Resumo

ANDRADE-MONTEMAYOR, H.; HERNANDEZ, F.; MADRID, J.  e  MEGIAS, M.D.. Comparison of different models to estimate purine bases absorbed in goats. S. Afr. j. anim. sci. [online]. 2004, vol.34, n.5, pp.28-30. ISSN 2221-4062.

The purine bases absorbed (PBa) and microbial nitrogen flow (MNF) in the duodenum were estimated with five models proposed for sheep (1, 4), goats (2), cattle (5) and a goat-sheep mixed model (3). Data of purine derivatives excreted (PDe) in urine of eight digestibility trials were used. In these trials, eight adult male castrated Murciano-granadino goats (30.5 ± 4.95 kg of live weight) were used. Feed was offered as a total mixed ration and was based on alfalfa hay or barley straw and concentrates (50:50). The range in variation for daily DM intake, OM digestibility and nitrogen balance of the different rations were: 38 to 42 g/kg LW^0.75, 68 to 71% and 0.35 to -0.11 g/d respectively. The estimation to PBa, MNF and microbial yield, were different between equations. The estimation of PBa in equation 4 was underestimated by too high recovery of endogenous fraction of PDe in urine considered in this equation. The ratio between N content in the microbial population of the rumen (MNR) and PBa was lower in the equation 2 (0.55 mmol/day) than equations 1, 3, 4 and 5 (0.727 mmol/day). The variability of the factors used in the equations to estimate PDa and MNF within and among species limits its use.

Palavras-chave : Endogenous purine derivative; digestible organic matter intake; microbial nitrogen synthesis; purine metabolism.

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