The response of gene expression associated with intramuscular fat deposition in the longissimus dorsi muscle of Simmental × Yellow breed cattle to different energy levels of diets

This study was designed to estimate dietary energy level on intramuscular fat (IMF) deposition in Simmental × Yellow breed cattle. Results showed that ultimate weight and average daily gain in high and medium energy groups were significantly higher than low‐energy group, yet feed conversion ratio was significantly lower. IMF content was significantly increased by dietary energy increasing, whereas longissimus muscle shear force significantly decreased. Serum‐free fatty acids, triglycerides and glucose significantly increased by dietary energy increasing, whereas growth hormone (GH) significantly decreased. Enzyme activities of lipoprotein lipase (LPL), fatty acid synthase (FAS), and acetyl‐CoA carboxylase (ACC) significantly increased by dietary energy increasing, whereas hormone‐sensitive lipase (HSL) and carnitine palmitoyltransferase‐1 (CPT‐1) significantly diminished. Peroxisome proliferator‐activated receptor γ, sterol regulatory element‐binding protein 1, stearoyl‐CoA desaturase, adipocyte‐fatty acid‐binding proteins, ACC, LPL, and FAS gene or protein expression significantly increased by dietary energy increasing, whereas HSL, CPT‐1, and GH gene or protein expression significantly decreased. These results indicated that high dietary energy promoting IMF deposition is mainly by downregulating pituitary GH gene expression, decreasing serum GH concentration, increasing lipogenic genes levels of mRNA, enzyme activities and protein expression, and decreasing lipolytic genes levels of mRNA, enzyme activities, and protein expression.     

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.     

Dietary supplementation with dimethylglycine affects broiler performance and plasma metabolites depending on dose and dietary fatty acid profile

The effect of dietary supplementation with N,N‐dimethylglycine sodium salt (Na‐DMG) was evaluated in a feeding trial with 1500 1‐day‐old broiler chicks (Cobb 500). DMG was supplemented at 0, 0.1, 0.2, 0.5 or 1 g Na‐DMG/kg feed to a ration with either animal fat (chicken fat) or vegetal fat (soy oil) as main fat source. In the vegetal fat diets, production value was significantly linearly improved by supplementation with DMG up to 11%. Irrespective of dietary fat source, abdominal fat percentage was significantly linearly reduced up to 24% and meat yield tended to increase linearly with DMG level up to 4%. In the vegetal fat groups, DMG significantly lowered abdominal fat pad by up to 38% and tended to increase meat yield up to 6% at the highest dose. Fasted non‐esterified fatty acid level significantly decreased with increasing DMG level up to 36% and thiobarbituric acid reactive species (TBARS) decreased with a statistical trend up to 46% at the highest dose. In vegetal fat diets, addition of DMG resulted in significant lower TBARS level by 56% at the highest dose. Finally, a significant quadratic effect on ascites heart index was present in the vegetal fat diets, with a minimal value at 0.5 g Na‐DMG/kg. In conclusion, dietary supplementation with DMG may improve technical and slaughter performance, and may reduce oxidative stress and pulmonary hypertension, but the degree of effects is modulated by fatty acid profile of the diet. Herewith, effects are more pronounced in a diet rich in polyunsaturated fatty acids compared with a diet rich in saturated and monounsaturated fatty acids.     

Interactions between dietary crude protein and essential amino acid intake on performance in broilers

1. The effect of diets with increasing concentrations of crude protein at either fixed essential amino acid concentrations or at fixed essential amino acid:dietary crude protein ratios on performance was examined in 1- to 4-week-old male Cobb chicks. Increasing crude protein intakes at constant essential amino acid concentrations was carried out at two dietary energy contents. 2. Increasing crude protein resulted in a linear decrease in feed intake while weight gain and feed efficiency changed quadratically with a smaller positive effect at the highest crude protein intakes. Feed intake decreased and feed efficiency increased with higher dietary energy and interactions between protein and energy were significant. Abdominal fat content and the efficiency of protein retention decreased with increasing dietary protein intake. 3. Using constant essential amino acid:crude protein ratios at increasing crude protein intakes resulted in (Trial 3) feed intake, weight gain and feed efficiency all increasing before reaching a plateau. Abdominal fat decreased with protein intake and the efficiency of protein retention was quadratic, decreasing at the higher protein intakes. 4. Multiple regression analysis of the results of the three trials indicated that partition of energy intake into maintenance, fat-free tissue growth, fat and the energy required to transform protein intake in excess of retention explained more than 98% of variation. 5. It is proposed that broiler performance at the lower protein intakes was limited by either non-essential amino acid (Trials 1 and 2) or essential amino acid (Trial 3) intake whereas at high protein intakes the decreased efficiency of amino acid utilisation after growth requirements are fulfilled resulted in poorer performance.     

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.     

Interaction of dietary magnesium level on the feeding value of supplemental fat in finishing diets for feedlot steers

A feeding trial involving 160 crossbred steers (357 kg) and a metabolism trial involving eight Holstein steers (189 kg) cannulated in the rumen and proximal duodenum were conducted to evaluate the interaction of dietary Mg level (.18 vs .32%, DM basis) and supplemental fat (0% supplemental fat vs 4% tallow [T], yellow grease [YG], or griddle grease [GG]) on growth performance and NE value of the diet. Dietary Mg level did not influence (P > .10) growth performance. Daily weight gain was lower (11%, P < .05) for steers fed GG than for those fed YG. Supplemental fat decreased (5%, P < .10) DMI and increased (P < .05) gain efficiency (7%). There was a fat x Mg level interaction (P < .01) for dietary NE. The increase in dietary NEg with T and YG supplementation was similar (8.6 vs 8.0%) for diets containing .18 and .32% Mg. In contrast, the increase in dietary NEg with GG supplementation was 8.9% with .18% dietary Mg, but the NEg value of the diet did not increase when GG was added to diets with .32% dietary Mg. Dressing percentage was lower (1.5%, P < .1) and retail yield was greater (2.2%, P < .05) for steers fed GG- than for steers fed YG-supplemented diets. Increasing dietary Mg level increased kidney, pelvic, and heart fat (5.5%, P < .05). There was a fat x Mg level interaction (P < .1) for marbling score. With diets containing no supplemental fat, increasing dietary Mg decreased (15.2%) the marbling score, and with diets containing supplemental fat, increasing dietary Mg increased (7.2%) the marbling score. Fat supplementation decreased (P < .01) ruminal and total tract digestion of OM (10 and 3.5%, respectively) and NDF (37 and 17%, respectively). Supplemental fat did not affect (P > .10) Ca digestion but decreased (41.7%, P < .01) apparent Mg digestion. Increasing dietary Mg level increased (77.7%, P < .05) apparent Mg digestion. There were no treatment effects (P > .10) on postruminal fatty acid digestion. Fat supplementation decreased (17.3%, P < .01) the acetate:propionate molar ratio. Total ruminal protozoal counts were increased (12.7%, P < .05) by increasing dietary Mg level and decreased (12.9%, P < .05) by fat supplementation. We conclude that supplemental fats may depress Mg absorption. Increasing dietary magnesium levels beyond current recommendations may increase marbling scores in cattle fed fat-supplemented diets but may not affect growth performance or dietary NE. The NE value of fat is a predictable function of level of fat intake.     

Effect of type and level of fish oil supplementation on yolk fat composition and n-3 fatty acids retention efficiency in laying hens

1. Laying hen performance and yolk fat fatty acid (FA) concentrations were evaluated with respect to the inclusion in the diet of different sources and levels of marine fish oil (MFO). 2. Twelve diets were arranged factorially, with three sources (MFO1, MFO2_EPA, MFO3_DHA) and four levels of inclusion (15, 30, 45 and 60 g/kg) of MFO. 3. Type of diet had little effect on egg production traits, although laying rate and shell thickness slightly decreased at the highest level of MFO supplementation. 4. An increase in level of inclusion of MFO from 15 to 60 g/kg linearly increased concentrations of C20:5 n-3, C22:5 n-3, C22:6 n-3 and total n-3 FA in yolk fat, but greatly impaired their efficiencies of deposition (g retained/g ingested). 5. An interaction between type and dietary concentration of MFO was found, as the reduction in efficiency of retention of n-3 FA in egg fat with level of MFO was less when the proportion of n-3 in total FA decreased or when that of DHA in total n-3 FA increased. 6. MFO3_ DHA was more efficiently used for total n-3 FA yolk deposition than MFO2_EPA at a similar total n-3 FA intake. 7. Dietary inclusion of MFO reduced LC n-6 FA yolk fat content, which additionally decreased the ratio between total n-6 and total n-3 FA in egg fat. 8. Regression equations were calculated in order to predict efficiency of retention and n-3 FA concentration of yolk fat in the range of diets studied.     

饲粮添加脂肪酸钙对热应激肉牛生长性能和外周血淋巴细胞凋亡的影响

本试验旨在研究饲粮添加不同水平脂肪酸钙对热应激肉牛生长性能、生理指标及外周血淋巴细胞凋亡的影响.试验选择30头体重相近[(450±10) kg]的西门塔尔杂交牛随机分为3组,每组10头,对照组(Ⅰ组)饲喂基础饲粮,Ⅱ组和Ⅲ组分别在每头牛每天的基础饲粮中添加100和200 g脂肪酸钙,试验期39 d.结果表明,饲粮中添加脂肪酸钙对热应激肉牛的直肠温度和呼吸频率无显著影响(P＞0.05).与对照组相比,Ⅱ组和Ⅲ组的平均日增重分别提高了37.5％ (P ＜0.05)和20.8％ (P ＞0.05),料重比分别降低了24.38％ (P ＜0.05)和15.79％(P＞0.05).肉牛饲粮中中性洗涤纤维、酸性洗涤纤维和钙的表观消化率随脂肪酸钙添加量的增加而增加(P＞0.05),磷的表观消化率随脂肪酸钙添加量的增加呈现先升高后降低的趋势(P＞0.05),饲粮中添加脂肪酸钙对粗蛋白质、粗脂肪的表观消化率无显著影响(P＞0.05).肉牛血清中三碘甲腺原氨酸(T3)和甲状腺素(T4)的浓度随着脂肪酸钙添加量的增加呈现为先升高后降低的趋势(P＞0.05),其中Ⅱ组血清T3浓度与对照组相比提高了27.73％ (P ＞0.05),Ⅲ组血清T3浓度与对照组相比降低了4.5％(P＞0.05).肉牛血清中皮质醇的浓度随着脂肪酸钙添加量的增加而极显著升高(P＜0.01).饲粮中添加脂肪酸钙对肉牛血清中葡萄糖、尿素氮、总蛋白含量以及超氧化物歧化酶活性无显著影响(P＞0.05),Ⅲ组丙二醛含量极显著高于对照组(P＜0.01).200 g脂肪酸钙添加量可以极显著降低热应激肉牛外周血淋巴细胞早期凋亡率(P＜0.01)、晚期凋亡率(P＜0.01)和总凋亡率(P＜0.01),但对外周血淋巴细胞周期和淋巴细胞比例(P＞0.05)无明显影响.综合各项指标,在热应激条件下,肉牛饲粮中适宜的脂肪酸钙的添加水平为每天每头100g.     

Effects of dietary energy level on lipid metabolism‐related gene expression in subcutaneous adipose tissue of Yellow breed × Simmental cattle

This study was conducted to estimate the effect of dietary energy level on lipid metabolism‐related gene expression of subcutaneous adipose tissue in Yellow breed × Simmental cattle. The experiment was conducted for 60 days. The results showed that final weight, average daily gain, average backfat thickness, (testicles + kidney + pelvic) fat percentage and subcutaneous fat percentage in the high and medium energy groups were significantly higher than in the low‐energy group but that the feed conversion ratio was significantly lower. The glucose, triglycerides, cholesterol, high‐density lipoprotein and low‐density lipoprotein in the high‐energy group were significantly higher than in the low‐energy group. With dietary energy increasing the activities of lipoprotein lipase (LPL), fatty acid synthase (FAS) and acetyl‐CoA carboxylase (ACC) significantly increased, whereas hormone‐sensitive lipase (HSL) and carnitine palmitoyltransferase‐1 (CPT‐1) significantly diminished. Peroxisome proliferator‐activated receptor γ (PPARγ), LPL, FAS, sterol regulatory element binding protein 1 (SREBP‐1), ACC, stearoyl‐CoA desaturase (SCD) and adipocyte‐fatty acid binding proteins (A‐FABP) gene expression were significantly increased by dietary energy increasing, and HSL and CPT‐1 gene expression were significantly decreased. These results indicated that with dietary energy increasing, the subcutaneous fat accumulation mainly increased due to adipose tissue lipogenic gene expression and decreased lipolytic gene expression.     

Dietary structured lipids for post-weaning piglets: fat digestibility, nitrogen retention and fatty acid profiles of tissues

In four groups of post-weaning piglets the effects of triacylglycerol structure and fatty acid profiles of four dietary fats on apparent faecal nutrient digestibility, nitrogen retention and fatty acid profiles of platelet and erythrocyte membranes, liver, adipose tissue and skeletal muscle were examined. Dietary fats included as 10% (w/w) of the diets were two structured fats of rapeseed oil interesterified with tridecanoin (R1) or coconut oil (R2), respectively, one mixture of rapeseed oil and coconut oil (R3) and rapeseed oil as control (R4). Faeces and urine from piglets weaned at 28 days of age were collected quantitatively during three periods each of 5 days, in which the piglets were kept in metabolism cages for measurement of apparent faecal nutrient and energy digestibility and nitrogen retention. Apparent faecal fat digestibilities were significantly improved in groups fed interesterified fats or the physical mixtures (R1, R2 and R3) compared with rapeseed oil (R4). Apparent faecal nitrogen digestibility and retention were similar in all four groups in the three periods, but increased with time. Apparent faecal fat digestibilities were significantly improved from the first to the third week in the groups R1 and R2. Fatty acid profiles in platelet and erythrocyte membranes and in tissues reflected the fatty acid profile of the dietary fat, except for medium-chain fatty acids, which were only found in low proportions, indicating that 10:0 was mainly used as an energy source.     

Antioxidative and oxidative status in muscles of pigs fed rapeseed oil, vitamin E, and copper

The susceptibility of a given muscle tissue to lipid oxidation may not only depend on the presence of unsaturated fatty acids and the balance between antioxidants and prooxidants, but also on the composition of the skeletal muscle. In the present study, the effects of dietary supplementation of vitamin E (dl-alpha-tocopheryl acetate) and copper in combination with a high level of monounsaturated fatty acids were examined with regard to the antioxidant concentration and the susceptibility to lipid oxidation of two muscles, longissimus (LD) and psoas major (PM), representing different oxidative capacity. In addition, fatty acid profiles of the backfat and the intramuscular lipids, as well as fresh meat quality traits, were studied. Pigs were allotted to a 3x3 factorial experiment with three levels of dl-alpha-tocopheryl acetate (0, 100, and 200 mg/kg of feed) and three levels of copper (0, 35, and 175 mg/kg of feed) added to a diet containing 6% rapeseed oil. A basal diet (without rapeseed oil) was added to the experimental design, giving a total of 10 dietary treatments. Muscle alpha-tocopherol concentrations increased (P<.001) with increasing dl-alpha-tocopheryl acetate in the feed. The antioxidative status was higher in PM than in LD, when considering the concentration of alpha-tocopherol (P<.001) and the activity of antioxidant enzymes (superoxide dismutase, P<.001; glutathione peroxidase, P = .06). Supplemental copper did not give rise to any deposition of copper in muscle tissue or backfat, but the antioxidant status of PM increased. The susceptibility to lipid oxidation was reduced in LD with increasing dietary dl-alpha-tocopheryl acetate and in PM with increasing dietary copper. Supplemental dl-alpha-tocopherol acetate improved the water-holding capacity of LD (P = .005) and PM (P = .003). The fatty acid composition of the backfat and the triglyceride fraction of the intramuscular fat became more unsaturated with the addition of rapeseed oil to the feed. Higher intakes of monounsaturated fatty acids due to the rapeseed oil were also reflected in the phospholipid fraction of the intramuscular fat, but no influence on the proportion of saturated fatty acids was seen. The susceptibility to lipid oxidation of PM was lower for pigs on the rapeseed oil-based diet than for those on the basal diet. The energy metabolic status of the muscles and the accumulation of calcium by the sarcoplasmic reticulum were not influenced by the dietary treatments, but there were differences between muscle types. The addition of rapeseed oil to the diet reduced the muscular content of glycogen (LD, P = .02; PM, P = .06) and elevated the plasma concentration of free fatty acids (P = .05). Overall, dietary fat, dl-alpha-tocopherol acetate, and copper affected the oxidative status of pig muscles, and the results differed depending on muscle type.     

饲粮全棉籽比例对奶牛泌乳性能及乳脂脂肪酸组成的影响

本试验旨在研究饲粮全棉籽比例对奶牛泌乳性能和乳脂脂肪酸组成的影响.试验采用4×4拉丁方试验设计,选择8头泌乳早期的经产中国荷斯坦奶牛(产奶量、胎次、产犊日期接近,健康无疾病),分为4组,每组2个重复,每个重复1头牛.A组饲喂基础饲粮,B、C和D组分别饲喂含5％、10％、15％全棉籽的试验饲粮.每期试验28 d,其中预试期为7d,正试期为21 d.结果表明:随着饲粮全棉籽比例的增加,奶牛产奶量有提高趋势(P＞0.05),校正乳产量极显著提高(P＜0.01).全棉籽极显著地提高了奶牛的乳脂率(P＜0.01),对乳蛋白率、乳糖率和乳非脂固形物率无显著影响(P＞0.05).全棉籽极显著降低了饱和脂肪酸( SFA)的含量(P＜0.01),不同程度地提高了乳中多不饱和脂肪酸( PUFA)和单不饱和脂肪酸(MUFA)的含量(P＜0.05或P＜0.01);短链脂肪酸和中链脂肪酸含量都显著降低(P＜0.05),长链脂肪酸含量有不同程度的提高(P＜0.05或P＜0.01).结果提示,饲粮中添加全棉籽可以提高奶牛产奶量,优化乳脂脂肪酸组成,改善乳脂品质,并以10％为泌乳早期奶牛最佳饲粮全棉籽比例.     

Effects of dietary concentration and degree of polyunsaturation of dietary fat on endogenous synthesis and deposition of fatty acids in chickens

Two experiments were performed to assess the effect of different amounts of dietary polyunsaturated fatty acids (PUFA) on fatty acid composition of chickens. The contribution of de novo fatty acid synthesis to fatty acid profile was also estimated. In trial 1, different fat sources were blended in different ratios allowing a gradient of dietary PUFA (from 15 to 61 g/kg), keeping added fat constant (9%). In trial 2, PUFA-rich oil was added at increasing inclusion rates (2, 4, 6 and 8%), achieving a dietary PUFA content ranging between 27 and 59 g/kg. Increasing dietary PUFA inclusion resulted in an increase in PUFA deposition, with higher efficiency when dietary fat also provided saturated (SFA) and monounsaturated (MUFA) fatty acids (trial 1). Increasing dietary PUFA in both trials resulted in a decrease in SFA and MUFA concentration in the whole body. The estimated deposition of fatty acids from de novo synthesis was reduced when dietary fat content increased from 0 to 10%, varying between 35.34 and 17.66% for SFA and between 52.70 and 7.01% for MUFA in the whole body. The greater variation range for the MUFA supports the existence of a mechanism maintaining the SFA: (MUFA + PUFA) ratio within a specific range in biological membranes.     

饲粮中添加泛酸对生长獭兔肝脏脂肪代谢的影响

本试验旨在研究饲粮中添加泛酸对生长獭兔肝脏脂肪代谢的影响。试验选用体重相似的断奶獭兔160只,随机分为4组,每组40个重复,每个重复1只。对照组獭兔饲喂基础饲粮,试验组獭兔分别饲喂在基础饲粮中添加10、20和40 mg/kg泛酸的饲粮。预试期7 d,正试期56 d。结果表明:与对照组相比,饲粮中添加40 mg/kg泛酸显著降低了生长獭兔肩胛、胃周和肾周脂肪沉积率(P0.05);饲粮中添加10~20 mg/kg泛酸显著降低了生长獭兔肝脏中脂滴的含量(P0.05)。饲粮中泛酸添加水平对生长獭兔血浆中总胆固醇和白蛋白的含量无显著影响(P0.05);随着饲粮中泛酸添加水平的升高,生长獭兔血浆中甘油三酯的含量先降低后趋于稳定,20、40 mg/kg添加组显著低于对照组(P0.05);与对照组相比,饲粮中添加20~40 mg/kg泛酸显著升高了生长獭兔血浆中极低密度脂蛋白的含量(P0.05)。与对照组相比,饲粮中添加40 mg/kg泛酸显著增加了肝脏中激素敏感脂酶(HSL)和骨骼肌中脂肪酸转运蛋白(FATP)基因的表达量(P0.05);饲粮中添加20~40 mg/kg泛酸显著增加了肝脏中肉毒碱棕榈酰转移酶1(CPT1)基因的表达量(P0.05);饲粮中添加10~40 mg/kg泛酸显著增加了肝脏中脂肪酸合成酶(FAS)基因和骨骼肌中CPT1基因的表达量(P0.05)。综上所述,饲粮中添加泛酸影响生长獭兔肝脏内脂肪代谢,泛酸添加水平为40 mg/kg时可降低肝脏内脂肪的沉积,并能降低机体脂肪沉积率,增加骨骼肌对脂肪酸的摄取和利用。     

Effect of dietary energy supply and fat source on the fatty acid pattern of adipose and lean tissues and lipogenesis in the pig

Forty Large White barrows were used to determine whether the effects of dietary fat source (tallow or soy oil at 5% of the diet) on lipogenesis and fatty acid profile of porcine adipose and lean tissue were dependent on dietary digestible energy density (8.8 vs 14.0 MJ DE/kg). Barrows were allocated to one of four groups and offered a fixed amount of feed (170 g x BW0.569/d) from 27 to 105 kg BW. The fatty acid composition of the backfat layers (BF), omental fat (OF), and i.m. adipose tissue of longissimus muscle as well as the activity of lipogenic enzymes of the adipose tissues were determined. Growth performance and carcass characteristics were affected by the dietary energy level (P < 0.01) but not by fat source. In accordance with the lower carcass fat deposition, the activity of lipogenic enzymes were decreased in the low-energy groups (P < 0.01). Within dietary energy level, inclusion of soy oil resulted in increased proportion of PUFA that was compensated by decreased saturated (SFA) and monounsaturated fatty acid (MUFA) proportions (P < 0.01). The SFA changes accounted for 23 (BF) and 24% (OF) of the PUFA changes in the high-energy and 31 (BF) and 39% (OF) in the low-energy diets. The differences in the fatty acid proportions between the soy oil and tallow group were more pronounced in the low-energy groups (fat source x energy density interactions: P < 0.01). Pigs fed the soy oil, low-energy diet had decreased SFA (BF: 28%; OF: 30%) and MUFA (BF: 13%; OF: 19%) concentration, whereas PUFA concentration was increased (BF: 59%; OF: 88%) compared with pigs fed the soy oil, high-energy diet. However, in the tallow groups, pigs fed the low-energy diets had slightly decreased SFA (BF: 14%; OF: 12%) and relatively constant MUFA (BF: 3%; OF: 1%), whereas PUFA concentration increased (BF: 39%; OF: 62%) relative to pigs fed the tallow high-energy diet. Lipid content of the i.m. adipose tissue was decreased in the low-energy groups (P < 0.05). Contrary to what was observed in the adipose tissues, increased PUFA concentration in the neutral and polar lipid fractions of the longissimus muscle was predominantly compensated by reduced MUFA deposition. In the polar lipid fraction, the proportions of both SFA and MUFA were decreased by the low-energy diet. Thus, the extent to which tissue concentration of fatty acids are altered from dietary fats differing in the degree of unsaturation depends on the dietary energy level.     

Relationship between body weight and level of fat supplementation on fatty acid digestion in feedlot cattle

Eight Holstein steers with cannulas in the rumen and proximal duodenum were used in a split-plot design experiment to evaluate the interaction of body weight (175 vs. 370 kg) and level of fat supplementation (0, 3, 6, and 9% yellow grease) on characteristics of digestion and feeding value of fat in finishing diets. Dry matter intake was restricted to 2% of BW. There were no interactions between BW and level of fat supplementation (P > 0.10) on ruminal or total-tract digestion. Level of supplemental fat decreased (linear, P < 0.01) ruminal digestion of OM and NDF, and increased (linear, P < 0.05) ruminal N efficiency. There were no treatment effects (P > 0.10) on postruminal digestion of OM, NDF, and N. There tended to be an interaction (P < 0.10) between BW and level of fat supplementation on postruminal starch digestion. Increasing level of fat supplementation increased postruminal digestion of starch in heavier steers but did not affect starch digestion in lighter steers. There were no interactions (P > 0.10) between BW and level of fat supplementation on postruminal fatty acid digestion. Increasing level of fat supplementation decreased (linear, P < 0.01) postruminal fatty acid digestion, which was due to a decreased (linear, P < 0.01) postruminal digestion of C16:0 and C18:0. Supplemental fat decreased (linear, P < 0.01) total-tract digestion of OM and NDF. The estimated NEm (Mcal/kg) of yellow grease averaged (linear, P < 0.01) 6.02, 5.70, and 5.06 for the 3, 6, and 9% of level supplementation, respectively. We conclude that intestinal fatty acid digestion (FAD, %) is a predictable function (r2 = 0.89; P < 0.01) of total fatty acid intake per unit body weight (FAI, g/kg BW): FAD = 87.560 - 8.591FAI. Depressions in fatty acid digestion with increasing level of intake were due primarily to decreased intestinal absorption of palmitic and stearic acid. Level of fatty acids intake did not appreciably affect intestinal absorption of unsaturated fatty acid. Changes in intestinal fatty acid digestion accounted for most of the variation in the NE value of supplemental fat.     

Use of solid fat in dry mixed feed for rainbow trout (Salmo gairdneri). 2. Fatty acid composition of feed and tissue lipids

The effect of supplemental dietary fat on the fatty acid composition of some tissue lipids of rainbow trout fingerlings was studied. Data showed that dietary fatty acids were deposited nearly unchanged in the adipose tissue. The level of eicosapentaenoic acid, however, dropped significantly. Muscle showed remarkable capacity for deposition of dietary fat, while only minor changes were observed in the fatty acid composition of liver lipids. Levels of some polyenoic acid (e.g. 18: 2 omega 6, 20:4 omega 6, 20:5 omega 3, 22:6 omega 3) showed, that the fish converted lower unsaturated fatty acids to highly unsaturated fatty acids. It was observed that dietary acids had little effect on the fatty acid composition of tissue phospholipids. This result shows, that 17% fat in the diet are tolerated by trout, without alterations in the fat composition of the liver tissue. Probably the low rearing temperature (11 degrees C) had a more pronounced effect on the fatty acid composition of phospholipids than the diet.     

Effects of supplemental fat on growth performance and quality of beef from steers fed corn finishing diets

To measure the effects of dietary fat on feedlot performance and carcass characteristics, and on beef appearance, moisture binding, shelf life, palatability, and fatty acid content, 126 crossbred beef steers (321.1 +/- 0.57 kg of BW) were allotted to a randomized complete block (3) design with a 3 x 2 + 1 factorial arrangement of dietary treatments. The main effects were level of yellow grease (0, 3, or 6%) and alfalfa hay (3.5 or 7%) in corn-based diets containing 15% potato by-product (PB). The added treatment was 6% tallow and 7% alfalfa in a barley-based diet containing 15% PB. Dry matter intake and ADG were not affected by diet; however, G:F and diet NE content increased linearly (P < 0.10) with yellow grease. Kidney, pelvic, and heart fat (2.0 to 2.3 +/- 0.07) and yield grade (2.8 to 3.1 +/- 0.09) increased linearly (P < or = 0.05) with yellow grease. Steers fed corn plus 6% yellow grease had lower (P < 0.05) beef firmness and beef texture scores but greater (P < 0.01) fat color score than those fed barley plus 6% tallow. Moisture retention of beef was not affected by dietary treatment, except purge score during retail storage, which was decreased linearly (P < 0.01) from 2.1 to 1.6 +/- 0.06 by level of yellow grease. Steaks from steers fed barley plus 6% tallow had greater (P < 0.05) shear force than those from steers fed corn plus 6% yellow grease, and beef flavor increased linearly (P < 0.05) from 6.2 to 6.7 +/- 0.11 as the level of yellow grease increased. Level of yellow grease linearly increased (P < 0.01) transvaccenic acid (TVA) by 61% and CLA content of beef by 48%. Beef from steers fed corn plus yellow grease had lower (P < 0.05) palmitoleic and oleic acids and greater (P < 0.05) linoleic, TVA, and CLA than beef from steers fed the barley-tallow diet. Feeding yellow grease increased diet energy content, which increased carcass fatness, and altered beef fatty acid content, which increased beef flavor without affecting moisture retention, shelf life, or cooking properties of the beef. Additionally, beef from steers fed corn plus 6% yellow grease was more tender and had more polyunsaturated fatty acid content and CLA than beef from steers fed barley plus 6% tallow.     

Effects of different levels of protein supplementary diet on gene expressions related to intramuscular deposition in early‐weaned yaks

This study was conducted to estimate different levels of protein supplementary diet on gene expressions related to intramuscular deposition in early‐weaned yaks. Results showed that supplementary dietary protein significantly increased final weight, average daily gain (ADG), intramuscular fat (IMF), serum free fatty acid (FFA), total triglycerides, total cholesterol (Ch), low‐density lipoprotein cholesterol (LDL) and high‐density lipoprotein cholesterol (HDL) content. There was a quadratic response of ADG, IMF, FFA, Ch, HDL and LDL to dietary crude protein (CP) level. Lipoprotein lipase (LPL), fatty acid synthase (FAS) and acetyl‐CoA carboxylase (ACC) enzyme activities were significantly increased by supplementary dietary CP, while hormone‐sensitive lipase (HSL) and carnitine palmitoyltransferase‐1 (CPT‐1) activities were significantly decreased. LPL, ACC and FAS enzyme activities showed quadratic increase as dietary CP increased. Peroxisome proliferator‐activated receptor γ (PPARγ), LPL, FAS, sterol regulatory element binding protein 1 (SREBP‐1), ACC, stearoyl‐CoA desaturase (SCD) and heart fatty‐acid binding protein (H‐FABP) gene expression were significantly increased by supplementary dietary CP, while HSL and CPT‐1 gene expression were significantly decreased. PPARγ, LPL, SREBP‐1, ACC and H‐FABP gene expression showed quadratic increase as dietary CP increased. These results indicated that supplementary dietary protein increased IMF accumulation mainly to increased intramuscular lipogenic gene expression and decreased lipolytic gene expression.     

Effects of dietary fat type and xylanase supplementation in rye containing diets on energy metabolism in male broilers

Xylanase supplementation of rye-based diets which contained 10% beef tallow was shown to markedly improve the digestibility of fat whereas the enzyme effect in diets containing 10% soya oil was much less pronounced (Dänicke et al. 1997b). Such interactions between fat type and xylanase supplementation have also been reported for wheat–rye-based diets (Langhout et al. 1997) and wheat-based diets (Allen et al. 1997) and were attributed mainly to the fatty acid composition of different types of fat and to changes in digesta viscosity caused by soluble pentosan. The apparent metabolizable energy, N-corrected (AME_N) contents of such diets were affected in a similar manner suggesting that energy metabolism is also influenced by xylanase supplementation and the type of dietary fat. However, changes in the metabolizability of gross energy does not necessarily indicate whether the efficiency of metabolizable energy (ME) for energy gain is changed nor if different proportions of ME are used for maintaining an energy equilibrium, i.e. ME maintenance requirement. In addition, studies suggest that both dietary fat level and fat type might exert effects on the efficiency of utilization of ME for energy retention (Carew and Hill 1964; de Groote et al. 1971; Fuller and Rendon 1979; Brue and Latshaw 1985). Hence, the aim of this study was to investigate the partitioning of ME between maintenance needs and energy retained as protein and as fat when feeding rye-based diets. The diets contained either soya oil or beef tallow and were either unsupplemented or xylanase-supplemented.