Resumen

SOBALVARRO-MENA, Jorge Luis; ELIZONDO-SALAZAR, Jorge Alberto  y  ROJAS-BOURILLON, Augusto. In vitro gas production to estimate net energy of lactation. Agron. Mesoam [online]. 2020, vol.31, n.2, pp.311-328. ISSN 2215-3608.  http://dx.doi.org/10.15517/am.v31i2.38497.

Introduction. The energy content of forages is a limitation for milk production in grazing systems, and the net energy of lactation is the parameter most used to express the energy requirements of dairy cattle. Objective. To compare the net energy of lactation in feeds, obtained from equations based on in vitro gas production, with that estimated by the National Research Council (NRC) model. Materials and methods. The experiment was carried out from August to December 2017 at the Animal Nutrition Research Center of the Universidad de Costa Rica, San Jose, Costa Rica. In vitro gas production was determined in samples of star grass, ryegrass, corn silage, mulberry, and concentrate. Five equations that incorporated accumulated gas production at 24 hours were evaluated. Results. Gas production showed differences (p<0.001) between feeds. The highest volume of gas produced and content of net lactation energy (NEL) was obtained with concentrate. Equation 3 showed de highest precision for the estimation of NEL, which also reached the highest concordance correlation index (r2=0.92). The use of equations by type of feed improved the accuracy for the NEL prediction. Equation 1 was more precise in concentrate while in corn silage it was equation 4, and in mulberry, star grass and ryegrass it was equation 3. Lin’s concordance index explained the differences in prediction of NEL1x better than the Pearson correlation index. Conclusion. The in vitro gas production technique with the application of equation 3 was a reliable method to estimate the NEL1x content in five feeds used in dairy cows

Palabras clave : forage; animal nutrition; dairy cattle; rumen digestion; rumen.

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