ABSTRACT The objectives of this study were to genotype single nucleotide polymorphisms (SNP) AF159246:g.2959A>G (CAST/DdeI) and AF248054.2:g.6545C>T (CAPN4751) in beef cattle by PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Length Polymorphism), using the restriction enzyme DdeI for both SNP, and describe the use of these genotyping methodologies for the first time. For the SNP located in the CAST gene, new primers were designed, and for the SNP of the CAPN1 gene, the same primers previously described in the literature were used. Bonsmara, Caracu, Senepol, Nelore, and Angus bulls were chosen from among the most used bulls in breeding programs according to their genealogy and the lowest possible degree of parentage between them to ensure an experimental sample representative of the genetic variability in each breed. For the CAST and CAPN1 genes, respectively, the following number of animals were analyzed: Bonsmara (n = 25/22), Caracu (n = 25/26), Senepol (n = 25/24), Nelore (n = 26/26), and Angus (n = 25/24). The accuracy of these methodologies was confirmed by direct sequencing of PCR products generated for the two polymorphisms. The new primers developed for CAST/DdeI SNP detection and the use of DdeI enzyme for CAPN4751 SNP detection were effective in genotyping, since no inconclusive genotypes were observed for these genes. Thus, the genotyping of beef cattle using the PCR-RFLP technique for CAST and CAPN1 genes is robust, relatively inexpensive, and easy to perform in any basic molecular biology laboratory. If the association of these markers with traits of economic interest in beef cattle is confirmed in new studies, these methodologies may contribute to the selection of animals with superior genetics, i.e., with the potential to produce better-quality meat, either by marker-assisted selection or by the inclusion of these polymorphisms in high-density marker panels.

ABSTRACT: The system of differential equations proposed by Oltjen et al. [1986, named Davis Growth Model (DGM)] to represent cattle growth has been parameterized with data from Bos taurus (British) and Bos indicus (Nellore) breeds. The DGM has been successfully used for simulation and decision support in the United States. However, the effect of about 30 years of genetic improvement and the use of different breeds may affect the model parameter values, which also may need to be re-estimated for crossbred animals. The aim of this study was to estimate parameter values and confidence intervals for the DGM with growth and body composition data from Zebu crossbred animals. Confidence intervals and asymptotic distribution were generated through nonparametric bootstrap with data from a field experiment conducted in Brazil. The parameters showed normal probability distribution for most scenarios. The rate constant for deoxyribonucleic acid (DNA) synthesis had a minimum increase of 156 % and the maximum of 389 %, compared to the original values and the maintenance requirement had a minimum increase of 126 % and maximum of 160 % compared to the original values. Lower limits of 95 % confidence intervals for the parameters related to maintenance and protein accretion rates were higher than the original estimates of the DGM, evidencing genetic differences of the Zebu crossbred animals in relation to the original DGM parameters.

ResumoO objetivo com este estudo foi avaliar a eficiência alimentar, qualidade da carne e digestibilidade dos nutrientes em 31 novilhas de corte mestiças durante 84 dias de confinamento. A relação volumoso:concentrado da dieta oferecidaad libitumfoi de 60:40 (EM= 2,73 Mcal/kg MS, PB= 11,90% MS). Baseado no consumo alimentar residual (CAR), os animais foram classificados em três grupos de eficiência alimentar: Alto CAR (média= 0,776; n = 9), médio CAR (média= -0,010; n = 11) e baixo CAR (média = - 0,624; n = 11). Novilhas alto CAR consumiram 4,56% a mais de MS diária comparadas à novilhas baixo CAR (P<0,05). O ganho médio diário não diferiu (P>0,05) entre animais de diferentes grupos de eficiência (1,40kg/dia). Não houveram diferenças para a digestibilidade dos nutrientes entre os grupos avaliados: MS (64,00%), PB (60,01%), EE (72,90%), FDN (54,80%) e CNF (78,91%). Não houveram diferenças entre alto e baixo CAR para peso ao abate (475,00 vs. 479,55kg), peso de carcaça quente (259,09 vs. 261,44kg), área do músculo Longissimus dorsi(LD) (69,02 vs. 68,11 cm2), espessura de gordura subcutânea (5,74 vs. 6,26cm), maciez (5,45 vs. 5,19kg), características sensoriais do músculo LD, coloração do músculo LD (intensidades L=40,47 a*=24,74 e b*=16,13) ou rendimento de cortes comerciais. Novilhas baixo CAR apresentaram similar qualidade de carcaça e carne à novilhas classificadas como alto CAR, entretanto novilhas baixo CAR apresentaram um menor consumo de MS (kg/d).

AbstractThis study aimed to evaluate feed efficiency and meat quality of 31 three-crossbred beef heifers during 84 days in a feedlot system. A 60:40 concentrate and sorghum silage ration on DM basis (ME = 2.73Mcal/kg of DM, CP = 11.90% DM) was fed ad libitum. Based on residual feed intake (RFI) calculations, the heifers were ranked in three groups of feed efficiency: High RFI (average mean = 0.776; n = 9), medium RFI (average mean = -0.010; n = 11), and low RFI (average mean = - 0.624; n = 11). High RFI heifers consumed 4.56% more DM per day than low RFI heifers (P <0.05). The ADG did not differ (P> 0.05) among RFI groups (1.40kg/day). No differences (P>0.05) were detected for digestibility of the nutrients: DM (64.00%), CP (60.01%), crude fat (72.90%), NDF (54.80%) and non-fibrous carbohydrate (NFC) (78.91%). There were no differences between low and high RFI groups for slaughter weight (475.00 vs. 479.55kg), hot carcass weight (259.09 vs. 261.44kg), Longissimus dorsi (LD) area (69.02 vs. 68.11 cm2), back-fat thickness (5.74 vs. 6.26 cm), shear force (5.45 vs. 5.19kg), sensorial traits of LD muscle, LD color (intensities L=40.47 a*=24.74 and b*=16.13) or commercial cuts yield. Low RFI heifers presented similar meat quality and carcass traits as high RFI heifers, however low RFI heifers consumed less DM (kg/d).

The objective was to evaluate the effect of weight, age and production efficiency of cows from genetic groups based on the calf weight at calving and at weaning. For a period of five years, data of 120 cows (60 Angus-Nellore (AN) and 60 Simmental-Nellore (SN)) at four to nine-years of age were evaluated. All cows were maintained on Brachiaria decumbens pastures, with two forage availability levels (high and low), distributed in a randomized-block design. The cows were placed together with Canchim bulls to generate the crossbred calves. A supplement, consisting of 200 g/kg crude protein and 820 g/kg of total digestible nutrients, was provided to the calves in creep feeding until 210 days-old (weaning). Supplement had a significant effect on the weight of the cow at calving and weaning. The average weights of the Angus-Nellore cows were 529.19 and 514.23 kg at calving and on the weaning day, respectively. These values were higher for Simmental-Nellore cows, which presented 569.60 and 542.59 kg, respectively. The male-calf weight at weaning was 254.69 kg, which was higher than the females (237.70 kg). Genetic group had no effect on weaning weight. The average weight for Canchim × Angus-Nellore calves was 243.41 kg and for Canchim × Simmental-Nellore it was 248.98 kg. Cow age affected weaning weight, promoting a linear increase of 0.804 kg in the weaning weight each year. Younger and smaller cows (Angus-Nellore) are more efficient for calf production.

To provide information that can contribute to the genetic evaluation and selection in Tabapuã cattle, genetic parameters were estimated for growth traits using a multi-trait animal model. (Co)variance components were estimated by a Bayesian approach using the Gibbs Sampler. Moderate and similar responses to selection are expected when selecting for weights at the four ages evaluated, since the direct heritability estimates were similar and of average magnitude (0.18 to 0.19). The direct and maternal additive genetic correlations between all pairs of weights were higher than 0.70, indicating a high degree of association between the four traits. This suggests that using any of them as selection criteria will result in correlated response in the others and that multi-trait analysis are recommended for the genetic evaluation of growth traits in beef cattle for exploiting this association.

The objective of the present study was to estimate the allelic and genotypic frequencies of the polymorphisms E2FB (AY138588.1: c.305C> T), located in the leptin gene (LEP), and TG5 (X05380.1:g.-422C>T), located in the thyroglobulin gene (TG), and evaluate the association of these polymorphisms in crossbred cattle of seven distinct genetic groups with the following traits: slaughter weight (SW), hot carcass weight (HCW), hot carcass yield (HCY), carcass fat thickness (CFT), ribeye area (REA), marbling (MARM) and shear force (SF). The animals were genotyped using the PCR-RFLP (Polymorphism Chain Reaction-Restriction Fragment Length Polymorphism) technique, using 201 products obtained from F1 Caracu × Nellore, Angus × Nellore and Valdostana × Nellore cows, mated to Canchim, Caracu and Red Angus bulls (only Caracu × Nellore cows were used with Red Angus bulls). The allelic and genotypic frequencies were compared using the Chi-squared test. Associations between the genotype of each polymorphism and the traits were analyzed using the General Linear Model (GLM) of statistical software SAS. The least squares means of genotypes of the polymorphisms were compared using Student's t test. The E2FB polymorphism in the LEP gene was associated with CFT, showing the potential for use in national programs for genetic improvement of beef cattle, through the inclusion of SNP in genotyping commercial tests. The TG5 polymorphism in the TG gene was not associated with any of the evaluated traits and was considered ineffective for selection of beef cattle in Brazilian herds.

The objective of the present study was to analyze models with genetic and/or residual heteroskedasticity for genetic evaluation of the weaning weight of Charolais-Zebu crossbred calves. Weaning weight data from 56,965 crossbred calves were analyzed using animal models with different combinations of genetic and residual heteroskedasticity and/or homoskedasticity. The inference on a posteriori distributions of genetic parameters were by the Monte Carlo method via Markov chains. The model with genetic and residual heteroskedasticity was the best fit on the data. Groups of animals with different genetic compositions, expressed as percentages of Charolais-Zebu breed alleles and individual and maternal heterozygosis, had different genetic variances. These genetic variances could be modeled by linear functions of the Charolais and Zebu genetic variances and the variance attributed to segregation. The breed compositions, the individual and maternal heterozygosis, the sex and age of dam at calving were significant sources of residual heteroskedasticity. The a posteriori means for heritabilities and sire and dam classifications were altered due to genetic and residual heteroskedasticity.

Este trabalho foi realizado com o objetivo de avaliar alternativas para modelagem de efeitos genéticos e ambientais que influenciam o peso à desmama de bezerros mestiços Charolês-Zebu. Foram utilizados os dados de peso à desmama de 56.965 bezerros, com percentuais de alelos de origem da raça Charolesa variando entre 23% e 66%. Os modelos considerados diferiram quanto à inclusão de efeitos genéticos aditivos e não-aditivos médios, individuais e maternos, bem como quanto à maneira de modelar estes efeitos (regressão múltipla ou variável classificatória). Também foi avaliada a inclusão da interação entre o grupo genético do bezerro e seu grupo de contemporâneos, como um efeito aleatório não correlacionado. De acordo com os critérios de ajuste utilizados, a interação entre o grupo genético e o grupo de contemporâneos representa parte significativa da variação observada para o peso à desmama de bezerros Charolês-Zebu e os efeitos dos percentuais de alelos de origem da raça Charolesa e de heterozigoses, individuais e maternos, podem ser modelados por meio da utilização de regressão múltipla.

This study was carried out to evaluate some alternatives for modeling of genetic and environmental effects influencing the weaning weight of Charolais-Zebu crossbred calves. The weaning weight data of 56,965 calves with alleles' percentage from the Charolais breed varying from 23% to 66% were used. The models under comparison differed for the inclusion of the individual and maternal additive and non-additive genetic effects, as well as the way to model those effects (multiple regression or discrete variable). The inclusion of the interaction between the calf genetic group and its contemporary group was also evaluated as a random uncorrelated effect. The adjustment criteria pointed out the interaction between the calf genetic group and its contemporary group to represent a significant part of the variation observed for the weaning weight of the Charolais-Zebu crossbred calves, and the effects of alleles' percentage from the Charolais breed and the heterozygosity, individual and maternal, can be modeled by using the multiple regression.

Os efeitos de ano e época de nascimento, propriedade, sexo do bezerro, regime alimentar, idade do bezerro e idade da vaca ao parto, os efeitos aditivos direto e materno da raça Charolesa e o efeito de heterose materna entre as raças Charolesa e zebu foram avaliados pelo método dos quadrados míninos sobre características de importância econômica, como peso, perímetro escrotal e escores visuais de conformação frigorífica, de umbigo e de pelame à desmama em bovinos da raça Canchim. Utilizaram-se dados de 12.334 animais Canchim nascidos de 1999 a 2005. O ano e a época de nascimento, a propriedade, o regime alimentar e a idade da vaca ao parto (linear e quadrático) tiveram efeitos significativos sobre todas as características estudadas. Houve efeitos do sexo sobre o peso do bezerro à desmama e o escore de umbigo; da idade do bezerro sobre peso, perímetro escrotal e escores de conformação frigorífica e de pelame; e das proporções de Charolês no bezerro e na mãe sobre o peso, a conformação frigorífica e a qualidade de pelagem; e da heterozigose materna sobre peso, perímetro escrotal e escores de conformação frigorífica e de umbigo. Os efeitos aditivos diretos da raça Charolesa como desvio do zebu foram negativos sobre peso, conformação frigorífica e qualidade da pelagem à demama, enquanto os efeitos aditivos maternos foram positivos. Os efeitos heteróticos maternos foram positivos sobre peso, perímetro escrotal e escores de conformação frigorífica e de umbigo. Em geral, essas fontes de variação devem ser consideradas nas estimativas de parâmetros genéticos e nas avaliações genéticas dos animais Canchim para as características estudadas.

The effects of calving year and season, property, sex of the calf, feeding regime, age of calf and age of dam at calving, maternal and direct additive effects of Charolais breed, and maternal heterosis effects among Charolais and zebu breeds were evaluated by the method of least squares on economical importance traits such as weight, scrotal circumference and visual scores for slaughter conformation, navel score and hair coat at weaning of the Canchim breed. Data from 12,334 Canchim calves born from 1999 to 2005 were used. Calving year and season, property, feeding regime and age of dam (linear and quadratic) had significant effects on all the studied characteristics. There were effects of sex on weaning weight and navel score; of age of the calf on weight, scrotal circumference and slaughter conformation and hair coat scores; and of proportion of Charolais on the calf and on the dam on weaning weight, and on scores of slaughter conformation and hair coat; and of maternal heterozygose on weight, scrotal circumference, slaughter conformation and navel scores. Additive direct effects of the Charolais as deviation of zebu were negative on weight, slaughter conformation and hair coat score at weaning, while the maternal additive effects were positive. Maternal heterotic effects were positive on weight, scrotal circumference, slaughter conformation and navel scores. In general, these sources of variation have to be taken into account on estimates of genetic parameters and on genetic evaluations of Canchim animals for the studied characteristics.

O objetivo deste trabalho foi estabelecer o modelo mais adequado para avaliação genética de bovinos Canchim e estimar os parâmetros genéticos de características produtivas à desmama. Foram utilizados dados de: 12.103 animais, quanto ao peso (PD); 5.278, quanto ao perímetro escrotal (PE); 8.343, quanto ao escore visual da conformação frigorífica (CF); 9.111, quanto ao escore de umbigo (UM); e 7.986, quanto ao escore de pelame (PEL). Os modelos estatísticos incluíram os efeitos fixos e os efeitos aleatórios genéticos aditivos direto, materno e de ambiente permanente materno, em diferentes combinações. As análises foram feitas pelo método da máxima verossimilhança restrita livre de derivadas. O modelo completo foi o mais adequado para PD, PE, CF e UM, enquanto o modelo com uso apenas dos efeitos genéticos aditivos direto e materno foi o mais adequado para PEL. As estimativas de herdabilidade direta foram 0,17, 0,13, 0,20, 0,18, e 0,52 para PD, PE, CF, UM e PEL, respectivamente, o que indica a possibilidade de se obter progresso genético por meio da seleção para essas características, principalmente para PEL. As correlações genéticas aditivas diretas entre as características variaram de -0,16 a 0,61. As correlações entre PD e PE e entre PD e CF indicam que a seleção para PD deve proporcionar ganho genético em PE e CF

The objective of this study was to establish the best-fit model for the genetic evaluation of Canchim cattle and to estimate the genetic parameters for productive characters at weaning. The data used were related to: 12,103 animals, for weight (PD); 5,278, for scrotal circumference (PE), 8,343, for slaughter conformation visual score (CF); 9,111, for sheath and navel scores (UM), and 7,986, for hair coat score (PEL). Statistical models included fixed effects and random additive direct, maternal and maternal permanent environmental effects, in different combinations. The analyses were done by the derivative-free restricted maximum likelihood method. The complete model was the most suited for PD, PE, CF and UM, while the model with only additive direct and additive maternal random effects was the best for PEL. Direct heritability estimates were 0.17, 0.13, 0.20, 0.18, and 0.52 for PD, PE, CF, UM and PEL, respectively, which indicates that it is possible to obtain genetic progress through selection for these traits, mainly for PEL. The additive direct genetic correlations among traits varied from -0.16 to 0.61. The correlations between PD and PE and between PD and CF indicate that selection for PD should result in genetic gain in PE and CF

Este trabalho foi realizado com o objetivo de avaliar alternativas para modelar a interação entre idade ao parto e grupo genético da vaca (GGV) sobre o peso à desmama de bezerros mestiços Charolês-Zebu. Dados de peso à desmama de 56.965 bezerros Charolês-Zebu foram analisados utilizando o método de quadrados mínimos. Foram estimados coeficientes de regressão para idade da vaca ao parto (IVP) dentro de cada grupo genético da vaca (modelo CLA); para IVP × fração esperada de alelos de origem da raça Charolesa na vaca (IVP × FCh) e IVP × fração esperada dos loci da vaca com um alelo proveniente da raça Charolesa e outro proveniente de raças zebuínas (IVP × FH) (modelo FChFH); para IVP × FCh (modelo FCh); para IVP × FH (modelo FH); ou apenas para IVP (modelo SINT). A forma geral do efeito da IVP sobre o peso à desmama foi modelada por polinômios segmentados com efeitos linear e quadrático gerais e quadráticos específicos, a partir de cada nó (6,33 e 10,66 anos). Os coeficientes de regressão foram estimados dentro de cada sexo do bezerro em todas as situações. De acordo com o teste F para redução da soma de quadrados do resíduo, a inclusão da interação IVP × FH não melhorou significativamente os ajustes e o modelo CLA foi o que melhor se ajustou aos dados. Contudo, para classes de GGV × sexo do bezerro com reduzido número de observações, o modelo CLA proporcionou estimativas inconsistentes para o efeito da interação IVP × GGV e o modelo FCh mostrou-se adequado. Para as classes de GGV × sexo do bezerro com grande número de observações, as diferenças entre as estimativas do efeito da interação IVP × GGV obtidas pelos modelos CLA e FCh foram de pequena magnitude.

The objective of this study was to evaluate alternatives for modeling the interaction between age of dam at calving (AOD) and the dam genetic group (DGG) on the weaning weight (W225) of Charolais-Zebu (Ch-Z) crossbred calves. Data from 56,965 crossbred calves were analyzed by the least square method. Regression coefficients for age of dam at calving were estimated nested into each class of the dam genetic group (CLA model); for age of dam at calving × dam Charolais percentage (age of dam at calving × FCh) and age of dam at calving × dam heterozygosity (age of dam at calving × FH) (FChFH model); for age of dam at calving × dam Charolais percentage (FCh model); for age of dam at calving × FH (FH model); or only for age of dam at calving (NINT model). Segmented polynomials were used to model the general shape of the age of dam at calving effect and its interaction with dam genetic group. The knots were at 6.33 and 10.66 years of age of dam at calving and general linear and quadratic coefficient regression and specific quadratic coefficient regression after each knot were fitted. The regression coefficients were estimated nested within sex of the calf in all situations. According to the F test for sum of squared residuals differences, the inclusion of the age of dam at calving × FH interaction did not improve the fit of the model and the CLA model provided the best fit. However, the estimates of the age of dam at calving and dam genetic group interaction from the CLA model for dam genetic group × sex of the calf classes with few records were not appropriate, but the estimates of the age of dam at calving and dam genetic group interaction from the FCh model for those classes were appropriate. The differences were small in the estimates of the age of dam of calving and dam genetic group interaction from the CLA or FCh models for dam genetic group × sex of the calf classes with many records.

O experimento foi realizado para avaliar o valor nutritivo da forragem, o desempenho e a conversão alimentar de novilhos em pastos de Panicum maximum Jacq. cv. Tanzânia submetidos a duas intensidades de pastejo rotativo (resíduos de 25 e 50 cm), associadas a intervalo de pastejo correspondente ao tempo necessário para que o dossel forrageiro interceptasse 95% da luz incidente durante a rebrotação. O delineamento experimental utilizado foi o de blocos completos casualizados, com duas repetições. Foram avaliados a altura do dossel pré-pastejo, os intervalos de pastejo, o ganho de peso individual, a conversão alimentar, a taxa de lotação e o ganho de peso por unidade de área. Pastos manejados com o resíduo 50 cm apresentaram maior número de ciclos de pastejo em relação àqueles manejados com resíduo de 25 cm. O maior ganho de peso médio diário foi registrado nos pastos manejados com 50 cm de resíduo (801 g/dia) em relação àqueles manejados com de 25 cm de resíduo (664 g/dia). Em contrapartida, a taxa de lotação foi mais alta nos pastos manejados com o resíduo 25 cm, fazendo com que os ganhos de peso por unidade de área fossem 601 e 559 kg/ha para os resíduos de 25 e 50 cm, respectivamente. O manejo do pasto visando altura de resíduo de 25 cm proporciona maiores ganhos de peso por unidade de área e maior uniformidade de produção e o resíduo de 50 cm promove maior ganho individual e maior número de ciclos de pastejo.

The objective of this experiment was to evaluate the nutritive value, animal performance and feed conversion of beef cattle steers grazing Panicum maximum Jacq. cv. Tanzania pasture subjected to intensities of rotational grazing. Treatments corresponded to two grazing intensities (post-grazing residues of 25 and 50 cm) associated with a grazing interval corresponding to the time necessary for a 95% canopy light interception (LI) condition during regrowth. A randomized complete block design was used, with two replications. The pre-grazing sward height, grazing interval, weight gain, stocking rate and weight gain per unit area were assessed. Pastures managed with 50 cm residue post-grazing condition resulted in a larger number of grazing cycles than the 25 cm residue. The highest daily average weight gain was observed in the pastures managed with 50 cm residue (801 g/.day) compared to those managed with 25cm residue (664 g/day). However, the 25 cm post-grazing condition allowed for higher of stocking rate values, resulting in 601 and 559 kg weight gain/ha for the 25 and 50 cm conditions, respectively. Grazing management with a post-grazing residue of 25 cm result in higher weight gain per unit area and a more stable pattern of animal performance while management with 50 cm residue result in higher individual performance and a larger number of grazing cycles.

Este trabalho foi realizado com o objetivo de avaliar alternativas para a modelagem do efeito da idade da vaca ao parto sobre o peso à desmama de bezerros mestiços Charolês-Zebu. Os dados de 56.965 bezerros foram analisados por meio de modelos estatísticos, considerando os efeitos fixos de grupo de contemporâneos, grupos genéticos do touro e da vaca e da idade da vaca ao parto. O efeito da idade da vaca ao parto foi modelado utilizando-se classes anuais de idade, polinômios ordinários (PO) de ordem quadrática até quíntica, ou polinômios segmentados com 2, 3, 4, 6 ou 12 intervalos do mesmo tamanho. No caso dos polinômios segmentados, consideraram-se os efeitos linear e quadrático gerais e apenas o quadrático a partir de cada nó. Os efeitos da idade da vaca ao parto foram considerados aninhados em sexo do bezerro em todos os casos. De acordo com os critérios de ajuste utilizados, ou seja, o teste F para diferenças de soma de quadrados, coeficiente de determinação do modelo, soma de quadrados do resíduo e média dos resíduos ao quadrado, o polinômio segmentado com três intervalos (dois nós) se ajustou tão bem aos dados quanto os polinômios mais complexos.

The objective of this study was to evaluate alternatives for modeling the age of dam at calving (AOD) effect on the weaning weight of Charolais-Zebu crossbred calves. Data from 56,965 calves were analyzed, using statistical models considering the fixed effects of the contemporary groups, sire and dam genetic groups, and AOD. The AOD effect was fitted to models using annual age classes, and ordinary quadratic to quintic-ordered polynomials (OP) or segmented polynomials (SP) with two, three, four, six and twelve evenly spaced intervals. In the case of segmented polynomials, general linear and quadratic effects and only one quadratic additional term from each knot were considered. The AOD effects were nested within sex of calf in all cases. According to the fitting criteria, the F-test for the reduction of residual sum of squares, coefficient of determination, residual sum of squares and mean of squared residuals, the three interval segmented polynomial (two knots) fitted to the data as well as the more complex polynomials.

O objetivo deste trabalho foi avaliar o desempenho em confinamento de tourinhos de quatro grupos genéticos distintos tratados com dietas com diferentes teores de gordura. Foram utilizados nove animais Nelore, nove Caracu, dez ½ Caracu ¼ Angus ¼ Nelore e dez ½ Red Angus ¼ Caracu ¼ Nelore, com massa corporal inicial de 227±33 kg e dez meses de idade, distribuídos aleatoriamente em dois tratamentos nutricionais: baixo teor de gordura (3,15% de extrato etéreo) e alto teor de gordura (7,28% de extrato etéreo). A ingestão de matéria seca (IMS) foi quantificada durante 208 dias e as pesagens dos animais foram realizadas a cada 28 dias. Os animais alimentados com as dietas de alto e de baixo teor de gordura apresentaram resultados similares de ganho médio diário de peso (1,511x1,487 kg por dia, respectivamente) e de eficiência alimentar (194x180 g de ganho por quilograma de MS ingerida, respectivamente); a IMS, em percentagem do peso vivo, foi menor nos animais alimentados com dieta de alto teor de gordura (2,25x2,40, respectivamente). Os animais cruzados apresentaram maior ganho de massa corporal e IMS que os Nelore. A dieta com alto teor de gordura pode ser utilizada em confinamento para melhorar o desempenho de tourinhos ½ Caracu ¼ Angus ¼ Nelore, pois é eficiente para reduzir a ingestão de matéria seca e não prejudica o ganho de massa corporal dos animais.

This work aimed to evaluate the feedlot performance of bullocks of four distinct genetic groups receiving diets with different levels of fat. Nine Nelore; nine Caracu; ten ½ Caracu ¼ Angus ¼ Nelore and ten ½ Red Angus ¼ Caracu ¼ Nelore bullocks, with a mean initial weight of 227±33 kg and ten months of age, were randomly assigned to two nutritional treatments and fed either with low-fat (3.15% ether extract) or high-fat diet (7.28% ether extract). Dry matter intake (DMI) was quantified during 208 days and the animals were weighed every 28 days. Animals fed with the high-fat and the low-fat diet presented similar results for average daily weight gain (1.511x1.487 kg day-1, respectively) and feed efficiency (194x180 g gain per kg DMI, respectively); the DMI, expressed as live weight percentage, was lower in animals receiving high-fat diet (2.25x2.40, respectively). Crossbred animals presented greater daily weight gain and DMI than Nelore. The high-fat diet can be used in feedlot to improve the performance of ½ Caracu ¼ Angus ¼ Nelore bullocks, since it is efficient in reducing the DMI without compromising weight gain.

O objetivo neste trabalho foi avaliar o comportamento ingestivo, o consumo e a eficiência de pastejo de novilhos em pastos de Panicum maximum Jacq. cv. Tanzânia submetidos a diversas intensidades de pastejo rotativo. Os tratamentos corresponderam a duas condições de pós-pastejo (25 e 50 cm) associadas a uma condição de pré-pastejo (95% de interceptação da luz incidente dossel forrageiro). O tempo de pastejo aumentou linearmente com o período de ocupação (475 a 630 minutos/dia). Em piquetes manejados com resíduo de 25 cm, a taxa de bocados aumentou linearmente ao longo do período de ocupação, com média de 42,5 bocados/minuto. Em piquetes manejados com resíduo de 50 cm, a taxa de bocados foi estável e igual a 39 bocados/minuto. Não houve diferença no consumo de forragem entre as intensidades de pastejo. No entanto, nos pastos manejados com 25 cm de resíduo, verificou-se maior remoção de forragem (68,0 vs 45,6%) e maior eficiência de pastejo (90,4 vs 49,8%) que naqueles manejados com 50 cm de resíduo. Resíduos pós-pastejo em capim-tanzânia sob lotação rotativa podem ser fixados em 25 ou 50 cm, pois o consumo de forragem não é afetado nessa amplitude de intensidade de pastejo. A remoção de forragem e a eficiência de pastejo são mais baixas nos pastos manejados com 50 cm de resíduo e o tempo de pastejo aumenta com longos períodos de ocupação dos piquetes.

The objective of this experiment was to evaluate the ingestive behaviour, herbage intake and grazing efficiency of beef cattle steers grazing on Panicum maximum Jacq. cv. Tanzania subjected to different rotational stocking intensities. Treatments corresponded to two post-grazing conditions (residues of 25 and 50 cm) associated with a pre-grazing condition of 95% sward canopy light interception during regrowth (LI). The grazing time increased linearly with the duration of the occupation period (475 to 630 minutes/day). On paddocks grazed down to a residue of 25 cm, the bite rate increased linearly along the occupation period, with an average of 42.5 bites/minute. On paddocks grazed down to a residue of 50 cm, the bite rate was stable and equal to 39 bites/minute. There was no difference in herbage intake between grazing intensities. However, grazing at 25 cm residue resulted in greater herbage removal (68.0 vs. 45.6%) and greater grazing efficiency (90.4 vs. 49.8%) than grazing at 50 cm residue. Post-grazing residues of Tanzania guineagrass under rotational stocking management may be set at either 25 or 50 cm, since the herbage intake was not affected within this grazing intensity range. However, herbage removal and grazing efficiency were reduced with the 50 cm post-grazing height and grazing time increased with long occupation periods.