ABSTRACT The main objective of this study was to evaluate the effects of phenotypic, genotypic, and auction characteristics that may influence the selling prices of bulls. Data from 1,540 Braford and 1,179 Brangus bulls sold at auctions in the state of Rio Grande do Sul, Brazil, were collected and evaluated individually. Body condition score (BCS), muscularity, frame, foreskin size, presence or absence of horns, and data regarding the auction such as name/venue, event edition, forms of payment, among others, were considered. Information such as weight at the time of sale, scrotal circumference (SC), expected profit differences, selection indexes, and date of birth were collected from the catalogs supplied at the auctions. To obtain the influence of the selected explanatory variables throughout the conditional distribution of bull prices, a quantile regression was used, and the quantiles were established as follows: 10th, 25th, 50th, 75th, and 90th. The buyers of Braford and Brangus bulls valued characteristics such as age, weight, and SC in relation to frame, muscularity, BCS, and foreskin size. In addition, the price behavior at different auctions was positively related to the operation time of the auction in this market and with the reputation of the seller. Regarding genetic variables of Brangus bulls, these had little or no influence on the selling price. There was a positive influence on the weaning index in the 90th quantile and on the final index in the 50th and 75th quantiles. Buyers of synthetic bull breeds at auctions value the phenotypic characteristics of bulls more than they do genetic characteristics, which may not reflect permanent gains in the cattle herd.

Resumen Este estudio compara el desempeño técnico y financiero de diferentes sistemas de producción de ganado para carne y evalúa la comercialización oportunista practicada en estos sistemas. Se evaluaron datos de cuatro unidades de producción ubicadas en el sur de Brasil: vaca-cría en pastos nativos (VCPN; 1,155 ha; 1,529 animales); vaca-cría con agricultura (VCA; 1,008 ha; 1,313 animales); recría-engorda (URE; 360 ha; 435 animales); y engorda (UE; 205 ha; 168 animales) así como un sistema integrado que simula los parámetros físicos y económicos de las cuatro unidades (SIA; 2,728 ha; 3,445 animales). Las cuatro unidades independientes fueron consideradas como de comercialización oportunista y el SIA como no oportunistas. El mayor rendimiento se obtuvo para URE (297 kg/ha), seguido de SIA (114 kg/ha), UE (98 kg/ha), VCPN (87 kg/ha) y VCA (83 kg/ha). La VCPN fue la más económicamente eficiente, considerando el margen bruto por kilogramo (MB/kg) (US$ 0.93). El valor del MB/kg del SIA (US$ 0.74) fue un 37 % superior en comparación con la suma del promedio de las cuatro unidades (US$ 0.54), y el SIA tuvo los costos totales de producción por kg más bajos (22.5 %). Se llegó a la conclusión de que cada unidad independiente podría aumentar el MB/kg (37 %) y el MB/ha (3.8 %) y utilizar crías en una unidad de recría-engorda para su posterior venta. Por lo tanto, la integración de los sistemas de producción de carne de res aumenta el margen bruto de las empresas, presentando una ventaja comercial rentable para los empresarios rurales a través de la comercialización no oportunista.

Abstract This study compares the technical and financial performance of different beef cattle production systems and assesses the opportunistic commercialization practiced in these systems. It was evaluated data from four production units located in southern Brazil: cow-calf in native pastures (CCNP; 1,155 ha; 1,529 animals); cow-calf with agriculture (CCA; 1,008 ha; 1,313 animals); rearing-fattening (RFU; 360 ha; 435 animals); and fattening (FU; 205 ha; 168 animals) as well as an integrated system simulating the physical and economic parameters of the four units (IAS; 2,728 ha; 3,445 animals). The four independent units were considered as opportunistic commercialization and IAS as non-opportunistic. The highest yield was obtained for RFU (297 kg/ha), followed by IAS (114 kg/ha), FU (98 kg/ha), CCNP (87 kg/ha), and CCA (83 kg/ha). The CCNP was the most economically efficient, considering the gross margin per kilogram (GM/kg) (US$ 0.93). The GM/kg value of IAS (US$ 0.74) was 37 % higher compared to the sum of the average of the four units (US$ 0.54), and IAS had the lowest total production costs per kg (22.5 %). It was concluded that each independent unit could increase GM/kg (37 %) and GM/ha (3.8 %) and use calves in a rearing-fattening unit for further sale. Hence, the integration of beef production systems increases the gross margin of firms, presenting a profitable business advantage to rural entrepreneurs through non-opportunistic commercialization.

ABSTRACT This study was intended to evaluate body size structure and growth parameters of crossbred heifers fed at four nutritional levels to achieve puberty earlier. Animals were classified depending on their level of crossing between Nelore and Hereford and subjected to four nutritional levels (kg day−1) as follows: 0.5 (light; n = 32), 0.75 (medium; n = 32), 1.00 (high; n = 29), and 1.25 (very high; n = 27). Heifers at puberty and at weaning were individually classified for growth parameters. The fat thickness and longissimus muscle area throughout the experimental period were determined by ultrasonography. The height, heart girth, frame, and weight:height ratio were variables used to evaluate body traits. Univariate analysis of variance using the GLIM MIXED procedure os SPSS was performed and the significance level was set at 0.05. Age and body weight at puberty were 388±1.9 days and 331.4±1.3 kg, respectively. Body condition score demonstrated an interaction between nutritional level and crossbred degree. Heifers with the highest degree of Nelore had higher fat thickness and lower weight:height ratio compared with other racial groups at puberty. Pearson correlation coefficient showed a negative association for body condition score (−0.34) and fat thickness (−0.58) compared with age at puberty. The increased fat thickness at younger ages at puberty was observed in all racial groups. The increased weight:height ratio at younger ages at puberty was observed in all racial groups. We observed higher values for a frame in animals at the higher level of supplementation. There is a greater correlation between live weight gain and phenotypic traits during weaning to achieve puberty at an earlier age in crossbred heifers.