Carbohydrate metabolism in meat animals

Abstract

Oxidative energy production is by far dominant in living animal muscles, with the exception the short periods of severe stress, where the aerobic capacity is exceeded, and formation of large amounts of lactic acid will take place. Energy consumption in muscle cells continues post mortem with formation of large amounts of lactate and formation of protons, because the aerobic processes for energy production are not available. Post mortem, the fall in pH is delayed only by buffering capacity of the muscle fibres. In living animals, in addition to buffering capacity, both respiration and transport of lactate and protons out of the muscle fibres by monocarboxylate transporters participate in the regulation of muscle fibre pH which never falls as low as the ultimate pH of the meat. Understanding the regulation of pH in muscle is important both for the welfare of living animals and from the technological point of view as a factor influencing meat quality.

The significance of the activity of glycogen debranching enzyme in glycolysis in porcine and bovine muscles

“…In these muscles aerobic energy production is preferred, because of better blood supply, higher amounts of myoglobin, more mitochondria and more active pathway from glycogen through the Krebs cycle to CO 2 and H 2 O than in FG ones (Beecher, Briskey & Hoekstra, 1965a;Beecher et al 1965b;Bendall, 1975;Laborde et al, 1985;Pearson & Young, 1989;Talmant et al, 1986;Pösö & Puolanne, 2004). Also the glycogen content is lower in SO than in FG muscles (Karlsson, Klont & Fernandez, 1999;Lefaucheur et al, 1989;Monin et al, 1987) and similar results was obtained in the present study.…”

“…Secondly, porcine muscles are less aerobic and produce ATP by oxidative phosphorylation for a shorter period after slaughter than bovine muscles. Thus, the delay in the time of onset of anaerobic glycolysis in bovine muscles is a result of high amounts of oxygen binding myoglobin, abundant mitochondria and high activity of oxidative enzymes (Lawrie, 1985, Pösö & Puolanne, 2004. Thirdly, the activities of glycolytic enzymes, such as phoshorylase (Talmant et al 1986), glyceraldehydes-3-phosphate dehydrogenase (pig, Laborde, Talmant & Monin, 1985;bovine, Talmant et al, 1986) and lactate dehydrogenase (Hamm & El-Badawi, 1991) depending, however, on the muscle concerned, are higher in porcine muscles than in bovine muscles.…”

“…The pH decrease is a result of efforts to maintain the ATP level constant by the anaerobic breakdown of glycogen to lactate. Normally higher rate of ATP turnover (Pearson & Young, 1989;Pösö & Puolanne, 2004) and shorter time to onset of anaerobic glycolysis due to lower oxygen stores (Hamm & El-Badawi, 1991;Livingston & Brown, 1981;Pearson & Young, 1989) is observed in porcine than in bovine muscles, thus the rate of post-mortem pH decrease being faster in the former.…”

Intrinsic factors affecting sheep meat quality: a review

“…Due to selection for production under grazing conditions, oxidative fibers (1 and 2A) may be prevalent in the muscle of these animals. These fibers are characterized by low levels of glycogen, which is closely related to high final pH values in the muscle (Pösö and Puolanne, 2005).…”

“…Another possible hypothesis is that the higher reactivity of males is promoted by testosterone and depletes muscle glycogen faster via catecholamines. Adrenaline recruits glucose to the bloodstream and stimulates muscle glycolysis (Pösö and Puolanne, 2005). Okeudo and Moss (2008) evaluated the influence of sex (intact males, castrated males, vasectomized males, and females) on meat quality of sheep (Table 3).…”