Resumen Aunque existe tecnología de bajo costo para que los sistemas ganaderos incrementen su rentabilidad y disminuyan el riesgo económico, los métodos para incrementar su adopción por los ganaderos requieren mayor atención. Aquí reportamos cuatro casos de estudio donde tecnología de bajo costo y alto impacto fue aplicada en ganaderías comerciales para demostrar cómo incrementar la productividad física, en lo que llamamos 'Sitios Demostrativos'. La oferta de forraje (FA) afecta la producción y consumo de forraje por los animales así como la partición de los nutrientes hacia mantenimiento o producción. Decidimos demostrar los beneficios de controlar la FA en niveles específicos recomendados por resultados experimentales. Aunque nos enfocamos en la FA, otras herramientas, ej. restricción del amamantamiento y suplementación energética durante el entore, fueron recomendadas en diferentes contextos y momentos para mejorar la respuesta animal. Aunque demostramos incrementos en la productividad en tres de los cuatro casos, solamente dos ganaderos se mostraron interesados en continuar implementando las medidas subsecuentemente. Concluimos que el control de la FA mejoró el consumo de energía y la productividad animal. Para que este tipo de aproximación resulte en mayor adopción, es importante involucrar a los ganaderos en las discusiones sobre los cambios propuestos así como también en el monitoreo durante el progreso de la demostración.

Abstract While low-cost technology can be applied within beef cattle systems to improve economic output and decrease economic risk, methodologies to increase adoption by farmers deserve attention. Here we report 4 case studies where low-cost, high-impact technology was applied on commercial farms in an endeavor to demonstrate increased physical output in what we describe as 'Producer Demonstration Sites'. Forage allowance (FA) affects forage growth, forage intake by animals and energy partitioning to maintenance or production. We decided to demonstrate the benefits to production from controlling forage allowance at specific recommended levels. While we focused on FA, other management tools, e.g. suckling restriction and energy supplementation of cows prior to breeding, were tested in different contexts and time periods to improve the critical responses mentioned. While increases in production from 3 of the farms were demonstrated, only 2 of the farmers showed interest in implementing the strategies on their farms subsequently. We conclude that control of forage allowance improved energy intake and animal productivity. For this approach to be successful and increase adoption, it is important to involve the farmers in discussions regarding the proposed changes from the outset as well as the monitoring of progress during the demonstration.

The objective of this study was to evaluate the effect of a short-term supplementation with rice bran (2 kg/cows/day) on the endocrine and metabolic profiles and hepatic gene expression, associated with the reproductive response in beef cows in grazing conditions. Thirty-eight primiparous beef cows (Hereford, Angus and Hereford × Angus) were used in a randomized block design according to genotype, calving date and body condition score at calving (BCS). At 64±14 days postpartum (day 0 of the experiment), cows were assigned to two nutritional treatments: i) control, grazing native pastures (CON, n=19) and ii) supplemented (SUP, n = 19) for 21 days (days 1 to 21 of the experiment). Blood samples were collected at 0, 7 and 22 days and liver biopsies were obtained at day 22 to determine the abundance of mRNA of growth hormone receptor (GHR), insulin-like growth factor -I (IGF1), and its binding proteins -2 and -3 (IGFBP2 and IGFBP3), and insulin receptor (INSR) using SYBR-Green real-time RT-PCR with hypoxanthine phosphoribosyltransferase as endogenous control. Short-term supplementation with rice bran did not modify either cow BCS or BW, or calf BW or average daily gain. However, it decreased by 11 days the length of postpartum anestrus of primiparous cows in grazing conditions, associated with increased concentrations of glucose and insulin, and reduced hepatic expression of IGFBP2 mRNA at the end of the experimental period.