and an animal of 450 kg BW would require 6.426, 3.453, 0.913, 1.552, and 0.205 g/kg EBG of Ca, P, Na, K, and Mg, respectively. The net requirements of Ca, P, Na, K, and Mg for growth decrease as BW increase. [ABSTRACT FROM AUTHOR]

Net protein requirement for gain (NPg) depends on the lean tissue content of the empty body gain (EBG), which may vary among gender, breed, and growth rate. A comparative slaughter trial was conducted at the Federal University of Vicosa in Brazil with 36 F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg BW. Three animals from each gender were slaughtered at the beginning of the trial to determine the initial body composition. The remaining calves (3 animals of each gender) were randomly assigned to three treatments: maintenance level (70% of corn silage, DM basis) or fed at 0.75 or 1.5% of BW with corn silage being offered ad libitum. The diets were isonitrogenous (12.5% CP, DM basis). After three growing periods of 28 d, all animals were slaughtered. The cleaned gastrointestinal tract, organs, carcass, head, hide, tail, feet, blood and tissues were weighed to assess empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. For each animal, within a period, the DMI was measured daily. There were no differences (P>0.05) in the NPg among genders. The NPg (g/kg EBG) equation of the pooled data was 0.5795×EBG×EBW-0.2425, indicating an NPg requirement of 148 and 128 g for animals with 250 and 450 kg BW, respectively. The percentage of RE deposited as protein (REp) increased as content of RE in the gain (REc, Mcal/kg EBG) decreased. The REp equation of the pooled data was 0.3671 - 0.0461×REc. Our findings support the hypothesis that REp is negatively correlated with REc. However, our data indicated no differences in NPg for bulls, steers and heifers of Nellore x Red Angus crossbreds fed high levels of forage. [ABSTRACT FROM AUTHOR]

Context: Previously feed-restricted cattle may exhibit compensatory growth during the finishing phase. However, the efficiency in converting feed into carcass should be evaluated since cattle undergoing compensatory growth usually have high non-carcass weight gain. Aims: The objective of this study was to evaluate the effect of growth rate throughout the post-weaning growing phase on subsequent feed efficiency, carcass gain, and gain composition. Methods: Thirty-nine weaned young Nellore bulls averaging 230.4 ± 5.62 kg of bodyweight and 8.5 ± 0.25 months of age were used. Initially, five bulls were slaughtered as a reference initial group. The remaining bulls were randomly assigned to one of three nutritional plans to achieve Low (0 kg/day), Medium (0.6 kg/day) or High (1.2 kg/day) average daily gain (ADG) throughout the post-weaning growing phase, followed by high growth rate during the finishing phase. One-half of the bulls from each treatment were slaughtered at the end of the post-weaning growing phase, and the other one-half after the finishing phase. During both phases the feed intake, apparent digestibility, performance, and body composition were evaluated. Key results: Throughout the post-weaning growing phase, High bulls had greater ADG and more efficiently converted feed into carcass, compared with other nutritional plans (P < 0.01). Throughout the finishing phase, Low bulls had greater ADG, carcass gain, and feed efficiency than High and Medium bulls (P < 0.01). Previous feed restriction did not affect (P > 0.05) apparent digestibility. During the finishing phase, previously restricted bulls fully compensated for the lost visceral organ weight, whereas the losses of bodyweight and carcass weight were only partially compensated. Throughout finishing, Low bulls had the greatest feed efficiency and profitability among nutritional plans. However, considering the overall experiment, Hight bulls converted feed into carcass more efficiently than Low bulls (P = 0.02), but did not differ from Medium (P > 0.05). Conclusions: Although previously restricted bulls had greater performance and efficiency throughout finishing, the improvement was not enough to reach the same carcass weight at the same age of the unrestricted bulls. Implications: Despite the greater profitability of previously restricted bulls throughout finishing, unrestricted bulls were more profitable considering both growing and finishing phases. Compensatory growth is described as faster than normal growth after a period of growth deprivation. However, cattle exhibiting compensatory growth have greater gain of viscera rather than carcass. Although visceral gain is important, its low economic value can impact the real economic benefit of compensatory growth for the beef industry. Our results confirmed that cattle undergoing compensatory growth might be more profitable throughout finishing, whereas it is less profitable considering the whole production system. [ABSTRACT FROM AUTHOR]

• Castration increased the postmortem desmin degradation. • Carcass pH and temperature decline postmortem were not affected by castration. • Time on feed affected pH decline rate but not ultimate pH. • Carcass shrinkage reduced as time on feed increased. The objective of this study was to evaluate the effect of castration on carcass and meat quality traits of Nellore cattle harvested after 0, 100 or 200 days on feed. Thirty-six Nellore calves averaging 256.1 ± 3.05 kg of body weight and 8.2 ± 0.07 months of age were used. Half of the calves were randomly selected for surgical castration one-week prior to weaning. Post-weaning calves were penned and adapted to a common finishing diet. Six bulls and six steers were selected to be harvested after 0, 100 or 200 days on feed. Carcass and meat quality traits were evaluated. Data were analyzed as a completely randomized design with a 2 × 3 factorial arrangement of treatments including two sex conditions and three harvest times. Castration by time on feed interaction was found (P < 0.01) for intramuscular fat and for kidney, pelvic and heart fat. The bull carcasses were heavier (P < 0.05) than those of steer. Regardless of time on feed, castration increased (P < 0.05) backfat thickness. Although unaged meat shear force was similar (P > 0.05) between bulls and steers, castration reduced (P > 0.05) shear force and increased myofibrillar fragmentation index of 14 days aged meat. Castration increased (P < 0.05) postmortem desmin degradation. All carcass traits were improved (P < 0.05) by time on feed, except dressing. Carcasses from cattle harvested at 0 day on feed had higher (P < 0.05) chilling rate and lower pH decline (P < 0.05). Shear force change from 1 to 14 days postmortem reduced (P < 0.05) as time on feed increased. In conclusion, although intensively raised young bulls have similar unaged meat quality than steers, castration improves aged meat tenderness and intramuscular fat. Overall, increasing time on feed improves carcass and meat quality traits. Image, graphical abstract [ABSTRACT FROM AUTHOR]