Feedlot Nellore Cattle Research Articles

Identification of genomic regions and pathways associated with traits related to rumen acidosis in feedlot Nellore cattle.

There may be an increased risk of metabolic disorders, such as rumen acidosis, in cattle fed high-concentrate diets, particularly those from Bos taurus indicus genotypes, which have shown to be more sensitive to ruminal acidification. Therefore, this study aimed to estimate (co)variance components and identify genomic regions and pathways associated with ruminal acidosis in feedlot Nellore cattle fed high-concentrate diets. It was utilized a dataset containing a total of 642 Nellore bulls that were genotyped from seven feedlot nutrition studies. The GGP Indicus 35k panel was used with the single step genome-wide association study methodology in which the effects of the markers were obtained from the genomic values estimated by the GBLUP model. A bivariate model to estimate genetic correlations between the economically important traits and indicator traits for acidosis was used. The traits evaluated in this study that were nutritionally related to rumen acidosis included average daily gain (ADG), final body weight, time spent eating (TSE), time spent ruminating, rumenitis score (RUM), rumen absorptive surface area (ASA), rumen keratinized layer thickness (KER) and hot carcass weight (HCW). The identified candidate genes were mainly involved in the negative or non-regulation of the apoptotic process, salivary secretion, and transmembrane transport. The genetic correlation between HCW and ASA was low positive (0.27 ± 0.23), and between ADG and ASA was high moderate (0.58 ± 0.59). A positive genetic correlation between RUM and all performance traits was observed, and TSE correlated negatively with HCW (-0.33 ± 0.21), ASA (-0.75 ± 0.48), and KER (-0.40 ± 0.27). The genetic association between economically important traits and indicator traits for acidosis suggested that Nellore cattle may be more sensitive to acidosis in feedlot systems.

Protein profiles identified by LC-MS/MS demonstrate change in beta oxidation, ketogenesis, and propionate metabolism in rumen epithelium with different additives

Replacement of ionophore feed additives by essential oils demonstrates differences in energy metabolism. The mechanism of action of essential oils depends on the ruminal pH, therefore, feedlot diets with high starch inclusions tend to show greater effectiveness of these natural additives. The aim of this study is to map the proteome of the ruminal epithelium of feedlot Nellore cattle (n = 60) with different additives (monensin, blend of essential oils + exogenous α-amylase) and varying levels of starch (25% and 45%) Two-dimensional polyacrylamide gel electrophoresis was used to separate the proteome of ruminal epithelium. The differentially expressed protein spots were characterized by isoelectric point, molecular mass, volume, and intensity of the spots and identified by liquid chromatography tandem mass spectrometry (LC-MS/MS). Diets using an essential oil blend associated with exogenous amylase promoted greater expression of macromolecules from the degradation of carbohydrates through the glycolytic and ketogenesis pathway. Fourteen proteins were identified in upregulation and the presence of proteins involved in glucose oxidation as well as HydroxymethylglutarylCoA lyase (HMGCL), which catalyzes part of the metabolic intermediate metabolism—a key step in ketogenesis. Our results suggest that there was an increase in glycolysis from the oxidation of Glyceraldehyde-3-phosphate dehydrogenase (GAPDH GAPD), which participates in the first step of acetate and butyrate production and the oxidative decarboxylation of the ruminal epithelium of feedlot Nellore cattle. Monensin increased precursors of propionate, such as methylmalonyl-CoA mutase (MUT), which suggests greater synthesis of propionate via propionyl-CoA upon entry into the citric acid cycle as succinyl-CoA, which can increase feed efficiency and reduces feed intake.

Dried distiller’s grains for feedlot Nellore cattle fed non-forage-based diets

This study aimed to evaluate intake, animal performance and carcass traits with the inclusion of corn dried distiller grains (DDGs) replacing cornmeal (Zea mays L.) in non-forage-based diets for finishing feedlot Nellore cattle. Sixty-four uncastrated Nellore cattle weighing 267.22 ± 20.4kg and 18 ± 3months old were distributed in 16 pens. Experimental diets were based on cornmeal, cottonseed cake, a mineral mixture and increased levels of DDG replacing cornmeal (0, 10, 20 and 30% on a dry matter basis). The study lasted 135days, and the intake of nutrients and body weight gain were monitored. At the end of the study, the animals were slaughtered to measure their carcass traits. During the first 34days of the study, the DDG levels linearly increased dry matter intake and intake of all nutrients. In other phases of the feedlot, the DDG levels did not have any effect on DMI or ADG but caused a quadratic effect on hot carcass weight. Thus, DDG can replace cornmeal in non-forage diets fed to feedlot Nellore cattle without any negative effect on intake or animal performance.

Effect of thyme essential oil supplementation on feed intake, apparent digestibility, rumen fermentation, blood parameters and in vitro methane yield of Nellore cattle

The objective of this study was to evaluate the effects of thyme essential oil (TEO) supplementation, which has recognized antimicrobial and antioxidant activity, on feed intake, feeding behavior, ruminal fermentation and blood parameters of feedlot Nellore cattle, aiming to indicate the ideal TEO dose. Four ruminally-cannulated Nellore steers (500 ± 44 kg body weight) were randomly assigned in a 4 × 4 Latin square design and received one of the following experimental treatments: CON = control, with no TEO (423 g thymol/kg DM); T2 = 2 mL/d of TEO; T4 = 4 mL/d of TEO; and T8 = 8 mL/d of TEO. Each experimental period lasted 21 d (14 d for adaptation and 7 d for data collection). Dry matter (DM) intake and digestibility were not affected by TEO infusion (P≥0.11). Among feeding behavior variables, only “standing still” activity differed with TEO inclusion (Linear, P=0.03), with greater values observed when greater TEO doses were used. The in vitro total gas production was quadratically affected by TEO infusion (P=0.05). Ruminal pH tended to increase linearly from CON to T8 (P=0.09), while ammonia nitrogen concentrations tended to be quadratically affected (P=0.09). No TEO effect was observed for short-chain fatty acids (P≥0.11). TEO also did not affected blood parameters evaluated in this trial (erythrogram, leucogram, metabolites and liver enzymes [P≥0.11]). The TEO infusion of up to 8 mL/d did not promote deleterious effects on in vitro and in vivo nutritional and metabolic parameters of feedlot Nellore cattle. Further studies should be conducted to investigate the ideal TEO dose to improve beef cattle efficiency.

Phosphorus supplementation does not affect the intake, digestibility, and meat quality of Nellore young bulls fed with high-grain diets

This study evaluated the effect of phosphorus (P) supplementation on the intake, digestibility, and quality of aged meat from Nellore young bulls fed on high-grain diets finished in feedlot. Forty young bulls (30 months old) with an initial body weight (IBW) of 296 ± 25 kg were used. It was distributed in a completely randomized experimental design. The treatments were: without P supplementation (CO), commercial mineral supplement (CM), and supplementation with dicalcium phosphate (DP) with 2.4, 4.2, or 5.0 g of P per kg of dry matter (DM), respectively. Diets were composed of sugarcane bagasse (200 g kg-1) plus concentrate (800 g kg-1) on a dry matter (DM) basis. The meat quality parameters analyzed were pH, color, cooking losses, shear force, and water-holding capacity. P supplementation did not affect the intake and digestibility of nutrients There was no interaction (p > 0.05%) between diets and the aging time for the meat quality parameters. However, bulls fed with DP exhibited lower pH (5.98) compared to CO and CM (6.19 and 6.14, respectively). The longer aging time increased the cooking losses and intensity of yellow (b*). Under Brazilian conditions, feedlot Nellore cattle fed with high-grain diets do not require additional mineral supplements.

Feedlot performance, feeding behavior, carcass and rumen morphometrics characteristics of Nellore cattle submitted to strategic diets prior the adaptation period

The study was designed to evaluate the effects of either nutritional restriction or intake of concentrate feedstuffs before beginning the adaptation period on days to adapt, feedlot performance, feeding behavior, carcass characteristics, rumen and cecum morphometric of Nellore cattle. The experiment was designed as a completely randomized block, replicated 8 times (4 animals/pen), in which 96 Nellore bulls with an initial body weight (BW) of 365.52 ± 39.19 kg were fed in 24 pens according to the treatments, as follows: Restriction (Tifton hay fed at 1.4% of BW + mineral supplement); Control (Tifton hay fed ad libitum + mineral supplement) and Concentrate (Tifton hay fed ad libitum + 0.5% of BW of a mix of concentrate feedstuffs and mineral supplement). This study lasted 144-d, divided into 2 periods, as follows: 32-d of preadaptation, in which cattle were submitted to the treatments previously described, and 112-d of finishing period, where all cattle were fed the same diets. At the end of preadaptation period, one animal per pen was slaughtered (n = 24) for carcass, cecum and rumen evaluations, and the remaining 72 animals were harvested after 112-d of finishing period. No significant (P > 0.10) treatment effect was observed for days to adapt to the high-concentrate diet, which was 14 days (SEM: 0.63). Cattle submitted to restriction had greater (P < 0.10) ADG in kg (Restriction: 1.29; Control: 1.06; Concentrate: 1.18; SEM: 0.04), DMI in kg (Restriction: 9.19; Control: 8.56; Concentrate: 8.86; SEM: 0.28), G:F ratio (Restriction: 0.140; Control: 0.124; Concentrate: 0.133; SEM: 0.004), number of papillae (Restriction: 72.76; Control: 63.28; Concentrate: 62.99; SEM: 3.41) and absorptive surface area in cm2 of rumen wall (Restriction: 26.89; Control: 22.29; Concentrate: 22.30; SEM: 1.36) compared with cattle in the control group at the end of the study. Cattle submitted to either restriction or concentrate supplementation had greater (P < 0.10) final HCW in kg (Restriction: 285.35; Control: 274.10; Concentrate: 287.30; SEM: 4.51), final 12th rib fat in mm (Restriction: 4.57; Control: 3.93; Concentrate: 4.50; SEM: 0.21) and final Biceps femoris fat thickness in mm (Restriction: 6.14; Control: 5.23; Concentrate: 5.91; SEM: 0.23) compared with cattle in the control group at the end of the study. Thus, either restriction or concentrate supplementation before beginning the adaptation period to high-concentrate diets did not impact adaptation length, and both may be used as nutritional strategies to improve performance and carcass characteristics of feedlot Nellore cattle.

PSV-24 Effect of pre-weaning, post-weaning and fattening growth rate on carcass and meat traits in feedlot Nellore cattle

Abstract The goal of this study was to evaluate the effect of contrasting growth rate in pre and post-weaning period on carcass traits and meat quality of feedlot Nellore cattle. To high weight gain, in pre and post-weaning period, were be considered management groups with mean weight gain above the third quartile of pre-weaning (PREW) or post-weaning (PROW) weight gain distribution of population to group of moderate gain were be considered management lots with daily average gains between the first and third quartiles of PREW or PROW weight gain distribution of population. In the low gain group will be considered management lots with daily average gains lower than the first quartile of PREW or PROW weight gain distribution of population. We used a total of 500 bulls, registered in the National Association of Breeders and Researchers, fed during 90 days with the same diet, confined and slaughtered. The PREW presented a weight gain rate (WGR) of 57.1, 67.3, and 77.7 kg for low, moderate and high WGR, respectively; and the PROW of 110.3, 113.4, and 119.4 kg for low, moderate and high WGR, respectively. The hot carcass weight influenced WGR in pre-weaning (297.56±11.80, 323.53±10.09, and 364.31±18.88 kg) for low, moderate and high, respectively (P = 0.03). The carcass dressing was affected by weaning period in WGR (pre-weaning: 54.18, 54.33, and 57.88 %; P = 0.034, and post-weaning 55.52, 56.23, and 54.66%; P = 0.471) for low, moderate and high WGR, respectively. The contrasting weight gain groups did not influence the marbling score in PREW (P = 0.128) and PROW (P = 0.772), back fat thickness in PREW (P = 0.719) and PROW (P = 0.833), ribeye area in PREW (P = 0.472) and PROW (P = 0.833), tenderness in PREW (P = 0.936) and PROW (P = 0.911). In general, the gain rate did not improve the carcass traits and meat quality of feedlot Nellore cattle.

Effect of adding crude glycerine to diets with feed additives on the feed intake, ruminal degradability, volatile fatty acid concentrations and in vitro gas production of feedlot Nellore cattle.

The effects of adding crude glycerine with sodium monensin or essential oils to beef cattle diets on the intake, degradability of DM and nutrients, rumen concentration of volatile fatty acids (VFA) and in vitro gas production were evaluated. Five ruminally cannulated Nellore steers were randomly assigned to a 5×5 Latin square design. The treatments were as follows: CONT, without crude glycerine and additives; EO, with essential oils and without crude glycerine; MON, with sodium monensin and without crude glycerine; EOG, with essential oils and crude glycerine; MONG, with sodium monensin and crude glycerine. Treatments with essential oil and sodium monensin increased the NDF and STC intake and the DM degradability. When crude glycerine was combined with either sodium monensin or essential oil, there was a reduction in DM, NDF and STC intake and an increase in DM and CP degradability of the diets. The adding crude glycerine to essential oil diets reduced the CH4 production. Sodium monensin treatments reduced DM and NDF intake and the production of total gas, CH4 , total VFA and acetic acid concentration. In conclusion, the adding crude glycerine (200g/kgDM) with either sodium monensin (0.03g/kgDM) or essential oil (0.5g/kgDM) can be utilized in diets for Nellore cattle without causing detrimental effects on feed intake and improving the DM degradability.

Different doses of sodium monensin on feedlot performance, carcass characteristics and digestibility of Nellore cattle

The objective of this study was to determine the effects of different doses of sodium monensin on feedlot performance, carcass characteristics and nutrient digestibility of Nellore cattle. The experiment was designed as a completely randomized block, replicated 12 times, in which 60 20-months old yearling Nellore bulls (402.52 ± 33.02 kg) were fed in individual pens for 84 days according to the different doses of monensin expressed in ppm (dry matter basis): 0, 9, 18, 27 and 36. As doses of monensin increased, final body weight, average daily gain, gain-to-feed ratio, and dressing percentage were affected cubically (P &lt; 0.03), where animals fed 9 ppm of monensin presented greater average daily gain and better gain-to-feed ratio. Likewise, as dose of monensin increased, dry matter intake, hot carcass weight, and neutral detergent fiber and fecal starch digestibility in finishing period decreased linearly (P &lt; 0.05). In addition, neutral detergent fiber digestibility in adaptation period in creased linearly (P = 0.01) as doses of monensin increased. Thus, based on the results of this study, if monens in is going to be included in finishing diets for feedlot Nellore cattle, the dose of 9 ppm should be considered as the most feasible option.

Changes in ruminal fermentation and microbial population of feedlot Nellore cattle fed crude glycerin and virginiamycin

The objective of this experiment was to evaluate the effects of crude glycerin (CG) and virginiamycin (VM) diets on ruminal fermentation and microbial population of feedlot Nellore cattle. Eight rumen fistulated bulls (BW = 600 ± 34 kg; 26 ± 3 months) were used in a replicated 4 × 4 Latin square (21-d periods) with 2 × 2 factorial arrangement of treatments: diets without virginiamycin (VM−) or virginiamycin at 25 mg/kg DM (VM+) combined with diets without crude glycerin (CG−) or CG (80% glycerol) at 100 g/kg DM (CG+). The sugar cane bagasse was used as the exclusive roughage in the proportion of 200 g/kg in dry matter of diet and crude glycerin replaced corn in the diet formulation. Ruminal samples were collected immediately before feeding and at 3, 6, 12 and 18 h post feeding on days 20 and 21 of the sampling week. Data were analyzed in a replicated 4 × 4 Latin square with a 2 × 2 factorial using the MIXED procedure of SAS (SAS Inst., Inc., Cary, NC). There were no CG × VM interactions for any variable measured (P ≥ 0.10). The intake of DM had a tendency to be greater in CG+ than CG− diets (P = 0.07). Apparent total tract digestibilities of nutrients were similar among diets (P ≥ 0.10). Diets with CG or VM had similar values of pH (mean = 6.15; P ≥ 0.10). Data showed that CG or VM did not affect the concentration of total VFA (116.92 mM; P ≥ 0.10). The proportion of propionate increased 27.5% in CG+ diets, regardless of VM inclusion (P = 0.01). Acetate:propionate ratio was lower in CG+ compared to CG− diets (3.58 vs. 2.12; P ≥ 0.10). Valerate and butyrate proportion was greater in CG+ than CG− diets (P < 0.05). The inclusion of VM or CG did not alter the relative abundance of fibrolityc bacteria (P ≥ 0.10). Total protozoa counts (P = 0.052) and Metadinium spp. (P = 0.058) had a tendency to decrease in VM+ than VM− diets (P < 0.10). Crude glycerin had positive effects on rumen fermentation products and can replace virginiamycin with increment of Megasphaera elsdenii abundance. However, combining virginiamycin and glycerin does not affect positively rumen fermentation and growth of bacteria that metabolize lactate.

Fatty acid profile and carcass traits of feedlot Nellore cattle fed crude glycerin and virginiamycin

Forty-eight bulls with an initial body weight (BW) of 408.4 ± 22.2 kg (age = 21 ± 2 months) were used in a randomized complete block design arranged in a 2 × 2 factorial design. The treatments were diets without virginiamycin (VM−) or with virginiamycin, at 25 mg/kg of dry matter (DM, VM+), and diets without crude glycerin (CG−) or with crude glycerin, at 100 g/kg DM (CG+). The cold carcass weight and cold carcass dressing (P ≤ 0.05) was greater in bulls fed crude glycerin diets. Total unsaturated fatty acids (UFA) were 6.08% higher, and cooking weight loss was 10% lower in bulls fed CG+ diets, compared to bulls fed CG− diets (P = 0.0081). Crude glycerin at 100 g/kg DM could be a suitable replacement for VM, as it led to a slight increase in UFA deposition in meat. However, simultaneous administration of VM and CG did not positively affect performance and carcass traits of feedlot Nellore cattle.

Fatty Acid Profile of Nellore Bulls Supplemented With Different Fat Sources during Feedlot Finishing

ObjectivesInclusion of lipids in finishing diets may improve feed efficiency and improve carcass quality. The objective of this study was to evaluate the effects of supplementation of different fat sources in the diet on meat fatty acids profile of feedlot Nellore cattle. Materials and MethodsNellore bulls (n = 96), with an initial body weight of 399.90 ± 19.32, were divided into 24 pens, where pen was considered the experimental unit. The experiment was a randomized block design, divided in 4 treatments: 1- with addition of natural sources of fat, from cottonseed and corn germ; 2- including a source of by-pass fat from soybean oil; 3- with inclusion of a combination of by-pass fat from one blend of vegetable sources and 4- with addition of natural sources of fat, from cottonseed, corn germ and combination of by-pass fat from one blend of vegetable sources. Feed and water were supplied ad libitum. After 108-d of feeding, animals were slaughtered, and samples of the Longissimos dorsi muscle were collected for fatty acid analysis. ResultsTreatments containing natural sources of fat had greater levels (P 0.05) in CLA cis7-trans9, but were greater (P < 0.05) than all other treatments. Increasing unsaturated fatty acids in meat, like CLA, is perceived to be desirable to consumers due to potential positive impacts on health. ConclusionIn conclusion, treatments with inclusion of by-pass fat presented less concentration of stearic fatty acid. The results of this study indicate that meat fatty acid composition may be influenced by feedlot fat supplements. Therefore, there exists potential toward producing meat products with targeted fatty acid composition that meets consumer preferences.

Roughage levels impact on performance and carcass traits of finishing Nellore cattle fed whole corn grain diets.

This study was carried out to evaluate the effects of chopped hay levels in high-concentrate diets with whole corn grain (WCG) on performance and carcass traits of finishing Nellore cattle. One hundred and eight 24-month-old Nellore intact males (453±75kg) were fed one of three WCG-based diets that differed in roughage level: without roughage (WCG), with 5% chopped hay included (WCG5), or with 12% chopped hay included (WCG12) in a block design (based on initial body weight) for 86days. Animals fed WCG5 or WCG12 had significantly improved on final body weight, dry matter intake, average daily gain, feed efficiency, hot carcass weight, and dressing percentage when compared to those fed WCG. The Longissimus muscle area (P=0.1108), backfat thickness (BFT; P=0.6089), and rump fat thickness (P=0.1798) were not affected by roughage levels. Therefore, using WCG diets without roughage negatively affects the performance of feedlot Nellore cattle but does not affect carcass traits and does lead to the minimum BFT required by the industry.

Phosphorus supplementation with or without other minerals, ionophore and antibiotic did not affect performance of Nellore bulls receiving high-grain diets, but increased phosphorus excretion and dietary costs

This study was conducted to evaluate the effect of phosphorus (P) supplementation, with or without addition of other minerals, ionophore and antibiotic, on performance, P utilisation and profitability in finishing Nellore bulls in a feedlot. Forty-two animals, with an initial bodyweight of 296 ± 25 kg, were distributed in a completely randomised design consisting of three treatments and 14 replicates. The treatments were without P supplementation (T1), commercial mineral supplement specific for feedlot cattle (T2) and supplementation with dicalcium phosphate (T3). The T3 was formulated to achieve a P concentration similar to that of T2, but without adding other additives (e.g. vitamins, ionophores, yeast and chelates) in the mineral mix. The P concentrations were 2.4, 4.2 or 5.0 g P/kg of dry matter (DM), respectively, for T1, T2 and T3. The diet, on a DM basis, comprised sugarcane bagasse (200 g/kg) plus concentrate (800 g/kg). The DM, crude protein and neutral detergent fibre intakes and apparent DM digestibility were similar among the three treatments (P &gt; 0.05). Despite the numerical difference on P concentration in T2 and T3 treatments, P intakes were similar in these treatments. The addition of commercial mineral supplement specific for feedlot cattle or dicalcium phosphate in diets increased P excretion in the faeces and urine, increased P retention and reduced the profitability of the feedlot. Performance and carcass traits were not affected by diet P concentrations (P &gt; 0.05). The profit per head in T1 treatment was US$13.7 and the addition of the dicalcium phosphate and mineral mix in T2 and T3 did not result in profit, these treatments gave economic losses of US$6.80 and US$6.20 per head, respectively. Under Brazilian conditions, feedlot Nellore cattle fed high-grain diets do not require any additional mineral supplements. P concentration of 2.4 g/kg DM, as used in the control diet, was adequate to ensure animal performance and reduce faecal P excretion, which is in agreement with NRC and CSIRO recommendations. Lower values may also be appropriate, but were not tested here.

Performance of Nellore males under different artificial shading levels in the feedlot

The objective of this study was to evaluate the influence of artificial shading on weight gain and meat quality of male Nellore cattle in an intensive production system. The experiment was conducted in the experimental feedlot of the Course of Animal Science at Universidade Estadual de Goiás, from July to October 2014. Forty-eight male Nellore cattle with an average initial weight of 310 kg were kept in double 24-m2 stalls, in a total of 24 stalls. Of these, six were in the open air; six were covered with black shade netting of 30% light interception; six with black shade netting 50%; and six with black shade netting 80%, providing 6 m2 of shade per stall. The ration supplied to the animals and the orts left in the trough were weighed daily to determine intake, and the temperature-humidity index (THI) was measured twice weekly. Animals were weighed for the first time at the start of the experiment, and then another three times until the end, which was followed by the slaughter and assessments of performance and meat quality. A difference (p &amp;lt; 0.05) was observed between the average THI values, with the highest value found in the stalls without artificial shading. No difference (p &amp;gt; 0.05) was observed for feed intake, initial weight, final weight, total weight gain, average daily weight gain, carcass yield, marbling, texture, fatness, backfat thickness, loin-eye area, color, thigh length and circumference, leg length and circumference, or carcass length between the animals on the different treatments. The use of artificial shading does not have a significant effect on performance or meat quality of feedlot Nellore cattle when the ambient temperature is within the thermal comfort zone.

Perfil de ácidos graxos e características da carne de bovinos Nelore confinados com diferentes fontes lipídicas protegidas

O objetivo deste trabalho foi avaliar os efeitos da adição de fontes de lipídeos naturais e protegidos da degradação ruminal na dieta de bovinos Nelore confinados sobre características da carne, concentrações de lipoproteínas sanguíneas e perfil de ácidos graxos da gordura do músculo Longissimus dorsi. Foram utilizados 120 bovinos Nelore, não castrados (366,9±28,7kg), com aproximadamente 24 meses. O delineamento experimental foi inteiramente casualizado, com três tratamentos: (CONTR) sem fonte adicional de lipídeo, (GDESP) com fonte de lipídeo natural (torta de algodão) e (GPROT) com fonte de lipídeo protegido rico em ácidos graxos poli-insaturados. Foram utilizadas 24 baias, cinco animais/baia, com oito repetições/tratamento, sendo as baias consideradas unidades experimentais. Foi observada (P&lt;0,05) interação entre tratamento e dias de mensuração para colesterol e LDL, com maiores valores do tratamento GPROT nos dias 1 e 15, tendo o dia 84 valor intermediário aos demais tratamentos. Observaram-se efeitos de dias de mensuração, em que VLDL e triglicerídeos apresentaram valores crescentes nos dias 15, 84 e 1; enquanto o HDL teve maior valor no dia 1. Foi observado efeito (P&lt;0,05) de tratamento para o perfil de ácidos graxos, com diminuição do C14:1, C16:1 e C17:1 e aumento do ácido transvaccênico, C18:2, ácidos graxos poli-insaturados (AGPI) e da relação AGPI: AGMI (ácidos graxos monoinsaturados) para os tratamentos GPROT e GDESP. Adição de lipídios na dieta, independentemente da fonte, promove melhora na composição de ácidos graxos da carne de bovinos Nelore confinados, aumentando a quantidade de ácidos graxos insaturados sem alterar as características qualitativas da carne.

Effects of different doses of sodium monensin on feeding behaviour, dry matter intake variation and selective consumption of feedlot Nellore cattle

The experiment was designed to determine the effects of different doses of sodium monensin (MON) on feeding behaviour, dry matter intake (DMI) variation and selective consumption of feedlot Nellore cattle. The experiment was a randomised complete block design, replicated 12 times, in which 60 20-month-old yearling Nellore bulls (402.52 ± 33.0 kg) were fed the following different doses of MON (expressed in mg per kg, on a DM basis) in individual pens for 84 days: 0, 9, 18, 27 and 36. The adaptation program consisted of ad libitum feeding of two adaptation diets over a period of 14 days with concentrate level increasing from 68% to 84% of diet DM. Orthogonal contrasts were used to assess linear, quadratic, cubic and quartic relationships between doses of MON and the dependent variable. As the dose of MON increased, the time spent ruminating (P &lt; 0.01), feeding efficiency of DM (P &lt; 0.05) and feeding efficiency of neutral detergent fibre (NDF; P &lt; 0.05) were affected linearly during the period of adaptation. For the finishing period, as the dose of MON increased, time spent eating and ruminating, and feeding efficiency of DM were affected quadratically (P &lt; 0.05), in which animals fed 9 ppm of MON presented better feeding efficiency of DM. Thus, as animals fed 9 ppm of MON presented better feeding efficiency of DM and NDF during the adaptation and finishing periods, it should be the dose of choice for feedlot Nellore cattle.

Utilização de probiótico e monensina sódica sobre o desempenho produtivo e características de carcaça de bovinos Nelore terminados em confinamento

O objetivo com este estudo foi avaliar o efeito do probiótico a base de bactérias produtoras de lactato (DBR) e da monensina sódica (MON) sobre o desempenho produtivo e características de carcaça de bovinos Nelore terminados em confinamento. Foram utilizados 18 machos, não castrados, com média de idade de 18 meses e 362,0 ±30,0kg de peso vivo inicial, divididos em três tratamentos: 1) 2g de DBR; 2) 1g de DBR + 138mg de MON e; 3) 275mg de MON, caracterizando delineamento inteiramente casualizado, com 6 animais por tratamento, divididos em 18 baias (1 animal/baia) em sistema de alimentação do tipo Calan Gate. O experimento teve duração de 84 dias, os animais foram pesados e submetidos a avaliações de ultrassonografia a cada 28 dias. Não houve efeito dos aditivos alimentares em relação ao peso vivo final e consumo de massa seca em percentagem do peso vivo. O ganho de peso diário foi menor nos primeiros 28 e 56 dias de estudo para animais que consumiram MON e DBR+MON, porém não foram observadas diferenças entre os tratamentos no período total. Animais alimentados com DBR+MON apresentaram maior consumo de massa seca durante todo o estudo, porém pior conversão alimentar que aqueles alimentados com DBR ou MON. Animais alimentados com DBR+MON apresentaram menor rendimento de carcaça que aqueles suplementados com DBR apenas e animais suplementados com MON tiveram maior espessura de gordura subcutânea ao final do estudo. A suplementação com o DBR apenas, pode ser uma alternativa para substituir a monensina.

Crude glycerin in diets for feedlot Nellore cattle

Two studies were conducted to evaluate the effects of crude glycerin on feed intake, performance, carcass characteristics, and total digestibility of Nellore bulls. In experiment 1, cattle (n = 30) were fed a control diet without crude glycerin and diets containing 7.5, 15, 22.5, and 30% crude glycerin, for 103 d. Animals were harvested and data of carcass characteristics were collected. In experiment 2, a digestibility trial was performed using indigestible acid detergent fiber (iADF) as internal marker, and five rumen-cannulated steers. Both experiments were conducted as a randomized complete block design and data were analyzed using mixed procedures. In experiment 1 no differences were observed among treatments on dry matter intake, and performance variables. Regarding carcass characteristics, no effect was observed, except for carcass fat estimates, which were greater in treatments with crude glycerin. In experiment 2, crude glycerin promoted a decrease in digestibility of fibrous fractions NDF and HEM, and increased digestibility of crude protein by 6%. Although it caused negative effect on digestibility of fibrous fraction of diets, crude glycerin can be a good energy source for Nellore bulls, since no losses are observed on performance and carcass characteristics when animals are fed up to 30% of this by-product.

Effects of different doses of sodium monensin on rumen papillae and tissue histology of feedlot Nellore cattle

The experiment was designed to determine the effects of different doses of sodium monensin (MON) on rumen papillae and tissue histology of feedlot Nellore cattle. The experiment was designed as a completely randomised block, replicated 12 times, in which 60 20-month-old yearling Nellore bulls (402.52 ± 33.0 kg) were fed in individual pens for 84 days according to the following doses of MON expressed in ppm (on a dry-matter basis): 0, 9, 18, 27 and 36. The adaptation program consisted of ad libitum feeding of two adaptation diets over a period of 14 days, with concentrate level increasing from 68% to 84% of diet dry matter. Orthogonal contrasts were used to assess linear, quadratic, cubic and quartic relationships between doses of MON and the dependent variable. No significant (P &gt; 0.10) MON effect was observed for number of papillae, mean papillae area, papillae area as a percentage of absorptive surface and rumenitis incidence. However, as the dose of MON increased, the absorptive surface area, papillae surface area and mitotic index were affected (P &lt; 0.05) cubically, in which animals fed 9 and 36 ppm presented larger absorptive surface area and greater number of cells in mitosis. Thus, based on the results, feeding of MON affected rumen papillae and tissue histology of feedlot Nellore cattle. The doses of 9 or 36 ppm of MON should be considered as the most feasible options, because they promote better development of rumen epithelium.