Margrethe Therkildsen

Feeding and meat quality - a future approach.

The continuous demand for high standards of quality assurance in the meat production of today and tomorrow calls for development of new tools capable of meeting such demands. The present paper aims to re-think the traditional way of using feeding as a quality control tool in the production of meat and to introduce the potential of a nutrigenomic approach as a first step in the development of pro-active quality control systems which fulfil future demands from industry and consumers. A few chosen examples present how specific feeding strategies can manipulate (i) muscle protein turnover and thereby meat tenderness as well as the cost and sustainability of the production and (ii) muscle energy levels at slaughter and thereby the pH decline, water-holding capacity and the sensory characteristics of meats. The examples are discussed in relation to exploiting essential and basic understanding of physiological and physical processes, which can subsequently be included in a systems biology line of thought of importance for development of unique decision support systems in future meat production.

Compensatory growth response in pigs, muscle protein turn-over and meat texture: effects of restriction/realimentation period

The present experiment was designed to evaluate the effect of different time spans of ad libitum feeding of pigs prior to slaughter after a period of restricted feeding on performance and texture characteristics of the meat. Te n litters of five pigs (Duroc ✕ Landrace ✕ Large White crosses) were allocated to five feeding treatments (AA, R28A42, R43A27, R52A18 and R60A10) at the age of 70 days. AA-pigs were given ad libitum a concentrate diet from day 70 to slaughter at day 140 (approx. 100 kg live weight). R28A42, R43A27, R52A18 and R60A10 pigs were given food at a restricted level (0·6 of ad libitum) for 28, 43, 52 and 60 days, respectively, followed by ad libitum feeding for 42, 27, 18 and 10 days, respectively, until slaughter at day 140. All pigs that had been given food at a restricted level for a period (R28A42, R43A27, R52A18 and R60A10) showed a compensatory growth response in the subsequent ad libitum period. However, only pigs on ad libitum for a minimum of 27 days prior to slaughter (R28A42 and R43A27) had carcass weights and muscle mass similar to that of the control pigs (AA) at slaughter. The restricted feeding increased meat proportion, whereas the feeding strategies had no effect on technological meat quality traits (pH24, drip loss and CIE-colour traits: L*, a* and b*). During compensatory growth, protein turn-over was increased and positively related to the length of the ad libitum period as indicated by the concentration of elongation factor-2 (eEF-2) (P

In vitro study to evaluate the degradation of bovine muscle proteins post-mortem by proteasome and μ-calpain.

The degradation of bovine muscle proteins by proteasome and ubiquitous calpains was explored via 2D gel proteome analysis by inhibition of the physiological level of the proteases by specific inhibitors. The inhibition of the proteasome chymotrypsin- and trypsin-like activity results in the lack of degradation of several fragments of structural proteins such as actin, troponin T, myosin light chain and nebulin. In addition the degradation of several sarcoplasmatic proteins was eliminated when proteasome was inhibited. The inhibition of the ubiquitous calpain only resulted in minor changes in the degradation pattern, which might indicate that p94, which is not inhibited by calpastatin, is involved in the degradation post-mortem. The results of the present study indicate a sequential degradation of the structural proteins post-mortem, where calpain initiates the disruption and destabilisation of the myofibrillar structure, and thereby allows the proteasome to act.

Effect of growth rate on tenderness development and final tenderness of meat from Friesian calves

The present study was conducted to determine the effect of growth rate of calves on the activity of the calpain system post mortem, post mortem desmin degradation, myofibrillar fragmentation index and meat tenderness of m. longissimus lumborum (LL) and m. supraspinatus (SS). Twenty-four Friesian heifer calves were allocated to two treatment groups: MM and HH. The MM calves were given food to achieve a moderate growth rate (678 g/day from 5 days of age to 90 kg body weight (BW) (period I) and 770 g/day from 90 kg BW to slaughter at 250 kg BW (period II)) and the HH calves were given food to achieve a high growth rate (period I: 895 g/day and period II: 1204 g/day). The myofibril fragmentation index (MFI), desmin degradation and the activity of µ-calpain, m-calpain and calpastatin were measured in LL and SS at slaughter, and 1 and 7 days post mortem. Shear force was measured in LL and SS after 1 and 7 days of ageing and a sensory panel evaluated the eating quality of the loin aged 7 days. MFI (P

Novel aspects of health promoting compounds in meat.

Meat is an integral part of the human diet. Besides essential amino acids and nutritive factors of high quality and availability, meat provides often overlooked components of importance for human health. These are amino acids and bioactive compounds that may be very important in i) preventing muscle wasting diseases, such as in sarcopenia, ii) reducing food and caloric intake to prevent metabolic syndrome, iii) blood pressure homeostasis via ACE-inhibitory components from connective tissue, and iv) maintaining functional gut environment through meat-derived nucleotides and nucleosides. In addition, meat could be an important source of phytanic acid, conjugated linoleic acids and antioxidants. Further, it becomes increasingly apparent that design of in vitro meat will be possible, and that this development may lead to improved health benefits from commercially viable and sustainable meat products.

Novel method for determination of myofibril fragmentation post-mortem

Multi angle light scattering was used to determine the myofibril fragmentation of pig longissimus dorsi muscle which was then compared with results from the common turbidity method. The method is based on measurement of the myofibril particle size distribution with the use of a special optical unit containing several individual detectors. The method was able to determine post-mortem changes in a pig muscle homogenate without purification of the myofibrils and is therefore simpler and much faster than the traditional turbidity method. There was a significant correlation (p<0.01) between Warner-Bratzler shear force (WBSF) and particle size distribution. The root mean square error of prediction was found to be 6.1N (10-15% of the measured WBSF) when multivariate data analysis was used to make a prediction model for WBSF. Multi angle light scattering is very useful for estimation of myofibril fragmentation since the method is fast and the sample preparation is simple.

Feeding strategy for improving tenderness has opposite effects in two different muscles

Compensatory growth has been shown to affect rate of muscle protein turnover and may potentially improve tenderness of beef. Thus, a study of tenderness in relation to feeding regime and slaughtering at a time with maximal muscle protein degradation was performed. Friesian bull calves (5-month-old) were fed either ad libitum (n=6) (AA) or restrictively for 3 months followed by re-alimentation for 6 weeks (n=6) (RA) before slaughter at 10 months. At slaughter the fractional breakdown rate of muscle protein was 2.4% in RA compared with 1.6% in AA (P<0.06). Sensory profiling revealed superior texture of M. semimembranosus from RA compared with AA, whereas M. longissimus was superior in texture from AA compared with RA, with no difference in proteolysis and shear force. In conclusion it was clear that different muscles in terms of tenderness responded very differently to the nutritional manipulation.

Meat Science And Muscle Biology Symposium: In utero nutrition related to fetal development, postnatal performance, and meat quality of pork

Intrauterine growth restriction (IUGR) occurs naturally in pigs and leads to low birth weight of piglets due to undernutrition caused by placental insufficiency. For 2 main reasons, low birth weight causes economic loss. First, low birth weight pigs have a greater mortality and increasing the litter size causes more low birth weight piglets within litters. Second, surviving low birth weight piglets have reduced performance (i.e., ADG, feed conversion rate, and percentage meat). To develop dietary strategies for preventing IUGR, knowledge of the biological basis of IUGR is required. Muscle fiber number, formed during myogenesis, is correlated positively with performance traits and has been shown in several studies to be reduced in low birth weight pigs. Postnatal muscle hypertrophy is due to satellite cell number per fiber at birth and their rate of proliferation as well as protein deposition (i.e., protein synthesis and degradation). Previous studies and some recent ones indicate that low birth weight littermates in mice are born with fewer satellite cells and studies on pigs show that the rate of satellite cell proliferation may vary within litters. Proteomics studies show that protein synthesis and degradation is downregulated in IUGR pigs and low birth weight pigs also produce meat with less tenderness. Alternative maternal feeding strategies to prevent IUGR have been examined. Increasing maternal global nutrition had no beneficial effect on performance and muscle growth traits in several studies. Feeding excess maternal dietary protein also did not influence muscle growth traits whereas moderately decreased maternal dietary protein may decrease muscle fiber number and performance. On the other hand, addition of L-carnitine to the maternal gestation or lactation diet may increase birth and weaning weights or the muscle fiber number, respectively, in low birth weight pig offspring. Finally, promising data have been obtained on reproductive traits in pigs after addition of functional AA, such as arginine and glutamine, to the gestational diet. Although much is known about the biological basis of IUGR, we still need to learn much more about the mode of action before maternal dietary strategies can be developed to prevent IUGR.

Angiotensin I–converting enzyme–inhibitory peptides from bovine collagen: insights into inhibitory mechanism and transepithelial transport

The inhibitory mechanism and transepithelial transport of angiotensin I-converting enzyme (ACE)-inhibitory peptides (VGPV and GPRGF) derived from Alcalase®- and papain-hydrolyzed bovine collagen were investigated. The inhibitory mechanism of VGPV and GPRGF was experimentally determined to be non-competitive and the results were supported by molecular docking data. In silico and in vitro gastrointestinal digestion indicated that VGPV remained resistant to digestive enzymes, while GPRGF was degraded into smaller ACE-inhibitory peptides (GPR and GF). VGPV and GPRGF were transported across monolayers of human intestinal epithelial Caco-2 cells through paracellular pathway and retained their ACE-inhibitory activities. The present study suggests that VGPV and GPRGF may possibly be absorbed and exert antihypertensive effects in vivo.

EFFECT OF FEEDING LEVEL, GRAZING AND FINISHING ON GROWTH AND CARCASS QUALITY OF YOUNG FRIESIAN BULLS

Forty‐one autumn‐born Friesian bull calves were allocated to extensive (E) and intensive (I) production systems. The extensive system included 21 loose‐housed animals fed a roughage‐based diet the first winter, allowing a daily gain of 664 g, followed by a 5‐month grazing period. Ten of these animals were slaughtered directly from pasture (live weight ∼360 kg), and the remaining 11 animals after a further 10‐week finishing period with concentrates in tie‐stalls (live weight ∼460 kg). In the intensive system, animals were housed in tie‐stalls, offered concentrates ad libitum and slaughtered at about 360 kg (n = 11) and 460 kg (n = 9) live weight. Overall, daily gain of E‐bulls was 926 g compared with 1478 g for the I‐bulls (p< 0.001). At pasture, E‐bulls gained 1108 g/day. Compared with I‐bulls of similar live weights, the E‐bulls slaughtered directly from pasture had a lower dressing percentage (p < 0.05), a higher lean content (p < 0.05), a much lower fat content (p < 0.05) and darker meat colour (p < 0....