Abstract
BackgroundIdentifying regulatory measures to promote glucose oxidative metabolism while simultaneously reducing amino acid oxidative metabolism is one of the foremost challenges in formulating low-protein (LP) diets designed to reduce the excretion of nitrogen-containing substances known to be potential pollutants. In this study, we investigated the effects of adding sodium dichloroacetate (DCA) to a LP diet on nitrogen balance and amino acid metabolism in the portal-drained viscera (PDV) and liver of pigs.To measure nitrogen balance, 18 barrows (40 ± 1.0 kg) were fed one of three diets (n = 6 per group): 18% crude protein (CP, control), 13.5% CP (LP), and 13.5% CP + 100 mg DCA/kg dry matter (LP-DCA). To measure amino acid metabolism in the PDV and liver, 15 barrows (40 ± 1.0 kg) were randomly assigned to one of the three diets (n = 5 per group). Four essential amino acids (Lys, Met, Thr, and Trp) were added to the LP diets such that these had amino acid levels comparable to those of the control diet.ResultsThe LP-DCA diet reduced nitrogen excretion in pigs relative to that of pigs fed the control diet (P < 0.05), without any negative effects on nitrogen retention (P > 0.05). There were no differences between the control and LP-DCA groups with respect to amino acid supply to the liver and extra-hepatic tissues in pigs (P > 0.05). The net release of ammonia into the portal vein and production rate of urea in the liver of pigs fed the LP-DCA diet was reduced relative to that of pigs fed the control and LP diets (P < 0.05).ConclusionThe results indicated that addition of DCA to a LP diet can efficiently reduce nitrogen excretion in pigs and maximize the supply of amino acids to the liver and extra-hepatic tissues.
Highlights
Identifying regulatory measures to promote glucose oxidative metabolism while simultaneously reducing amino acid oxidative metabolism is one of the foremost challenges in formulating low-protein (LP) diets designed to reduce the excretion of nitrogen-containing substances known to be potential pollutants
Glucose is a primary source of metabolic fuel that can be universally metabolized, large amounts of amino acids are metabolized in the portal-drained viscera (PDV), for example, a large part of all non-essential amino acids (NEAAs) are oxidized by the absorptive epithelial cells of mammalian small intestines [18,19,20]; 30–50% of essential amino acids (EAAs) in the diet may be catabolized by the small intestines in first-pass metabolism [21]
We found that the digestive energy digestibility and metabolic energy/digestive energy ratio of pigs in the LP-DCA group were both higher than those of pigs in the control group (P < 0.05)
Summary
Identifying regulatory measures to promote glucose oxidative metabolism while simultaneously reducing amino acid oxidative metabolism is one of the foremost challenges in formulating low-protein (LP) diets designed to reduce the excretion of nitrogen-containing substances known to be potential pollutants. Ammonia (NH3), which is a direct nitrogen donor for urea, is mainly derived from the catabolism of amino acids, those that represent a source of metabolic fuel and undergo extensive oxidative metabolism in the portal-drained viscera (PDV; including stomach, small and large intestines, pancreas, spleen, and omental fat) [16, 17]. Identifying the regulatory measures that promote glucose oxidation in the presence of amino acids is an important step for reducing nitrogen excretion and modifying LP diets
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