Doctor of Philosophy / Department of Animal Sciences and Industry / James S. Drouillard / Four studies evaluated effects of mineral supplementation on feedlot performance, carcass characteristics and ruminal fermentation of finishing cattle. Study 1 supplemented 0 or 3.3 g/d yeast combined with Cr propionate to steers separated into light and heavy groups. No treatment x weight group interactions were observed for ADG, DMI, final BW, carcass traits, or plasma glucose of lactate concentrations (P ≥ 0.06). A treatment x weight group interaction was observed for G:F (P = 0.03). In study 2, steers were supplemented 60 or 300 mg Zn/kg DM with or without zilpaterol hydrochloride (ZH). No interactions or effects of Zn or ZH were observed for IGF-1, plasma glucose, or lactate concentrations (P > 0.05). Plasma urea nitrogen (PUN) concentration decreased with ZH (P < 0.01). No interactions or effects of Zn or ZH were detected for ADG, DMI, final BW, G:F, and carcass traits were minimally affected (P ≥ 0.05). Study 3 evaluated effects of supplementing 30 or 100 mg Zn/kg DM (30 or 100Zn) with and without ractopamine hydrochloride (RH; 200 mg/d). No interactions or effects of Zn were observed for feedlot performance or PUN (P ≥ 0.07). Final BW, ADG, and HCW increased when heifers were fed RH (P ≤ 0.02). Zinc x RH interactions were observed for LM area and yield grade (P ≤ 0.01), but other carcass traits were not affected (P ≥ 0.08). In study 4, heifers were supplemented 0, 30, 60, or 90 mg Zn/kg DM. Zinc supplementation did not affect final BW, ADG, or DMI (P ≥ 0.07), but G:F increased linearly (P = 0.02). Carcass traits were not affected by Zn supplementation (P ≥ 0.07). Effects of in vitro Zn titration (0, 30, 60, 60, 90, 120, or 150 mg/kg Zn) were evaluated using ground corn and soybean meal as substrate. In vitro fermentation was not affected by added Zn (P ≥ 0.05). These studies suggest Cr and Zn supplementation minimally affected carcass traits, but Zn supplementation up to 60 mg/kg improved feed efficiency with minimal impact on ruminal fermentation. Supplementing increased Zn concentrations may alter fat and muscle deposition when fed with RH.

The Cattle Value Discovery System (CVDS) was developed to predict growth and feed requirements of individual cattle fed in groups based on animal, diet, and environment information (Tedeschi et al., 2006). Evaluations of the CVDS using several databases of finishing cattle were conducted to determine the accuracy and precision of the model in predicted dry matter required (DMR) of pen-fed cattle. As well, the sensitivity of the model's predictions to deviations from actual ration metabolizable energy (ME) value was conducted. A meta-analysis of growing and finishing steers evaluated to model's accuracy in predicting DMR of individually fed steers, and the relationships between several model-predicted variables and actual performance and efficiency measures. Results for the first CVDS model evaluation involving pen-fed Santa Gertrudis cattle fed finishing diets revealed that accurate predictions of DMR are possible. The average mean bias for both steers and heifers was 2.43%. The sensitivity analysis of dietary ME values revealed that the model tends to consistently over- and under-predict DMR when the ME values are under- and over-estimated, respectively. However the ranking of pens was not affected by this mis-estimation of diet ME. In the second evaluations, both methods (mean body weight; MBW, dynamic iterative model; DIM) of CVDS were highly accurate and precise in allocating feed to pens of steers fed diverse types of diets and environmental conditions, with both models having a mean bias under 4%. The DIM model was slightly more accurate than the MBW model in predicting DMR. An evaluation of sources of variation revealed that for both models a large portion of the error was random, indicating that further work is needed to account for this variation. The meta-analysis study revealed that the model was able to account for 64% and 67% of the variation in observed dry matter intake (DMI) for growing and finishing steers, respectively. The two model-predicted efficiency measures, the ratio of DMR to average daily gain (ADG) and predicted intake difference (PID), were strongly to moderately correlated with their observed efficiency counterparts. In growing and finishing steers, DMR: ADG was able to account for 76% and 64% of the variation in observed feed conversion ratio (FCR) in growing and finishing studies, respectively. Strong correlations were also found between residual feed intake (RFI) and PID, suggesting that there may also be some similarity on these two measurements.

The Cattle Value Discovery System (CVDS) was developed to predict growth and feed requirements of individual cattle fed in groups based on animal, diet, and environment information (Tedeschi et al., 2006). Evaluations of the CVDS using several databases of finishing cattle were conducted to determine the accuracy and precision of the model in predicted dry matter required (DMR) of pen-fed cattle. As well, the sensitivity of the model’s predictions to deviations from actual ration metabolizable energy (ME) value was conducted. A meta-analysis of growing and finishing steers evaluated to model’s accuracy in predicting DMR of individually fed steers, and the relationships between several model-predicted variables and actual performance and efficiency measures. Results for the first CVDS model evaluation involving pen-fed Santa Gertrudis cattle fed finishing diets revealed that accurate predictions of DMR are possible. The average mean bias for both steers and heifers was 2.43%. The sensitivity analysis of dietary ME values revealed that the model tends to consistently over- and under-predict DMR when the ME values are under- and over-estimated, respectively. However the ranking of pens was not affected by this mis-estimation of diet ME. In the second evaluations, both methods (mean body weight; MBW, dynamic iterative model; DIM) of CVDS were highly accurate and precise in allocating feed to pens of steers fed diverse types of diets and environmental conditions, with both models having a mean bias under 4%. The DIM model was slightly more accurate than the MBW model in predicting DMR. An evaluation of sources of variation revealed that for both models a large portion of the error was random, indicating that further work is needed to account for this variation. The meta-analysis study revealed that the model was able to account for 64% and 67% of the variation in observed dry matter intake (DMI) for growing and finishing steers, respectively. The two model-predicted efficiency measures, the ratio of DMR to average daily gain (ADG) and predicted intake difference (PID), were strongly to moderately correlated with their observed efficiency counterparts. In growing and finishing steers, DMR: ADG was able to account for 76% and 64% of the variation in observed feed conversion ratio (FCR) in growing and finishing studies, respectively. Strong correlations were also found between residual feed intake (RFI) and PID, suggesting that there may also be some similarity on these two measurements.

The Cattle Value Discovery System (CVDS) was developed to predict growth and feed requirements of individual cattle fed in groups based on animal, diet, and environment information (Tedeschi et al., 2006). Evaluations of the CVDS using several databases of finishing cattle were conducted to determine the accuracy and precision of the model in predicted dry matter required (DMR) of pen-fed cattle. As well, the sensitivity of the model’s predictions to deviations from actual ration metabolizable energy (ME) value was conducted. A meta-analysis of growing and finishing steers evaluated to model’s accuracy in predicting DMR of individually fed steers, and the relationships between several model-predicted variables and actual performance and efficiency measures. Results for the first CVDS model evaluation involving pen-fed Santa Gertrudis cattle fed finishing diets revealed that accurate predictions of DMR are possible. The average mean bias for both steers and heifers was 2.43%. The sensitivity analysis of dietary ME values revealed that the model tends to consistently over- and under-predict DMR when the ME values are under- and over-estimated, respectively. However the ranking of pens was not affected by this mis-estimation of diet ME. In the second evaluations, both methods (mean body weight; MBW, dynamic iterative model; DIM) of CVDS were highly accurate and precise in allocating feed to pens of steers fed diverse types of diets and environmental conditions, with both models having a mean bias under 4%. The DIM model was slightly more accurate than the MBW model in predicting DMR. An evaluation of sources of variation revealed that for both models a large portion of the error was random, indicating that further work is needed to account for this variation. The meta-analysis study revealed that the model was able to account for 64% and 67% of the variation in observed dry matter intake (DMI) for growing and finishing steers, respectively. The two model-predicted efficiency measures, the ratio of DMR to average daily gain (ADG) and predicted intake difference (PID), were strongly to moderately correlated with their observed efficiency counterparts. In growing and finishing steers, DMR: ADG was able to account for 76% and 64% of the variation in observed feed conversion ratio (FCR) in growing and finishing studies, respectively. Strong correlations were also found between residual feed intake (RFI) and PID, suggesting that there may also be some similarity on these two measurements.

The Cattle Value Discovery System (CVDS) was developed to predict growth and feed requirements of individual cattle fed in groups based on animal, diet, and environment information (Tedeschi et al., 2006). Evaluations of the CVDS using several databases of finishing cattle were conducted to determine the accuracy and precision of the model in predicted dry matter required (DMR) of pen-fed cattle. As well, the sensitivity of the model's predictions to deviations from actual ration metabolizable energy (ME) value was conducted. A meta-analysis of growing and finishing steers evaluated to model's accuracy in predicting DMR of individually fed steers, and the relationships between several model-predicted variables and actual performance and efficiency measures. Results for the first CVDS model evaluation involving pen-fed Santa Gertrudis cattle fed finishing diets revealed that accurate predictions of DMR are possible. The average mean bias for both steers and heifers was 2.43%. The sensitivity analysis of dietary ME values revealed that the model tends to consistently over- and under-predict DMR when the ME values are under- and over-estimated, respectively. However the ranking of pens was not affected by this mis-estimation of diet ME. In the second evaluations, both methods (mean body weight; MBW, dynamic iterative model; DIM) of CVDS were highly accurate and precise in allocating feed to pens of steers fed diverse types of diets and environmental conditions, with both models having a mean bias under 4%. The DIM model was slightly more accurate than the MBW model in predicting DMR. An evaluation of sources of variation revealed that for both models a large portion of the error was random, indicating that further work is needed to account for this variation. The meta-analysis study revealed that the model was able to account for 64% and 67% of the variation in observed dry matter intake (DMI) for growing and finishing steers, respectively. The two model-predicted efficiency measures, the ratio of DMR to average daily gain (ADG) and predicted intake difference (PID), were strongly to moderately correlated with their observed efficiency counterparts. In growing and finishing steers, DMR: ADG was able to account for 76% and 64% of the variation in observed feed conversion ratio (FCR) in growing and finishing studies, respectively. Strong correlations were also found between residual feed intake (RFI) and PID, suggesting that there may also be some similarity on these two measurements.

Master of Science / Department of Animal Sciences and Industry / James S. Drouillard / A trial was conducted replacing portions of steam-flaked corn with either dry-rolled corn or dried distiller’s grains with solubles to evaluate effects on performance, carcass characteristics, carcass composition, meat color stability, and meat sensory attributes. Seven hundred crossbred yearling heifers (302 ± 65 kg initial BW) were used in a randomized complete block experiment with a 2 x 2 factorial arrangement of treatments. All diets contained steam-flaked corn (SFC), and factors consisted of the levels of dry-rolled corn (DRC; 0 or 25%) and dried corn distiller’s grains with solubles (DDGS; 0 or 25%). Results revealed no interactions between DRC and DDGS in terms of effects on feedlot performance, and only minor interactive effects were observed for carcass characteristics and meat quality attributes. Feedlot performance and carcass characteristics were not affected by the addition of DRC or DDGS (P > 0.05). Carcass composition and meat quality attributes were measured to determine if fat content of carcasses was altered by feeding DDGS. Diet had no significant effects, as carcasses from the four treatments contained similar amounts of separable portions of muscle, adipose, and bone; and similar percentages of protein, moisture, and ether extract. Compositions of both adipose and muscle tissue were evaluated to assess differences in fatty acid profile. Minimal effects were noted on the fatty acid profiles of the muscle and adipose tissue from cattle fed DDGS or DRC. Feeding cattle DDGS decreased alpha tocopherol (vitamin E) content of meat (P < 0.05). Meat quality attributes were largely unaffected by addition of DRC or DDGS to the diet, as retail color display life, lipid oxidation, sensory attributes, and heterocyclic amine concentrations were not different among treatments. Overall, DRC or DDGS can replace portions of SFC without negatively altering feedlot performance, carcass characteristics, meat composition, or meat quality attributes.

A pecuária de corte extensiva se mostra incapaz de competir em termos de resultados econômicos com outras alternativas de uso da terra em regiões de terras valorizadas, fato que pode ser comprovado pela substituição gradativa de áreas de pastagens por culturas agrícolas. Nessas regiões, a adubação intensiva de pastagens tem se tornado a opção freqüentemente utilizada para o incremento da produtividade animal que é imprescindível para a viabilização econômica da pecuária frente a demais alternativas de uso da terra. A irrigação aliada à adubação de pastagens cresceu muito desde o final da década de 90 no Brasil Central, crescimento motivado pela expectativa de resultados produtivos elevados como os divulgados por revistas técnicas especializadas. Com o intuito de comparar os resultados produtivos e econômicos de pastagens adubadas intensivamente com e sem o uso da irrigação, foram conduzidos dois experimentos ao longo de um ano em pastagens de Panicum maximum cv tanzânia. Foram avaliados desempenho animal, taxa de lotação e produtividade nos experimentos. A avaliação econômica foi efetuada com a determinação dos indicadores lucro líquido, taxa de retorno sobre o ativo e taxa interna de retorno, por meio de simulações determinísticas e estocásticas. Enquanto no experimento em sequeiro os valores de desempenho animal e de taxa de lotação médios obtidos foram de 0,615 kg GPD e 5,6 UA/ha, respectivamente, no experimento irrigado foram obtidos 0,492 kg GPD e 5,9 UA/ha. A irrigação só foi efetiva no incremento da taxa de lotação na transição entre os períodos de "seca" e "águas", não confirmando o potencial da irrigação de pastagens no incremento da taxa de lotação. A diferença de produtividade animal entre os experimentos foi minimizada pelo maior desempenho animal do experimento sem irrigação em alguns períodos. Foram obtidas produtividades de 1.628 kg PV/ha no experimento irrigado e 1.672 kg PV/ha no em sequeiro, corroborando o potencial de produtividade de pastagens adubadas intensivamente. A análise de viabilidade sem a consideração de risco apresentou resultados de lucro líquido, taxa de retorno sobre o ativo e taxa interna de retorno, respectivamente de R$ - 164,91 por hectare, - 1,0% e - 6,1%, para o sistema irrigado e R$ 574,90 por hectare, 4,4% e 17,2% para o em sequeiro. Contudo, essa análise subestimou os resultados dos indicadores de viabilidade econômica em ambos sistemas. A análise de risco apontou o sistema irrigado como inviável economicamente, enquanto para o sistema sem irrigação a probabilidade de um resultado econômico que apontasse inviabilidade foi baixa. / Extensive beef production cannot compete with others uses of land for agricultural productions, mainly where land costs are high, therefore a gradual substitution of pasture areas for agricultural crops is occurring. High levels of fertilizer application to pastures have been used for improving beef productivity and, consequently, improve the economic profitability of this activity. Irrigation of pasture increased since 90’s in Central Brazil, motivated by the expectation of high productivities as presented in technical magazines. The objective of this research was to compare the productivity and economic results of highly fertilized pasture, with and without irrigation. Two experiments were conducted for a year in Panicum maximum cv tanzânia pastures. Weight gain, stocking rate and beef productivity were evaluated. In the economic evaluation was determined net margin, simple rate of return and internal rate of return, using deterministic and stochastic simulations. In the non-irrigated experiment the weight gain was 0,615 kg/day and the stocking rate 5,6 AU/ha, and in the irrigated one, 0,492 kg/day and 5,9 AU/ha, respectively. The irrigation only increased the stocking rate in the season transition between dry and rainy period, not confirming the potential for pasture irrigation in the Central South part of Brazil by increasing stocking rate. Productivity difference in irrigated and non-irrigated pastures was minimized by the high weight gain of non-irrigated area in some periods. The animal live weigh gain was 1.628 kg/ha in irrigated experiment, and 1.678 kg/ha in non-irrigated one, indicating high potential for productivity of highly fertilized pasture. The analysis without risk consideration showed results of net margin, simple rate of return and internal rate of return, respectively of R$ -164,91 per hectare, - 1,0% and -6,1% for irrigated system, and R$ 574,90 per hectare, 4,4% and 17,2% for non-irrigated one. Deterministic analysis sub estimated the results of economic viability indicators. Risk analysis showed weak probability of economic viability for irrigated system. Non-irrigated system with high levels of fertilizer application indicated weak probability for not been an economic activity.

A pecuária de corte extensiva se mostra incapaz de competir em termos de resultados econômicos com outras alternativas de uso da terra em regiões de terras valorizadas, fato que pode ser comprovado pela substituição gradativa de áreas de pastagens por culturas agrícolas. Nessas regiões, a adubação intensiva de pastagens tem se tornado a opção freqüentemente utilizada para o incremento da produtividade animal que é imprescindível para a viabilização econômica da pecuária frente a demais alternativas de uso da terra. A irrigação aliada à adubação de pastagens cresceu muito desde o final da década de 90 no Brasil Central, crescimento motivado pela expectativa de resultados produtivos elevados como os divulgados por revistas técnicas especializadas. Com o intuito de comparar os resultados produtivos e econômicos de pastagens adubadas intensivamente com e sem o uso da irrigação, foram conduzidos dois experimentos ao longo de um ano em pastagens de Panicum maximum cv tanzânia. Foram avaliados desempenho animal, taxa de lotação e produtividade nos experimentos. A avaliação econômica foi efetuada com a determinação dos indicadores lucro líquido, taxa de retorno sobre o ativo e taxa interna de retorno, por meio de simulações determinísticas e estocásticas. Enquanto no experimento em sequeiro os valores de desempenho animal e de taxa de lotação médios obtidos foram de 0,615 kg GPD e 5,6 UA/ha, respectivamente, no experimento irrigado foram obtidos 0,492 kg GPD e 5,9 UA/ha. A irrigação só foi efetiva no incremento da taxa de lotação na transição entre os períodos de “seca” e “águas”, não confirmando o potencial da irrigação de pastagens no incremento da taxa de lotação. A diferença de produtividade animal entre os experimentos foi minimizada pelo maior desempenho animal do experimento sem irrigação em alguns períodos. Foram obtidas produtividades de 1.628 kg PV/ha no experimento irrigado e 1.672 kg PV/ha no em sequeiro, corroborando o potencial de produtividade de pastagens adubadas intensivamente. A análise de viabilidade sem a consideração de risco apresentou resultados de lucro líquido, taxa de retorno sobre o ativo e taxa interna de retorno, respectivamente de R$ - 164,91 por hectare, - 1,0% e – 6,1%, para o sistema irrigado e R$ 574,90 por hectare, 4,4% e 17,2% para o em sequeiro. Contudo, essa análise subestimou os resultados dos indicadores de viabilidade econômica em ambos sistemas. A análise de risco apontou o sistema irrigado como inviável economicamente, enquanto para o sistema sem irrigação a probabilidade de um resultado econômico que apontasse inviabilidade foi baixa. / Extensive beef production cannot compete with others uses of land for agricultural productions, mainly where land costs are high, therefore a gradual substitution of pasture areas for agricultural crops is occurring. High levels of fertilizer application to pastures have been used for improving beef productivity and, consequently, improve the economic profitability of this activity. Irrigation of pasture increased since 90’s in Central Brazil, motivated by the expectation of high productivities as presented in technical magazines. The objective of this research was to compare the productivity and economic results of highly fertilized pasture, with and without irrigation. Two experiments were conducted for a year in Panicum maximum cv tanzânia pastures. Weight gain, stocking rate and beef productivity were evaluated. In the economic evaluation was determined net margin, simple rate of return and internal rate of return, using deterministic and stochastic simulations. In the non-irrigated experiment the weight gain was 0,615 kg/day and the stocking rate 5,6 AU/ha, and in the irrigated one, 0,492 kg/day and 5,9 AU/ha, respectively. The irrigation only increased the stocking rate in the season transition between dry and rainy period, not confirming the potential for pasture irrigation in the Central South part of Brazil by increasing stocking rate. Productivity difference in irrigated and non-irrigated pastures was minimized by the high weight gain of non-irrigated area in some periods. The animal live weigh gain was 1.628 kg/ha in irrigated experiment, and 1.678 kg/ha in non-irrigated one, indicating high potential for productivity of highly fertilized pasture. The analysis without risk consideration showed results of net margin, simple rate of return and internal rate of return, respectively of R$ -164,91 per hectare, - 1,0% and -6,1% for irrigated system, and R$ 574,90 per hectare, 4,4% and 17,2% for non-irrigated one. Deterministic analysis sub estimated the results of economic viability indicators. Risk analysis showed weak probability of economic viability for irrigated system. Non-irrigated system with high levels of fertilizer application indicated weak probability for not been an economic activity.

Foram conduzidos três experimentos no confinamento experimental do Departamento de Zootecnia da ESALQ/USP com o objetivo de estudar os efeitos de diferentes aditivos em rações para bovinos terminados em confinamento. No experimento 1 foram utilizados 100 bovinos machos Nelore castrados (392 kg), distribuídos em 20 baias, por 60 dias. As rações continham 41% de sorgo moído, 40% de polpa cítrica peletizada e 15% de silagem de cana-de-açúcar. Os tratamentos foram: (1) controle, (2) monesina sódica Rumensin (MON1), (3) monensina sódica Rumenfort (MON2), levedura Saccharomyces cerevisiae Yea-Sacc 1026 (LEV1) e levedura Saccharomyces cerevisiae Biosaf SC47 (LEV2). A IMS foi reduzida pelo tratamento MON1 (P<0,05), quando comparada ao tratamento controle. O GPD dos animais não foi afetado pelos tratamentos (P>0,05). A EA dos animais não foi afetada pelos tratamentos (P>0,05). O tratamento MON2 apresentou um menor rendimento de carcaça (P<0,05) e o tratamento MON 1 apresentou uma maior AOL (P<0,05). No experimento 2 foram utilizados 96 tourinhos Nelore não castrados (396 kg), distribuídos em 16 baias por 95 dias. Os tratamentos foram: (1) Controle, (2) levedura Saccharomyces cerevisiae Biosaf SC47 (LEV), (3) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 1g /bovino/dia (PROB1) e (4) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 3g/bovino/dia (PROB2). As rações continham 59% de polpa cítrica peletizada, 35% de farelo de glúten de milho úmido e 5% de feno de tifton 65. A adição dos aditivos levedura (Saccharomyces cerevisae) e a combinação de leveduras e bactérias probióticas não afetou a IMS o GPD e a EA dos animais (P>0,05). A energia líquida de manutenção e de ganho das rações também não foi afetada pelos tratamentos (P>0,05), assim como os dados de carcaça. No experimento 3, que avaliou a digestibilidade das rações, foram utilizados 20 tourinhos Nelore, alocados em 20 baias individuais durante 15 dias, sendo 10 dias de adaptação ao marcador e 5 dias de coleta de fezes. A ração foi a mesma utilizada no experimento 2, e o marcador utilizado foi o óxido de cromo. Os tramentos utilizados foram: (1) Controle, (2) monensina sódica Rumenfort (MON), (3) levedura Saccharomyces cerevisiae Biosaf SC47 (LEV), (4) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 1g /bovino/dia (PROB1) e (5) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 3g/bovino/dia (PROB2). Os aditivos testados não afetaram as digestibilidades da MS, da MO, da FDN e da PB das rações (P>0,05). Com os resultados obtidos é possível afirmar que bovinos Nelore, castrados ou não, confinados com rações com altos teores de concentrado ricos em co-produtos como polpa cítrica e farelo de glúten de milho úmido não apresentam melhor desempenho nem melhor digestibilidade dos nutrientes quando suplementados com monensina sódica ou com micorganismos probióticos. / Three trials were conducted at the ESALQ/USP Animal Sciences Department experimental feedlot to evaluate the effects of different feed additives in feedlot finished cattle. On trial 1 100 Nellore steers (392kg) were allocated to 20 pens for 60 days. Experimental rations had 41% ground milo, 40% dried citrus pulp and 15% sugarcane silage. Treatments were: (1) control, (2) sodium monensin Rumensin (MON1), (3) sodium monensin Rumenfort (MON2), (4) yeast culture Saccharomyces cerevisiae Yea-Sacc 1026 (LEV1) and (5) yeast culture Saccharomyces cerevisiae Biosaf SC47 (LEV2). DMI was reduced by MON1 trestment (P<0,05) in relation to control. WDG was not affected by treatments (P>0,05). Treatments did not affect FE (P>0,05). Animals on treatment MON2 showed the lowest dressing percentage (DP) and those on MON1 showed the highest rib eye area (REA) (P<0,05). Trial 2 used 96 young Nellore bulls (396kg), allocated to 16 pens for 95 days. Treatments were: (1) control, (2) Saccharomyces cerevisiae Biosaf SC47 (LEV), (3) Saccharomyces cerevisiae and probiotic bacteria mix at 1g /animal/day dose (PROB1) and (4) Saccharomyces cerevisiae probiotic bacteria mix at 3g/animal/day dose (PROB2). Rations contained 59% dried citrus pulp, 35% wet corn gluten feed and 5% Tifton 65 hay. Treatments didnt affect DMI, WDG and FE (P>0,05). Rations net energy for maintenance and gain were also not affect by treatments (P>0,05), well as carcass data. Trial 3 utilized 20 young Nellore bulls allocated to individual pens for 15 days (10 days for adaptation to marker and 5 days for data collection) to evaluate rations digestibility. Experimental ration was the same utilized on trial 2, with chromium oxide as an external marker. Treatments were (1) control, (2) sodium monensin Rumenfort (MON1), (3) yeast culture Saccharomyces cerevisiae Biosaf SC47 (LEV), (4) Saccharomyces cerevisiae and probiotic bacteria mix at 1g /animal/day dose (PROB1) and (5) Saccharomyces cerevisiae probiotic bacteria mix at 3g/animal/day dose (PROB2). Treatments did not affect rations DM, OM, NDF and CP digestibilities (P>0,05). Results show that Nellore cattle, castrated or not, feedlot finished receiving rations with high levels of byproducts such as dried citrus pulp and wet corn gluten feed dont have higher performance nor better nutrients digestibility when supplemented with sodium monensin or probiotic microorganisms.

Foram conduzidos três experimentos no confinamento experimental do Departamento de Zootecnia da ESALQ/USP com o objetivo de estudar os efeitos de diferentes aditivos em rações para bovinos terminados em confinamento. No experimento 1 foram utilizados 100 bovinos machos Nelore castrados (392 kg), distribuídos em 20 baias, por 60 dias. As rações continham 41% de sorgo moído, 40% de polpa cítrica peletizada e 15% de silagem de cana-de-açúcar. Os tratamentos foram: (1) controle, (2) monesina sódica Rumensin (MON1), (3) monensina sódica Rumenfort (MON2), levedura Saccharomyces cerevisiae Yea-Sacc 1026 (LEV1) e levedura Saccharomyces cerevisiae Biosaf SC47 (LEV2). A IMS foi reduzida pelo tratamento MON1 (P<0,05), quando comparada ao tratamento controle. O GPD dos animais não foi afetado pelos tratamentos (P>0,05). A EA dos animais não foi afetada pelos tratamentos (P>0,05). O tratamento MON2 apresentou um menor rendimento de carcaça (P<0,05) e o tratamento MON 1 apresentou uma maior AOL (P<0,05). No experimento 2 foram utilizados 96 tourinhos Nelore não castrados (396 kg), distribuídos em 16 baias por 95 dias. Os tratamentos foram: (1) Controle, (2) levedura Saccharomyces cerevisiae Biosaf SC47 (LEV), (3) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 1g /bovino/dia (PROB1) e (4) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 3g/bovino/dia (PROB2). As rações continham 59% de polpa cítrica peletizada, 35% de farelo de glúten de milho úmido e 5% de feno de tifton 65. A adição dos aditivos levedura (Saccharomyces cerevisae) e a combinação de leveduras e bactérias probióticas não afetou a IMS o GPD e a EA dos animais (P>0,05). A energia líquida de manutenção e de ganho das rações também não foi afetada pelos tratamentos (P>0,05), assim como os dados de carcaça. No experimento 3, que avaliou a digestibilidade das rações, foram utilizados 20 tourinhos Nelore, alocados em 20 baias individuais durante 15 dias, sendo 10 dias de adaptação ao marcador e 5 dias de coleta de fezes. A ração foi a mesma utilizada no experimento 2, e o marcador utilizado foi o óxido de cromo. Os tramentos utilizados foram: (1) Controle, (2) monensina sódica Rumenfort (MON), (3) levedura Saccharomyces cerevisiae Biosaf SC47 (LEV), (4) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 1g /bovino/dia (PROB1) e (5) combinação de levedura Saccharomyces cerevisiae e bactérias probióticas na dose de 3g/bovino/dia (PROB2). Os aditivos testados não afetaram as digestibilidades da MS, da MO, da FDN e da PB das rações (P>0,05). Com os resultados obtidos é possível afirmar que bovinos Nelore, castrados ou não, confinados com rações com altos teores de concentrado ricos em co-produtos como polpa cítrica e farelo de glúten de milho úmido não apresentam melhor desempenho nem melhor digestibilidade dos nutrientes quando suplementados com monensina sódica ou com micorganismos probióticos. / Three trials were conducted at the ESALQ/USP Animal Sciences Department experimental feedlot to evaluate the effects of different feed additives in feedlot finished cattle. On trial 1 100 Nellore steers (392kg) were allocated to 20 pens for 60 days. Experimental rations had 41% ground milo, 40% dried citrus pulp and 15% sugarcane silage. Treatments were: (1) control, (2) sodium monensin Rumensin (MON1), (3) sodium monensin Rumenfort (MON2), (4) yeast culture Saccharomyces cerevisiae Yea-Sacc 1026 (LEV1) and (5) yeast culture Saccharomyces cerevisiae Biosaf SC47 (LEV2). DMI was reduced by MON1 trestment (P<0,05) in relation to control. WDG was not affected by treatments (P>0,05). Treatments did not affect FE (P>0,05). Animals on treatment MON2 showed the lowest dressing percentage (DP) and those on MON1 showed the highest rib eye area (REA) (P<0,05). Trial 2 used 96 young Nellore bulls (396kg), allocated to 16 pens for 95 days. Treatments were: (1) control, (2) Saccharomyces cerevisiae Biosaf SC47 (LEV), (3) Saccharomyces cerevisiae and probiotic bacteria mix at 1g /animal/day dose (PROB1) and (4) Saccharomyces cerevisiae probiotic bacteria mix at 3g/animal/day dose (PROB2). Rations contained 59% dried citrus pulp, 35% wet corn gluten feed and 5% Tifton 65 hay. Treatments didnt affect DMI, WDG and FE (P>0,05). Rations net energy for maintenance and gain were also not affect by treatments (P>0,05), well as carcass data. Trial 3 utilized 20 young Nellore bulls allocated to individual pens for 15 days (10 days for adaptation to marker and 5 days for data collection) to evaluate rations digestibility. Experimental ration was the same utilized on trial 2, with chromium oxide as an external marker. Treatments were (1) control, (2) sodium monensin Rumenfort (MON1), (3) yeast culture Saccharomyces cerevisiae Biosaf SC47 (LEV), (4) Saccharomyces cerevisiae and probiotic bacteria mix at 1g /animal/day dose (PROB1) and (5) Saccharomyces cerevisiae probiotic bacteria mix at 3g/animal/day dose (PROB2). Treatments did not affect rations DM, OM, NDF and CP digestibilities (P>0,05). Results show that Nellore cattle, castrated or not, feedlot finished receiving rations with high levels of byproducts such as dried citrus pulp and wet corn gluten feed dont have higher performance nor better nutrients digestibility when supplemented with sodium monensin or probiotic microorganisms.