Influence of the sex-linked dwarfing gene (dw) on the contribution of dietary lipid to yolk lipid synthesis

1. The efficiency and time course of dietary fatty acid incorporation into lipids of egg yolk and abdominal adipose tissue was compared in "White Leghorn", normal (Dw) and dwarf (dw) laying hens at 56 weeks of age, using 14C labelled linoleic acid. 2. The sex-linked dwarfing gene, dw, was shown to reduce not only body weight and abdominal fat pad deposition, but also yolk production and the average clutch size. 3. Higher peak incorporation and total recovery of the linoleic acid radioactivity into yolk lipids, but lower label recovery into adipose tissue triglycerides were found in dwarf hens. 4. The higher esterification of the dietary linoleic acid in its native form into dwarf yolk triglycerides indicates that dwarf hens use more dietary lipids to synthesise yolk lipids but these results also suggest that the dw allele might reduce the lipogenic capacities of the liver and adipose tissue in laying hens.     

Biological activities of conjugated linoleic acid (CLA) and effects of CLA on animal products

Conjugated linoleic acid (CLA) is a collective term for a group of positional (c8, c10; c9, c11; c10, c12, and c11, c13) and geometric (cis,cis; cis,trans; trans,cis; and trans,trans) isomers of octadecadienoic acid (linoleic acid) with conjugated double bond system. Dietary CLA increased the ratio of saturated fatty acid (SFA) and decreased unsaturated fatty acid (USFA) in the egg yolk and CLA sources for fat improved the color stability possibly by inhibition of lipid oxidation and oxymyoglobin oxidation in beef patties. Also dietary CLA reduced purge loss in pork loin, it could be due not only to high intramuscular fat content but also to stability of cell membrane lipids assumed by the observed delay in lipid oxidation for CLA. Cholesterol content in egg yolk was significantly decreased by a supply of dietary CLA for 5 weeks feeding. Dietary CLA and storage of CLA eggs increased the firmness of hard-cooked egg yolk and the texture of yolks from hard-cooked CLA eggs was rubbery and elastic and yolk were more difficult to break using an Instron. The eggs produced by hens fed CLA were hard and were characterized by a reddish yolk when cooled to 4 °C for 10 weeks. Several studies have determined the antioxidant property of CLA. The oxidative reactions could influence CLA concentrations by either causing the formation of linoleic acid radicals, which in turn could be converted to CLA by hydrogen donors, or causing the oxidative destruction of the conjugated double-bond system of CLA.     

共轭亚油酸的生物学功能及其在肉鸡上的应用

本文就共轭亚油酸的生物学功能及其对肉鸡生产性能、脂肪沉积、脂肪酸组成、免疫机能、屠宰性能和胴体品质影响方面进行综述。     

Development of divergent lines of lean and fat broilers using plasma very low density lipoprotein concentration as selection criterion; results over the fourth generation and lack of effect of dietary fat on performance and carcase fat content

Comparisons were made of the performance and carcase composition of lean and fat broilers from the 4th generation of a breeding experiment which were fed diets containing 25 or 80 g fat/kg. Selection over the 4th generation resulted in continued divergence in the selection trait and the correlated responses of total body lipid and protein contents and the efficiencies of conversion of food and dietary protein. In both lines body weight, efficiency of food utilisation and total body lipid and protein contents were unaffected by dietary fat content. Tissue fatty acid composition was influenced by dietary and genetic factors: dietary fat increased the proportions of linoleic and oleic acids at the expense of palmitic, palmitoleic and stearic acids whilst greater body fatness increased the proportion of palmitoleic at the expense of linoleic acid.     

Brain, liver and plasma unsaturated aldehydes in nutritional encephalomalacia of chicks

Vitamin E deficiency and linoleic acid-feeding lead to nutritional encephalomalacia (NE) in chicks, affecting the cerebellum exclusively. The relevance of lipid peroxidation (LPO) products to the pathogenesis of the disease was studied. Laying hens received a diet low in vitamin E. Resulting chicks were assigned to four groups fed either with linoleic (C18: 2n-6) or linolenic (C18: 3n-3) acid together with 1 or 50 p.p.m. vitamin E. Nine days post-hatching NE occurred in the vitamin E-deficient group fed linoleic acid. With each chick showing NE, a healthy one from all four groups was killed. Unsaturated aldehydes were determined in plasma, liver, cerebrum and cerebellum. Results underlined that the type of dietary fat is decisive for the aldehyde pattern. In the liver of linoleic acid-fed animals total aldehydes were increased. Diseased animals had increased aldehydes stemming from n-3 fatty acids. In plasma, vitamin E deficiency led to higher malondialdehyde and OH-nonenal concentrations. In brain, neither vitamin E deficiency nor NE were accompanied by increased aldehyde concentrations. In consequence a direct role of unsaturated aldehydes for the development of NE in the cerebellum is not probable.     

Comparisons of sorghum grain (milo) and maize as the principal cereal grain source in poultry rations

Three trials were performed during consecutive years, involving a total of 972 Leghorn hens, in order to compare all‐vegetable layer diets of marginal protein con‐tent based either on milo or on maize as the only cereal grain.

Under the conditions of this study the only consistent, and at times significant, effect due to the source of cereals was the reduction of egg size due to milo. Methio‐nine supplementation of milo diets equalised egg weights. The calculated sulphur amino acid requirement for optimal egg size appeared to be about 560 mg/bird d.

Maize contains decidedly higher levels of linoleic acid than milo, especially on a whole grain basis (2.3% as compared with 1.5%); the difference is reflected in the fatty acid pattern of the yolk lipids of eggs produced by hens‐fed these diets. The dietary to yolk linoleic acid ratio appeared to be 1 to 9–10, for dietary levels ranging from 1.0 to 1.7%.

Milo‐soya diets containing 1.1–1.2% dietary linoleic acid were adequate for optimal egg size, on the condition that methionine requirements had been met, that daily food consumption was not less than 110 g/bird, and that the pre‐layer diets had been rich in linoleic acid. If the pre‐layer diets had been composed of practical ingredients relatively low in this essential fatty acid, a minimum level of 1.5–1.6% dietary linoleic acid was indicated. Acidulated soya soapstock proved a practical linoleic acid supplement.     

The effect of feeding various fats and fat by-products on the fatty acid and cholesterol composition of eggs

Various fats and fat by‐products were added to practical type laying diets. The highly saturated fat products used resulted in an increase in oleic acid and a decrease in linoleic acid content of the egg yolk fat. The more unsaturated fats such as soyabean oil and safflower oil resulted in a marked increase in linoleic acid and a decrease in oleic acid as compared with the basal ration. Regardless of the level of soyabean oil or safflower oil used it was not possible to increase the linoleic acid content of the yolk fat above 40 per cent.

There was an indication that the cholesterol level of the egg yolk increased as the degree of unsaturation of the dietary fat increased.     

Effect of dietary flaxseed, flax oil and n-3 fatty acid supplement on hepatic and plasma characteristics relevant to fatty liver haemorrhagic syndrome in laying hens

1. Two experiments were carried out to investigate the effect of dietary flaxseed, flax oil and n-3 fatty acid supplementation (Dry n-3) on hepatic fat content, plasma triglycerides, hepatic haemorrhage score, egg production, food intake and body weight in an inbred line of Single Comb White Leghorns (UCD-003) predisposed to fatty liver haemorrhagic syndrome (FLHS) and normal SCWL hens. 2. Feeding diets containing 100 g/kg ground flaxseed, 40 g/kg flax oil, or 100 g/kg Dry n-3 reduced body weight and significantly reduced hepatic fat content compared to feeding the control diet with animal and vegetable oil as a fat source. 3. Hepatic malondialdehyde, an indicator of lipid peroxidation within the liver, was not significantly affected by dietary treatment. 4. Normal SCWL hens tended to have higher egg production, greater body weight, greater food intake and higher blood triglyceride concentrations than UCD-003 hens, although the strain effects were not significant. Liver weight as a percent of body weight was significantly lower in normal SCWL hens. Treatments by strain interactions were not found. 5. The result suggested that dietary flaxseed, flax oil and Dry n-3 decrease hepatic fat content and reduce body weight, 2 of the predisposing factors believed to contribute to FLHS onset. However, haemorrhages were still apparent in both strains regardless of treatment, indicating that other unknown underlying mechanisms may also be responsible for FLHS.     

The effects of dietary fat sources,levels, and feeding intervals on pork fatty acid composition

Two experiments investigated the quantitative relationship between dietary fat and fatty acid composition of pork. Experiment 1 was designed to establish the rate of decline for linoleic acid and iodine value of pork fat during the late fattening phase following a dietary reduction. Gilts (n = 288) were fed diets varying in linoleic acid content from 4.11 to 1.56% for 4, 6, or 8 wk prior to slaughter. The maximum rate of decline was 2% 18:2 per week and 2.5 iodine value units per week. Experiment 2 evaluated the effects of dietary fat source and level on carcass fatty acid composition and on pork quality characteristics. Barrows (n = 147) and gilts (n = 147) were allocated to seven dietary treatments for the last 6 wk of the finishing phase. Diets contained 0, 2.5, or 5% dietary fat comprised of 100, 50, or 0% beef tallow. The balance was provided by animal-vegetable blended fat. As the level of tallow increased there was a linear decrease (P < 0.05) in 18:2 content and iodine value of carcass fat. Conversely, 16:1 and 18:1 increased linearly (P < 0.05) as tallow increased. However, 16:1 decreased linearly (P < 0.05) as level of fat increased. As the level of tallow was increased a greater reduction in 18:2 and iodine value was observed in diets with 5% dietary fat compared to diets with 2.5% fat (P < 0.05). These results indicate that reduction of dietary PUFA content had the desired effect of lowering 18:2 content and iodine value of pork fat and that significant alterations could be elicited in as little as 6 to 8 wk of feeding.     

Qualitative and quantitative studies on the metabolism of fatty acids, in particular on that of linoleic acid in calves]

24 calves of the breed "Deutsche Schwarzbunte Rasse" were used for qualitative and quantitative investigations on the metabolism of fatty acids, particularly that of linoleic acid. The trial comprised 6 calves in 4 groups. The experimental rations consisted of powdered skim milk, oat meal, milk sugar, coco fat and varying proportions of linoleic acid (1.0%, 1.5%, 2.5%). The control group received the basal ration without supplements of linoleic acid. After a short period of adjustment the metabolic trial was started with 9 periods each lasting 7 days. The composition of fatty acids in the faecal lipids was analysed by gas chromatography. The studies led to the conclusion that the fatty acids contained in the faecal fat were not immediately derived from the dietary fat. The results of the trial also showed that the major proportion of all the fatty acids present in the faecal lipids consisted of only 4 fatty acids, viz. oleic acid, palmitic acid, lauric acid and myristic acid. Changes observed for the content of linoleic acid in faecal lipids were negligible so that the assumption may be made that all of the linoleic acid added was completely digested.     

The necessity of supplementing laying hen diets with linoleic acid

Results from four experiments with laying hens have been re‐examined using the means of individual 28‐d periods during egg production to investigate the influence of the developing ovary and linoleate storage during growth on the linoleic acid requirement of the laying hen.

Apart from a possible beneficial effect during the first few weeks of production, little increase in egg weight occurs when birds are fed on conventional rearing diets and then fed on laying diets containing linoleic acid in excess of requirement.

After depletion of linoleate reserves, dietary supplementation with linoleic acid significantly increases egg weight at any age.

The necessity of supplementing diets for laying hens with linoleic acid is discussed.     

Comparative evaluation of rumen-protected fat, coconut oil and various oilseeds supplemented to fattening bulls. 2. Effects on composition and oxidative stability of adipose tissues.

The effects of five different dietary fat supplements on fatty acid composition and oxidative stability of subcutaneous and kidney fat were evaluated in 36 Brown Swiss bulls and compared to a low fat diet in a monofactorial design. The following fat supplements were provided as additional fat at 30 g per kg feed dry matter: crystalline rumen-protected fat, coconut oil, and three types of crushed whole oilseeds (rapeseed, sunflower seed and linseed). Adipose tissues reflected differences (P < 0.05) in dietary fatty acid composition although to a lower extent. Using protected fat, which contained elevated levels of trans fatty acids, and sunflower seed, containing a high proportion of linoleic acid, significantly increased C18:1 trans fatty acid proportion in the adipose tissues. The use of sunflower seed increased conjugated linoleic acid. The oilseeds resulted in lower amounts of C16:0 in favour of C18:0. Except for linseed, all fat supplemented groups improved oxidative stability of adipose tissues as compared with control. This was explained by lower proportions of unsaturated fatty acids in adipose tissue (protected fat), by elevated alpha-tocopherol contents (rapeseed, sunflower seed) or by a combination of both (coconut oil). Fat colour remained unaffected by treatments. Compared to other fat supplements oilseeds, especially sunflower seed and rapeseed, can therefore be recommended to be fed to bulls in order to increase the proportions of C18 unsaturated fatty acids in adipose tissues and to maintain or improve oxidative stability.     

Growth and carcass composition of broilers fed sunflower oil and olive oil

Sunflower and olive oils were fed at the same dietary inclusion levels to male broilers as a means of varying the dietary linoleic acid concentration while maintaining similar concentrations of total fat and total unsaturated fatty acids. The type of oil and the dietary supplementation level influenced growth rate, food utilisation and carcass composition. Birds grew faster and utilised food more efficiently when fed the sunflower oil and had higher concentrations of body fat. Increasing the level of supplementation with either oil decreased body fat content. The different responses to the two oils were not related to differences in dietary amino acid balance, ME: protein ratios or rates of food passage through the digestive tract.     

共轭亚油酸对猪脂肪代谢调控及其作用机制的研究进展

共轭亚油酸(CLA)具有多种生理学作用,其中改变体脂沉积、调控脂肪代谢的功能是近来研究的热点。现有研究表明,CLA可以减少动物皮下脂肪、增加肌内脂肪、改变脂肪酸组成。本文从CLA的代谢途径、对猪脂肪沉积的调控作用及其作用机制作一综述,以期为进一步研究提供参考。     

Effects of dietary conjugated linoleic acid on fatty acid composition, lipid oxidation, color, and water-holding capacity of pork loin

The effects of dietary conjugated linoleic acid (CLA) on fatty acid composition, lipid oxidation, and pork quality were investigated. Pigs (n = 20) were fed a diet containing 0, 1, 2.5, or 5% CLA for 4 wk and slaughtered at 105 kg. The longissimus thoracis et lumborum muscle was collected at 24 h postmortem. Pork loin chops (3 cm thick) were packaged aerobically and stored at 4 degrees C for 7 d. Samples were analyzed for ultimate pH, intramuscular fat content, fatty acid composition, thiobarbituric acid-reactive substances, color (L*, a*, b*), and water-holding capacity. Dietary CLA reduced the concentration of linoleic acid and increased CLA concentration in intramuscular fat of pork loin (P < 0.05). The concentration of CLA in muscle was increased with dietary CLA level and did not change during storage. Thiobarbituric acid-reactive substance value of control was higher than that of the CLA-fed groups (P < 0.05). Intramuscular fat content was increased by dietary CLA, and less purge loss was observed with samples from CLA-fed pigs (P < 0.05). Dietary CLA improved the color stability of pork loin during cold storage. After 7 d, lightness (L*) and yellowness (b*) of the 5% CLA-fed group were significantly lower than those of control (P < 0.05). The results indicated that the water-holding capacity of pork loin was increased with increased intramuscular fat content apparently caused by dietary CLA. Also, the data indicated that color stability of pork was improved with inhibition of lipid oxidation and changing of fatty acid composition by dietary CLA.     

饲粮中配合橡胶籽饼对蛋鸡蛋黄脂肪酸组成的影响

本试验通过在海兰褐蛋鸡饲粮中配合不同比例的橡胶籽饼,评价其对蛋黄脂肪酸组成及胆固醇含量的影响。选取72只25周龄的健康海兰褐蛋鸡,随机分成6个组,每组4个重复,每个重复3只鸡。对照组饲喂玉米-豆粕型基础饲粮,Ⅰ~Ⅴ组饲粮分别配合5.00%、10.00%、15.00%、20.00%和25.00%的橡胶籽饼。各组饲粮的营养水平一致。试验期6周。结果表明:饲粮中配合不同比例橡胶籽饼对蛋鸡蛋黄饱和脂肪酸(SFA)含量无显著影响(P0.05);但蛋黄亚油酸(LA)、α-亚麻酸(ALA)、二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)含量随饲粮橡胶籽饼配合比例的增加呈增加趋势,且各试验组蛋黄DHA含量与对照组相比差异显著(P0.05);随饲粮橡胶籽饼配合比例的增加,蛋黄总多不饱和脂肪酸(PUFA)、n-6 PUFA和n-3 PUFA含量呈增加趋势,n-6/n-3 PUFA呈降低趋势;各试验组蛋黄胆固醇含量与对照组相比差异不显著(P0.05),但均低于对照组。由此可见,饲粮中配合一定比例的橡胶籽饼能够获得较低的n-6/n-3PUFA,达到提高蛋黄总PUFA、n-6 PUFA和n-3 PUFA含量的效果。     

Supplemental fat source affects feedlot performance and carcass traits of finishing yearling steers and estimated diet net energy value

Two trials that utilized 356 yearling steers were conducted to evaluate the effects of fat sources (3.5% of diet dry matter) in steam-flaked milo finishing diets. Fats differed in fatty acid composition and level of free fatty acids. In Trial 1, soybean oil, tallow and yellow grease were compared to a nonfat control. Feeding fat increased (P less than .05) daily gain, feed efficiency, estimated diet NE concentration, carcass weight and dressing percentage of steers. In Trial 2, fat treatments were control, acidulated soybean soapstock (SBSS), tallow, a blend of 70% SBSS:30% tallow, and yellow grease. Feeding tallow or the SBSS:tallow blend improved (P less than .05) feed efficiency and estimated dietary NE compared to control. Proportions of palmitic, stearic, oleic, linoleic and linolenic acid in longissimus muscle of steers were altered (P less than .05) by source of supplemental fat. Potential variability in animal response to fat blends was demonstrated by differences in animal response to yellow grease in the two trials. It was concluded that fats vary in feeding value and may alter carcass composition, contrary to putative thought. Further, potential associative effects of fat blends and interactions of fat with other dietary components in high-grain finishing diets require further investigation.     

Interactions of dietary polyunsaturated fatty acids and vitamin E with regard to vitamin E status,fat composition and antibody responsiveness in layer hens

1. Effects of dietary polyunsaturated fatty acids (PUFA) and vitamin E (VE) on an immune response may interact because VE may protect PUFA from in vivo oxidation. The present study was designed to study the presence of such an interaction in growing layer chickens. 2. Three dietary concentration of linoleic acid (LA, 3.3, 6.6 and 10%), in combination with 4 concentration of dietary VE (5, 20, 40 and 80 mg/kg) were used. Effects of LA and VE on circulating VE concentration, fatty acid composition of bursal and adipose fat, and antibody kinetics against keyhole limpet hemocyanin and Mycobacterim butyricum were established. 3. At high dietary LA concentration, bursal and adipose LA were higher but bursal arachidonic acid and long chain n-3 PUFA decreased. The dietary VE level did not consistently affect the deposition of PUFA in tissue. Plasma VE concentrations were affected by the dietary VE and LA content, but not by their interaction. Antibody responses before and 7 d after immunisation were affected by the dietary treatments. Antibody concentration were not affected by tissue fatty acid content. 4. In conclusion, the interaction effects of dietary PUFA and VE on fat deposition and immune responses are of minor importance compared to separate PUFA and VE effects. This implies that, within the studied range, adding extra VE to preserve or affect the effects of dietary PUFA on antibody responsiveness is unnecessary.     

The effect of feeding hemp seed meal to laying hens

Seed of the hemp cultivar Unika-b was cold-pressed to obtain hemp seed meal (HSM) containing 307 g/kg crude protein and 164 g/kg ether extract (60 g/kg linoleic acid, 120 g/kg alpha-linolenic acid, 160 g/kg oleic acid, lesser amounts of palmitic, stearic, and gamma-linolenic acids). For 4 weeks, 102 43-week-old DeKalb Sigma hens were fed on isonitrogenous and isoenergetic diets containing 0, 50, 100 or 200 g/kg HSM. Eggs were collected for fatty acid analysis during the fourth week of feeding these diets. No significant differences were found between feed treatments for egg production, feed consumption, feed efficiency, body weight change or egg quality. Increasing dietary inclusion of HSM produced eggs with lower concentrations of palmitic acid and higher concentrations of linoleic and alpha-linolenic acids.     

Exogenous enzyme complexes and linoleic acid to laying hens

The aim of this research was to evaluate how the decrease of fat inclusion (and therefore compounds essential for animal development, such as linoleic acid) and the use of exogenous enzyme complexes can affect the performance of layers. Treatments consisted of diets with different levels of linoleic acid, the negative control (NC) with 2.41 g/100g and positive control (PC) with 3.75g/100g. Treatment 3 (RLLA) was reformulated using enzymes and low levels of linoleic acid equal to the NC, treatment 4 (RILA) and treatment 5 (RHLA) were reformulated using enzymes, but with linoleic acid at moderate (3.08 g/100g) and high levels (3.75 g/100g), respectively. The formulation of treatments 3, 4, and 5 used enzymes reformulated using an enzyme nutritional matrix. The variables analyzed in each period were the feed intake (g/bird/day); egg production (%); egg weight (g); egg mass (g); feed conversion per egg mass (kg/kg) and per dozen eggs (kg/dozen); weight (g) of yolk, albumen, and shell; specific gravity (g/cm³); Haugh unit; and shell thickness (mm). The commercial enzyme supplementation was effective in supporting the productive performance of the laying hens. Nutritional reduction in diets reformulated with supplementation of the commercial enzymes can be an alternative to reduce production costs without compromising the productive performance of hens.