Scale of Patchiness Affects the Relation Between Forage Quality and Patch Choice by Cattle

We predicted and tested the effects of scale of heterogeneity on movements and selectivity of a large grazer in a controlled field experiment. We created random mosaics of short/high quality and tall/low quality grass patches in equal proportion at grid sizes of 2x2 m and 5x5 m. Subsequently, we monitored the foraging behavior of four steers in 16 20x40 m plots over 30-minute periods. As predicted, the animals selected the short patches both by walking in a nonrandom manner and by concentrating their grazing time. Selectivity was more pronounced in large patches than in small ones. In contrast, the number of bites per feeding station was not affected by patch size, suggesting that selection between and within feeding stations are essentially different processes. We conclude that selectivity is facilitated by large scale heterogeneity, particularly by enhancing discrimination between feeding stations and larger selection units

Cospectral analysis of high frequency signal loss in eddy covariance measurements

International audienceThe cospectra of momentum (M), sensible heat (H), latent heat (LE), and carbon dioxide (Fc) fluxes measured by eddy covariance (EC) over a shortgrass steppe are calculated for over 800 time intervals spanning a range of wind, surface heating, evaporative, and photosynthetic conditions. The power spectrum of the vertical wind clearly shows that the inertial subrange is not sufficiently captured. The cospectra of the different fluxes show that the lack of measurement resolution in the high frequency results in a loss of flux, especially as stability approaches neutral. A procedure is outlined to use statistics from the cospectrum to estimate the amount of high-frequency flux that remains unmeasured for each time interval. The greatest loss of flux was for H (14% on average for 0>z/L>0.001 where z/L is the dimensionless stability), consistent with other studies which indicate temperature fluctuations actively produce turbulence at high frequencies. LE and Fc showed less than half as much loss of flux as H. This differential loss of flux has direct implications for addressing energy balance closure in EC studies, as well as reconciling biases of fluxes measured by EC with the Modified Bowen Ratio technique. It is recommended that the cospectra of fluxes be examined while setting the height of instrumentation in order to insure that high frequency eddies are resolved

Can social interactions affect food searching efficiency of cattle?

Experienced members of a herd of cattle, referred to as social models in this paper, may play an important part in the searching pattern of naive animals. Naive animals may distribute themselves more evenly because their expectations of preferred areas are not as developed as the expectations of experienced animals. We tested three treatments to investigate if social models tend to transmit information about places of grazing to naive ones or if food distribution tends to be more uniform when animals have less experience with the area. A fenced paddock with 192 trays spaced at about 5 m apart was used to conduct this experiment. Treatment one was the clumped distribution treatment (CDT). Food trays were placed as sets of four. Treatment two was the scattered distribution treatment (SDT). Food trays were placed evenly covering different areas of the paddock. In these two treatments, steers were allowed to find 32 trays with feed in the presence of a social model. Treatment three is a control (CT). Steers were allowed to find 32 trays containing feed with no social model present. The experiment lasted seven days and starting on day four, CDT had a higher FL/NL (ratio of found locations to new locations) than CT (P<0.05). This suggests that naive animals tend to be more efficient in finding preferred food locations in the presence of an experienced model. CDT had a higher FLNL than SDT on days three, six and seven of the experiment (P<0.05). This suggests that the initial distribution of food affected the searching efficiency of naive animals. Moreover, within three days steers in all three treatments did better than expected by chance in locating food. Key words: Grazing, searching, distribution, spatial memor

MODELING EXTENSIVE LIVESTOCK PRODUCTION SYSTEMS: AN APPLICATION TO SHEEP PRODUCTION IN KAZAKHSTAN

A stochastic dynamic programming model for extensive livestock systems is developed. The model optimizes sales/retention decisions when future forage production, which affects animal performance and hence profitability, is uncertain. The model is applied to sheep production in Kazakhstan to evaluate policy alternatives.Livestock Production/Industries,

Bayesian hierarchical models to improve estimation of diet composition by alkane profiles.

Alkane profiles in forage and feces are used to determine diet composition, essentially by inverting a linear mixing equation. Depending on the number of dietary components, number of alkanes and difference in forage profiles, the linear equations can be over or underdetermined. We compared the typical non-negative least squares (NNLS) method against a novel Bayesian hierarchical model (BHM) where diet composition is represented as latent variables modeled with parameters shared by the models for fecal and forage profiles. Forage and fecal profiles were obtained from steers grazing either Brachiaria brizantha cv Marandu, Panicum maximum cv. Mombaça, or Pennisetum purpureum cv. Cameroon at Embrapa Beef Cattle, Campo Grande, MS, Brazil. Herbage and fecal samples were collected in the dry and early wet seasons. Herbage was sampled by 20-cm horizons sorted into stem/sheath and leaf blade as dietary components. Feces were collected from 6 animals in the morning and afternoon. Fecal profiles were corrected by faecal recoveries using mean values from the literature. Distributions of diets estimated by NNLS were obtained by Monte Carlo simulation of profiles using parameters and covariance matrices estimated from data. The BHM yielded posterior distributions directly by using Monte Carlo Markov Chains. NNLS resulted in highly variables diets with distributions that were clearly non-normal. BHM resulted in quasi-normal posterior distributions. We conclude that both approaches are better than the normal approach where diet covariances are calculated ad-hoc. The BHM method has the potential to be vastly superior because it allows the simultaneous integration in a formally correct manner, however, convergence can be difficult

Правове життя та правова активність: співвідношення понять

В статті розкрито теоретичний аспект пізнання двох юридичних категорій: «правове життя» і «правова активність», а також проаналізовано поняття «активність», «соціальна активність», «правова активність», їх взаємозвязок та взаємозалежність. Ключові слова: правове життя, активність, соціальна активність, правова активність, позитивна правова активність, негативна правова активність.В статье раскрыт теоретический аспект познания двух юридических категорий: «правовая жизнь» и «правовая активность», а также проанализировано понятия «активность», «социальная активность», «правовая активность», их взаимосвязь и взаимозависимость. Ключевые слова: правовая жизнь, активность, социальная активность, правовая активность, позитивная правовая активность, негативная правовая активность.The theoretical aspect of two legal categories «legal life» and «legal activity» cognition were researched in this article, the conception of "activity", «social activity», «legal activity, their interrelation and interdependence were analyzed. Key words: a legal life, activity, social activity, legal activity, positive legal activity, negative legal activit

Diet switching by mammalian herbivores in response to exotic grass invasion.

Invasion by exotic grasses is a severe threat to the integrity of grassland ecosystems all over the world. Because grasslands are typically grazed by livestock and wildlife, the invasion is a community process modulated by herbivory. We hypothesized that the invasion of native South American grasslands by Eragrostis plana Nees, an exotic tussock-forming grass from Africa, could be deterred by grazing if grazers switched dietary preferences and included the invasive grass as a large proportion of their diets

Uso del sonido para discriminar las especies consumidas por vacas

El objetivo de este trabajo fue evaluar el potencial uso del sonido para determinar la composición de la dieta de vacas en pastoreo. La hipótesis fue que es posible identificar con precisión las diferentes especies forrajeras consumidas a través del análisis del espectro y otras variables complementarias de los sonidos producidos durante la ingestión. Se utilizaron registros de sonido de cuatro vacas Holando Argentino (620±18,3 kg) pastoreando cuatro especies forrajeras: alfalfa (Medicago sativa), trébol blanco (Trifolium repens), avena (Avena sativa) y festuca alta (Festuca arundinacea) en estado vegetativo. Las especies se ofrecieron en grupos de macetas, de a una especie por vez. Las sesiones de pastoreo se realizaron en forma individual y ordenadas al azar durante seis días consecutivos.Fil: Galli, J.. Universidad Nacional de Rosario; ArgentinaFil: Milone, Diego Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación en Señales, Sistemas e Inteligencia Computacional. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Instituto de Investigación en Señales, Sistemas e Inteligencia Computacional; ArgentinaFil: Cangiano, Carlos Alberto. Universidad Nacional del Litoral; ArgentinaFil: Pece, Mariela Alejandra. Universidad Nacional del Litoral; ArgentinaFil: Larripa, M.. Universidad Nacional del Litoral; ArgentinaFil: Rufiner, Hugo Leonardo. Universidad Nacional del Litoral; ArgentinaFil: Laca, E. A.. University of California; Estados Unido