Effects of age and sex on the structural, chemical and technological characteristics of mule duck meat

1. The aim of the study was to analyse the effect of age and sex on the chemical, structural and technological characteristics of mule duck meat. 2. Ten males and 10 females were weighed and slaughtered at 8, 10, 11, 12 and 13 weeks of age. Weight, pH value, colour, tenderness and juice loss of breast muscle were determined. 3. The activities of 3 enzymes (citrate synthase, beta-hydroxyacyl CoA dehydrogenase, lactate dehydrogenase) which indicate muscular metabolic activity were assayed. 4. Chemical composition (moisture, lipids, proteins, minerals, lipid and phospholipid classes, fatty acid composition) of breast muscle was analysed. 5. Fibre type, fibre type percentage and cross-sectional areas were determined using histochemistry and an image analysis system. 6. For growth performance and muscular structure, the ideal slaughter age of mule ducks is 10 weeks of age. Chemical and technological analysis indicated that muscular maturity in Pectoralis major was reached at 11 weeks of age, but, at this age, breast lipid content is high. Moreover, after 10 weeks of age, food costs rapidly increased. 7. Lastly, sexual dimorphism for body weight is minor. In this study, at any given age, no significant differences between males and females were shown. Thus, it is possible to rear both sexes together and to slaughter them at the same age.

Differential channelling of liver lipids in relation to susceptibility to hepatic steatosis in the goose

In response to overfeeding for the production of "foie gras," the Poland goose differs from the Landes goose by a lesser susceptibility to hepatic steatosis, resulting in a lower accumulation of hepatic triacylglycerol (TG), together with a greater exportation of hepatic phospholipid (PL) in very low density lipoproteins (VLDL) and high density lipoproteins (HDL) (Fournier et al., 1997). A study was designed 1) to compare the liver composition in overfed and nonoverfed geese of the two breeds of geese and 2) to determine whether the differential channelling of lipids in response to overfeeding is reflected in the PL and fatty acid profiles of the different hepatic lipids, whether stored or secreted. In nonoverfed geese, there were no breed-related differences in liver weight (approximately 90 to 100 g), hepatic lipid content (3 to 4%), and lipid and PL composition. However, plasma VLDL and HDL of the Landes breed contained a higher phosphatidylcholine (PC) to phosphatidylethanolamine (PE) ratio than those of the Poland breed (20.7 and 33.8 vs 12.6 and 25.6 in VLDL and HDL, respectively). After 14 d of overfeeding, hepatic PL profiles were identical in the two breeds and similar to that in control livers; choline-containing PL accounted for 95% of total PL. In contrast, plasma HDL concentrations of the Landes geese were lower than those of the Poland geese (9.4 vs 12.9 g/L) and their PC:PE (13.6%) and PL-polyunsaturated fatty acids (PUFA) content (25%) were decreased compared with the Poland geese (21.2 and 30%). It is likely that the higher susceptibility to fatty liver of the Landes breed involves a differential channelling of PL, resulting in a greater hepatic retention of PC and PUFA that are necessary for plasma membrane growth and cell hypertrophy.

Effect of sex on growth, technological and organoleptic characteristics of the Muscovy duck breast muscle

1. The aim of our study was to analyse the consequences of sexual dimorphism on muscular growth and on technological and organoleptic characteristics of breast muscle. Ten males and 10 females of the R51 line (Grimaud) were weighed every fortnight, from 1-d-old to 15 weeks of age, and then slaughtered. Four muscles, Sartorius (SART), Anterior and Posterior latissimus dorsi (ALD, PLD), Pectoralis major (PM) were removed and weighed. The activities of 3 enzymes (citrate synthase, beta-hydroxyacyl CoA dehydrogenase, lactate dehydrogenase) which indicate muscular metabolic activity were assayed. pH value, colour and juice loss of breast muscle were measured on ducks slaughtered between 8 and 15 weeks of age. Sensory analysis, (tastes) was also carried out. 2. At 15 weeks of age, males weighed 4573 g and females 2879 g. Muscle weight and muscular glycolytic activity increased regularly with age. Females showed earlier muscular growth. Sexual dimorphism had a significant effect on muscular growth from 6 weeks of age for ALD, 8 weeks of age for PLD and SART and 10 weeks of age for PM. 3. With age, breasts became redder and darker. The post-mortem fall of pH and juice loss after 24 h of storage at 4 degrees C increased. Females displayed more precocious muscular maturity. The changes in organoleptic characteristics showed a decrease in tenderness, juiciness and mellowness and an increase in flavour and stringiness with age. At any given age, female breast muscles appeared less tender, less juicy and less mellow but had a more intense flavour and seemed more stringy than those of males.

Effects of selection, over three and four generations, on meat yield and fatness in Muscovy ducks

1. Two experiments were undertaken to analyse the effects of selection for lowering carcase fatness and improving meat yield of Muscovy ducks. The control generation N and the selected generations N + 3 and N + 4 of the same heavy line (Grimaud) were reared under similar conditions. 2. We compared growth, carcase characteristics, chemical composition of breasts and plasma concentrations of very low density lipoproteins (VLDL), triglycerides and phospholipids. 3. Selection induced an increase of body weight (+8% to 10% at slaughter age), a decrease of abdominal fat percentage (-10%) and an improvement of breast and thigh plus shank yields (+3% to 7% and +4% respectively). 4. The lipid content of breast meat decreased in the selected ducks (-14% to -20%), particularly phospholipids and triglycerides. Breasts appeared paler and less red which suggested modifications of muscular fibre composition. 5. We found no significant correlations between plasma VLDL, triglyceride and phospholipid concentrations and carcase fatness. It therefore seems difficult to use these variables as selection criteria for lowering carcase fatness of Muscovy ducklings.

Hybrid ducks overfed with boiled corn develop an acute hepatic steatosis with decreased choline and polyunsaturated fatty acid level in phospholipids

Hepatic and plasma lipid changes were investigated in hybrid ducks after steatosis was induced by overfeeding. Fourteen hybrid ducks were force-fed (11 kg corn in 13 days). The liver of the overfed ducks weighed ten times more than that of controls (695 vs 69 g). The phospholipid, ash, water and protein content of the liver were only slightly higher (2.6-, 3.6-, 4.4- and 3.2-fold, respectively) but the liver lipid concentration was 16.5 times higher after than before overfeeding (56.1 vs 3.4 g/100 g liver, respectively). Liver phosphatidylcholine concentration was higher in the control group (32.4 vs 22.9 mol/100 mol phospholipid) revealing a choline deficiency that could contribute to the development of liver steatosis. In liver phospholipid, the level of linoleic and arachidonic acids were markedly decreased in the overfed ducks, from 5 and 18.1 to 3.7 and 7.1 mol/100 mol fatty acids, respectively, and were mainly replaced by oleic acid. Plasma triacylglycerols increased 5.9-fold, cholesterol 2.2-fold and phospholipid 1.6-fold. Heat-induced (50 min at 105 degrees C) fat release, an index of poor liver integrity, was particularly high for the large, fat livers which contained low levels of phospholipids and phosphatidylcholine.

Plasma lipoproteins and liver lipids in two breeds of geese with different susceptibility to hepatic steatosis: changes induced by development and force-feeding

Susceptibility to fatty liver in the force-fed goose is partly under genetic control. However, the mechanisms leading to liver steatosis in this avian model are poorly understood, but may involve perturbation in hepatic lipoprotein synthesis. Plasma lipoproteins were fractionated by density gradient ultracentrifugation from plasma of geese differing in their susceptibility to liver steatosis (Landes breed, highly susceptible; Rhine breed, partly resistant). The concentrations and chemical compositions of the major lipoprotein classes (VLDL, IDL, LDL and HDL) were characterized at 8, 22 and 27 wk of age and compared to the lipid composition of the corresponding liver. In non-force-fed geese, the lipoprotein profile was typical of birds, with high-density lipoprotein (HDL) predominating (4-5 g/L). However, at 22 and 27 wk of age, very low-density lipoprotein (VLDL) levels were significantly lower in Landes geese suggesting that this breed may possess a lower ability to export liver lipids, which would explain its susceptibility to liver steatosis when overfed. The livers of force-fed geese were specifically enriched in triglyceride, and to a lesser extent, in cholesteryl esters and non-esterified fatty acids as compared to those of control geese of the same age (27 wk). This accumulation of lipids was more pronounced in the Landes breed and was responsible for the higher liver weight in that breed. In both breeds, liver steatosis was accompanied by an increase in plasma levels of HDL (11 g/L), whereas low-density lipoproteins were essentially absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between plasma lipoproteins and glucose in fasted chickens selected for leanness or fatness by three criteria

In order to identify the mechanisms which underlie fattening in commercial birds, lean and fat broiler chickens have been selected according to 3 different criteria: abdominal fat content, plasma glucose level and plasma concentration of very-low-density lipoproteins (VLDL), the latter being the main substrate from which bird adipose tissues accumulate triglycerides. Chickens selected for high abdominal fat content displayed a higher level of VLDL and a lower level of glucose than their lean counterparts. Conversely, selection for high plasma VLDL or low plasma glucose resulted in 2 fat lines of chickens. The differences in intermediate- and low-density lipoproteins reflected a different balance in synthesis and catabolism of VLDL among the lines, whereas there was no difference in high-density lipoproteins. These data clearly demonstrate the relationship between lipid and carbohydrate metabolism and their role in the susceptibility to fattening. They suggest a greater use of carbohydrate for hepatic lipogenesis in fat chickens, resulting in a higher synthesis and secretion of VLDL and of their subsequent accumulation of triglycerides in the adipose tissue.

Evidence of enhanced storage capacity in adipose tissue of genetically fat chickens

The storage capacity for plasma triglyceride in abdominal adipose tissue has been investigated in two lines of chickens selected for either high or low adiposity (fat line and lean line, respectively). Adipose tissue cellularity and lipoprotein lipase (LPL) activity were estimated in 2- and 5-wk-old birds. In 2-wk-old birds, cellularity and LPL and glycerophosphate dehydrogenase (GPDH) activity were evaluated in the stromavascular fraction. At both ages studied, the fat line exhibited a twofold increase in mature fat cell number and a marked hypertrophy. LPL activity per cell did not differ with genotype, regardless of the nutritional state; however, LPL activity per whole fat pad was higher in fat birds. In 2-wk-old fat chickens, the stromavascular fraction was characterized by an increase in cell number and a decrease in LPL activity, while GPDH was unchanged. Finally, adipocyte hyperplasia in the fat line appeared to reflect an excessive proliferation of precursor cells. The higher LPL activity in fat birds resulted mainly from cell hyperplasia, rather than from a greater intrinsic activity of adipocytes. Consequently, enhanced fatty acid uptake by adipose tissue represents a major factor in determination of adiposity in the chicken.

Effects of age and diet on plasma lipid and glucose concentrations in genetically lean or fat chickens

Three experiments were carried out to compare plasma lipid and glucose concentrations in genetically lean (LL) and fat (FL) male chickens. The fat birds always displayed lower glycemia than the lean ones, irrespective of the diet (low-fat or fatty) and nutritional state (fed or fasted). Conversely, triglyceridemia was higher in the fat than in the lean line, particularly in the fed condition. This difference was more pronounced in the birds fed on a low-fat diet and became still more marked as they aged. No consistent differences were found between the two lines as to cholesterolemia and non-esterified fatty acid concentrations. Injections of Triton WR 1339 increased triglyceridemia; this effect tended to be more pronounced in the fat birds. The rate of increase of triglyceridemia did not plateau as the dose of Triton increased. The injection of Triton frequently led to convulsions and death. It is concluded that this model of genetic fatness is different from the monogenic models of mammalian obesity since hypertriglyceridemia was not systematic and was not associated with hyperglycemia or hyperinsulinemia.