Evaluation of microhistology estimation criterias for Sphaeralcea bonariensis (cav.), pl Lorentz in different mixtures

Abstract

Sphaeralcea bonariensis (mallow) is a frequent component in goat diets in the semiarid silvopastoral systems of Santiago del Estero Province, Argentina. Quantification of mallow using the microhistological technique is difficult because trichomes often appear alone in the microscopic field of vision, detached from the epidermis. In an effort to better estimate the botanical composition of forage species in ruminant diets, four mixtures were prepared with different proportions of S. bonarieinsis, Tillandsia sp., Prosopis nigra and Sorghum halepensis. After collection, the botanical material was oven-dried, milled and prepared following the microhistological method, with 20 slides per mixture. Appearance frequency of species was determined microscopically to estimate the botanical composition of the mixtures. Readings were considered positive according to one of two criteria: 1) epidermis fragments only, and 2) epidermis fragments, or three or more detached hairs. A similarity index was used to compare the resulting values. The similarity index results were statistically analized (ANOVA) as a factorial experiment with a totally randomized design (4x2). The Anova between similarity index values showed significant differences between criterion x mixture. Criterion 1 was most accurate in quantifying mixtures with low (10 %) mallow content, and Criterion 2 was more effective in quantifying mixtures with more than 50% mallow. Proportions of 80 % mallow resulted in underestimation, independent of the estimation criterion applied.