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.     

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.     

Influence of free fatty acid content on the feeding value of yellow grease in finishing diets for feedlot cattle.

Holstein steers (n = 96; 375 kg) were used in a 144-d growth-performance trial to evaluate influence of level (42, 28.5, and 15%) of FFA content on feeding value of yellow grease. Two sources of yellow grease were compared: conventional yellow grease (CYG), containing 15% FFA, and griddle grease (GG), containing 42% FFA. Dietary treatments consisted of an 88% concentrate finishing diet supplemented with either 1) 0% fat, 2) 5% GG, 3) 2.5% GG and 2.5% CYG, or 4) 5% CYG. Fat supplementation increased ADG (11%; P<.05), feed efficiency (9%; P<.05), diet NE (6.4%; P<.05), carcass weight (4%; P<.10), dressing percentage (1%; P<.10), and kidney, pelvic, and heart fat (20%, P<.05). Increasing the FFA in supplemental fat increased (linear effect, P<.10) DM intake, ADG, and feed efficiency and decreased (linear effect, P<.10) retail yield. These improvements in performance were primarily due to increased DM intake. The NEm and NEg values of supplemental fats were not affected by FFA content, averaging 4.98 and 3.85 Mcal/kg, respectively. Treatment effects on characteristics of ruminal and total tract digestion were evaluated using four Holstein steers (180 kg) with cannulas in the rumen and proximal duodenum. Supplemental fat did not influence (P>.10) ruminal or total tract digestion of OM, ADF, starch or N. Postruminal fatty acid digestion was less (P<.10) for fat-supplemented diets than for unsupplemented diets (73.0 vs. 78.6%). The decrease in postruminal fatty acid digestibility with fat supplementation was mainly due to a decreased (16.7%; P<.05) digestibility of C18:0. Postruminal digestibility of the supplemental fat was 68%. There were no treatment effects (P>.10) on ruminal pH. Ruminal biohydrogenation of fatty acids was directly proportional to estimates of methane production. We conclude that the feeding value of conventional yellow grease and griddle grease is similar and that differences in the FFA content of yellow grease will not negatively affect diet acceptability and growth performance of feedlot cattle.     

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.     

Effect of conjugated linoleic acid on meat quality,lipid metabolism,and sensory characteristics of dry-cured hams from heavy pigs

We investigated conjugated linoleic acid (CLA) supplementation administered to heavy pigs, assessing carcass characteristics, meat quality, and sensory characteristics of dry-cured (Parma) ham. Thirty-six pigs, averaging 97 kg BW, were assigned randomly to three feeding groups in which diets were supplemented with either 0, 0.25, or 0.5% (as-fed basis) of a CLA preparation containing 65% CLA isomers. All pigs were slaughtered at 172 kg BW. No (P > 0.05) differences were observed in dressing percentage, loin and ham weight, or pH and color of longissimus and semimembranosus muscle. Tenth-rib backfat thickness tended to be lower (P < 0.10) in carcasses from CLA-fed pigs. The oxidative stability of longissimus muscle was greater (P < 0.05) in pigs fed CLA than control, but only at the longer (300 min) oxidation time. Acetyl-CoA carboxylase activity in adipose tissue of CLA-fed pigs was less (P < 0.05) than that of pigs fed diets devoid of supplemental CLA. Composition of ham fat was markedly affected (P < 0.01) by dietary CLA, with higher saturated fatty acids, lower monounsaturated fatty acids, and higher CLA in the fat of CLA-fed pigs regardless of supplementation level. Although melting quality was improved (P < 0.05), most sensory characteristics and the chemical composition of dry-cured hams were not (P > 0.05) affected by incorporation of CLA. Results indicated that dietary CLA alters lipid metabolism, producing lower concentrations of monounsaturated fatty acids and increased concentrations of CLA isomers in the fat of heavy pigs. Moreover, supplementing diets with CLA produced only minimal improvements in Parma ham sensory traits and had no appreciable effects on fresh pork quality.     

Influences of wet feeding and supplementation with ascorbic acid on performance and carcass composition of broiler chicks exposed to a high ambient temperature.

In two experiments was investigated whether feeding with an air-dry feed mixed with different amounts of water and/or supplemental ascorbic acid affect performance and carcass compositions of broilers exposed to a high ambient temperature (35 to 37 degrees C for 8 h/d and thermoneutral for 16 h/d). In the first trial, 64 one-week-old male broiler chicks were fed ad libitum in four dietary treatment groups for a 6-week period. Experimental mash diets were prepared by mixing a maize-soybean based standard broiler starter or finisher with tap water in the ratios of 0.0:1.0, 0.5:1.0, 1.0:1.0 and 1.5:1.0 (water:air-dry feed, w/w). More water in the diet increased BWG, DMI, abdominal fat and carcass weight, carcass CP, crude fat, but it deteriorated DM conversion efficiency. In the second experiment, 64 one-week-old male broiler chicks were given air-dry or wet (water:feed, 1.5:1) starter or finisher diets without or with ascorbic acid supplementation (0 and 250 mg/kg air-dry feed, resp.) ad libitum for a 6-week period. Ascorbic acid supplementation increased BWG, carcass weight and carcass CP significantly, while reducing carcass crude fat content. However, feeding broilers with a diet mixed with water in a ratio of 1.5:1.0 increased BWG, DMI, carcass weight and carcass lipid markedly, but deteriorated DM conversion efficiency. There was also a significant interaction between ascorbic acid and wet feeding, whereby ascorbic acid supplementation induced a significant reduction in carcass lipid contents of broilers fed on air-dry diets but not on wet diets. It is concluded that wet feeding, especially an addition of 150% water to produce a porridge like consistency, improved growth performance by increasing fat, ash and protein deposition in the body, while reducing DM conversion efficiency. It is also concluded that under heat stress supplemental ascorbic acid in air-dry diets stimulates broiler performance but not in wet diets.     

Effects of supplemental fat source on nutrient digestion and ruminal fermentation in steers

Five Holstein steers (235 kg of BW) fitted with ruminal, duodenal, and ileal cannulas were used in a 5 x 5 Latin square design experiment to determine the effects of supplemental fat source on site and extent of nutrient digestion and ruminal fermentation. Treatments were diets based on steam-flaked corn containing no supplemental fat (control) or 4% (DM basis) supplemental fat as tallow, dried full-fat corn germ (corn germ), corn oil, or flax oil. Fat supplementation decreased (P < 0.08) ruminal starch digestion but increased (P < 0.03) small intestinal starch digestion as a percentage of intake. Feeding corn germ decreased (P < 0.09) ruminal starch digestion and increased (P < 0.03) large intestinal starch digestion compared with steers fed corn oil. Large intestinal starch digestion was less (P < 0.04), and ruminal NDF digestion was greater (P < 0.09) for steers fed tallow compared with steers fed other fat sources. Small intestinal (P < 0.08) and total tract NDF digestibilities were greater (P < 0.02) for steers fed corn germ than for those fed corn oil. Feeding tallow increased total ruminal VFA (P < 0.03) and NH(3) (P < 0.07) concentrations compared with steers fed the other fat sources. Feeding corn germ led to a greater (P < 0.02) rate of ruminal liquid outflow compared with corn oil. A diet x hour interaction (P < 0.04) occurred for ruminal pH, with steers fed corn oil having the greatest ruminal pH 18 h after feeding, without differences at other time points. Fat supplementation increased (P < 0.09) ruminal concentrations of Fusobacterium necrophorum. Duodenal flow of C18:3n-3 was greater (P < 0.01) for steers fed flax oil compared with those fed corn oil. Feeding corn germ led to less (P < 0.01) ruminal biohydrogenation of fatty acids compared with corn oil. Steers fed tallow had greater small intestinal digestibility of C14:0 (P < 0.02) and C16:1 (P < 0.04) than steers fed the other fat sources. Fat supplementation decreased (P < 0.06) small intestinal digestibility of C18:0. Feeding corn germ decreased (P < 0.10) small intestinal digestibility of C18:1 compared with corn oil. It appears that source of supplemental fat can affect the site and extent of fatty acid and nutrient digestion in steers fed diets based on steam-flaked corn.     

Effects of dietary supplementation with L-carnitine and fat on blood acid-base responses to handling in slaughter weight pigs

Blood acid-base responses to handling were evaluated in slaughter weight pigs fed diets supplemented with l-carnitine and fat. The study was carried out as a randomized block design with a 2 x 2 factorial arrangement of treatments: 1) dietary L-carnitine supplementation (0 vs. 150 ppm, as-fed basis); and 2) dietary fat supplementation (0 vs. 5%, as-fed basis). Sixty pigs (91.1 +/- 5.14 kg BW) were housed in mixed-gender groups of five and had ad libitum access to test diets (0.68% true ileal digestible lysine, 3,340 kcal of ME/kg, as-fed basis) for 3 wk. At the end of the feeding period (110.3 +/- 7.52 kg BW), pigs were subjected to a standard handling procedure, which consisted of moving individual animals through a facility (12.2 m long x 0.91 m wide) for eight laps (up and down the facility), using electric prods (two times per lap). There was no interaction between dietary L-carnitine and fat supplementation for any measurement. Pigs fed 150 ppm of supplemental L-carnitine had lower baseline blood glucose (P < 0.05) and higher baseline blood lactate (P < 0.05) concentrations than the nonsupplemented pigs. After handling, pigs fed L-carnitine-supplemented diets had a higher (P < 0.05) blood pH and showed a smaller (P < 0.05) decrease in blood pH and base excess than those fed the nonsupplemental diets. Baseline plasma FFA concentrations were higher (P < 0.01) in pigs fed the 5% fat diet. After the handling procedure, blood glucose, lactate, and plasma FFA were higher (P < 0.05) in pigs fed the 5 vs. 0% fat diets, but blood pH, bicarbonate, and base excess were not affected by dietary fat. The handling procedure decreased (P < 0.01) blood pH, bicarbonate, base excess, and total carbon dioxide and increased (P < 0.01) blood lactate, partial pressure of oxygen, and glucose, and also increased (P < 0.01) rectal temperature. Free fatty acid concentrations were increased by handling in pigs fed both 0 and 5% fat and 150 ppm L-carnitine. In conclusion, dietary L-carnitine supplementation at the level and for the feeding period evaluated in the current study had a relatively small but positive effect on decreasing blood pH changes in finishing pigs submitted to handling stress; however, dietary fat supplementation had little effect on blood acid-base balance.     

Influence of level and source of dietary fat on its comparative feeding value in finishing diets for steers: feedlot cattle growth and performance

Two hundred twenty-eight crossbred steers (304 kg) were used in a 125-d comparative slaughter trial to evaluate the influence of level and source of supplemental fats on their feeding value for feedlot cattle. Dietary treatments consisted of a steam-rolled, barley-based finishing diet containing 1) no supplemental fat; 2) 4% yellow grease (YG); 3) 4% blended animal-vegetable fat (BVF); 4) 8% YG; 5) 8% BVF or 6) 6% BVF and 2% crude soybean lecithin. Increasing level of supplemental fat in the diet resulted in linear improvements (P less than .01) in weight gain, feed conversion and NE value of the diet. Estimated NE values of YG and BVF were similar and did not appear to be influenced by level of supplementation, averaging 5.78 and 4.61 Mcal/kg for maintenance and gain, respectively. Fat supplementation resulted in linear increases in empty body fat (P less than .01), kidney, pelvic and heart fat (P less than .01) and marbling score (P less than .05). Partially replacing BVF with lecithin did not influence (P greater than .10) steer performance, carcass merit or estimated NE value of the diet. The comparative feeding value (in terms of both diet acceptability and NE value) of the supplemental fats tested was similar and was apparently not influenced by level of supplementation up to 8% of diet DM.     

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.     

Comparative feeding value of supplemental fat in steam-flaked corn- and steam-flaked wheat-based finishing diets for feedlot steers.

One hundred thirty crossbred steers (324 kg) were used in a 121-d comparative slaughter trial to evaluate the feeding value of fat in steam-flaked corn- (SFC) or wheat- (SFW) based diets. Treatments consisted of an 88% concentrate finishing diet containing 1) SFC, no fat; 2) SFC, 6% yellow grease (YG); 3) SFC, 6% cottonseed oil soapstock (COS); 4) SFW, no fat; 5) SFW, 6% YG; and 6) SFW, 6% COS. There were no interactions (P greater than .10) between grain type and performance response to supplemental fat. Fat supplementation increased (P less than .05) ADG by 7.3% and decreased (P less than .01) DMI/gain by 10.6%. Fat supplementation decreased (P less than .05) ruminal OM digestion by 5% and net flow of microbial N to the small intestine by 14.5% but did not affect (P greater than .10) total tract digestion of OM, ADF, or starch. Substituting SFW for SFC did not influence (P greater than .10) ADG but tended (P greater than .10) to increase DMI/gain and decreased (P less than .05) the NEm and NEg of the diet by 3.4 and 4.3%, respectively. Ruminal OM digestion was similar (P greater than .10) for SFC and SFW. Flow of microbial N to the small intestine was 12% greater (P less than .05) with SFW. Total tract digestibilities of OM and starch were similar (P greater than .10) for both grains. However, ADF digestion was lower (34%, P less than .01) with SFW. It is concluded that the feeding value of supplemental fat is similar for wheat- and corn-based finishing diets. The performance response to supplemental YG and COS was similar. The NEm and NEg values of YG were 6.35 and 4.93 Mcal/kg, respectively, whereas the corresponding values for COS were 5.69 and 4.60 Mcal/kg. Supplementation of growing-finishing diets with up to 6% (.45 kilograms/day) of fat did not directly influence body composition. The NE value of SFW was approximately 96% of the value of SFC.     

Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.     

Supplemental safflower oil affects the fatty acid profile, including conjugated linoleic acid, of lamb

The objective of this study was to determine whether increasing levels of dietary safflower oil would alter unsaturated fat (especially CLA) and tocopherol content of lamb, animal performance, carcass characteristics, or color stability of lamb muscle tissue. Targhee x Rambouillet wethers (n = 60) were assigned to one of three diets (four pens per treatment with five lambs per pen) in a completely random design. Diets were formulated with supplemental safflower oil at 0 (control), 3, or 6% (as-fed basis) of the diet. Diets containing approximately 80% concentrate and 20% roughage were formulated, on a DM basis, to be isocaloric and isonitrogenous and to meet or exceed NRC requirements for Ca, P, and other nutrients. A subsample of 12 wethers per treatment was selected based on average BW (54 kg) and slaughtered. Carcass data (LM area, fat thickness, and internal fat content) and wholesale cut weight (leg, loin, rack, shoulder, breast, and foreshank), along with fatty acid, tocopherol, and color analysis, were determined on each carcass. The LM and infraspinatus were sampled for fatty acid profile. Increasing safflower oil supplementation from 0 to 3 or 6% increased the proportion of linoleic acid in the diet from 49.93 to 55.32 to 62.38%, respectively, whereas the percentage of oleic acid decreased from 27.94 to 23.80 to 20.73%, respectively. The percentage of oil in the diet did not (P > or = 0.11) alter the growth and carcass characteristics of lambs, nor did it alter the tocopherol content or color stability of meat. Increasing levels of safflower oil in lamb diets decreased (P < 0.01) the weight percentage of oleic acid in the infraspinatus and LM, and increased linoleic acid (P < 0.01). Oil supplementation increased (P < 0.01) the weight percentage of various isomers of CLA in muscle, with the greatest change in the cis-9,trans-11 isomer. Supplementation of sheep diets with safflower oil, up to 6% of the diet, resulted in increasing levels of unsaturated fatty acids and CLA in the lean tissue, without adversely affecting growth performance, carcass characteristics, or color stability of lamb.     

The influence of dietary linoleic and alpha-linolenic acid on body composition and the activities of key enzymes of hepatic lipogenesis and fatty acid oxidation in mice

We have recently suggested that feeding the C18 polyunsaturated fatty acid, alpha-linolenic acid (ALA), instead of linoleic acid (LA) reduced body fat in mice. However, the difference in body fat did not reach statistical significance, which prompted us to carry out this study using more animals and diets with higher contents of ALA and LA so that the contrast would be greater. The diets contained either 12% (w/w) LA and 3% ALA or 12% ALA and 4% LA. A low-fat diet was used as control. The diets were fed for 35 days. The proportion of body fat was not influenced by the type of dietary fatty acid. Plasma total cholesterol and phospholipids were significantly lower in ALA-fed mice than in mice fed LA. Activities of enzymes in the fatty acid oxidation pathway were significantly raised by these two diets when compared with the control diet. alpha-Linolenic acid vs. LA did not affect fatty acid oxidation enzymes. In mice fed the diet with LA activities of enzymes of de novo fatty acid synthesis were significantly decreased when compared with mice fed the control diet. alpha-Linolenic acid vs. LA feeding did not influence lipogenic enzymes. It is concluded that feeding mice for 35 days with diets either rich in LA or ALA did not significantly influence body composition.     

Influence of ruminal biohydrogenation on the feeding value of fat in finishing diets for feedlot cattle

Four Holstein steers (212 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to study the influence of degree of ruminal biohydrogenation (BH) on the feeding value of supplemental fat. Treatments consisted of an 88% concentrate finishing diet supplemented with 1) 2% yellow grease (control); 2) 4% formaldehyde-protected fat (Rumentek), 2% yellow grease (LBH); 3) 2% Rumentek, 4% yellow grease (MBH); or 4) 6% yellow grease (HBH). Ruminal BH of HBH, MBH, and LBH diets was 74, 68, and 54%, respectively. High-fat supplementation decreased (7%, P < .05) intestinal digestibility of 18:0 but increased intestinal digestibility of 18:1 (3%, P < .10), 18:2 (14%, P < .01), and 18:3 (23%, P < .05). Increases in intestinal digestibility of 18:0 (quadratic effect, P < .05), 18:1 (linear effect, P < .01), 18:2 (linear effect, P < .01), 18:3 (linear effect, P < .05), and total fatty acids (linear effect, P < .05) were inversely related to BH. For every 1% increase in the proportion of 18:1 fat entering the small intestine, the digestibility of 18:0 increased 1%. High-fat supplementation depressed ruminal digestion of OM (11%, P < .05), NDF (16%, P < .05), starch (6%, P < .05), and feed N (12%, P < .01). Formaldehyde-protein protection of fat diminished its depressing effects on ruminal digestion of NDF (quadratic effect, P < .10) and enhanced ruminal escape of feed N (linear effect, P < .10). Postruminal digestion of OM was greater (4.6%, P < .10) for high-fat diets. High-fat diets decreased (P < .05) total tract digestion of OM (1.9%), NDF (7.4%), and starch (.5%). Postruminal and total tract digestibility of OM, NDF, N, and starch was not affected (P > .10) by BH. In a 125-d finishing trial, 100 yearling steers (362 kg) were used to evaluate treatment effects on growth performance. High-fat diets did not affect (P > .10) ADG but increased (P < .10) feed efficiency (9%, P < .10), dietary NEm (7.6%, P < .05), and dressing percentage (9%, P < .05). The magnitude of the increase in dressing percentage was inversely related (linear effect, P < .10) to BH. We conclude that decreasing ruminal BH will increase postruminal digestibility of fat, and hence the NE value of dietary fat. The synergistic effect of increasing the proportion of 18:1 on intestinal digestion of fat enables higher levels of fat supplementation. Protecting fat from BH minimizes the detrimental effects of supplemental fat on fiber digestion.     

Comparison of effects of dietary olive oil,tallow and vitamin E on the quality of broiler meat and meat products

1. The effect of dietary fat and vitamin E supplementation on quality attributes (drip loss, oxidative stability, sensory quality) in chicken meat and meat products was investigated. Broiler chicks were fed on diets containing tallow (60 g/kg) or olive oil (60 g/kg) at a basal (30 mg/kg diet) or supplemental (200 mg/kg diet) concentration of alpha-tocopheryl acetate for 8 weeks. The alpha-tocopherol content and fatty acid composition of breast and thigh meat was determined. Drip loss was determined in breast fillets. Lipid oxidation (thiobarbituric acid-reacting substances/TBARS) and sensory quality (warmed-over flavour development/WOF) were assessed in minced thigh meat during storage. 2. Dietary olive oil increased the ratio of monounsaturated to saturated fatty acids (MUFA/SFA) in the diets. In breast and thigh, this resulted in approximately a two-fold increase in the MUFA/SFA ratio. Supplemental alpha-tocopherol increased the alpha-tocopherol content of muscles. 3. Dietary fat did not influence drip loss in thawed breast fillets during refrigerated storage, but supplemental alpha-tocopherol reduced drip loss. 4. TBARS and WOF development in minced thigh meat patties were also reduced by supplemental alpha-tocopherol following frozen storage, or cooking and refrigerated storage. Storage stability was not adversely affected by dietary fat. 5. Overall, the results showed that increasing the monounsaturated profile of chicken meat lipids did not adversely affect quality characteristics. Dietary alpha-tocopherol supplementation was a more important factor in the determination of broiler meat quality.     

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.     

Effects of saturated and unsaturated fats with vitamin E supplementation on the antioxidant status of broiler chicken tissues

The influence of fish oil (highly unsaturated) and beef tallow (highly saturated) with vitamin E (100 IU/kg) supplementation on the antioxidant status of broiler chicken cockerels was investigated. Chicks were fed a control diet with no added fat, 40 g/kg each of fish oil and beef tallow diets, respectively, from 11 to 42 days of age. Tocopherol concentration and the rate of lipid peroxidation, thiobarbituric acid reactive substance (TBARS) in liver, fatty acid composition of the liver lipids, blood serum total antioxidant status (TAS), and reduced glutathione (GSH) content were determined. Vitamin E supplementation of the diet increased liver alpha-tocopherol content in chicks regardless of the type of dietary fat. Fish oil diet resulted in higher liver TBARS value while beef tallow diet showed lower values compared to the control diet. Vitamin E supplementation reduced liver TBARS as well as serum GSH, and raised serum TAS for all diets. Serum GSH was the same for vitamin E supplemented diets regardless of the fat supplement. Fish oil diets resulted in a significant increase in hepatic lipid n-3 PUFA content. A significant positive correlation was found between liver TBARS and n-3 PUFA content. No relationships were established, however, between liver TBARS and n-6 PUFA or saturated fatty acids. The results suggest that feeding oils rich in n-3 PUFA increases tissue concentration of these fatty acids, consequently increasing tissue lipid peroxidation and reducing the antioxidative status of broiler chickens. Supplementing high levels of vitamin E with such oils may increase tissue oxidative stability. Serum TAS or GSH may be used as a measure of antioxidative status in chickens.     

Effect of dietary vitamin A concentration and roasted soybean inclusion on marbling, adipose cellularity, and fatty acid composition of beef

A feedlot trial was conducted to determine the effect of dietary vitamin A concentration and roasted soybean (SB) inclusion on carcass characteristics, adipose tissue cellularity, and muscle fatty acid composition. Angus-crossbred steers (n = 168; 295 +/- 1.8 kg) were allotted to 24 pens (7 steers each). Four treatments, in a 2 x 2 factorial arrangement, were investigated: no supplemental vitamin A, no roasted soybeans (NANS); no vitamin A, roasted SB (20% of the diet on a DM basis; NASB); with supplemental (2,700 IU/kg) vitamin A, no roasted SB (WANS); and with supplemental vitamin A, roasted SB (WASB). Diets included high moisture corn, 5% corn silage, 10 to 20% supplement, and 20% roasted SB in the SB treatments on a DM basis. The calculated vitamin A concentration in the basal diet was < 1,300 IU/kg of DM. Blood samples (2 steers/pen) were collected for serum vitamin A determination. Steers were slaughtered after 168 d on feed. Carcass characteristics and LM composition were determined. Fatty acid composition of LM was analyzed, and adipose cellularity in the i.m. and s.c. depots was determined. No vitamin A x SB interactions were detected (P > 0.10) for cattle performance, carcass composition, or muscle fatty acid composition. Low vitamin A diets (NA) did not affect (P > 0.05) ADG, DMI, or G:F. Quality grade tended (P = 0.07) to be greater in NA steers. Marbling scores and the percentage of carcasses grading > or = Choice(-) were 10% greater for NA steers, although these trends were not significant (P = 0.11 and 0.13, respectively). Backfat thickness and yield grade were not affected (P > 0.26) by vitamin A supplementation. Composition of the LM was not affected (P > 0.15) by vitamin A or SB supplementation. Serum retinol at slaughter was 44% lower (P < 0.01) for steers fed NA than for steers supplemented with vitamin A (23.0 vs. 41.1 microg/dL). A vitamin A x SB interaction occurred (P < 0.05) for adipose cellularity in the i.m. depot; when no SB was fed, vitamin A supplementation decreased cell density and increased cell size. However, when SB was fed, vitamin A supplementation did not affect adipose cellularity. Adipose cellularity at the s.c. depot was not affected (P > 0.18) by vitamin A or SB treatments. Fatty acid profile of the LM was not affected by vitamin A (P > 0.05), but SB increased (P < 0.05) PUFA (7.88 vs. 4.30 g/100 g). It was concluded that feeding NA tended to increase marbling without affecting back-fat and yield grade. It appeared that NA induced hyperplasia in the i.m. but not in the s.c. fat depot.     

Effects of supplemental rumen-protected conjugated linoleic acid or corn oil on fatty acid composition of adipose tissues in beef cattle

Thirty-six Angus x Hereford heifers (365 +/- 60 kg) were used to determine the effects of supplemental dietary lipid sources on fatty acid composition of i.m., perianal (p.a.), and s.c. lipid depots. Lipid was supplied to diets as either corn oil or a rumen-protected conjugated linoleic acid (CLA) salt for two specific treatment periods of either the final 32 or 60 d on feed. Following an initial 56-d feeding period, heifers were fed one of three dietary treatments (DM basis): 1) basal diet containing 88% concentrate and 12% grass hay (CON), 2) basal diet plus 4% corn oil (OIL), or 3) basal diet plus 2% rumen-protected CLA salt (RPCLA) containing 31% CLA. The trans-10, cis-12 CLA concentration was greatest (P < 0.05) for heifers fed RPCLA and OIL diets and least (P < 0.05) for CON, regardless of time on dietary treatment. Heifers fed supplemental RPCLA had greater (P < 0.05) total CLA content than either CON- or OIL-fed heifers. Adipose tissue concentration of trans-11 vaccenic acid (TVA) was less (P < 0.05) for CON than OIL or RPCLA, which did not differ (P > 0.05). Percentages of C18:1 trans-10 were least (P < 0.05) in i.m. lipid compared with p.a. and s.c., which did not differ (P > 0.05). Following 60 d of lipid supplementation, heifers fed OIL and RPCLA had lower (P < 0.05) concentrations of oleic acid and total monounsaturated fatty acids (MUFA) compared with CON. The ratio of cis-9, trans-11 CLA:TVA was higher (P < 0.05) for heifers fed 60 vs. 32 d, but did not differ (P > 0.05) between adipose depots. Feeding OIL increased (P < 0.05) adipose concentration of C18:2 fatty acid, whereas feeding RPCLA increased (P < 0.05) total CLA isomers by 22%. Intramuscular lipid contained the lowest (P < 0.05) percentage of cis-9, trans-11 CLA, total CLA, C18:1 cis-9, C18:1 trans-10, and TVA. Total CLA and cis-9, trans-11 CLA isomers were increased (P < 0.05) in p.a. and s.c. adipose depots, whereas i.m. adipose tissue contained increased (P < 0.05) amounts of total PUFA. Results from this study indicate that short-term lipid supplementation to feedlot cattle can increase adipose tissue CLA concentrations, but only marginally (8.3 to 17.5%). Moreover, observed decreases in oleic acid and total MUFA concentrations of adipose tissues from heifers fed rumen-protected CLA or corn oil suggest that lipid supplementation may decrease delta9 desaturase activity in adipose tissues, which in turn would lower the conversion of TVA to cis-9, trans-11 CLA isomer.