Estimativa da excreção urinária de derivados de purinas a partir do consumo de NDT e determinação da contribuição endógena em bovinos de corte / Estimation of urinary excretion of purines derivatives from TDN intake and determination of the endogenous contribution in beef cattle

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

11/03/2011

RESUMO

Two experiments were conducted with eight Nelore heifers (BW 267 17 kg ) to assess the excretion of purine derivatives (PD) from intake of TND, the intake and digestibilities of nutrients and the endogenous fraction of PD and nitrogen losses using the technique of fasting. In Exp.I the animal were fed a diet based on corn silage and concentrate in the proportions of 70 and 30% of dry matter (DM). The planned treatments were 4 different DMI: 1.0, 1.4, 1.8 and 2.2 % of BW (DM basis). The animals were allocated to two 4 x 4 Latin squares balanced for residual effect. The four experimental periods lasted for 14 d each. During the first 10 days, the animals were allowed to adapt to the level of ingestion. From d 11 to 14, the collection of feces and urine were performed. Dry matter intake (DMI) range was from 1.0 to 2.1% of BW. Total tract apparent digestibilities of all nutrients except ether extract decrease (P<0.05) with increase of DMI. The excretion of PD increased linearly (P<0.05) with the increase of DMI. Absorbed purines, microbial nitrogen compounds and the balance of nitrogenous compounds also linearly increased (P<0.05) with the increase of DMI. The excretion of purine derivatives (mmoldia) was a function of intake of digestible organic matter (DOM) in kg/d: ŶDP = 32.98 + 21.94* MOD (r2 = 0.44). The PD excretion (mmol/d) was a function of TDN intake (kg/d): ŶDP = 32.47 +20.40*TDN. The relationship between PD excretion (mmol/kgPC0,75) and CMS (g/kgPC0,75) resulted in the regression: ŶDP = 0.605 + 0.014 x (r2 = 0.46), where 0,605 mmol/kgPC0, 75 was the endogenous losses of PD. The Exp. II lasted for 16 d, in whith all animals were subjected to dietary restriction. During the first eight days the feed was supplied at 1% of the BW (DM basis) and during the ninth to 11th day the feed was supplied at 0.5% BW. During the 12th to 16th day the animals were fasted, with free access to water. The mean excretions of PD and nitrogen compounds in the last two days were used to estimate the respective endogenous losses. The endogenous losses of PD and nitrogen compounds were 0.332 mmol/kgBW0,75 and 0.384 gN/kgBW0,75, respectively. Consequently, a net protein requirement for maintenance of 2.4 g/kgBW0,75was estimated. In conclusion, there is a reduction of approximately 5% in TDN, when intake range is restricted to voluntary; it is possible the estimation of urinary excretion of PD from intake of TDN and MOD; the endogenous losses of PD is 0.332 0.063 mmol/kgBW0,75, and the endogenous nitrogen is 0.384 gN/kgBW 0, 75. Additionally, creatinine excretion is not affected by food restriction.

ASSUNTO(S)

novilhas energia da dieta proteína microbiana nutricao e alimentacao animal dietary energy heifers microbial protein

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