The aim of the present study was to assess the reliability of fecal indices as predictors of nutrient intake in sheep under extensive grazing conditions. Fecal concentrations of 2,6-diaminopimelic acid (DAPAf), nitrogen (FN) and phosphorous (FP) were determined in four sheep kept in an extensive grazing system on annual Mediterranean grassland in the vegetative, reproductive and dry phenological stages. Metabolizable energy (MEI), crude protein (CPI) and phosphorus (PI) intake were calculated using the botanical composition, metabolizable energy, crude protein and phosphorus concentrations in each vegetal species making up the animal’s diet. Significant differences were observed in the nutrient intake for each phenological stage (p < 0.0001). The highest MEI, CPI and PI were observed during the vegetative stage (p < 0.0001). FN and FP were different in each phenological stage (p < 0.0001), with significant correlations observed between these variables (r = 0.916; p < 0.0001). Regressions among nutrient intake and fecal indices were significant, except in the cases of DAPAf and MEI, and DAPAf and CPI. Based on these results, fecal indices could be used to estimate nutrient intake in sheep under extensive grazing on annual Mediterranean grassland.

Understanding the botanical composition of herbivores’ diets and their nutritional quality is an important question in the development of sustainable strategies for the management of natural resources. In Chilean highland vicuña-grazed grasslands, there is little information in this regard and, therefore, this study aimed to determine the year-round profile of the diet’s botanical composition and quality. In highland grasslands, on an area of 21.9 ha, continuously grazed for 3.06 VU/ha/year (18°03′ S, 69°13′ W; 4425 m.o.s.l), twelve feces piles were sampled monthly and were analyzed through microhistology, and the nitrogen concentration [NF, OM basis] was determined. The botanical composition, diversity (J) and selectivity index (Ei) of the main species were estimated. Diets were composed of dry–grassland grasses (37.7%), wet–grassland grasses (36.6%), graminoids (14.3%) and forbs (10.2%). The diet diversity ranged from 0.79 (dry–winter) to 0.87 (wet–summer). The main dominant grassland species obtained negative Ei values. The annual mean value of [NF] was estimated as 1.82%, with a higher value in summer months (2.21%), which coincides with the physiological states of higher nutritional demand. The vicuñas behave like generalist ungulates, having a high degree of selectivity towards grass species, which mostly fulfill a nutritional role in subsistence and a functional role in survival, applying foraging strategies that allow them to obtain a better quality diet during the season of greatest nutritional demand.

An analysis of the morphometric variables and zoometric index of a herd of creole goats in the Mediterranean area of central Chile was conducted, considering both females and males of three age categories (unweaned kids, growing kids, and adults). These variables were analysed using variance and principal components analysis. In most of the analysed variables, the effect of sex and age and their respective interaction was significant. The principal component analysis allowed to reduce the number of variables to be analysed (from 16 to 8 variables) establishing two major components, one related to the size and the other referring to the animal compactness which explained 70.86% of the data variability. The comparative analysis of the zoometric index allowed to characterise the animals of the studied herd as meat aptitude, mesacephalous (males), brachycephalic (females), mesomorphs, thin cannon bones, with the posterior body zone being less developed than the anterior body zone and great scapular development.

En zonas marginales donde se desarrollan sistemas extensivos de producción caprina, es frecuente no contar con la tecnología que permita efectuar pesaje de los animales. Por ello, se efectuó un estudio cuyo objetivo fue obtener ecuaciones de predicción del peso vivo en función de variables morfométricas. Se analizaron 382 registros de caprinos “criollos”, de diferentes edades y sexo, en los cuales se determinó el peso vivo y 15 variables morfométricas. A partir de un análisis de correlación entre las variables antes mencionadas, se seleccionaron las de más alta asociación con el peso vivo, incorporándolas en un modelo de regresión logarítmico, el cual fue calculado mediante un procedimiento “stepwise”. Las ecuaciones obtenidas fueron altamente significativas (p < 0,05) y explicaron una gran proporción de la variabilidad (R2 > 85%), e incluyeron como variables predictoras del peso vivo, al perímetro toráxico y los diámetros dorso esternal y/o longitudinal, siendo independientes del sexo del caprino. Cuando solamente se utilizó el perímetro toráxico como variable predictora del peso vivo del caprino, fue requerida una ecuación para cada sexo en forma independiente.

For an adequate management of natural grasslands, the knowledge and understanding of the dietary habits of herbivores and their trophic interactions are fundamental. During two summer seasons, in a mountain range of a sector of the Coquimbo Region, Chile, the botanical composition, diversity, and similarity of the diets of horses, European brown hares, and guanacos were studied, as was the selectivity of the main grassland plant species, using feces microhistology. The contribution of hydromorphic grasses was similar in the diets of guanacos (35.90 ± 7.27%) and horses (32.25 ± 4.50%), differing from that found in hares (16.32 ± 5.32%). Dryland grassland grasses contributed similarly to the diets of horses (13.21 ± 3.22%), guanacos (22.53 ± 5.21%) and hares (18.35 ± 3.81%), as well as graminoids, which averaged 47.79 ± 6.66%, 35.63 ± 10.76% and 38.94 ± 7.88%, in diets of horses, guanacos, and hares, respectively, without significant differences. The contribution of herbaceous dicotyledons was only important in hares (23.76 ± 3.76%), while that of shrubs was low (<3%) and similar among the three herbivores. Dietary diversity was similar among the three herbivore species (73–79%), with a higher degree of dietary overlap between horses and guanacos (55.7%), which was higher than that obtained between hares and guanacos (50%) and between horses and hares (48%), for which there would be a potential trophic competition between them. The most abundant species of dryland and wet grasslands generally fulfill a functional role of subsistence and a nutritional role of maintenance; however, for the three herbivores studied, a different selective behavior was evidenced, according to their physiological differences, with the selection process little affected by the relative abundance of these species in the grasslands. Due to the above, herbivores resort to the selection of certain species that, despite being not very abundant in grasslands, play an important nutritional and functional role, improving the quality of their diets.

El objetivo del trabajo fue estudiar la dieta del piuquén en praderas hidromórficas de altura, en la Región de Coquimbo, durante dos temporadas, a través de su composición botánica, estableciendo relaciones entre la alimentación y ciertos atributos del pastizal (producción de materia seca, diversidad, contribución de Eleocharis pseudoalbibracteata y Carex spp.). La dieta fue analizada mediante microhistología de heces y la caracterización del pastizal a través del método de Point Quadrat para la composición botánica y con el uso de exclusiones para estimar producción de materia seca. Nuestros resultados muestran que esta ave selecciona esencialmente especies gramíneas y graminoides, en especial E. pseudoalbibracteata , presentando valores de selectividad significativos y contribuciones en la dieta de hasta 48%, lo que se relacionó directamente con la diversidad del pastizal (r = 0,80; P = 0,0078) y con la presencia de la misma especie en el recurso forrajero (r = 0,75; P = 0,0123). No se encontraron diferencias entre temporadas para los grandes grupos de especies evaluadas en la dieta; sin embargo, los cambios significativos en la contribución de Carex spp. y E. pseudoalbibracteata indicarían que la modificación de la conducta de forrajeo sería en función de la ingesta de proteína de alta disponibilidad presente en algunas especies vegetales dentro del grupo de graminoides.

For a simple, non-invasive evaluation of nutritional status of sheep kept under extensive grazing conditions on annual rangeland, fecal indices (2,6 diaminopimelic acid, nitrogen, and phosphorus) obtained during the vegetative, reproductive, and dry grassland phenological stages, were correlated with ruminal physiological biomarkers (volatile fatty acids and ruminal ammonia). Through correlation analysis and linear regressions, the degree of association between the variables studied was established. The fecal indices that presented the highest degree of association with ruminal variables were FN and FP, being highly correlated with the production of branched-chain volatile fatty acids (isobutyrate and isovalerate) and with ruminal ammonia (r ≥ 0.65), establishing simple linear regression equations of high significance (p ≤ 0.05). Therefore, fecal indices, especially fecal concentrations of N and P, could reflect the metabolism at the ruminal level and with it the availability of compounds for microbial growth, which would help to establish the nutritional status of sheep herds under extensive grazing conditions.

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