Use of near-infrared reflectance spectroscopy on feces to estimate digestibility and dry matter intake of dietary nutritional characteristics under grazing conditions in Colombian creole steers.

Digestibility and intake are parameters difficult and expensive to estimate under grazing conditions; therefore, the aim of this study was to develop near-infrared reflectance spectroscopy (NIRS) calibrations applied to feces (F-NIRS) and evaluate their accuracy to predict dry matter digestibility (DMD) and dry matter intake (DMI) of Colombian creole cattle. Five digestibility trials using creole steers were conducted; indigestible neutral detergent fiber (iNDF) was used as internal marker and Cr2O3 and TiO2 as external markers. A total of 249 forage and 396 fecal samples from individual animals were collected, dried, and grinded for conventional chemical analysis. For spectral analysis, fecal samples were pooled across collection periods (77 samples). Chemometric analysis was performed using WinISI V4.10 software applying the modified partial least squares method. Cross-validation was performed to avoid overfitting the models. The goodness-of-fit statistics considered were the coefficient of determination in cross-validation and prediction sets (R2cv and r2, respectively) and the ratio performance deviation (RPD). Fecal NIRS calibrations developed for forage and supplement DMD showed a satisfactory fit (R2cv =0.87 and RPD=2.77 and R2cv=0.92 and RPD=3.50, respectively). The accuracy of fecal output equations using chromium (Cr) and titanium (Ti) was similar in terms of R2cv (0.92) and RPD (3.63 vs. 3.57). Total DMI equations using Ti performed better compared to Cr (R2cv = 0.82 vs. 0.78; RPD=2.41 vs. 2.17, respectively). The F-NIRS models were validated using a completely independent set of fecal samples showing a moderate fit (r2>0.8 and RPD>2.0). This study showed that F-NIRS is a feasible tool to predict DMD and DMI of creole steers under grazing conditions. However, previous to socialization, this requires an improvement in accuracy of the calibrated equations related to grazing animals in different production contexts.

El kikuyo, una gramínea presente en los sistemas de rumiantes en trópico alto colombiano / Kikuyu, present grass in ruminant production systems in tropic Colombian highlands / Kikuyo, uma gramínea presente em sistemas de ruminantes no alto trópico colombiano

Resumen Los sistemas de producción de rumiantes en Colombia están soportados en el uso de forrajes, principalmente el kikuyo en el trópico alto (Cenchrus clandestinus, previamente Pennisetum clandestinum). El objetivo de este trabajo fue recopilar la información relacionada con el kikuyo e identificar nuevos campos de investigación que permitan promover un manejo eficiente y sostenible de los sistemas de producción bovino soportados en praderas de kikuyo. Los trabajos sugieren que el kikuyo presenta gran resiliencia ante condiciones ambientales adversas, lo que lo perfilan como una especie de interés ante los nuevos escenarios de variabilidad climática. Además, la literatura reporta estrategias de manejo que promueven el aumento en la producción animal, el mejoramiento en la calidad final del producto y la disminución en el impacto sobre el ambiente. Sin embargo, el kikuyo presenta limitaciones en la respuesta agronómica y composicional que hace necesario desarrollar trabajos de investigación que permitan profundizar en el conocimiento de las relaciones entre las condiciones edafoclimáticas y de manejo que promueva el desarrollo de modelos de optimización de los sistemas de producción. Finalmente, se debe promover programas que permitan conocer las características fenotípicas y genotípicas del kikuyo y definir programas de mejoramiento genético que potencialicen la expresión de esta gramínea en condiciones ambientales específicas.

Abstract Colombian ruminants' systems are supported in grasslands, mainly kikuyu in highlands (Cenchrus clandestinus, previously Pennisetum clandestinum). The objective of this work was to compile information related to kikuyu and identify new research areas to promote an efficient and sustainable ruminants' systems supported in kikuyu. The literature suggests that kikuyu presents great resilience to adverse environmental conditions, especially in new scenarios of climatic variability. In addition, literature reports management strategies to improve animal production, product quality and reduce environmental impact. However, kikuyu presents limitations of agronomic and compositional response, that makes necessary to develop research works that allow increase knowledge between edafo-climatic relations and management conditions to development optimization models for kikuyu production systems. Finally, it is necessary to promote phenotype and genotype studies and define genetic improvement programs to enhance grass expression under specific environmental conditions.

Resumo Os sistemas de produção de ruminantes na Colômbia são baseados na utilização de forragens, principalmente kikuyo nos trópicos superiores (Cenchrus clandestinus, anteriormente Pennisetum clandestinum). O objetivo deste trabalho foi coletar informações relacionadas à kikuyo e identificar novos campos de pesquisa que promovam o manejo eficiente e sustentável de sistemas de produção bovino alimentados com pastagens de kikuyo. Estudos sugerem que o kikuyo tem grande resiliência a condições ambientais adversas, despertando grande interesse tendo em vista os novos cenários de variabilidade climática. Além disso, a literatura relata estratégias de manejo que promovem o aumento da produção animal, a melhoria na qualidade final do produto e a diminuição do impacto no meio ambiente. Entretanto, o kikuyo apresenta limitações no que diz respeito à resposta agronômica e composição necessárias para desenvolver pesquisas que aprofundem a compreensão das relações entre as condições e manejo do solo e o clima que promovam o desenvolvimento de sistemas de modelos de otimização da produção. Finalmente, devem ser desenvolvidos programas que permitam conhecer as características fenotípicas e genotípicas desta forragem, além de definir programas de melhoramento genético que potencializem a expressão dessa gramínea em condições ambientais específicas.