Mathematical Models Comparison for Illustration of Ruminal Degradability Curves of Citrus Pulp

  • Valiollah Palangi Department of Animal Science, Ataturk University, Erzurum, 25240 Turkey
Keywords: citrus pulps, model selection, nonlinear regression


Food security is of global concern, which requires more attention on the identification of alternative sources. To combat and marginally prevent the issue, human edible grains can be excluded from the livestock feed. These grains can be substituted by nutrient rich process discards and by-products such as citrus pulp. In this study, four mathematical models were used to describe the ruminal disappearance of dry matter (DM) and crude protein (CP) of orange, grapefruit, lemon, and tangerine pulps: (I) non-lagged simple Mitscherlich or exponential, (II) lagged simple Mitscherlich or exponential, (III) Gompertz and (IV) generalized Mitscherlich. Results of DM and CP degradability characteristics showed that all the models fitted well (r2 > 0.95) to the disappearance data and there were minor differences between the models in terms of statistical evaluations. Results also revealed that the models differed in the estimated parameters depending on the nature and structure of the model, and parameters included. Model III estimated negative values for the studied parameters making those biologically unacceptable. Only models I and II can be used for estimating the degradability of DM and CP of citrus pulps. Citrus pulps, containing a large amount of ruminal degradable fractions, can be used as feed source in ruminants.