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The validity of a synaptosomal model to monitor drug-induced changes in the y-aminobutyric acid (GABA) content of nerve endings is reviewed. Examples of data obtained using the model are presented and the possibility of using the model for research on antipsychotic drugs is discussed.
Nutritional approaches are the most important strategy for altering the fatty acid composition of muscle lipids (Scollan et al., 2006). Grass relative to concentrate feeding increases the content of n-3 polyunsaturated fatty acids (PUFA) resulting in a low n-6:n-3 PUFA ratio. Ruminally protected plant lipids enhance PUFA content very significantly resulting in beneficial P:S and n-6:n-3 ratios (Scollan et al., 2006). This study considered the effects of finishing steers (1) outdoors on grass ± concentrate versus (2) indoors on straw/concentrate ± a protected lipid supplement with one of two levels of vitamin E on the fatty acid composition of the m. longissimus thoracis et lumborum.
Dietary supplements of a mixture of CLA isomers have been shown to reduce body fat accretion in mice and pigs with the trans-10, cis-12 isomer probably being responsible for the anti-lipogenic effects. The efficacy of calcium salts of a mixture of CLA methyl esters containing trans-10, cis-12, on milk fat synthesis, is relatively low (Bernal-Santos et al., 2003) and reported lack of effects on growth may be due to low efficacy and the short duration of CLA supplementation, during the last 32 or 60 days before slaughter, and the relatively low level of trans-10, cis-12 CLA fed. Shingfield et al (2004) demonstrated the potential of rumen protected supplements of a mixture of CLA isomers to reduce milk fat content and improve the energy status of dairy cows during early lactation. The current experiment used a lipid-encapsulated supplement containing equal amounts of cis-9, trans-11 and trans-10, cis-12 CLA methyl esters to study the effects on the performance and carcass characteristics of Limousin steers during a 100d finishing period.
Diet has a large impact on the fatty acid composition of muscle lipids in cattle (Scollan et al., 2006). Grass relative to concentrate feeding increases the content of n-3 polyunsaturated fatty acids (PUFA) resulting in a low n-6:n-3 PUFA ratio and also increases the concentration of the antioxidant, vitamin E, in the meat. Ruminally protected plant lipids enhance PUFA content very significantly resulting in beneficial P:S and n-6:n-3 ratios, but without extra antioxidant input can lead to lipid oxidation and reduced colour shelf life. This study considered the effects of finishing steers (1) outdoors on grass ± concentrate versus (2) indoors on straw/concentrate ± a protected lipid supplemental with one of two levels of vitamin E on the sensory quality and lipid and colour stability of the loin muscle.
Previous studies have demonstrated that including fish oil (FO) in the diet of beef cattle resulted in increased long chain C20n -3 PUFA (20:5n -3 and 22:6n -3) in muscle resulting in a lower n -6:n -3 ratio (Scollan et al., 2001). However, it may result in negative effects on colour shelf life and organoleptic properties (Vatansever et al., 2000). Fish oil is also a good inhibitor of biohydrogenation in the rumen, resulting in increased production of 18:1trans (TVA), the precursor for conjugated linoleic acid (CLA cis -9, trans -11) in muscle. This study investigated the effects of incremental levels of fish oil in the diet on the fatty acid composition of the m. longissimus dorsi and meat quality.
The use of dietary fats and oils to manipulate the fatty acid profile in meat animals to produce higher quality, healthier meat has been well documented, for example by Enser, et al (2000). In Ghana and other developing countries, agro-industrial by products containing oil have been examined because they reduce feed costs. These include palm products and inclusion levels have been recommended (Okai, 1998). However, there is no information on the effect of these palm products on the fatty acid profile and the quality of pork and pork fat. The objective of this study was to evaluate the effects of palm and palm kernel oils on the fatty acid composition of pork fat and fat firmness.
The processing characteristics of pork fat are influenced by its fatty acid composition. Poor slicing quality of floppy belly bacon is caused largely by soft fat. High concentrations of saturated fatty acids (SFA) particularly stearic acid (18:0) and low concentrations of unsaturated fatty acids (USFA) mainly, linoleic (18: 2) improve firmness/hardness of fatty tissues (Wood et al, 1985). The physical properties of fat also influence the stability of emulsion-type meat products through fat loss during cooking. Losses of 0.8 from hard pork flare fat and 0.2 from soft jaw fat have been reported (Evans and Ranken, 1975). The objectives of this study were to evaluate the effects of breed, diet and slaughter weight on the fatty composition of pork fat and the quality of belly bacon and frankfurter sausage.
Effective ruminal protection of dietary polyunsaturated fatty acids (PUFA) is very useful in helping to reduce microbial biohydrogenation of PUFA and results in major improvements in the ratio of polyunsaturated:saturated fatty acids (P:S) in beef muscle (Scollan et al., 2003). However, in that study the protected lipid study (PLS) used which consisted of soya beans, linseed and sunflower oils mixed to give a 2.4:1 ratio of 18:2n -6:18:3n -3, was less successful in improving the n -6:n -3 ratio in beef muscle. This study reports the effects of including in the diet a PLS with a lower ratio of 18:2n -6:18:3n -3 on the fatty acid composition of the m. longissimus.
The nutritionally important fatty acid cis-9, trans-11 18:2 (conjugated linoleic acid, CLA) is formed from the major plant fatty acid cis-9, cis-12 18:2 in the rumen. An important intermediate in the biohydrogenation process is trans-11 18:1 (18:1 tr) and CLA is also synthesized from 18:1 tr in adipose tissue by the action of stearoyl CoA ∆-9 desaturase. Diet is known to affect CLA levels in meat (particularly adipose tissue) and this study examined the effects of a predominantly grass or concentrate diet fed to cattle and slaughtered at 3 ages.
Understanding the mechanisms that regulate the formation of subcutaneous and intramuscular fat (IF) Is important in improving meat quality. Formation of IF is a process, which occurs in the later stages of development, perhaps due to age-related changes in expression of lipogenic enzymes. Acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS) are the key enzymes in the process of de novo synthesis of fatty acids. Delta-9-desaturase (d-9-d) is another key lipogenic enzyme, which catalyses conversion of saturated fatty acids (synthesised de novo as well as dietary) to monounsaturated. The objective of the present research was to investigate the levels of ACC, FAS and d-9-d in the subcutaneous fat and muscles of pigs of different ages.
Breed and diet are important production factors in pigs, affecting growth rate and fat deposition. Subcutaneous fat and intramuscular (marbling) fat are important for carcass and meat quality and this study has investigated how these two fat depots are affected by breed and diet.
A total of 74 pigs representing three commercially available crossbred types, Landrace (50%), Pietrain (50%) and Meishan (25%), were given food ad libitum over a 25- to 115-kg growth period and serially slaughtered for physical and chemical analysis in five groups at 32, 42, 63, 82 and 114 kg live weight (W). Results are presented in the order of pig type as above. Pig types grew at similar overall rates of live body gain, but the Meishan type ate more food and had greater back fat depth. The Pietrain type was least fat. Dissected fatty tissue grew substantially faster than the carcass as a whole; allometric exponents being 1·64, 1·34 and 1·52 (P < 0·05) for the Landrace, Pietrain and Meishan types respectively. Dissected lean tissue gains were 0·419, 0·427 and 0·308 kg daily (P < 0·01), and dissected fatty tissue gains were 0·251, 0·158 and 0·218 kg daily (P < 0·05); the Meishan type being slowest for lean gain and the Pietrain type slowest for fatty tissue gain. The Pietrain type had the largest cross-sectional area of the longissimus dorsi muscle, and the Meishan type the smallest. The pelvic limb of the Meishan type lost density (as measured by specific gravity) fastest, and that of the Pietrain slowest as the pigs grew. The Meishan type had a lower proportion of its carcass lean and a higher proportion of its carcass fat in the pelvic limb than did the other two types. For each kg of live-weight gain, 0·037, 0·041 and 0·032 kg (P < 0·05) of chemical protein was deposited in the pelvic limb of the three types respectively. Equivalent values for chemical lipid were 0·041, 0·035 and 0·041 (P < 0·05). The Meishan type retained protein at a relatively slower rate in the pelvic limb than in the body as a whole. The Pietrain type had the greatest ultimate protein mass in the pelvic limb. Estimation of whole body protein content as a linear function of pig live weight gives coefficients of 0·154, 0·178 and 0·168 kg (P < 0·05) for the three types respectively. Equivalent values for whole body lipid content were 0·269, 0·214 and 0·274 (P < 0·05). Best estimates of the daily rates of protein retention in the body of the whole live pig were 0·152, 0·197 and 0·142 kg/day for the Landrace, Pietrain and Meishan types respectively.
Some studies with beef cattle have shown that breed and diet affect tissue fatty acid composition and meat quality (Choi et al., 2000; Scollan et al., 2001). However, the effects of breed are often confounded with differences in growth rate and body composition. Diet also affects fatty acid composition, however, feed composition studies are often confounded by the use of mixed diets and few have compared all-forage with all-concentrate diets. This study, therefore, was designed to compare Aberdeen Angus and Holstein-Friesian breeds growing at similar rates and fed either all-forage or a high concentrate diet.
Vitamin E protects the animal from oxidative stress in vivo and when it is administered at supranutritional levels it enhances the oxidative stability of meat. Studies have shown that poor absorption of vitamin E often occurs when concentrates are fed to lambs. Distribution of vitamin E in plasma, skeletal muscle, liver (short-term and fast release depot) and adipose tissue (long-term and slow release depot) provides useful information about the overall vitamin E status of the animals. This work studied the distribution of vitamin E in the tissues after supplementation in relation to diet and to the dietary level.
Lamb is characterized as having a low ratio of polyunsaturated (PUFA) to saturated fatty acids (P:S ratio) of approximately 0.1-0.2; considerably less than the minimum recommended ratio of 0.45 for the human diet as a whole (Department of Health 1994). Offset against this, lamb has a favourable ratio of the beneficial PUFA of the n -3 series with the n -6/n -3 ratio being well within the recommended value of < 4.0, and is a particularly rich source of the longer chain n -3 PUFA. One of the major obstacles to improving the P:S ratio of lamb is the extensive biohydrogenation of PUFA in the rumen, resulting in some form of protection being required. The objective of the current experiment was to manipulate the P:S ratio in lamb, whilst maintaining the n- 6/n -3 ratio, through feeding protected fat sources.
The Department of Health (1994) recommended people to reduce their intake of total fat and saturated fat and increase that of n -3 polyunsaturated fatty acids (PUFA) to 200 mg/d. The ratio of PUFA:saturated fatty acids (P:S ratio) in the total diet should be >0.4 with an n -6:n -3 ratio of <4. Since fish consumption, a major source of dietary long-chain n -3 PUFA, is low in the UK, research has focused on improving the fatty acid balance of other meats. The objective of this paper is to summarise studies by IGER and the University of Bristol on manipulating fatty acid composition of beef.
Ruminant meat products have a relatively saturated fatty acid profile so lipid oxidation during the postmortem period, which could lead to off-odours and flavours and trigger undesirable colour changes, is usually minor. However, attempts to increase levels of PUFA in meat for health reasons could be compromised by increased lipid oxidation. This paper is a summary of recently completed work between University of Bristol and IGER on the links between fatty acid composition and oxidative stability in beef and seeks to draw general conclusions.
During cooking, chemical reactions within the muscle produce volatile and non-volatile compounds characteristic of meat aroma and taste. Polyunsaturated fatty acids (PUFA) are essential in these reactions (Mottram and Edwards, 1983). In ruminants, differences in intramuscular PUFA composition have been classically associated with high n-3 content in grass fed animals and high n-6 content in concentrate fed animals. We investigated the effect on odour perception of in vitro reactions between linoleic and α-linolenic acids in the presence of cysteine and ribose, when they were present in ratios similar to those found in meat from animals reared on forage- or concentrate-based diets.
Nutrition during the rearing period has significant effects on subsequent milk production and reproductive performance of dairy herd replacements. Carson et al. (2002) reported that heifers reared to calve down at 620 kg, in contrast to 540 kg live weight, produced 11% more milk, lost more weight and body condition score (BCS) post-calving and had a 30 day longer calving interval. This suggests that a higher BCS at calving and/or a greater rate of BCS loss during lactation appear to be correlated with poorer fertility. The objectives of this experiment were to investigate the effect of (1) diet composition during the rearing period and (2) live weight at first calving on body size and condition score changes during the first lactation and to assess linkages with metabolic hormone concentrations.