Mathematical models describing disappearance of Lucerne hay in the rumen using the nylon bag technique

V Palangi,A.R Bayat,M Macit

doi:10.4314/sajas.v50i5.9

V Palangi, A.R Bayat + Show 1 more

Open Access

https://doi.org/10.4314/sajas.v50i5.9

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Abstract

It is essential to study the dynamics of rumen degradation of feeds before their potential use in formulating diets for ruminants. Various mathematical models have been developed to describe this degradation. The non-lagged exponential model (Model I), the lagged exponential model (Model II), the Gompertz model (Model III), and the generalized Mitscherlich model (Model IV) were examined using two alternative software (SAS and MATLAB) to determine their efficacy in accounting for variation in ruminal disappearance of dry matter (DM) and crude protein (CP) of lucerne hay from three cuttings. All models described DM degradability well (R2 >0.98). Only Models I and II converged when fitted to CP degradability data (R2 >0.98). It was concluded that any of these models could be used to describe the degradation of DM, whereas only Models I and II could be used to describe the degradation of CP from three cuttings of Lucerne hay. All the models that were fitted to the DM degradation data performed reasonably well, with only minor differences in goodness of fit. However, these models differed in values of the parameter estimates. Additionally, SAS failed to converge in the analyses of CP with Models III and IV, and MATLAB converged to nonsensical values with Model III. Model I might be recommended because it fitted the data well and required estimates of the fewest parameters Keywords: alfalfa hay, in situ digestion, model selection, nonlinear regression

Highlights

Forage is an important component of rations for ruminant animals
The variation in crude protein (CP) was least in the lucerne from the third cutting and most in the second cutting, with the first cutting samples being intermediate
A comparison of these fitted models for dry matter (DM) degradability of various cuttings of lucerne hay based on R2 showed that Models IV, III and II were best fit for the data from the first, second and third cuttings, respectively (Table 1)

Summary

Introduction

Lucerne (Medicago sativa L.) is important because of its high protein content and digestibility in comparison with many other forages (Ferdinand & Jung, 2005). Changes in digestive processes are of nutritional importance, because they determine the quantity of nutrients that are available to the animal (Sauvant & Noziere, 2016; Van Soest, 2018). Formulating appropriate diets for ruminants requires detailed descriptions of the nutritional value of feeds and their degradation kinetics in the rumen (Tedeschi, 2019; da Costa et al, 2020). Accurate estimates of degradation parameters are required to fit various mathematical models and to select best fit models for describing the in situ ruminal incubation of feeds. The nylon bag technique has been used widely to estimate ruminal nutrient degradation because it is relatively simple and low cost compared with methods that involve intestinally cannulated animals (Tassone et al, 2020)

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