Resumen El objetivo del estudio fue determinar el efecto del tipo y la intensidad de utilización de pasto buffel cultivado en condiciones naturales de lluvia o riego en la producción y valor nutritivo de la materia seca. Dieciséis parcelas (cada una de 64 m2) fueron pastoreadas por ganado Charolais para obtener una intensidad de utilización del 50 % (G50%) o de 75 % (G75%). Ocho parcelas (40 m2 cada una) se recortaron a mano hasta 50 % (H50%). La cosecha anual de forraje fue mayor (P<0.05) para G50 que para H50 (1,491 vs 954 kg de MS/ha). No se encontraron diferencias (P>0.05) en la producción de materia seca por hectárea entre G50 y G75 (1,707 vs 954 kg de MS/ha). El riego aumentó un 22 % (P<0.05) la producción de materia seca comparado con secano (1,524 vs 1,245 kg de MS/ha). No se encontraron diferencias (P>0.05) debido al tipo y la intensidad de utilización en el contenido de PC, NDF y ADF, sin embargo, la ADF aumentó (P<0.05) en las parcelas irrigadas. De la misma manera la digestibilidad in vitro de la MS fue mayor (P<0.05) en H50 que en las parcelas de pastoreo G50 y G75 (55.7, 53.0 y 52.7%). Se concluye que la producción de zacate buffel se incrementó con el pastoreo, pero la DIVMS fue mejor en el forraje recortado manualmente.

Abstract This study aimed to determine the effect of the type and intensity of utilization of buffelgrass grown under natural rainfall or irrigation conditions on the production and nutritional value of the dry matter. Sixteen plots (64 m2 each) were grazed by Charolais cattle to obtain a utilization intensity of 50 % (GR 50) or 75 % (GR 75). Eight plots (40 m2 each) were hand-cut up to 50 % (CU 50). The annual forage harvest was higher (P≤0.05) for GR 50 than for CU 50 (1,491 vs 954 kg DM/ha). No differences (P≥0.05) were found in dry matter production per hectare between GR 50 and GR 75 (1,707 vs 1,491 kg DM/ha). Irrigation increased dry matter production by 22 % (P≤0.05) compared to rainfed conditions (1,524 vs 1,245 kg DM/ha). There were no differences (P>0.05) due to the type and intensity of utilization in the content of CP, NDF, and ADF; however, ADF increased (P≤0.05) in irrigated plots. In the same way, the in vitro digestibility of DM was higher (P≤0.05) in CU 50 than in grazing plots GR 50 and G75 (55.7, 53.0, and 52.7 %). Finally, it can be conclude that buffelgrass production increased with grazing, but the IVDDM was better in hand-cut forage.

ABSTRACT Background: The level of accumulated caloric load of the ITH (CCA) during the 6 months prior to weaning on the weaning weight (PD) was evaluated in Charolais animals as an expression of thermal stress (ST), as well as its possible genetic component. Methods: 19,466 PD records from the Manuel Fajardo Enterprise, Jiguaní, Granma, born between 1988 and 2017 in 16 herds, were analyzed. A Reaction Norm model was used considering a fixed effect of quarters-years-herds (859 classes), sex of the calf (2) and number of calving of the mother (11), a fixed covariate using a Legendre polynomial (L) of order 3 to represent the PD response curve in the CCA trajectory. As random: residual and the deviation of the animal that produces the record that was modeled by an L of order 1. With the standardized genetic values (VG) a principal components analysis was done and with the eigenvector coefficients an index of the results. Results: The regression analysis showed that PD is depressed by b=-0,807±0,04 kg per unit of CCA (R2=90,2%). 3 zones were differentiated: cold CCA<=439; neutral CCA>=440 to <=450 and hot CCA>=451, with PD= 149,3; 140,5 and 134,1 kg respectively. The variation in VG is greater in the cold zone, but the correlations were very low (0,33), evidencing genotype-environment interaction (Ige). Conclusions: The existence of a genetic basis for tolerance to ST with Ige manifestations was demonstrated, and the order of merit changes in extreme conditions.

RESUMEN Antecedentes: El nivel de carga calórica acumulada del ITH (CCA) durante los 6 meses previos al destete sobre el peso al destete (PD), fue evaluado en animales Charoláis como expresión de stress térmico (ST), así como su posible componente genético. Métodos: Se analizaron 19 466 registros de PD de la Empresa Manuel Fajardo, Jiguaní, Granma, nacidos entre 1988 y 2017 en 16 rebaños. Se utilizó un modelo de Norma de Reacción considerando efecto fijo cuatrimestres-años-rebaños (859 clases), sexo del ternero (2) y número de partos de la madre (11), una covariable fija mediante un polinomio de Legendre (L) de orden 3 para representar la curva de respuesta del PD en la trayectoria de CCA. Como aleatorios: residuo y la desviación del animal que produce el registro que se modeló por un L de orden 1. Con los valores genéticos estandarizados (VG) se hizo un análisis de componentes principales y con los coeficientes de los eigenvector se construyó un índice de los resultados. Resultados: El análisis de regresión arrojó que el PD se deprime en b=-0,807±0,04 kg por unidad de CCA (R2=90,2%). Se diferenciaron tres zonas: fría CCA<=439; neutra CCA>=440' a <=450 y caliente CCA >=451, con PD= 149,3; 140,5 y 134,1 kg respectivamente. La variación en VG es mayor en la zona fría, pero las correlaciones fueron muy bajas (0,33) evidenciando interacción genotipo ambiente (Ige). Conclusiones: Se demostró existencia de una base genética para tolerancia a ST con manifestaciones de Ige, y cambia el orden de mérito en condiciones extremas.

Resumen Se estimó la exactitud de la predicción (EP) de valores genómicos estimados (GEBV) para variables de peso vivo de ganado Charolais utilizando dos métodos de validación cruzada. Se ajustó un modelo BLUP y diferentes métodos de predicción genómica (PG) Genomic-based best linear unbiased prediction (GBLUP), Bayes C (BC) y Single-step Bayesian regression (SSBR). La EP fue comparada mediante grupos de validación (GV) formados aleatoriamente y mediante GC. Los resultados mostraron que los tres métodos de PG proporcionaron exactitudes de predicción similares entre los GV pero no exactitudes de predicción superiores a BLUP. La exactitud de predicción de GBLUP y BLUP fue 0.35 y 0.37 para PN, y de 0.30 y 0.41 para PD, respectivamente. Los resultados muestran bajas exactitudes de PG bajo los escenarios evaluados; por lo que para su correcta implementación es necesario incrementar el número de animales y usar valorees genéticos desregresados como variables de respuesta.

Abstract The accuracy of the estimation (AE) of the genomic breeding values (GEBV) of live weight traits of registered Charolais cattle using two cross validation methods was assessed. A BLUP model and different genomic prediction (PG) methods were fitted: Genomic-based best linear unbiased prediction (GBLUP), Bayes C (BC) and Single-step Bayesian regression (SSBR). AE was compared using randomly formed validation groups (VGs) and CGs. The results showed that all three PG methods provided similar prediction accuracies among GVs but not higher prediction accuracies than BLUP. The prediction accuracy of GBLUP and BLUP was 0.35 and 0.37 for PN, and 0.30 and 0.41 for PD, respectively. The results show that the PG accuracies under the evaluated scenarios are low; Therefore, for its correct implementation, it is necessary to increase the number of animals and use de-returned genetic values as response variables.

Abstract This study aimed to investigate the feasibility of using ground soybean hulls and white oat grains to finish steers reared exclusively on concentrated feed. We used 33 steers, predominantly of Charolais or Nellore breeds, and randomly assigned the animals to the treatments, blocking them according to genetic predominance. The diets were isonitrogenous, and the treatments consisted of soybean hulls, white oats, and mix these in equal parts, supplemented with calcitic limestone and a protein nucleus. The study measured variables related to the dry matter intake (DMI) and bromatological fractions of diets, as well as performance of steers. No significant differences were observed between treatments in terms of DMI during the experimental period. Although DMI intake was similar across treatments, steers receiving the mixed diet exhibited significantly higher weight gain than those on the soybean hull diet (1.300 vs. 0.972 kg day-1). However, both these treatments showed comparable results to the white oat grain diet (1.203 kg day-1), achieving a similar final weight (387.22 kg). Implementing 100% concentrate diets is technically feasible for steers fed with white oat grain and the mixture of soybean hull and white oat grain, which also demonstrated superior performance compared to the soybean hull treatment. feed 3 breeds predominance isonitrogenous oats parts nucleus (DMI period 1.300 1300 1 300 (1.30 vs 0972 0 972 0.97 day1. day1 day . day-1) However 1.203 1203 203 (1.20 day1, , 387.22 38722 387 22 (387.2 kg. kg) 100 treatment 1.30 130 30 (1.3 097 97 0.9 day-1 1.20 120 20 (1.2 387.2 3872 38 2 (387. 10 1.3 13 (1. 09 9 0. day- 1.2 12 387. (387 1. (1 (38 ( (3

Abstract The objective of this study was to evaluate the effect of different levels of concentrate supplementation on carcass characteristics of heifers finished on Tifton 85 pasture. Thirty-two cross-breed heifers (Charolais and Nellore) on average aged 25.51 months and weighing 298 kg were used in a completely randomized experiment. The animals were distributed uniformly to receive four different levels of concentrates based on the body weight: 0.0; 0.4; 0.8 and 1.2%. Animals were slaughtered at 29 months of age. There was increasing linear effect of levels energy supplementation on: slaughter weight, hot and cold carcass weights,hot and cold dressing percentage, thigh thickness, carcass compactness, and L* and b* color values. It was observed quadratic effect of levels of energy supplementation on the percentage of fat in the carcass. Different levels of energy supplementation did not modify the accumulation of vital organs and visceral fat or the sensory attributes of the meat. Higher levels of energy supplementation promote increases in carcass traits of heifers when finished on Tifton 85 pasture.

Resumen: Se observaron desgarros y desprendimientos de piel en un ternero recién nacido, luego de la revisión umbilical. El diagnóstico presuntivo de dermatosparaxis se realizó con base en la anamnesis y los signos clínicos típicos de la enfermedad, como alta fragilidad y desprendimientos totales de fragmentos de piel. Para la confirmación se realizaron estudios histopatológicos mediante tinciones HE, PAS y tricrómica de Masson sobre muestras de piel del animal afectado, usando como control muestras de piel de la misma región de un animal sano de igual edad y cruza, proveniente del mismo establecimiento de origen. Se complementó el diagnóstico con técnicas moleculares mediante la extracción de ADN, PCR y electroforesis. Finalmente, los resultados histopatológicos confirmaron compatibilidad con la enfermedad de colágeno planteada. No se pudo comprobar que la mutación fuera la misma ya descrita en bovinos. Según lo investigado, este es el primer reporte de dermatosparaxis en esta especie en Uruguay.

Abstract: Tears and skin detachments were observed in a newborn calf after umbilical revision. The presumptive diagnosis of Dermatosparaxis was based on the anamnesis and the typical clinical signs of the disease, such as high fragility and total detachment of skin fragments. Three staining techniques (HE, PAS and Masson’s trichrome) were performed on skin samples from the affected animal, using skin samples from the same region of a normal animal with the same age and crossbreed, and from the same ranch used as control. The diagnosis was complemented with molecular techniques through DNA extraction, PCR, and electrophoresis. Finally, the histopathological results confirmed compatibility with this collagen disease. It could not be possible to confirm that the mutation was the same described in other cases of this clinical disease in cattle. As investigated, this is the first Dermatosparaxis report in calves in Uruguay.

Resumo: Pele rasgada e descamação foram observadas em um bezerro recém-nascido após revisão umbilical. O diagnóstico presuntivo de Dermatosparaxia foi feito com base na anamnese e nos sinais clínicos típicos da doença, como alta fragilidade e descolamento total de fragmentos de pele. Para confirmação, foram realizados estudos histopatológicos por meio das colorações HE, PAS e tricrômico de Masson em amostras de pele do animal afetado, utilizando como controle amostras de pele da mesma região de um animal sadio da mesma idade e cruzamento, do mesmo estabelecimento de origem. O diagnóstico foi complementado com técnicas moleculares por meio de extração de DNA, PCR e eletroforese. Por fim, os resultados histopatológicos confirmaram a compatibilidade com a doença do colágeno proposta. Não foi possível verificar que a mutação era a mesma já descrita em bovinos. De acordo com o que foi investigado, este é o primeiro relato de Dermatosparaxis nesta espécie no Uruguai.

Resumen La restricción de la ingesta de nutrientes por parte de las vacas de carne durante la gestación puede influir en el potencial de crecimiento posparto de la progenie, por lo que el objetivo del presente estudio fue evaluar los efectos de la restricción nutricional y de la nutrición adecuada o la sobrealimentación durante el último tercio de la gestación de las vacas cruzadas (Charolais x Nellore) criadas en el bioma pampeano, sobre el rendimiento productivo de la progenie hasta los 15 meses de edad. Ochenta y tres (83) vacas se dividieron en tres tipos de tratamiento: vacas de control en pastos naturales bajo restricción nutricional (RES); suplementación para satisfacer el 100 % de las necesidades (REQ); suplementación por encima de las necesidades (ALTO). Los terneros nacidos de vacas con tratamiento REQ y ALTO tuvieron un mayor peso corporal al nacimiento que los terneros de las vacas con tratamiento RES (39.28, 39.13 vs 34.58 kg), sin que esto haya influido en el rendimiento postnatal. Las hembras de las vacas con tratamiento REQ y ALTO presentaron un mejor rendimiento postnatal y, en consecuencia, un mayor peso a los 12 meses de edad en comparación con las crías de las vacas con tratamiento RES (300.71 y 311.79 frente a 259.47 kg). Estos terneros alcanzaron el 60 % del peso adulto temprano (358 y 345 vs 405 d) y tuvieron un mayor porcentaje de reproducción a los doce meses de edad (73.98 y 84.08 vs 34.08 %) que las hembras nacidas de las vacas con tratamiento RES. La suplementación de las vacas para satisfacer el 100 % de las necesidades, así como la sobrealimentación durante el último tercio de la gestación, mejora el rendimiento de las crías a los doce meses de edad, y los machos y las hembras responden de forma diferente a los insultos nutricionales de la madre durante este periodo.

Abstract The restriction of nutrient intake by beef cows during pregnancy may influence the progeny postpartum growth potential, therefore, the objective of the present study was to evaluate the effects of nutritional restriction and adequate nutrition or overfeeding during the final third of gestation of the crossbred cows (Charolais x Nellore) kept in the Pampa biome, on the productive performance of the progeny up to 15 mo of age. Eighty-three (83) cows were divided into: control cows on natural pasture under nutritional restriction (RES); Supplementation to meet 100 % of requirements (REQ); Supplementation above requirements (HIGH). REQ and HIGH calves had higher body weight at birth compared to calves from RES cows (39.28, 39.13 vs 34.58 kg), without influences on postnatal performance. Females from REQ and HIGH cows presented better postnatal performance and consequently higher weight at 12 mo of age in compared to offspring RES cows (300.71 and 311.79 vs 259.47 kg). These female calves reached 60 % of early adult weight (358 and 345 vs 405 d) and had a higher percentage of breeding at twelve months of age (73.98 and 84.08 vs 34.08 %) than females from RES cows. Supplementing cows to meet 100% requirements, as well as overfeeding during the final third of gestation, improves offspring performance at twelve months of age, with males and females responding differently to maternal nutritional insults during this period.

ABSTRACT: Heterosis plays an important role on yield and profitability of beef production systems. This study evaluates the morphometrics of purebred Nellore (N) and Charolais (C) animals and of the second (G2) and third (G3) generations of their alternating crosses, regarding the effects of genetic group and heterosis from birth to 365 days of age. The experiment comprised 159 calves (C = 29, N = 22, G2 - 3/4C 1/4N = 21, 3/4N 1/4C = 9, G3-5/8C 3/8N = 44 and 5/8N 3/8C = 34). The foreshank girth (FG), thoracic girth (TG), body length (BL), and hip height (HH) were measured after birth, and at 63, 210, and 365 days of age, and the total increases were calculated. The Charolais animals had greater FG, TG, and BL values than Nellore, while the latter had greater HH. For the offspring generations, the predominance of Charolais genes in the genotypes resulted in greater measurements for FG and TG in G2, whereas the predominance of Nellore genes resulted in higher HH values in both generations. The crossbred animals had greater values for all measurements than the purebreds, with more significant differences in FG, TG, and BL compared to Nellore purebreds and in HH compared to Charolais. Charolais animals show higher values for muscularity; while, Nellore animals are taller. Crossbred animals show greater development compared to purebreds, indicating a significant effect of heterosis.

The study investigated the effect of crossbreeding Charolais bulls with Nguni cows on carcass and lean yield and meat quality characteristics. The intact Charolais bulls (n=10) served as control group against the Charolais x Nguni (n=10). The Nguni dam proved a good option for a dam line because of the hardiness of the breed, its mothering ability, ease of calving, and low maintenance cost. In contrast, the Charolais had excellent growth and carcass characteristics. It was a late maturing breed with better growth performance and higher yields than Charolais x Nguni, which could be classified as a medium maturing beef breed. Over the same duration and conditions of feeding the Charolais calves had better feed conversion and growth rates and produced larger carcasses than Charolais x Nguni calves. Owing to the large difference in carcass size, the Charolais had better meat to bone ratio than the Charolais x Nguni (P <0.001). Both breeds produced meat with a desirable appearance and good eating quality and no differences were recorded in the related traits. It could be concluded that Charolais and Charolais x Nguni weaned calves were well suited to the grain-fed market and would produce meat of acceptable quality.

The aim of this study was to evaluate the effects of various dietary energy levels on the carcass and meat characteristics of feedlot-finished steers. A total of 27 purebred and crossbred Charolais and Nellore steers were used, with a mean initial age of 22 months and weight of 253 kg. The animals were allotted to a completely randomized design with three treatments and nine replicates each. Dietary treatments were arranged so that the average forage to concentrate ratio (FCR) was equivalent to that of a constant FCR treatment. The treatments consisted of CT (constant FCR at 60 to 40), CT5 (starting with 70: 30 FCR and finishing with 50: 50 FCR, that is, a mean overall FCR of 60: 40), and CT10 (starting with 80: 20 FCR and finishing with 40: 60, that is, a mean overall FCR of 60: 40). The dietary treatments did not affect slaughter weight, carcass weight, carcass conformation, physiological maturity, subcutaneous fat thickness, ribeye area, marbling score, and carcass measurements or the yield of commercial cuts. Chilling loss was higher in CT10 steers (2.41%) than in CT (2.26%) and CT5 (2.15%).

Resumen El objetivo fue presentar resultados de investigación sobre mejoramiento genético de bovinos productores de carne realizados por el Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, así como los retos y perspectivas de investigación a corto, mediano y largo plazo en dicha área del conocimiento. Se utilizaron tesis de maestría, trabajos de congresos y artículos científicos publicados de 1987 a 2020. En los últimos 34 años, se logró caracterizar productiva y reproductivamente animales Bos indicus y Bos taurus x Bos indicus en condiciones tropicales, implementar evaluaciones genéticas multirraciales para las poblaciones Simmental-Simbrah y Charolais-Charbray, determinar la importancia de los efectos maternos en características de crecimiento y estimar la heredabilidad y correlaciones genéticas para características de crecimiento y reproductivas de machos y hembras en animales Bos taurus y Bos indicus, comprobar que la interacción genotipo-ambiente es un factor importante en la expresión de peso al destete en Simmental, desarrollar factores de ajuste de edad de la madre para pesos al nacimiento y destete, desarrollar un prototipo de evaluación genética nacional para permanencia productiva y otro para fertilidad de vaquillas, estimar la diversidad genética de las poblaciones Simmental, Charolais y Simbrah, e identificar SNP asociados a características de crecimiento en Simmental y Simbrah. En el corto plazo, se espera desarrollar índices de selección y predecir el mérito genético de características de canal; en el mediano, realizar evaluaciones genómicas para tolerancia al estrés calórico, consumo de alimento residual y características de salud; y a largo plazo, realizar predicciones genómicas a través de razas.

Abstract The National Institute of Forestry, Agricultural and Livestock Research in Mexico has been active for decades in researching genetic improvement in beef cattle. This review uses master theses, congress papers and scientific articles published from 1987 to 2020 to summarize much of the relevant research, and addresses research challenges and outlook over the short-, medium- and long-term in this area. Research done over the last 34 yr has evaluated the productive and reproductive performance of Bos indicus and Bos taurus x Bos indicus beef cattle raised under tropical conditions. Multibreed genetic evaluations have been done for Simmental-Simbrah and Charolais-Charbray populations in Mexico. Analyses have quantified the importance of maternal effects on growth traits, and estimated heritability and genetic correlations for growth and reproductive traits in male and female Bos taurus and Bos indicus animals. The genotype-environment interaction has been confirmed to influence expression of weaning weight in Simmental cattle. Age adjustment factors have been developed for maternal age for weights at birth and weaning, and prototypes of national genetic evaluation were developed for stayability and heifer fertility. Genetic diversity has been quantified for Simmental, Charolais and Simbrah populations, and SNPs identified that are associated with growth traits in Simmental and Simbrah populations. Short-term goals include development of selection indices and prediction of the genetic merit of carcass traits. Over the medium-term, emphasis is needed on genomic evaluations for tolerance to heat stress, residual feed intake and health traits, while in the long-term the goal is to make inter-breed genomic predictions.

Resumen El objetivo del estudio fue analizar las frecuencias alélicas de 28 Polimorfismos de un solo nucleótido (SNP) localizados en genes candidatos para crecimiento en bovinos, así como determinar su efecto sobre rasgos de peso vivo en hatos de las razas Charolais y Simmental. Se tomaron muestras de pelo de 313 animales provenientes de cinco hatos ubicados en cuatro municipios de Tamaulipas y se genotipificaron con la tecnología de Sequenom Mass Array. Todos los marcadores resultaron ser polimórficos en las poblaciones evaluadas y sus frecuencias alélicas fueron significativamente diferentes entre razas (P<0.05). El análisis de asociación determinó que en los animales de la raza Charolais, el marcador PRL+2723 tiene un efecto significativo (P=0.0350) sobre el peso al nacimiento y el marcador localizado en el gen GHR (GHR-6.1), sobre peso al destete (P=0.0226). El GHR-6.1 también se asoció con el peso al año en los animales de la raza Simmental. El marcador LEP-3100 (P=0.0249) también tuvo un efecto significativo sobre el peso al destete en los animales Simmental. El panel probado es polimórfico en las dos razas evaluadas y tres de los marcadores tuvieron efecto significativo en los parámetros de peso vivo evaluados, por lo que tienen el potencial de validarse y usarse como una herramienta adicional en la selección y mejoramiento genético del ganado de carne en Tamaulipas.

Abstract A full understanding of how specific genes affect live weight variables is required for their incorporation into genetic improvement programs. An analysis was done of the allelic frequencies of 28 single nucleotide polymorphisms (SNP) located in candidate genes for growth in cattle to identify their effect on live weight traits in Charolais and Simmental herds in the state of Tamaulipas, Mexico. Hair samples were collected from 313 animals and genotyped using the Sequenom MassARRAY system. Genotype analysis showed that all the markers were polymorphic in the evaluated populations and their allelic frequencies were significantly different between the two breeds (P<0.05). An association analysis found that in the Charolais population the marker PRL + 2723 had a significant effect (P= 0.0350) on birth weight and the marker GHR-6.1 affected weaning weight (P= 0.0226). In the Simmental population GHR-6.1 was associated with yearling weight and the marker LEP-3100 (P=0.0249) had a significant effect on weaning weight. The tested 28 SNP panel is polymorphic in both breeds and three of the markers had a significant effect on the evaluated live weight parameters. They can therefore be potentially validated for use as tools in the selection and breeding of beef cattle in Tamaulipas.

Resumo: O objetivo deste trabalho foi avaliar o efeito do grupo genético e da heterose na relação entre peso corporal e medidas morfométricas, em bezerros puros e mestiços das raças Nelore e Charolesa de segunda (G2) e terceira (G3) gerações. Peso corporal (PC), ganho de peso médio diário (GMD), circunferência da perna dianteira (CPD), circunferência torácica (CT), comprimento corporal (CC) e altura da garupa (AG) foram medidos ao nascimento e aos 63, 210 e 365 dias de idade, nos animais de G2 e G3. Os animais da raça Charolesa foram superiores aos da Nelore quanto aos ganhos de PC, GMD, CC e CT, e para a razão entre o ganho de PC e o de AG; os animais Nelore foram superiores quanto aos ganhos de AG. Animais mestiços de ambas as gerações foram superiores aos animais puros quanto aos ganhos de PC, CC e AG. Na G2, a predominância dos genes da raça Charolesa resultou em maiores ganhos de PC, GMD, CPD e CT. Os animais da G3 foram superiores aos puros quanto a GMD, CPD e CT. Não se encontraram diferenças na proporção entre os ganhos nas medidas de peso e morfometria. Heterose e complementaridade são aparentes para as medidas de peso e corporais de bezerros mestiços de cruzamentos rotacionais.

Abstract: The objective of this work was to assess the effect of genetic group and heterosis on the relationship between body weight and morphometric measurements, in purebred and crossbred animals from the second (G2) and third (G3) generations of Nellore and Charolais calves. Body weight (BW), average daily weight gain (ADG), foreleg circumference (FC), thoracic girth (TG), body length (BL), and croup height (CH) were measured at birth and at 63, 210, and 365 days of age in animals from G2 and G3. Charolais animals were superior to Nellore ones for gains BW, ADG, BL, and TG, as well as for the ratio between BW gain and CH gain; Nellore animals were superior for CH gains. Crossbred animals of both generations were superior to the purebred animals for gains of BW, BL, and CH. In G2, the predominance of Charolais genes resulted in greater gains of BW, ADG, FC, and TG. The G3 animals were superior to the purebred animals for ADG, FC, and TG. No differences were found for the ratio between gains of weight and morphometric measurements. Heterosis and complementarity are apparent for weight and body measurements of crossbred calves from rotational crossings.

Resumo O objetivo desta pesquisa foi mensurar o comportamento ingestivo de novilhos terminados exclusivamente com concentrado contendo casca do grão de soja (moída) e/ou grão de aveia branca. Foram utilizados 32 novilhos, com predominâncias raciais Charolês ou Nelore. Os animais foram distribuídos ao acaso nos tratamentos, bloqueados conforme predominância genética e alocados em baias individuais. As dietas foram isonitrogenadas, sendo os tratamentos: Casca do grão de soja; Grão de aveia branca e a Mistura (partes iguais), acrescidos de calcário calcítico e núcleo proteico. Os animais que receberam dieta à base de casca de soja permaneceram mais tempo em ócio, comparados aos que receberam a mistura; estes, por sua vez, permaneceram mais tempo em ócio em relação aos que tiveram acesso à dieta à base de aveia branca. Os novilhos que consumiram dieta à base de casca de soja ruminaram menos tempo que os da mistura e estes, por sua vez, menos tempo que os novilhos alimentados à base de aveia branca. Dietas exclusivamente com concentrado à base de casca de soja, embora apresentem elevado teor de fibra solúvel em detergente neutro, não são suficientes para promover adequado comportamento ingestivo de novilhos de predominância racial Charolês ou Nelore.

Abstract The objective of this research was to measure the ingestive behavior of steers finished exclusively with concentrate containing soybean hulls (ground) and/or white oat grain.We used 32 steers with Charolais or Nellore predominance.The animals were randomly distributed in the treatments, blocked according to genetic predominance, and allocated in individual pens. Diets were isonitrogenous, being the treatments: Soybean hulls; White oat grain or the Mixture (equal parts), plus limestone and protein nucleus. Steers that received the diet based on soybean hulls remained more time in idle compared to the ones that received the mixture, and these remained more time in idle than the steers that received the diet based on white oat grain. Steers that received the diet based on soybean hulls ruminated less time than the steers fed the mixture, and these less time than those fed white oat grain. Exclusively concentrate diets based on soybean hulls although presenting high soluble fiber content in neutral detergent, are not sufficient to promote an appropriate ingestive behavior of steers of Charolais or Nelore racial predominance.

ABSTRACT The objective was to evaluate factors that influence calving probability in the first and second reproductive years of beef heifers that reached the minimum recommended body weight (BW) in the first breeding season. Two hundred twenty-seven 24-month-old Charolais × Nellore heifers that mated between 2003 and 2012 were analyzed. The parameters evaluated were: year effect; individual and maternal heterozygosis; percentage of Charolais genotype; average daily gain (ADG) from weaning to the end of the first breeding season; BW at 18 and 24 months of age, end of breeding season, parturition, and weaning; Julian date of calving; and adjusted calf weight at weaning. These variables were subjected to logistic regression. Calving rates in the first and second reproductive years were 58.1 and 49.5%, respectively. Performance until the end of the first breeding season, BW before the first breeding season, and individual heterozygosis affected the calving probability in the first breeding season. In the second breeding season, BW variation from the first breeding season and calving, Julian date of calving, and BW at the end of the second breeding season influenced calving probability. Until the end of the first breeding season, ADG of beef heifers responded positively to the calving probability, even after reaching the usually recommended BW for the first breeding season. Primiparous cows calving at the beginning of the breeding season and gaining more BW between the first and second breeding season are more likely to give birth in the second breeding season.