Is Hand Plucking an Accurate Method of Estimating Bite Mass and Instantaneous Intake of Grazing Herbivores?

Abstract

Instantaneous intake is central to the understanding of large herbivore foraging strategies and rangeland ecology. Unfortunately, its measurement under field conditions remains challenging because of the difficulty of estimating bite mass. The hand plucking method provides a simple, noninvasive method of estimating bite masses and thus instantaneous intake of grazing herbivores. However, many authors questioned its accuracy and interobserver repeatability. In this study, we tested the accuracy and the repeatability of the hand plucking method using four observers and two herbivore species (i.e., cattle and goats). We compared hand plucked bite mass estimates to actual bite mass of bites taken by the herbivores on natural patches of grass. Training of the observers was fundamental to obtaining accurate bite mass measurements. The mean daily accuracy of the observers' bite mass estimates increased from 60-80% to 80-94% within 5 d. After training, the relationship between bite mass estimates and actual bite mass was linear and not significantly different from a Y 5 X relationship. This means that individual bite mass estimates were centered on the real values and thus positive and negative errors canceled each other when combined. As a result, estimates of cumulative intake over about 10 feeding stations had accuracies of over 95%. Furthermore, neither the observer identity nor the herbivore species affected the accuracy of the measurements. The categorization of bites into different size categories proved to be essential in achieving accurate measurements. When observers are trained, hand plucking is a reliable and accurate method of estimating bites mass and instantaneous intake of grazing herbivores. This has important implications for rangeland research and management, as hand plucking is often the only practicable method available for estimating instantaneous intake of freeranging herbivores. 10 estaciones de pastoreo tuvo una exactitud superior al 95%. Además, la exactitud de las estimaciones no estuvieron afectadas por los observadores ni por la especie de herbívoro. La clasificación de los bocados en diversas categorías de tamañ o, fue esencial para el logro de estimaciones exactas. Cuando se cuenta con observadores entrenados, el método de cosecha manual es un me´todo confiable y preciso para la estimación de masa de bocado y el consumo instantáneo de los herbívoros. Esto tiene implicancias importantes para la investigación y el manejo de pastizales naturales, debido a que la cosecha manual es a menudo el único método disponible, para la estimación del consumoinstantáneo de los herbívoros en pastoreo.

Fire‐induced negative nutritional outcomes for cattle when sharing habitat with native ungulates in an African savanna

“…Bite mass was estimated by mimicking and hand‐plucking bites of the test steers (Bonnet et al . ). Bite mass sampling was executed by the same two observers who counted bites.…”

“…In accordance with Bonnet et al . (), the observers were trained for 1 week prior to sampling to minimize observer bias. Because there were five test steers in a given subplot, one observer sampled three steers while the other sampled the remaining two within a given experimental block, and vice versa for the next block.…”

Caracterización del uso directo del rastrojo de maíz (Zea mays L.) por bovinos

“…Para ello, se realizó simulación de pastoreo (Bonnet et al, 2011) con la finalidad de obtener muestras representativas de los componentes del rastrojo de maíz seleccionados y consumidos por el animal. Estas muestras se procesaron para determinar los patrones de tejido de cada una de ellas.…”

“…To do this, grazing simulation was performed (Bonnet et al, 2011) in order to obtain representative samples of selected components of corn stover and consumed by the animal. These samples were processed to determine tissue patterns each.…”

Caracterización de la ingestión por observación directa en rebaños ovinos del Sureste de Francia

“…Empleados desde hace más de treinta años, éstos han sido adaptados para el estudio de los animales en su ambiente natural privilegiando la observación del comportamiento de los individuos y del rebaño (Neff, 1974;Gillingham et al, 1997;Bonnet et al, 2011). Su validez ha sido probada por diferentes métodos (Meuret et al, 1985;Parker et al, 1993;Wallis de Vries, 1985).…”