Effect of force-feeding diets lacking leucine, valine, isoleucine, threonine or methionine on amino acid catabolism in rats

Histidine-imbalanced diets stimulate hepatic histidase gene expression in rats

A high protein concentration in the diet induces the gene expression of several amino acid degrading enzymes such as histidase (Hal) in rats. It is important to understand whether the amino acid pattern of the dietary protein affects the gene expression of these enzymes. The purpose of the present work was to study the effect of a histidine-imbalanced diet on the activity and mRNA concentration of rat hepatic histidase. Seven groups of six rats were fed one of the following diets: 1) 6% casein (basal), 2) 20% casein, 3) 35% casein, 4) an imbalance diet containing 6% casein plus a mixture of indispensable amino acids (IAA) equivalent to a 20% casein diet without histidine (I-20), 5) 6% casein plus a mixture of IAA equivalent to a 35% casein diet without histidine (I-35), 6) a corrected diet containing 6% casein plus IAA including histidine equivalent to a 20% casein diet, 7) a corrected diet containing 6% casein plus IAA including histidine equivalent to a 35% casein diet. Serum histidine concentration was inversely proportional to the protein content of the diet, and it was significantly higher in rats fed the corrected diets compared to their respective imbalanced diet groups. Hal activity increased as the protein content of the diet increased. Greater histidine imbalance resulted in lower food intake and higher Hal activity. Rats fed histidine-corrected diets had lower activity than their respective imbalanced groups. Differences in Hal activity were associated with differences in the concentration of Hal mRNA. These results indicate that rats fed a histidine-imbalanced diet exhibit reduced food intake and weight gain and increased Hal gene expression as a consequence of an increased amino acid catabolism.

Valine deficiency. 1. The effect of feeding a valine-deficient diet during the starter period on performance and feather structure of male broiler chicks

Experiments were designed to investigate the effect of feeding diets deficient in one or more of the three branched-chain amino acids (BCAA) on the performance of 3-wk-old male broilers. In the first experiment, levels of .96 and 1.46% Leu, .52 and .82% Ile, and .65 and .95% Val were used. Feeding the lowest combination of the three BCAA resulted in weight gain (WG) and feed conversion ratio (FC) of 344 g and 1.59 g:g, respectively. These parameters were not improved by adding dietary increments of the three BCAA individually. The greatest response, however, for both WG (435 g) and FC (1.41 g:g) was obtained by the addition of the three BCAA simultaneously. Chicks fed the low-Val diets in combinations with added levels of Ile and Leu exhibited feather and leg abnormalities. A second experiment was designed to investigate the effect of Val deficiency on feather protein, feather amino acids, and calcium content of the bone. Three treatments were used: a BCAA-deficient diet with .96% Leu, .52% Ile, and .63% Val; a Val-deficient diet, which contained 1.37, .82, and .63% of Leu, Ile, and Val, respectively; and a Val-supplemented diet, which was the same as the previous diets except that the Val content was .83%. Valine deficiency significantly decreased WG (243 g), FC (1.69 g:g), bone calcium (134 mg/g dry bone), and feather protein (82.7% of wet weight). Valine deficiency also decreased the level of Cys in feathers, but increased those of Asp, Glu, Met, Tyr, His, and Lys.(ABSTRACT TRUNCATED AT 250 WORDS)

Valine deficiency. 2. The effect of feeding a valine-deficient diet during the starter period on performance and leg abnormality of male broiler chicks

Using force-feeding and pair-feeding techniques, two experiments were conducted to investigate the problem of leg abnormality associated with feeding a Val-deficient diet as compared with a diet deficient in all the branched chain amino acids (BCAA) or a Val-supplemented diet. The BCAA-deficient diet contained .96, .52, and .63% of Leu, Ile, and Val, respectively. The Val-deficient diet contained 1.37 Leu, .82 Ile, and .63% Val. The Val-supplemented diet contained 1.37 Leu, .82 Ile, and .83% Val. In both studies birds fed the Val-supplemented gained more weight than birds in the other two groups. Although birds on Val-deficient and BCAA-deficient diets had similar weight gain, the former were lethargic and showed feather and leg abnormalities. Bone ash and bone calcium for Val-deficient birds were the lowest among the three groups studied (P < .05). The levels of the BCAA in plasma reflected those of the treatment diets. Plasma hydroxyproline was lowest in birds fed the Val-deficient diet (P < .05), indicating a reduction in bone collagen breakdown. Kidney function measurements were the same for birds on the Val-supplemented and Val-deficient diets. Fractional excretion of calcium in Val-deficient birds (.13%), however, was three times higher than that of Val-supplemented birds (P < .05). The results indicated that Val deficiency per se increased calcium excretion in urine and induced leg abnormality in young chickens.