Control of postmortem energy metabolism
Abstract
The purpose of this research was to understand postmortem energy metabolism in pig muscle. The first study determined the influence of the beta-adrenergic agonist ractopamine (RAC) feeding duration on postmortem energy metabolism. Pigs were fed diets containing RAC (20 mg/kg) for 0, l, 2, or 4 wk. The L* values were increased (P < 0.05) and a* values were reduced (P < 0.05) after inclusion of RAG in the diet for 4 wk. However, dietary RAC had no effect on subjective color, firmness and marbling scores. Pigs fed RAC for 4 wk had reduced (P < 0.05) muscle glycogen levels and increased (P < 0.05) glucose levels at all times postmortem. Postmortem muscle lactate levels were reduced ( P < 0.05) after feeding RAC for 1 wk and 2 wk. Postmortem muscle pH values were higher in pigs fed RAC for 2 wk compared with controls. These data showed that muscle glycogen stores can be reduced through 4 wk RAC feeding but had little positive effect on pork quality development and ultimate pH, suggesting that pork quality development is not predicted on initial muscle glycogen content. The objective of the second study was to reduce initial glycogen in halothane and Rendement Napole (RN) genotypes with RAC feeding. Pigs fed RAC had lower (P < 0.05) glycogen levels and numerically reduced initial lactate levels. Rapid early postmortem pH decline in halothane carrier pigs and lower pHu in RN carrier pigs were observed. In addition, pigs fed RAC has reduced (P < 0.05) color scores, but had no effect on firmness, marbling scores and water holding capacity. Feeding RAC increased (P < 0.05) objective L* values in halothane carrier pigs. Overall, these data suggest that the dietary RAC alters muscle carbohydrate metabolism, resulting in a 30% lower muscle glycogen content and ability of muscle to generate lactate. Furthermore, dietary RAC had no effect on pHu in RN carrier pigs even though initial muscle glycogen levels were reduced by RAC feeding, showing that adverse pork quality in RN carrier pigs was not altered by reducing muscle glycogen content. Therefore, reduced glycogen content may not be the primary factor dictating pHu in pig muscle.
Degree
Ph.D.
Advisors
Grant, Purdue University.
Subject Area
Livestock|Food science
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