Effect of different chilling rates on the quality parameters of mule duck fatty liver.

The aim of this experiment was to study the effect of chilling rates on the quality features of fatty livers. Three different chilling rates were applied: ultra-fast (UF), fast (FA), and slow (SL). Technological and proteomic results were compared at time T1 when the internal temperature of livers reached 10°C and at time T2=24 h post mortem. Samples from the UF group reached the T1 temperature at 50 min post mortem and had the least hard livers and the lowest cooking loss percentage (25±9%) at time T2=24 h post mortem (P-value of <0.01). The FA and SL groups reached the T1 temperature after 120 and 210 min post mortem and presented higher melting (36±9 and 41±9%, respectively, at time T2) and harder livers compared to the UF group. In parallel, we conducted semi-quantifications of proteins by electrophoresis and proteolytic activities by mono-dimensional zymography for three families of proteases: Matrix metalloproteases (MMP), Cathepsins, and Calpains. The proteomic assays revealed less modified proteolytic activities in samples from the UF group, and less associated proteins degradations than in samples from the FA and the SL groups. Effects of the different chilling rates were mainly significant at time T2 (24 h post mortem). As a conclusion we were able to highlight an indirect positive relation between proteolysis and melting yield in ducks' fatty liver.

Proteolytic activity alterations resulting from force-feeding in Muscovy and Pekin ducks.

We investigated liver protease activity in force-fed and non-force-fed ducks using zymography gels to better understand mechanisms underlying liver steatosis in palmipeds. Male Muscovy and Pekin ducks were slaughtered before and after a short period (13 d) while they were conventionally fed or force fed. The force-fed regimen contained a high level of carbohydrates and was delivered in large doses. Main hepatic proteases (matrix metalloprotease-2, calpains, and cathepsins) were extracted from raw liver and specifically activated within electrophoretic gels. Both force-fed Muscovy and Pekin ducks presented higher liver weights and BW associated with lower matrix metalloprotease-2 and m-calpain hepatic activities. On the other hand, hepatic cathepsin activity was not affected by force feeding. It was concluded that Muscovy and Pekin duck hepatic proteases are affected similarly by the force feeding. Thus, this cannot explain differences observed between Muscovy and Pekin ducks regarding their ability to develop hepatic steatosis generally reported in literature.

Proteomic profile evolution during steatosis development in ducks.

We investigated a protein profile evolution during steatosis in ducks using 2-dimensional electrophoresis gels to better understand the mechanisms underlying liver steatosis at the level of hepatic proteins in waterfowl. Two-dimensional electrophoresis gels were performed in the liver at different stages of steatosis in the duck. Mule ducks were slaughtered after 0, 14, or 23 meals of overfeeding, according to commercial conditions. Thirty-one proteic spots were differentially expressed between 3 or 2 durations of overfeeding: 3 spots were differentially expressed between the 3 times and 28 spots were differentially expressed between 2 times. The identified proteins (14) could be regrouped into 5 categories: enzymes, translation factors, proteins involved in cell structure, proteins with antioxidant properties, and proteins that can link calcium. This study opens new research areas in the understanding of steatosis in waterfowl, such as cell structure and oxidative stress.

Are one early muscle pH and one early temperature measurement sufficient to detect PSE breast meat in turkeys?

1. Within a large flock of turkey toms (2000 BUT9 conventionally reared and slaughtered), early muscle pH measurements were randomly done to distinguish two groups of birds presenting low (fast glycolysing, GR) or normal (normal glycolysing, GN) values. 2. Subsequently, ultimate pH values and meat quality parameters were also recorded. Meat quality parameters from GR or GN samples differ more or less indicating more or less severe PSE conditions. Proteins extracted from the samples at 20 min post mortem were similar while they differed greatly at 24 h post mortem. Moreover, among the GR birds, a subgroup of animals (called AB) presented SDS-PAGE profiles largely different from other GR or GN birds. 3. All the subsequent analysis developed on meat quality parameters as well as for protein extractabilities also differed between AB and other animals indicating that they must be considered differently in term of PSE syndrome development. 4. Western blots against Myosin Heavy Chain and actin at 24 h post mortem indicate that myofibrillar protein alterations are different in AB and GR or GN samples. 5. At 20 min post mortem, glycogen content was lowest in AB samples while the glycolytic potential was similar in all samples at the time of death. Measurements of PFK enzyme specific activity did not indicate a different regulation of post mortem glycolysis in AB samples. 6. Our results suggest that a unique pH measurement at 20 min post is insufficient to detect animals more prone to developing a severe PSE syndrome in turkeys. In consequence, it is suggested that a more precise evaluation of the kinetics of pH and temperature decrease has to be conducted to understand the aetiology of meat quality parameter alterations in poultry.

Carcase characteristics and qualitative meat traits of three Italian local chicken breeds.

1. An experiment involving 60 male chickens reared in an organic production system was carried out in order to investigate carcase characteristics and qualitative meat traits of three slow-growing Italian local breeds of chicken (Ermellinata, Padovana and Pepoi). 2. Chicks were randomly selected at hatch, raised together under the same conditions, slaughtered at 190 d of age, dissected for carcase traits, and meat (breast and thigh) stored for subsequent analysis of quality parameters. 3. Ermellinata (EA) chickens were significantly different from Padovana (PA) and Pepoi (PI) chickens for live, carcase and thigh weights. Breeds were also different for breast muscle protein content (EA > PI and PA), shear force (PA < EA and PI) and cooking loss (PI > PA and EA) values. 4. The CIE system values of lightness (L*), redness (a*), and yellowness (b*) evidenced a distinctive darker meat and lighter skin colour of PA breast meat. 5. Polyunsaturated fatty acids composition of breast meat was similar among the analysed breeds. EA had significantly higher saturated but significantly lower monounsaturated fatty acid contents than the other two breeds.

Apoptosis during the development of the hepatic steatosis in force-fed ducks and cooking yield implications.

Mule ducks were force-fed for 12 d to determine whether or not signs of apoptosis could occur during the development of the hepatic steatosis induced by the huge quantities of corn ingested twice daily by the birds. Presence of apoptosis in hepatocytes was assessed through the measurements of increased activities of capsase-3 +-7, -8, and -9. From d 0 of the force-feeding period until d 8, activities of the different caspases remained at a low level. On the contrary, at d 10 and d 12, activities of all measured caspases dramatically increased, indicating that apoptosis occurred at this stage, which corresponds to the time of accumulation of large quantities of lipids in the hepatic cells.The melting level of the liver issued from force-feeding ("foie gras") during cooking is a point of interest for processors because it could degrade the quality of this delicate dish. In this study, we used the levels of caspases activities to improve the predictability of foie gras cooking, in addition to other parameters usually used, such as its weight or lipid content. From this improvement, we suggest that part of the variability of melting during cooking of fatty livers could reside in more or less intense activity of hepatic proteases.

High postmortem temperature in muscle has very similar consequences in two turkey genetic lines.

In the present study, we artificially generated pale, soft, exudative turkey meat by holding muscles immediately after death at 40 degrees C for 6 h. Two genetic types (BUT9 and Label) were compared. When muscles were kept at 40 degrees C, BUT9 muscles exhibited higher lightness values than Label muscles. Drip, thawing, and cook losses were higher for muscles held at 40 degrees C, compared with those held at 4 degrees C, regardless of genetic type. A significant decrease in meat tenderness was found for muscles kept at 40 degrees C. For both genetic types, protein extractabilities either with low ionic strength or high ionic strength buffer decreased for muscles held at 40 degrees C. These fractions were analyzed by using SDS-PAGE, and proteins that differed from the 4 degrees C and 40 degrees C treatments were identified using a matrix-assisted laser desorption ionization time-of-flight mass spectrometer. We reported the alteration of various proteins, such as alpha-actinin, myosin heavy chain, myokinase, phosphorylase, and ATP synthase.

Effects of intramuscular fat levels on sensory characteristics of duck breast meat.

We conducted a study to evaluate the effects of intramuscular fat levels on the sensory characteristics of duck breast meat. Combining duck genotypes (Muscovy, Pekin, and their crossbreed hinny and mule ducks) and feeding levels (overfeeding between 12 and 14 wk of age vs. ad libitum feeding) enabled us to obtain a wide range of lipid levels in breast muscle. The average values were between 2.55 and 6.40 g per 100 g of muscle. Breast muscle from overfed ducks showed higher lipid and lower water levels than breast muscle from ducks fed ad libitum. Muscle from the overfed ducks was also paler in color and exhibited greater yellowness and cooking loss values. Juiciness was judged lower and flavor more pronounced in overfed ducks. Muscovy ducks exhibited higher breast weight and lower lipid levels than the other genotypes. At the other extreme, Pekin ducks exhibited the highest lipid levels and the lowest breast weights; values for these criteria were intermediate in hinny and mule ducks. Breast muscle of Muscovy ducks was paler, less red, and more yellow than that of other genotypes. Breast muscle of Pekin ducks exhibited the lowest values for lightness, yellowness, and energy necessary to shear meat, as well as the highest cooking loss values, and was judged more tender, juicy and less stringy than that of other genotypes. In contrast, scores for breast muscle of Muscovy ducks were the lowest for tenderness, juiciness, and flavor, and the highest for stringiness. Breast muscle of hinny and mule ducks scored the highest values for redness. Hinny ducks also scored the highest values for flavor. Genotype exerted a higher effect on the sensory quality of breast muscle than did feeding levels. Finally, increasing lipid levels in breast muscle increased lightness, yellowness, cooking loss, tenderness, and flavor, with correlation coefficients of 0.49, 0.47, 0.54, 0.43, and 0.28, respectively. However, breast meat color and tenderness were mainly influenced by genotype.

Effect of feed rationing during post-weaning growth on meat quality, muscle energy metabolism and fibre properties of Biceps femoris muscle in the rabbit.

During the weaning period (5 weeks of age), 50 hybrid rabbits were divided at random into five groups (or blocks). Animals from the block 1 were immediately slaughtered at this age and used as initial reference. The remaining rabbits were placed in individual cages and fed the same amount of food until slaughter, but differently rationed. From 5 to 8 weeks of age, the rabbits coming from blocks 2 and 4, and from blocks 3 and 5 received 70% and 90% of the ad libitum ration, respectively. Animals of blocks 2 and 3 were slaughtered at 8 weeks of age. Between 8 and 11 weeks of age, animals from blocks 4 and 5 were fed, respectively, 90% and 70% of the ad libitum ration, prior to sacrifice. At slaughter the Biceps femoris (BF) muscles were immediately removed from each rabbit and the ultimate pH (pHu) and meat colour L*a*b* parameters were measured. Thereafter, one BF was used for aldolase and isocitrate dehydrogenase (ICDH) activity determinations, while the other BF muscle was used for fibre distribution (% of ßR, αR and αW) and morphometric trait measurements. As expected, at 8 weeks of age, rabbits given for 3 weeks the strictest feed rationing (70% of the ad libitum ration) were lighter than rabbits fed the lowest feed rationing (90% of the ad libitum ration). At 11 weeks of age, rabbits given the 70% ration initially and then switched to 90% ration showed significantly higher body weights than rabbits fed the alternative diet (90% ration initially and then switched to 70% ration), and the best feed conversion ratio. Fibre type distribution, fibre cross-sectional area and compactness, colour and metabolic characteristics varied according to slaughter age. The effects of feeding treatment were low.

Influence of maternal feed rationing on metabolic and contractile properties of Longissimus lumborum muscle fibres in the rabbit offspring.

Thirty hybrid female rabbits of 15 weeks of age were divided into three groups and fed for 8 weeks (until the first parturition) on one of the three following diets: "C diet" (DE=11.71MJ/kg DM) fed ad libitum; "R diet" was the C diet fed at 80% of ad libitum, "F diet" rich in fibre (24.6% vs 18.7% for C diet; DE=9.77MJ/kg DM) fed ad libitum. Afterwards, all the does received the C diet ad libitum. One pup per litter was slaughtered at birth, one at 35d (weaning) and one at 81d of age. At the second parturition, another pup per litter was slaughtered at birth. Ten minutes post mortem the Longissimus lumborum (LL) muscle was sampled and the mean cross-sectional area, compactness index (CI) and sphericity of the fibres of the new-born rabbits were determined; on rabbits of 35 and 81d of age the fibre type distribution (ßR, αR or αW) was also measured. The two maternal rationed-diets significantly increased the CI of LL fibres of new-born rabbits of the first kindling, compared to the C diet. On weaning rabbits the greatest effect of maternal feed rationing was observed on the percentage of αW fibres (P<0.01), which was the highest for the F diet (85.2%), intermediate for the C diet (78.0%) and the lowest for the R diet (71.8%). At 81d of age, no effect of maternal dietary treatment was found on offspring.

Modification of glycolyzing enzymes lowers meat quality of turkey.

This paper presents the results of a study on meat quality and protein alterations of fast glycolyzing (FG) and normal glycolyzing (NG) turkey breast muscles. In a commercial processing plant, 34 breast muscles were sampled at 20 min postmortem from a large flock: 17 samples showing the lowest pH(20min) (6.04 +/- 0.09; FG) and 17 showing average pH(20min) (6.47 +/- 0.01; NG). Over a 9-d storage period at 4 degrees C, L* values did not differ between the 2 groups. The FG group showed higher drip, thawing, and cook loss values, and lower processing yield than the NG group. Warner-Bratzler shear force values of cooked meat were higher in the FG group than in the NG group. The FG meat presented a lower protein extractability with low ionic strength buffer than the NG meat. No differences in SDS-PAGE banding patterns were detectable for the different protein extracts between the 2 groups. On the contrary, when SDS-PAGE gels were performed on basic proteins, they showed differences in banding intensity for 2 proteins: glyceraldehyde-3-phosphate dehydrogenase and aldolase A.

Maintaining muscles at a high post-mortem temperature induces PSE-like meat in turkey.

The aim of the present study was to validate an experimental model which surely generates pale, soft, exudative (PSE) turkey meat. Immediately after exsanguination, Pectoralis major (n=15) were kept at various temperatures (4, 20 or 40 °C) for 6 h. All the muscles were then stored at 4 °C for 9 days. They had the same rate of pH fall. L(∗) values were higher in the 40 °C treatment muscles than in the two other treatment muscles between 1 and 9 h. Drip loss of the 40 °C treatment muscles was higher than in the two other treatment muscles. However, thawing and cook loss were not significantly different between treatments. Cooked meat from the 40 °C treatment muscle was tougher than the two other treatment muscles. Napole yield was lower for these muscles. Myofibrillar protein extractability was lower in the 40 °C treatment muscle whatever the considered time. We showed that the 40 °C treatment muscles were similar to PSE muscles.

Lipid characteristics associated with oxidative and glycolytic fibres in rabbit muscles.

The purpose of this study was to specify the intramuscular lipid characteristics which are related to the metabolic type of muscles. Two glycolytic muscles (Longissimus lumborum and Psoas major), two oxidative ones (Soleus and Semimembranosus propriosus) and an intermediate one (Gastrocnemius laterale) were dissected from rabbit carcasses. The results showed that:

In vivo assessment of the quantity of breast muscle by sonography in broilers.

Two experiments were conducted to estimate the amount and yield of breast meat in living chickens by sonography. Results from the first experiment showed that the use of some cross-sectional areas (CSAs) of the breast muscles (Pectoralis major and Pectoralis minor, PM) in combination with the body weight (BW) value could be used to predict breast muscle and yield. Values of the coefficient of determination (r(2)) were near 0.90 and 0.65 for the amount and yield of breast meat respectively. Accurate results were obtained by the combination of three chosen (among more than 40) CSAs of the PM muscle. In the second experiment, the use of the CSAs was limited to the three most explicative ones defined in the first experiment. This experiment was conducted with a larger number of animals and confirms that it is possible to predict in vivo the amount and yield of breast meat with a good accuracy in chickens.

Estimation of poultry breastmeat yield: magnetic resonance imaging as a tool to improve the positioning of ultrasonic scanners.

Magnetic resonance imaging (MRI) was used to reconstruct three-dimensional breast muscle volume of 30 broilers and to locate the most suitable cross-sections to estimate breast muscle yield by ultrasonic scanner. The high accuracy of the determination of the breast muscle yield (R(2)=0.92) from the volume calculated by the sum of 6 mm-spaced MRI transverse images justified the choice of MRI as a reference method. Treatment of the images showed that it was possible to obtain acceptable breast meat yield prediction by MRI from a combination of two or three muscle transverse cross-section area measurements. It also showed that the need to find interfaces reflecting ultrasound is a considerable handicap for optimizing the ultrasonic technique. The oblique echotomographic plane crossing the coracoid bone lengthwise and the fore part of the breast bone appears to be the most appropriate to improve significantly the determination provided by the transverse image situated at the fore part of the breast bone.

Occurrence of giant myofibres according to muscle type, pre- or post-rigor state and genetic background in turkeys.

Forty-five male turkeys were bred to 15 weeks of age. At this age, the birds weighed 4, 6 and 8 kg depending on their genetic origin. At 3 min and 24 h post mortem samples from the pectoralis major (PM) and iliotibialis lateralis (ITL) muscles were excised for biochemical and histochemical measurements. At 3 min post mortem, except in the size of the myofibres, no differences in types, shapes or luminance due to glycogen was seen between the three lines in the respective muscles. Birds from the fast growing line had bigger muscle fibres than the two other lines, but the muscles did not present more glycolytic or oxidative enzyme activities. No muscle abnormalities were noticed at this stage. At 24 h post mortem, the presence of giant fibres (GF) was seen which differed proportions according to muscle and in genetic background. The GF were found both in the fast (PM) or mixed type (ITL) muscles. In this latter muscle they were more prevalent in the slow contracting muscle fibres than the other fiber types. It was concluded that the occurrence of the GF is independent of the genetic background of the birds or the type of muscle, but is dependent on the biochemical events occurring during rigor mortis.

Effect of dietary fat and vitamin E on colour stability and on lipid and protein oxidation in Turkey meat during storage.

The objectives of the study were to investigate the effects of dietary fat (6% soya oil or rapeseed oil or tallow), together with tocopheryl acetate at either a basal (30 ppm) or a supplemented (400 ppm) level for 16 weeks on lipid and protein oxidation, including myoglobin, during refrigerated storage of turkey muscles. When turkeys were fed tallow in particular, vitamin E supplementation improved the vitamin E status of the muscles. Vitamin E supplementation significantly delayed lipid oxidation measured by TBARS, whatever the dietary fat. TBARS were highest in meat from animals fed soya oil. Vitamin E supplementation had no positive effect on colour stability of meat during refrigerated storage. Feeding soya oil induced significantly higher oxidation of proteins (carbonyl content) than rapeseed oil or tallow and vitamin E supplementation induced a slight decrease in carbonyl content at day 9 of storage for M. sartorius. SH content was significantly higher in vitamin E supplemented M. sartorius and M. pectoralis than in controls.

Broiler meat quality: effect of selection for increased carcass quality and estimates of genetic parameters.

Ultimate pH (pHu), color measurements, and water holding capacity of the chicken Pectoralis major muscle were compared between birds of an experimental line selected for 13 generations for increased BW and breast meat yield and reduced abdominal fat percentage and its control line. Ultimate pH differed slightly between lines after selection, with values of 5.78 +/- 0.10 and 5.68 +/- 0.12 in the selected and control birds, respectively. Drip loss was significantly lower in the selected birds. Although selection did not modify lightness L*, it led to paler meat, as redness a* and yellowness b* were significantly lower in the selected line than in the control line. Ultimate pH of the meat was related to lightness and drip loss (with mean correlations over both lines of -0.59 and -0.40, respectively). Storage of the meat resulted in similar color variation in both lines, with a significant increase in a* and b* until 3 d postslaughter and in L* after 6 d postslaughter. Estimates of the genetic parameters of the criteria of meat quality were calculated in the selected line. The estimates suggested that there is a predominant role of genetics in the control of these traits, with heritability estimates of 0.49 +/- 0.11 for pHu, 0.75 +/- 0.08 for L*, 0.81 +/- 0.04 for a*, and 0.64 +/- 0.06 for b*. A significant negative genetic correlation (-0.65) was found between pHu and L*. The genetic correlation between a* and b* measurements was estimated at 0.72.

The use of near-infrared reflectance spectroscopy in the prediction of the chemical composition of goose fatty liver.

The use of near-infrared reflectance spectroscopy (NIRS) on a meat product is described in this report. The aim of the study was to develop calibration equations to predict the chemical composition of goose fatty liver (foie gras) with lipid contents greater than 40% of the fresh pate. Spectra of 52 foie gras samples were collected in the visible and NIR region (400 to 2,498 nm). Calibration equations were computed for DM, CP, lipids and fatty acids using modified partial least-squares regression. R2 values were high for the total lipid content (0.805) and DM (0.908) but were low for ash (0.151) and relatively low for protein content (0.255). For the major fatty acids, R2 ranged from 0.886 for palmitic acid to 0.988 for oleic acid. Oleic acid, the main fatty acid of the liver, and the stearic acid had higher R2 values than the less represented fatty acids. This study suggests that the NIRS technique can be used to predict lipid content and the fatty acid composition of goose fatty livers, but calibration must be built on a larger number of samples to generate accurate predictions.

Current advances in proteomic analysis of (fatty) liver.

In this review, an overview on proteomic studies conducted in livers of farm animals is conducted with a special focus on liver steatosis in waterfowl. Several studies had interest in understanding liver metabolism in dairy cows under various conditions (e.g. fasting) or the evolution of liver proteome during embryonic phases or growing periods in chicken. Those studies provide interesting results leading to a better understanding of the liver metabolism. Liver steatosis development in waterfowl represents a special case and a focus on proteomic studies conducted in these birds will be done. Indeed, recent studies aimed at resolving protein evolution during overfeeding in duck. Proteomic analysis combining two complementary approaches (2-dimensional electrophoresis gels and shot gun strategy) in order to better understand the mechanisms underlying the variability of cooking yield of fatty liver will be presented.