viii SUMMARY The effect of essential oils and calcified marine algae as natural alternatives to ionophore antibiotics on performance of feedlot cattle by Emile Francois Haasbroek Supervisor: Prof. L.J. Erasmus Department: Animal and Wildlife Sciences Faculty: Natural and Agricultural Sciences Degree: MSc (Agric) Animal Science: Animal Nutrition Ionophore antibiotic supplementation is standard practice in almost all feedlots in the USA, South Africa and many other countries due to its effectiveness to increase feed efficiency and modulate feed intake. Public concern over the emergence of antibiotic resistant bacteria and the consumers’ demand for safe, high quality nutritious food has stimulated the search for natural alternatives to ionophores in ruminant diets. The objectives of this study were: (i) to compare the effect of a specific blend of essential oils (XTract X60 – 7065 (XTract)) and a rumen buffer (Acid Buf) to monensin and its effects on the performance of feedlot cattle under both experimental and commercial conditions (ii) to determine the effect of these feed additives on the health status of feedlot cattle and (iii) to determine whether Acid Buf can replace monensin as feed additive in high energy feedlot diets based on hominy chop. For the experimental growth trial 180 Bonsmara type animals were blocked into two groups and then allocated to 6 pens with 10 animals each per treatment using a randomised complete block design. The basal diets (starter, intermediate finisher and final finisher) were the same for the Control XTract and Acid Buf; the only difference being the Control treatment was supplemented with monensin (21 – 33 mg /kg DM), the XTract treatment supplemented with XTract (1000 – 1200 mg /h /d) and the Acid Buf treatment supplemented with Acid Buf at 0,6% dietary DM. For the commercial trial, animals were blocked according to the same criteria but for each treatment there were 3 pens, standing 130 head of cattle per pen, therefore 390 animals per treatment. The experimental pen trial was designed for evaluation of growth and the commercial pen trial for evaluation of health status and growth under practical feedlot conditions. In the small pen trial there were no differences (P > 0.05) in DMI, FCR or ADG between treatments. In the commercial trial the XTract supplemented cattle had a higher EW (429.3 vs. 417.5 kg) and ADG (1.77 kg /d vs. 1.70 kg /d) (P < 0.05) compared to monensin supplemented cattle and the Acid Buf supplemented cattle tended (P > 0.10) towards a higher EW (425.3 vs. 417.5 kg) and ADG (1.74 vs. 1.70 kg /d) compared to monensin supplemented cattle. The feed conversion ratios were 5.67 and 5.26 for XTract and monensin supplemented cattle and did not differ (P = 0.26). The feed conversion ratios were 5.22 and 5.26 respectively for Acid Buf and monensin supplemented cattle and did not differ (P = 0.86). Treatments affected health parameters in the commercial pens with 78% healthy animals (not pulled) in the monensin supplemented animals compared to 82% for XTract and 66% for the Acid Buf supplemented animals (P < 0.01). Rumen damage occurred in 73% of monensin supplemented animals compared to 51% for the Acid Buf supplemented animals and only 24% of the XTract supplemented animals (P < 0.01). Differences in health parameters did not seem to affect the overall growth performance of the cattle, suggesting a relatively minor effect on performance. Results from this large scale study should provide South African feedlot operators with sufficient information to make informed decisions on natural alternatives when the day comes that ionophores are placed on the banned list of ruminant feed additives. Further research, however, is needed on determining the optimal dose, dietary dependant responses, adaptation of rumen microbial populations and potential additive or synergistic effects when supplemented together with other rumen modifiers. Furthermore, the cost: benefit ratio should be determined under the prevailing conditions in different countries. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted

Orientador: Flávio Dutra de Resende / Resumo: Objetivou-se com o presente trabalho avaliar o efeito da suplementação com gordura protegida contendo ácidos graxos saturados e insaturados, durante a recria em pastagens e na terminação em confinamento de tourinhos Nelore. O experimento foi desenvolvido no Polo Regional de Desenvolvimento Tecnológico dos Agronegócios da Alta Mogiana, em Colina – SP. Foram utilizados 124 tourinhos, com 8 meses de idade e peso corporal (PC) médio inicial de 190 kg ± 25,1, blocados por peso e avaliados durante a primavera, verão e outono em pastejo de lotação contínua com taxa de lotação variável (fase de recria), distribuídos ao acaso em dois tratamentos: 1) Controle - suplementação proteica-energética 3 g/kg de PC (sem gordura protegida); 2) Gordura Protegida - Suplementação proteica-energética 3 g/kg de PC com adição de ácidos graxos saturados e insaturados na forma protegida (Blend, Nutricorp, Araras, São Paulo, Brasil). Após a recria (270 dias), os animais com média de 20 meses e 420 kg, foram confinados em 12 baias, por 106 dias, e distribuídos entre 4 tratamentos: 1) CONT – CONT: Controle da recria sem a presença de gordura protegida no confinamento; 2) CONT - GORP: Controle da recria com a presença de gordura protegida no confinamento; 3)GORP – CONT: Gordura protegida da recria sem a presença de gordura protegida no confinamento e 4)GORP – GORP: Gordura protegida da recria com a presença de gordura protegida no confinamento. Para os parâmetros sanguíneos durante a fase da recria, foram ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to evaluate the effect of supplementation with protected fat containing saturated and unsaturated fatty acids in diet of Nellore cattle during growing phase on pasture and finishing phase in the feedlot. The experiment was carried out at the Regional Technological Development Center of the Agribusiness of Alta Mogiana (APTA), in Colina - SP. One hundred twenty-four young bulls were used (months old) with initial body weight (BW) of 190 kg ± 25.1. The animals were blocked by BW and evaluated during the spring, summer and autumn in grazing systems through growing phase, randomly distributed into two treatments (with or without protected fat): 1) Control - protein-energy supplementation 3 g/kg BW (without protected fat); 2) Protected Fat - Protein-energetic supplementation 3 g/kg BW with addition of saturated and unsaturated fatty acids in protected form (Blend, Nutricorp, Araras, São Paulo, Brazil). Following the growing phase (270 days), the animals with an average of 20 months and 420 kg were finished in feedlot (106 days), three replicates (totalizing 12 pens) within each treatment were randomly assigned to one of two treatments (with or without protected fat during finishing phase). The treatments diets were: 1) CON - CON: Control without protected fat in feedlot; 2) CON - FAT: Control during the growing phase with protected fat in feedlot; 3) FAT - CON: Protected fat during the growing phase without protected fat in feedlot and 4) FAT - FAT:... (Complete abstract click electronic access below) / Doutor

This study compared feed lot finished beef and grazing standing corn beef from young steers for sensory acceptance, sensory quantitative descriptive analysis attributes palatability and Warner–Bratzler shear force values. In comparing both feeding treatments results indicated no differences (P > 0.05) between feeding treatments for all attributes including appearance, aroma (with handheld) and (with sniff bottle), texture, flavor and basic taste. However, there was difference (P < 0.05) in flavor, offlavor for different feeding systems by panelists. Analysis of variance for Warner- Bratzler shear force values revealed no differences (P > .05) between steaks from two treatments. Based on this research, the meat industry may wish to provide the consumer with the option of choosing beef that was traditionally feed lot finished or beef finished by grazing standing corn. Thus, grazing standing corn beef producers could utilize a practicable alternative feeding system with niche market appeal to represent a viable production option.

Master of Science / Department of Biological & Agricultural Engineering / Ronaldo G. Maghirang / Particulate matter (PM) emissions from open beef cattle feedlots depend heavily on the level of water on the pen surface. Wet pen surfaces are able to keep PM emissions low, while dry surfaces have much higher rates of emission. Current research shows that 20-25% surface water content is a critical threshold for minimizing PM emissions from open cattle feedlots. The amount of water on the pen surface will also dictate the level of gaseous emissions, such as ammonia, nitrous oxide, and hydrogen sulfide. Traditional methods of measuring pen surface water are not sufficient within a dense cattle feedlot and cannot provide a continuous method of measurement unattended. The process of using infrared thermometry and meteorological variables to remotely sense surface water provides an inexpensive, ground level approach. Testing in laboratory, outdoor, and feedlot conditions was conducted to analyze the potential of using the thermal inertia remote sensing approach. This approach involved continuous measurement of weighted soil water content, surface temperature of the soil, air temperature, solar radiation, wind speed, and relative humidity. Controlled laboratory testing performed the best at predicting soil water content from the difference in soil surface and air temperature, with the coefficient of determination (R2) at 0.91 for a Smolan silt loam and 0.83 for dry feedlot soil. Outdoor testing achieved mixed results with R2 values only as high as 0.38 for 10-cm soil layer and 0.67 for 5-cm soil layer. Testing in a cattle feedlot with dry, loose manure layer proved to be imprecise, but was able to differentiate surface water levels varying from 4.1% to 9.1% wet basis.

Master of Science / Department of Animal Sciences and Industry / Christopher D. Reinhardt / Angus steers (n = 17,919) fed at a single feedlot in southwestern Kansas between 1997 and 2007 were used to evaluate the effects of various demographic and phenotypic characteristics (season of arrival, geographic origin, health status, rate of gain, quality grade, and yield grade) on feedlot health, performance, and carcass traits. Cattle were not commingled and were predominantly preconditioned and backgrounded prior to shipment to the feedlot. Season of arrival was categorized as winter (December, January, and February), spring (March, April, and May), summer (June, July, and August), or fall (September, October, and November). Regions were: SC = Texas, Oklahoma, and New Mexico; C = Colorado and Kansas; NC = Montana, Nebraska, and Wyoming; and SE = Georgia, Mississippi, South Carolina, Tennessee, Virginia, and West Virginia. Steers that originated in SC had the poorest ADG (P < 0.01) and those originating in C had the greatest ADG, HCW, and quality grade (P < 0.01). Steers that arrived during fall had the lowest ADG and those arriving during the summer had the greatest morbidity (P < 0.01). Morbidity decreased and performance increased with increasing initial BW; quality grade was only minimally related to arrival BW in steers which were not treated for disease. After accounting for yield grade differences, the association between morbidity and carcass quality and between quality grade and heavier final BW and HCW were diminished, although ungraded cattle had lower ADG, final BW, and HCW (P < 0.01). Increasing yield grade from 1 and 2 to yield grade 3 increased percentage Choice by 12.1 points (P < 0.01); there was no additional gain in quality grade moving to yield grade 4 and 5. More rapidly gaining steers were heavier and fatter at marketing; this translated to greater quality grade in all but steers with initial BW > 375 kg. Performance was very similar among cattle which graded Prime, Choice, and Select, suggesting that producers do not need to choose between performance and quality grade; instead, much of the difference in quality grade can be explained by differences in yield grade.

Master of Science in Biomedical Sciences / Diagnostic Medicine/Pathobiology / Daniel U. Thomson / Auction derived feeder calves (n=1,601; initial BW = 273.5 ± 4.7 kg) were used to examine the effects of delayed administration of the initial steroid implant on health, performance, and carcass characteristics of feedlot cattle. Steers were procured from multiple-source auction markets in the southeastern United States and shipped to a central Kansas feedyard over a 6 week period from December 2009 to January 2010. Steers were rested overnight prior to processing, then were randomly assigned, within arrival block, to 1 of 2 treatments: 1) implanted with Revalor-XS (40 mg estradiol and 200 mg trenbolone acetate) immediately upon arrival (ARRIVAL); or 2) implanted with the same implant after 45 d (DELAYED). Cattle were weighed on a group scale immediately following processing of each block. Feed deliveries were measured using load cells on feed trucks and recorded daily. Cattle were evaluated daily for morbidity and mortality by trained feedyard health personnel. Sick or injured cattle were removed from the home pen for further diagnosis and treatment. Individual animal health data were obtained and recorded daily. Final BW was calculated by dividing HCW by the average dressing percent of the pen. Carcass data (quality grade and yield grade) were obtained by USDA personnel; presence of lung lesions, pleural adhesions, and liver abscesses was evaluated by trained university personnel. Delaying the initial implant tended to reduce morbidity (24.7 vs. 28.5%; P = 0.13) and reduced railer rates (1.8 vs. 3.3%; P = 0.02); however, there were no effects of timing of implant administration (P ≥ 0.31) on rates of retreatment, mortality, lung lesions, or pleural adhesions. Implanting immediately upon feedlot arrival resulted in numerical improvements in ADG and feed conversion, but these differences were not statistical (P ≥ 0.56). Cattle implanted upon arrival had numerically greater HCW and yield grade vs. cattle implanted on d 45; however, these differences were not statistical (P ≥ 0.16). Delaying the initial implant 45 d did not influence animal health, performance parameters or carcass characteristics in high risk feeder calves.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In this study, the effects of energy content of the feedlot diet as well as the length of the production period were investigated for Boer goat slaughter kids. The kids were housed in individual pens on the Elsenburg experimental farm, Western Cape, South Africa. Boer goat castrate kids were weaned at approximately 18 weeks of age (weighing 22.2 ± 3.5 kg) and were randomly allocated to one of three trial diets that varied in energy content; namely a low, medium and high energy diet (11.3, 12.0 and 12.7 MJ ME/ kg feed respectively) which were supplied ad libitum. The goats were further randomly allocated to one of five slaughter groups that were slaughtered at five week intervals at a commercial abattoir. The first group of goats was slaughtered at the start of the trial in order to serve as a baseline reference. During the study the effects of dietary energy content, and time spent in the feedlot were investigated for the feedlot production and slaughter characteristics of Boer goat kids. Additionally the effect of the energy content of the feedlot diets on the sensory and chemical properties of goat meat were evaluated. During the production period individual feed intake and live weight gain were monitored on a weekly basis. It was observed that live weight of the goats increased throughout the production period. Quadratic functions were used to describe the change in average daily gain and dry matter intake of the goats during the feeding period. Goats that were fed the low and medium energy diets exhibited higher daily gains (P= 0.02) and dry matter intakes (P< 0.01) than goats on the high energy diets. Dietary energy content and age of the animal in the feedlot did not influence the feed conversion ratio to produce a unit of live weight. A linear function was used to model the growth of the goats during this production period. The goats were not able to reach the point of inflection on the growth curve. Therefore the sigmoidal growth curve could not be plotted which could have been modelled by a function similar to the Gompertz model. Dressing percentages of the carcasses varied throughout the production period for all the diets, with goats on the low energy diet having the lowest dressing percentage (45.8%; P= 0.04). The energy content of the trial diets had no effect on the yield of the offal components and retail cuts of the carcass. Generally it was observed that the yields of the hindquarter and neck cuts decreased whilst that of the forequarter increased with the age of the goats at slaughter. The degree of carcass fatness increased with time spent in the feedlot, with the majority of fat being deposited in the abdominal cavity, rather than in the subcutaneous fat depot. Dietary energy content was expected to influence the levels of intramuscular fat, which in turn would affect the eating quality of the meat. However, the levels of energy in the diets fed to goats did not influence the tenderness, juiciness or the aroma and flavour profiles of the goat meat as observed during descriptive sensory analysis of the meat by a trained panel. Chemical analysis of the cooked meat samples also showed that the levels of intramuscular fat did not vary between the samples, resulting in the lack of differences detected between treatments in the sensory evaluation. / AFRIKAANSE OPSOMMING: In hierdie studie is die effek van die energie-inhoud van die voerkraal dieet, tesame met die lengte van die produksie tydperk, vir Boerbok lammers ondersoek. Die lammers is in individuele kampies gehuisves op die Elsenburg proefplaas, Wes- Kaap, Suid-Afrika. Die gekastreerde Boerbok lammers is gespeen op ’n ouderdom van ongeveer 18 weke (gewig van 22.2 ± 3.5 kg) en is ewekansig toegewys aan een van die drie proefdiëte waarvan die energie-inhoud gewissel het; naamlik 'n lae, medium en hoë-energie dieet (11.3, 12.0 en 12.7 MJ ME / kg voer onderskeidelik) wat ad libitum verskaf is. Die bokke is verder lukraak toegewys aan een van vyf slag groepe, wat met vyf weke tussenposes by ’n kommersiële abattoir geslag is. Die eerste groep bokke is aan die begin van die proef geslag om sodoende as basislyn verwysing te dien. Tydens die studie is die effek van die verskil in energie-inhoud van die dieet en die tyd wat in die voerkraal gespandeer is, op die voerkraal produksie en slag eienskappe van die Boerbok lammers ondersoek. Daarbenewens is die effek van die verskil in energie-inhoud van die voerkraal dieet op die sensoriese en chemiese eienskappe van bokvleis geëvalueer. Tydens die produksie periode is individuele voerinname en liggaamsgewig toename op ’n weeklikse basis gemonitor. Dit is waargeneem dat die liggaamsgewig van die bokke tydens die hele produksie tydperk toegeneem het. Kwadratiese funksies is gebruik om die verandering in die gemiddelde daaglikse toename tydens die voerperiode, sowel as die droëmateriaal inname van die bokke te beskryf. Bokke wat die lae en medium-energie diëte gevoer is, het hoër daaglikse toenames (P = 0.02) en droë materiaal inname (P< 0.01) as bokke op die hoë-energie dieet getoon. Die voeromset verhouding benodig om ’n eenheid lewendige gewig te produseer is nie beïnvloed deur die energie-inhoud van die dieet, of die ouderdom van die bokke in die voerkraal nie. ’n Lineêre funksie is toegepas om die groei van die bokke gedurende die produksie tydperk te modelleer. Die groei van die bokke kon nie die infleksiepunt van die groeikurwe bereik nie. Dus kon die sigmoïdale groeikurwe nie getrek word nie, wat deur ’n funksie soortgelyk aan die Gompertz model gemodelleer kon word. Uitslag persentasies van die karkasse het l regdeur die produksie tydperk varieër vir al die diëte; bokke op die lae-energie dieet het die laagste uitslagpersentasie gehad (45.8%; P = 0.04). Die energie-inhoud van die proefdiëte het geen effek op die opbrengs van die afval komponente en handelsnitte van die karkasse gehad nie. Oorhoofs is dit waargeneem dat die opbrengs van die agterkwart en neksnitte afgeneem het, terwyl dié van die voorkwart toegeneem het met slag ouderdom. Die vetheidsgraad van die karkas het toegeneem met tyd spandeer in die voerkraal, met die meerderheid van die vet gedeponeer in die buikholte, eerder as in die onderhuidse vetlaag. Daar is verwag dat die energie-inhoud van die dieet die vlakke van binnespierse vet sal beïnvloed, wat op sy beurt ‘n effek op die eetkwaliteit van die vleis sal hê.. Teenstrydig met verwagtinge het die vlakke van energie in die dieet van die bokke geen invloed gehad op die sagtheid, sappigheid of die aroma en geur profiele van bokvleis nie, soos waargeneem deur middel van beskrywende sintuiglike analise van die vleis deur 'n opgeleide paneele. Chemiese ontleding van die gaar vleismonsters het ook geen verskillein die vlakke van binnespierse vet tussen die verskillende monsters getoon nie, wat gelei het tot daar geen verskille tussen die behandelings in die sensoriese evaluasie waargeneem is nie.

Doctor of Philosophy / Department of Animal Sciences and Industry / James S. Drouillard / A series of studies were conducted to evaluate extrusion processing of finishing diets on growth performance, carcass characteristics, and meat quality attributes of feedlot cattle. Extruded diets were processed in a 24:1 (length/diameter) corotating, fully intermeshing twinscrew extruder (model BCTG-62, Bühler AG CH-9240, Uzwil, Switzerland). In Experiment 1, extrusion processing of corn based diets decreased dry matter intake (DMI) and improved gain efficiency (G:F) by 15% compared to heifers fed steam-flaked corn (SFC) diets. Carcass characteristics were not different between treatments. Steaks from heifers fed SFC diets were juicier and had a less pronounced off-flavor than steaks from heifers fed extruded diets. In Experiment 2, average daily gain (ADG), DMI, G:F, carcass characteristics, and meat quality attributes were not different between heifers fed SFC and extruded processed corn diets. In Experiment 3, we evaluated different degrees of extrusion processing by altering the level of process water added to the extruder. Mechanical energy inputs, die pressure, die temperature, and torque of drive motor decreased as the level of water added to the extruder increased from 4% to 12%. Water addition did not affect DMI or ADG of feedlot heifers. However, live body weight (BW) and G:F decreased as the level of process water increased. Gain efficiency (carcass-adjusted basis) was 3% greater for extruded corn diets processed with 4% water compared with SFC diets and was 6% poorer than SFC diets when processed with 12% water. Apparent total tract digestibility was not different, but IVDMD improved with increasing levels of water. Improvements in G:F when fed extruded feed was variable among the 3 studies. This may be due, in part to severe infestation by European Starlings during Experiment 1. Impact of feed depredation by starlings was therefore evaluated. Starlings consumed 86% of the SFC diet offered to them compared to, none of the extruded corn diets. In addition, starlings preferentially selected for the energy dense portion of the rations (steam-flaked corn). Therefore, it is plausible that a portion of the 15% improvement in G:F observed in Experiment 1 for heifers fed extruded corn diets can be attributed to differences in feed depredation by starlings. Finally, two studies were conducted to evaluate extrusion processing of sorghum-based diets. In the first experiment, DMI was greater and G:F was poorer for heifers fed extruded sorghum diets compared to heifers fed steam-flaked sorghum (SFS) diets. However, carcass characteristics and meat quality attributes were not different. In the second study, particle size of the ground sorghum added to the extruder was evaluated. Processing sorghum to a smaller particle size (581 μm) prior to extrusion processing decreased DMI, improved G:F, and increased apparent total tract digestibility compared with larger particle sizes (1,264 μm). However, heifers fed SFS diets were still more efficient that heifers fed extruded diets made with either particle size of sorghum. Overall, this research suggests that extruding complete diets into homogeneous pellets may improve G:F of cattle fed corn-based diets while reducing feed depredation of starlings. It is also clear from our results that G:F is improved to a greater extent to processing diets under high shear conditions (i.e., high mechanical energy inputs) than when processed under low shear conditions.

Master of Science / Department of Animal Sciences and Industry / James S. Drouillard / Two experiments were conducted to evaluate the efficacy of [italic]Megasphaera elsdenii[italic] strain NCIMB 41125 and its potential use in the mitigation of ruminal acidosis. In experiment 1, a metabolism study was conducted to evaluate ruminal parameters, quantify changes in ruminal bacterial populations, and determine in vitro capacity for lactate utilization following intraruminal dosing of a placebo or [italic]M. [italic]elsdenii strain NCIMB 41125 and an abrupt diet change. Angus crossbred steers (n=20; average BW=253 ± 24 kg) fitted with ruminal cannulas were blocked by BW and assigned randomly to treatments. Treatments consisted of intraruminal dosing with a placebo (100 mL of autoclaved culture), or 10, 100, or 1,000 mL of a live culture containing 1.62×108 CFU/mL of [italic]M. elsdenii[italic] strain NCIMB 41125. Prior to inoculation, cattle were placed into individual pens in an enclosed facility and allowed free access to alfalfa hay, salt, and water. Feed and water were removed for 24 h prior to administering treatments, after which, cattle were allowed free access to a diet consisting of 34% alfalfa hay and 66% steam-flaked corn-based concentrate. On d 7, cattle were fed an 80% concentrate diet. On d 12, steers were started on the final finishing diet of 94% concentrate. Ruminal pH and concentrations of lactate and VFAs were monitored following introduction of each concentrate diet. Ruminal samples were collected at 0, 2, 4, 6, 8, and 24 h after feeding for quantitative rt-PCR detection of native and introduced strains of [italic]M. elsdenii[italic], as well as total bacterial genomes. Capacity for metabolism of lactic acid was evaluated by inoculating 0.2 mL of strained ruminal fluid into anaerobic culture tubes containing 15 mL of semi-defined lactate medium. Tubes were incubated at 39˚C, and turbidity changes were determined by measuring absorbance at 2 h intervals up to 12 h. Experiment 2 was conducted in a commercial feedlot to evaluate the efficacy of [italic]M. elsdenii[italic] strain NCIMB 41125 for improving feedlot performance. A second objective of the study was to determine if oral dosing of [italic]M. elsdenii[italic] has the potential for reducing the number of cattle treated for bovine respiratory disease. Angus steers and heifers (n = 3179; average BW = 356 ± 58.4kg) were used in a randomized complete block design with two treatments. Cattle were assigned to treatment on an every-other-head basis such that every-other-animal was orally drenched with 100 mL of a culture medium containing 1.5×108 cfu/mL [italic]M. elsdenii[italic] strain NCIMB 41125 at processing. Cattle were blocked by gender and date of arrival. To maximize profitability, cattle were sorted via visual appraisal to identify cattle that were market ready. Cattle were shipped to a commercial abattoir in Lexington, NE for harvest. Data obtained for each pen of cattle included feedlot performance, morbidity, mortality, carcass characteristics, and grid-based program carcass qualifications. In trial 1, compared to the placebo group, cattle administered [italic]Megasphaera[italic] maintained higher ruminal pH 24 h after the carbohydrate challenge (P < 0.05). Ruminal lactate concentrations increased in response to the diet change (P < 0.05), but concentrations were lower for cattle that received [italic]Megasphaera[italic] compared to the placebo group (P < 0.05). Total number of bacterial genomes 24 h after inoculation was unaffected by intraruminal dosing of [italic]M. elsdenii[italic] strain NCIMB 41125 (P > 0.05), but populations of undifferentiated [italic]M. elsdenii[italic] and strain NCIMB 41125 increased by 24 h after inoculation (P < 0.05). Turbidity of cultures inoculated with ruminal fluid increased in response to [italic]M. elsdenii[italic] administration (P < 0.05), suggesting a greater capacity for lactate utilization in inoculated cattle compared to the placebo group. In trial 2, no differences in feed efficiency were observed (P > 0.05). Compared to cattle dosed with [italic]Megasphaera[italic], the control group had more USDA yield grade 2 carcasses (P < 0.05), and cattle dosed with [italic]M. elsdenii[italic] had more USDA yield grade 5 carcasses (P < 0.05). [italic]Megasphaera[italic] cattle also tended to have more USDA Prime carcasses (P = 0.14). No effects on incidence of liver abscesses were observed. Dosing cattle with [italic]M. elsdenii[italic] prior to introduction of typical concentrate diets may be useful in preventing ruminal lactate accumulation and associated depressions in ruminal pH. Inoculating cattle with [italic]M. elsdenii[italic] is effective in bolstering populations of ruminal lactate utilizers, and may be useful in preventing ruminal lactate accumulation in grain-fed cattle. No effects on reducing episodes of BRD were noted.

A utilização de volumoso em dietas de bovinos em terminação é importante para estimular a ingestão de energia, manter a saúde ruminal e diminuir distúrbios digestivos. A literatura é carente de informação, especialmente nas condições tropicais e em especial com animais zebuínos em relação à níveis e fontes de volumosos e seus efeitos no comportamento ingestivo, saúde e metabolismo ruminal de bovinos em terminação. Os objetivos desse experimento foram avaliar teores de FDN de feno (FDNf) de baixa qualidade, em dietas contendo alto teor de concentrado, quanto ao consumo, digestibilidade dos nutrientes, comportamento ingestivo e parâmetros ruminais de bovinos confinados. Foram utilizados cinco bovinos machos, castrados, da raça Nelore (PC inicial 337,0&#177;10,0kg) distribuídos em um delineamento em quadrado latino 5x5. Cada período experimental foi composto por 20 dias, sendo os 15 primeiros dias destinados à adaptação dos animais e os cinco dias restantes, às colheitas. As dietas experimentais foram formuladas para serem isoproteicas e conterem 4,5; 8,0; 11,5 e 15,0% de FDNf (% na MS) de baixa qualidade e 64,7, 60,7, 56,6, 52,5% de milho moído e 14,5, 14,3, 14,0, 13,8% de casca de soja. O quinto tratamento foi constituído por 18,5% de FDNf e 20,9% de casca de soja. Todos os tratamentos foram inclusos na análise de regressão e polinômios ortogonais (linear e quadrático) foram utilizados para avaliar o efeito de concentrações de FDNf para os quatro primeiros tratamentos. Foi realizado um contraste entre o quarto e o quinto tratamento. O aumento do teor de FDNf nas dietas ocasionou efeito quadrático (p < 0,1) para IMS, NDT e MO. Os consumos de CNF, CHOT, PB e EE não foram afetados pelos tratamentos (p > 0,1). As concentrações de NDT (p < 0,01), as digestibilidades aparentes totais da MS (p < 0,01), MO (p < 0,01), FDN (p= 0,05), CHOT (p < 0,01) e da PB (p = 0,06) foram reduzidas linearmente com o aumento do teor de FDNf na dieta. As digestibilidades aparentes totais de CNF (P = 0,70) e EE (P = 0,86) não foram afetadas pelos tratamentos. As concentrações de EM, ELm e de ELg foram reduzidas (p<0,01) de forma linear com a inclusão de FDNf nas dietas. A inclusão de FDNf nas dietas aumentou de forma quadrática (p<0,05) o tempo de ingestão, ruminação e mastigação dos animais. Por kg de MS, houve aumento linear no tempo ingestão (p<0,05), ruminação (p<0,01) e mastigação (p<0,01). Por kg de FDNf houve aumento linear no tempo de ruminação (p<0,1) e de mastigação (P,0,05). Aumentar o teor de FDNf nas dietas proporcionou aumento linear (p<0,05) no pH e no teor de N-NH3 ruminal do animais. Também houve aumento linear na proporção molar de acetato (p< 0,01), isobutirato (p = 0,10) e na relação C2:C3 (p< 0,05). A inclusão de 18,5% de FDNf e 20,9% de CS (% na MS) na dieta ocasionou aumento (p < 0,05) nos consumos de MS, NDT, MO e FDN, ELm (p<0,1) e ELg (p<0,1). Aumentar a inclusão de FDNf para 18% e CS para 20,9% na dieta aumentou a digestibilidade aparente total da FDN (p<0,1). A inclusão de 18,5% de FDNf e 20,9% de CS na dieta ocasionou aumento no tempo, expresso em min dia-1, de ingestão (p< 0,05) e mastigação (p< 0,05). Aumentar o teor de FDNf e CS na dieta ocasionou aumento na proporção molar de acetato (p<0,1) e aumento na relação C2:C3 (p< 0,05). A manipulação do teor de FDNf da dieta permite alterar a ingestão de energia, o comportamento ingestivo, a eficiência fermentativa no rúmen de animais confinados. / Roughage is included in beef cattle finishing diets to increase feed and energy intakes, while maintaining rumen health and reducing digestive disorders. The available literature is scarce regarding to the effects of levels of roughage in finishing diets for Zebu cattle on ingestive behavior and rumen parameters. The objectives of this experiment were to evaluate the effects of levels of NDF from hay of low quality in finishing diets containing high levels of concentrate on consumption, digestibility of nutrients, ingestive behavior and rumen parameters of zebu cattle. Five Nellore steers (337,0&#177;10,0kg IBW) were used in a 5x5 Latin-square design. Each experimental period lasted 20 days, the first 15 days were used for adaptation and the last 5 days for collection. The experimental diets were formulated to be isoprotein with 4,5; 8,0; 11,5 or 15,0% of NDF (% in DM) from low quality hay (rNDF) and 64.7, 60.7, 56.6, 52.5% ground corn and 14.5, 14.3, 14.0, 13.8% soybean hulls. The fifth treatment consisted of 18.5% of hay NDF and 20.9% of soybean hulls. All treatments were submitted to the regression analysis and orthogonal polynomials (linear and quadratic) were used to evaluate the effect of roughage NDF concentrations for the first four treatments. A contrast was used to compare the fourth and the fifth treatments. The increase of rNDF level in the diet caused a quadratic response (P < 0,1) on intakes of DM, OM and TDN (p<0.01), while the intakes of NFC, TCHO, CP and EE were not affected by treatments (p>0.1). The diets TDN (p<0.01) and the total tract apparent digestibilities of DM, (p<0.01), OM (p< 0.01), NDF (P=0.05), TCHO (p< 0.01) and CP (P = 0.06) decreased linearly as low quality hay NDF was included in the diets. The total tract apparent digestibilities of NFC (P = 0,70) and EE (P = 0,86) were not affected by treatments. The diet concentrations of ME, NEm and NEg, decreased linearly (p<0,01) as roughage NDF level increased in the diets. Inclusion of roughage NDF in the diets caused a quadratic increase (p<0.05) in ingestion time, rumination time and mastication time (minutes per day). When ingestive behavior was expressed per kg of DM there was a linear increase in ingestion time (p<0,05), rumination time (p<0,01) and mastication time (p<0,01). When ingestive behavior was expressed per kg of roughage NDF there was a linear increase in rumination time (p<0.1) and mastication time (p<0.05). Inclusion of roughage NDF in the diets caused a linear increase (p<0.05) in rumen pH (p<0.05), in rumen N-NH3 (p<0.05), in the molar proportions of acetate (p< 0,01) and isobutirate (p< 0,1), and in the rumen C2:C3 ratio (p< 0,05). The diet containing 18.5% of roughage NDF and 20.9% of soybean hulls (% of DM) increased the consumptions of DM (p<0.05), TDN (p<0,05), OM (p<0.05), NDF (p<0.05), NEm (p<0,1) and NEg (p<0,1) compared with the containing 15% of roughage NDF and 13.8% soybean hulls. Increasing roughage NDF to 18.5% and soybean hulls to 20.9% in the diet increased the total apparent digestibility of NDF (p<0,1), and ingestion (p<0.05) and chewing (p<0.05) times expressed in min.day-1. Increasing roughage NDF and soybean hulls in the diet increased the molar proportion of acetate (p< 0.1) and the C2:C3 ratio (P < 0,05). The manipulation of the roughage NDF content of finishing diets allows to manipulate energy intake, ingestive behavior and efficiency of rumen fermentation of Zebu cattle.