Previous research from our laboratory has shown that citric acid improves phytate P utilization in chicks fed a P-deficient corn-soybean meal diet. The current study was conducted to determine if other organic acids also are effective, with an emphasis on gluconic acid. Four experiments were conducted in which 4 replicate groups of 5 crossbred chicks (New Hampshire x Columbian) were fed a P-deficient diet (0.16% nonphyate P) from 8 to 22 d of age. In Experiment 1, chick weight gain and tibia ash were significantly increased (P < 0.05) by 1.5 and 3% sodium gluconate (NaGlu), 1.5% calcium gluconate (CaGlu), 1.5 and 3% glucono-delta-lactone, and 1% 2-hydroxy-4-methylthio butanoic acid (Alimet). In experiment 2, tibia ash was significantly increased (P < 0.05) by 2% NaGlu, CaGlu, and citric acid in chicks fed the P-deficient diet but not in chicks fed a 0.45% nonphytate P diet, indicating that the organic acid responses were due to increased P utilization. In experiments 3 and 4, tibia ash was significantly increased by 3% NaGlu and 3% citric acid, but not by 3% fumaric acid or 0.025, 0.05 and 0.1% EDTA. The results of this study showed that NaGlu, CaGlu, glucono-delta-lactone, Alimet, and citric acid, but not fumaric acid or EDTA, improved phytate P utilization in chicks fed a corn-soybean meal diet.

SUMMARY— Post‐mortem tension changes of rabbit psoas and beef geniohyoideus and semitendinosus muscle were studied. A special device was constructed and used to measure these changes while holding the muscle isometrically. It has been possible to demonstrate a pattern of tension development and cessation in rabbit muscle at 24°C and in beef muscle at 0°, 10°, and 24°C. With rabbit muscle no tension development was detected at 0° or 10°C. Initiation of tension development is affected by the ante‐mortem state of the animal as well as by temperature. The post‐mortem tension decline occurs after the disappearence of ATP and evidently is not related to ATP degradation. Possible relationships between post‐mortem tension changes and meat tenderness are discussed.

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SUMMARY: A study of the physical changes associated with rigor mortis in breast muscle was undertaken to assess the factors that may influence ultimate tenderness. Isometric tension changes and shortening were measured at temperatures 2–37°C. These changes were measured while holding the muscle strips in a phosphate buffer, pH 7.2. Isometric tension was measured by transducers and recorded on a physiograph. A pattern of tension development and gradual relaxation has been demonstrated to occur post‐mortem in strips of turkey breast muscle held isometrically. The time to maximum tension development occurs in 3.85 ± 0.19 hr and is not linearly related (P <.05) to temperature. The amount of maximum tension developed averaged 25 g/cm2 and was significantly (P < .05) related to temperature. Relaxation to about 50% of maximum occurs in 18 hr. The amount of shortening that occurs post‐mortem is linearly related (P < .01) to temperature. No “cold shortening” of turkey breast muscle was evident.