Estimation of endogenous contribution and urinary excretion of purine derivatives from the total digestible nutrient intake in Nellore heifers

Jercyane Maria Da Silva Braga,Sebastião De Campos Valadares Filho,Rilene Ferreira Diniz Valadares,Luciana Louzada Prates,Samantha Gusmão Pellizzoni,Luiz Fernando Costa E Silva

doi:10.1590/s1516-35982012000800014

Jercyane Maria Da Silva Braga, Sebastião De Campos Valadares Filho + Show 4 more

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https://doi.org/10.1590/s1516-35982012000800014

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Abstract

The objectives of this experiment were to estimate the endogenous excretion of purine derivatives (PD), the intake and digestibility of nutrients, the urinary excretion of PD from the intake of total digestible nutrients (TDN) and digestible organic matter (DOM) in Nellore heifers. Eight heifers, 267±17 kg body weight (BW), were assigned to two 4 × 4 latin squares. The planned treatments were four dry matter intake (DMI) levels: 10, 14, 18 and 22 g/kg BW. The diet contained 70% corn silage and 30% concentrate. The endogenous losses were obtained by regression between excretion of PD (mmol/BW0.75) and DMI (g/BW0.75). When PD excretion (mmol/d) was related to the intake of DOM and TDN (kg/d), the following equations were obtained: ŶPD= 32.98 + 21.94*DOM and ŶPD= 32.47 + 20.40*TDN, respectively. The excretion of PD (mmol/d) was a function of DMI (kg/d): ŶPD = 0.605 + 0.014 x (r² = 0.46), and 0.60 mmol/BW0.75 was the endogenous fraction of PD. The endogenous losses of PD and nitrogen compounds obtained when the animals were fasted for 5 d, with free access to water, were 0.332 mmol/BW0.75 and 0.384 gN/BW0.75, respectively. The net protein requirement for maintenance was estimated at 2.4 g/BW0.75. Creatinine excretion is not affected by feed restriction.

Highlights

IntroductionThe quantification of microbial protein production has been an important area of study in the nutrition of ruminants, once it is incorporated in all the current systems of protein evaluation used in different countries (Broderick & Merchen, 1992).The need for the development of non-invasive techniques in animal testing has favored the utilization of the excretion of purine derivatives (PD) in the urine for the determination of microbial protein production; considering that endogenous losses are subtracted from the total excretion of purine derivatives to quantify the production of microbial protein, one can observe that inadequate values may result in under- or overestimated microbial production (Susmel et al, 1994).at first, the urinary excretion of PD can be utilized as an identifier of the microbial protein synthesis, some factors utilized in the model which affect the excretion of PD are not yet completely elucidated
The need for the development of non-invasive techniques in animal testing has favored the utilization of the excretion of purine derivatives (PD) in the urine for the determination of microbial protein production; considering that endogenous losses are subtracted from the total excretion of purine derivatives to quantify the production of microbial protein, one can observe that inadequate values may result in under- or overestimated microbial production (Susmel et al, 1994)
The average dry matter (DM) intake values observed were 10.0; 13.9; 17.5 and 21.0 g/kg body weight (BW), to those planned for generating a wide range of microbial crude protein (CP) ruminal synthesis and, greater duodenal flow of purines and greater urinary excretion of PD

Summary

Introduction

The quantification of microbial protein production has been an important area of study in the nutrition of ruminants, once it is incorporated in all the current systems of protein evaluation used in different countries (Broderick & Merchen, 1992).The need for the development of non-invasive techniques in animal testing has favored the utilization of the excretion of purine derivatives (PD) in the urine for the determination of microbial protein production; considering that endogenous losses are subtracted from the total excretion of purine derivatives to quantify the production of microbial protein, one can observe that inadequate values may result in under- or overestimated microbial production (Susmel et al, 1994).at first, the urinary excretion of PD can be utilized as an identifier of the microbial protein synthesis, some factors utilized in the model which affect the excretion of PD are not yet completely elucidated. To estimate the endogenous fraction of the PD, the utilization of the intercept of the linear regression between the excretion of purine derivatives in the urine obtained with several intake levels is not an appropriate method for sheep (Chen et al, 1990), because the relation between excretion of PD and the absorption of purines is not linear. In cattle, this relation is linear (Chen & Gomes, 1992), allowing the application of this evaluation method

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