To quantify the effects of season of use on beef cattle distribution relative to the riparian area, 52 cow/calf pairs were used to evaluate 1) early summer grazing (mid-June to mid-July), and 2) late summer grazing (mid-August to mid-September) during the summers of 1998 and 1999. Within a block, cow/calf pairs used during early summer were also used during late summer grazing periods. Pastures were stocked to achieve 50% utilization of herbaceous vegetation after a 28-day grazing trial. Livestock location and ambient air temperature were recorded hourly during two, 4-day periods in each season of use. Locations were transcribed to a geographical information system for the study area. Ocular vegetation utilization estimates, forage quality, and fecal deposits within 1-m of the stream were recorded post-grazing. During early summer, cattle were further from the stream (P < 0.01) than late summer, averaging 161 and 99-m, respectively. Cows were observed closer (P < 0.01) to the stream when ambient air temperatures were higher. Fecal deposits within 1-m of the stream were similar (P = 0.13) following early and late summer grazing. Forage quality varied (P < 0.01) between seasons, with early summer forages having lower dry matter, greater crude protein, lower fiber, and greater in situ dry matter disappearance compared with late summer forages. Utilization of riparian vegetation was lower and use of upland vegetation greater during early summer than late summer (P < 0.05). In summary, season of use affected cattle distribution relative to the riparian area, with late summer pastures having more concentrated use of riparian vegetation.
ResumenDurante los veranos de 1998 y 1999 se utilizaron 52 pares de vaca-becerro para cuantificar los efectos de la epoca de uso en la distribucion del ganado en un area riberena y para ello se evaluaron los siguientes tratamientos: 1) apacentamiento a inicios de verano (mediados de junio a mediados de julio) y 2) apacentamiento a finales de verano (mediados de Agosto a mediados de Septiembre). Dentro de un bloque, los pares de vaca-becerro utilizados a inicios de verano tambien se usaron en los periodos de fines de verano. Los potreros se cargaron para alcanzar una utilizacion de 50% de la vegetacion herbacea en un periodo experimental de 28 dias. La ubicacion del ganado y la temperatura ambiente se registraron cada hora durante dos periodos de 4 dias en cada epoca de uso. Las ubicaciones se introdujeron a un sistema de informacion geografica para el area de estudio.Despues del periodo de apacentamiento se registraron estimaciones oculares de la utilizacion de la vegetacion, calidad del forraje y depositos fecales dentro de un area de 1 metro de la corriente. A inicio del verano el ganado se alejo mas de la corriente que a fines del verano (P < 0.01) promediando 161 y 99 m respectivamente. Cuando las temperature ambiente era mas alts se observaron las vacas significativamente (P < 0.01) mas cerca de la corriente. Los depositos fecales dentro de la franja de 1 m de la corrient...