Fatty acid digestibility and lactation performance by dairy cows fed fats varying in degree of saturation

Holstein cows fed fats varying in degree of saturation were used to evaluate lactation performance (35 multiparous and 15 primiparous cows) and fatty acid digestibility (5 cows). Data from wk 2 and 3 of lactation were used for covariable adjustment of data from wk 4 through 19. Diets were a basal diet (control) with no added fat and four diets with 5% added fat from tallow, tallow plus partially hydrogenated tallow in proportions of 2:1 or 1:2, or partially hydrogenated tallow; iodine values were 45, 35, 26, and 16 for the diets with added fat, respectively. Digestibilities of OM, NDF, and N were not affected by fat supplementation (mean of four fat treatments vs. control) or by degree of fat saturation. Fatty acid digestibility was lower for cows fed fat than for those fed the control diet and decreased linearly with increased fat saturation. In both trials, DMI increased linearly as fat saturation increased. In the digestion trial, cows fed fat tended to have lower DMI than those fed the control diet, primarily because of the unsaturated fat. In the production trial, DMI was similar for cows fed the control diet (22.3 kg/d) or the diet with added fat from tallow (22.1 kg/d) and tended to be higher for cows fed the diet containing partially hydrogenated tallow (23.9 kg/d). Milk production was higher for cows fed fat than for cows fed the control diet, but 4% FCM was unaffected. Milk fat and protein percentages were not affected by fat supplementation but increased linearly with increased fat saturation. Mean body condition score of cows increased as fat saturation increased. The lower digestibility of the diet with added fat from partially hydrogenated tallow was offset by higher DMI and percentages of milk fat and protein as fat became more saturated.     

Roasted soybeans, blood meal, and tallow as sources of fat and ruminally undegradable protein in the diets of lactating cows

The effect of roasted soybeans, blood meal, and tallow as sources of fat and RUP for lactating dairy cows was studied. Forty-five cows, blocked by age, calving date, and milk yield during the previous lactation, were assigned randomly to the following treatments (ingredient in the DM, RUP as a percentage of CP, and fat in the DM, respectively): 1) soybean meal (16, 35, and 3.2%), 2) whole roasted soybeans (18, 40, and 6.2%), 3) ground roasted soybeans (18, 40, and 6.2%), 4) blood meal (2.7, 40, and 3.2%), and 5) blood meal plus tallow (2.7 and 3, 40, and 6.2%). Diets were fed from wk 3 to 18 of lactation and consisted of 20% alfalfa silage, 30% corn silage, and 50% concentrate. The DMI of blood meal and whole roasted soybean diets was about 11% lower than DMI of the soybean meal diet. Milk yield (38.4 kg/d) and milk fat percentage (3.37%) were similar among diets. The roasted soybean diets resulted in the lowest milk protein percentage. Less than 2.7% blood meal might be advisable for diets fed to high yielding dairy cows to avoid reduced DMI.     

Early lactation responses of Holstein cows fed a rumen-inert fat prepartum, postpartum, or both

Primiparous (n = 22) and multiparous (n = 41) cows were randomly assigned by calving date and parity to one of four dietary sequences of supplemental fat from 14 d prepartum to 151 d postpartum. Partially hydrogenated tallow was added to diets at 0% prepartum and postpartum (control); 1% prepartum and 2% postpartum; 0% prepartum and 2% postpartum; and 0% prepartum, 0% from 1 to 34 d postpartum, and 2% from 35 to 151 d postpartum. Inclusion of partially hydrogenated tallow did not influence yields of milk or 3.5% FCM, milk composition, or DMI during the first 151 d postpartum. During the first 35 d postpartum, cows receiving partially hydrogenated tallow starting at parturition yielded milk with a higher fat content than those receiving fat prepartum and postpartum. Addition of partially hydrogenated tallow to diets starting 35 d postpartum resulted in cows being more persistent in yields of milk and 3.5% FCM from 60 to 151 d postpartum. Reproduction parameters measured were unaffected by time of fat addition to diets. Our data suggest that delaying the addition of partially hydrogenated tallow to diets until 35 d postpartum may improve the persistency of lactation.     

Assessment of the effects of iodine value on fatty acid digestibility, feed intake, and milk production

Data were pooled from 11 studies evaluating supplemental fat sources differing primarily in degree of saturation (tallow, animal-vegetable fat, vegetable oil, and hydrogenated fats). Data were standardized as proportions of the respective controls to reduce variation among individual studies and were subjected to stepwise multiple regression against the iodine value of fats, the percentage increases of total fatty acids in diets above the respective controls, or the ratio of total C16 to C18 fatty acids in fats (only for hydrogenated fats). Increased iodine value (increasing unsaturation) of fats increased apparent fatty acid digestibility, especially as iodine value increased from 11 to 27. For partially hydrogenated fat sources, as the ratio of C16 to C18 fatty acids increased, digestibility also increased, especially with increasing iodine value (positive interaction). Beneficial effects of higher C16:C18 ratio were reduced as amount of added fat increased (negative interaction). Dry matter intake and FCM production decreased as iodine value increased, perhaps because of inhibition of fiber digestion or metabolic regulation of DMI. Milk protein percentage depression averaged .2 percentage units for most fats. However, as partially hydrogenated fat sources became more saturated, milk protein depression appeared to be less evident; increased ratio of C16:C18 of fatty acids appeared to increase milk protein percentage. Despite the lower apparent digestibility of fatty acids of hydrogenated fats, increased milk production and percentages of fat and protein appeared to make them more economical than more unsaturated fats.     

Influence of sorghum grain processing on performance and nutrient digestibilities in dairy cows fed varying concentrations of fat

Forty Holstein cows averaging 85 +/- 50 d in milk were assigned to five dietary treatments for 56 d to determine the effects of ruminal starch degradability and supplemental fat on milk yield and composition and nutrient digestibilities. Treatments were 1) dry-rolled sorghum, no added fat; 2) dry-rolled sorghum plus 2.5% prilled fatty acids; 3) steam-flaked sorghum, no added fat; 4) steam-flaked sorghum plus 2.5% prilled fatty acids; and 5) steam-flaked sorghum plus 5% prilled fatty acids. Fat supplementation at 2.5 and 5% increased the content of fatty acids in diets from 3.0 to 5.4 and 7.7%, respectively. Milk yield was increased 2.0 kg/d when steam-flaked sorghum plus 0 or 2.5% added fat was fed and was 2.4 kg/d higher when prilled fatty acids were fed at 2.5 versus 0%. Cows fed supplemental fat at 5% did not increase milk yield over that of cows fed no added fat. For cows fed 2.5% fat, steam-flaking decreased dry matter intake 12% and increased efficiency of conversion of feed to milk 11%. Milk composition was unaffected by treatments, except that lactose was depressed by fat supplementation. Milk protein yield and efficiency of conversion of dietary protein to milk protein were increased when steam-flaked sorghum was fed. Starch digestibilities were increased from 92.6 to 98.2% when sorghum was steam-flaked compared with dry-rolled and fat supplementation tended to decrease digestibility of neutral detergent fiber. Steam-flaking tended to improve, and the addition of 2.5% fat did improve, the lactational performances of the cows. These effects appeared additive, but 5% fat appeared to be excessive.     

Interactions of tallow and hay particle size on yield and composition of milk from lactating Holstein cows

An 18-wk lactation study was conducted to determine whether the effects of tallow on the lactation performance of dairy cows were influenced by particle size of hay in the ration. A total mixed ration containing 50% concentrate, 25% corn silage, and 25% alfalfa hay (dry matter basis) was fed to Holstein cows. Four total mixed rations were developed based on differences in the percentage of tallow in the concentrate and particle size of alfalfa hay: 1) 0% tallow, long-cut hay; 2) 0% tallow, short-cut hay; 3) 5% tallow, long-cut hay; and 4) 5% tallow, short-cut hay. Ration had no effect on dry matter intake, body weight gain or change in body condition score. Tallow increased milk and milk protein yields but reduced milk protein concentration. However, the effects of tallow on milk and milk protein yields were the same, regardless of hay length in the ration. A tendency for an interaction of tallow and hay particle size was detected for fat-corrected milk (FCM) because tallow increased FCM more when hay was short. Ration had no effect on volatile fatty acids in ruminal samples collected via a stomach tube. In this study, the effects of tallow on milk yield and composition from Holstein cows were the same, regardless of hay particle size in the ration. The tendency for tallow to increase FCM more when hay was short suggests at least a limited role of forage particle size in the determination of how fat supplements in dairy rations affect lactation performance.     

Influence of fat source and sorghum grain treatment on performance and digestibilities of high yielding dairy cows

Forty-eight lactating Holstein cows averaging 81 d in milk were allotted to eight blocks based on milk yield during the 14-d pretreatment period and randomly assigned to six treatment groups in a 2 x 3 factorial arrangement of treatments for 64 d. Factors were type of sorghum grain processing [dry-rolled vs. steam-flaked; fed at 34% of dry matter (DM) in a total mixed ration (TMR) based on alfalfa] and type of supplemental fat (2.5% of DM as cottonseed oil, tallow, or prilled fatty acids). Compared with dry-rolled sorghum, steam-flaked sorghum did not affect milk yield, fat percentage, or fat yield but did increase milk protein percentage, body weight gains, and estimated net energy for lactation (22%). Fat source did not affect lactational response, but, compared with tallow, prilled fatty acids tended to decrease DM intake. Steam-flaked sorghum, compared with dry-rolled sorghum, increased digestibilities of DM, organic matter, crude protein, and starch, regardless of fat source. The TMR containing prilled fat had lower digestibilities of DM and organic matter than did TMR containing cottonseed oil or tallow; and TMR containing prilled fat had lower digestibilities of crude protein and total fatty acids than did TMR containing tallow. This study showed that steam-flaking of sorghum grain increased milk protein content, body weight gains, and estimated net energy for lactation, regardless of dietary fat source.     

Influence of the degree of hydrolysis of beef tallow on its absorption in the young pig

Beef tallow was hydrolyzed to produce a series of fats with 3, 10, 20, 46, and 100% free fatty acids, which were incorporated at the level of 10% into semipurified diets. These diets along with a low-fat control diet were each fed to five piglets from 10 to 22 days of age. Tridodecyl glycerol ether was used as an indicator of fat absorption. Feces samples were collected between 19 and 22 days of age and the pigs were killed to allow samples of digesta to be collected. Analysis of feces and digesta allowed the progress of fat absorption to be monitored through the digestive tract. The corrected absorbability of the total lipid was between 88 and 93% for the partially hydrolyzed tallows, but was only 75% for the completely hydrolyzed tallow. The oleic acid was well absorbed (95-99%) in all the diets; palmitic and stearic acids were also well absorbed in the intact and partially hydrolyzed tallow (82-84% and 63-77%, respectively, the for palmitic and stearic acids), but their absorption was impaired in the completely hydrolyzed tallow (62% and 38ll intestine is the major site of fat uptake. Comparison of the amounts of fatty acids in the ileal digesta and in thl feces showed that there was no change in the total amount of fat in the digesta as it passed through the large intestine.     

Production responses by early lactation cows to whole sunflower seed or tallow supplementation of a diet based on barley

A 2-yr study to evaluate the effectiveness of whole sunflower seed as a source of fat was conducted with 18 primiparous and 31 multiparous Holstein cows. The three diets evaluated were a basal diet based on barley (control), a basal diet supplemented with 2.7% tallow, and a basal diet supplemented with 7.1% whole sunflower seeds. The DMI of lactating cows during the 16-wk test period was not influenced by supplementation with either sunflower seeds or tallow. Milk production was 34.4, 34.6, and 35.5 kg/d for cows fed the control diet or the diets supplemented with sunflower or tallow, respectively, and was not influenced by diet. The production and concentrations of milk protein, fat, and SNF also were not influenced by diet. The concentrations of C6:0 to C14:1 fatty acids were highest in the milk of cows fed the control diet. The concentrations of C10:0 to C16:1 were higher when cows were fed the diet with the tallow supplement than when they were fed the diet with the sunflower supplement. However, the concentrations of C18:0 to C18:2 and C20:0 were higher in the milk of cows that were fed the sunflower supplement than in the milk of cows that were fed the tallow supplement or the control diet. Concentrations of individual VFA and the ratio of acetate to propionate were not influenced by diet. Body weight, body condition score, and reproduction parameters were similar for all diets, suggesting that there were no effects on subsequent production. The performance of cows fed whole sunflower seeds as a source of energy appeared to be similar to the performance of cows fed traditional high energy diets based on barley. The fatty acid profile of the milk of cows fed diets supplemented with sunflower seeds was more favorable than that of the milk of cows fed diets supplemented with tallow.     

Effect of dietary forage concentration and buffer addition on duodenal flow of trans-C18:1 fatty acids and milk fat production in dairy cows

The objective of the study was to determine the effects of dietary fat source on duodenal flow, apparent absorption, and milk fat incorporation of trans-C18:1 fatty acids. Four ruminally and duodenally cannulated multiparous Holsteins cows in mid to late lactation were fed a basal diet containing 36% corn silage, 24% alfalfa haylage, and 40% concentrate (dry matter basis). Diets contained 0% supplemental fat (control diet), 3.7% high oleic sunflower oil, 3.7% high linoleic sunflower oil, or 3.7% partially hydrogenated vegetable shortening; treatments were administered in a 4 x 4 Latin square design with 3-wk experimental periods. The flow of trans-C18:1 to the duodenum was higher for cows fed diets supplemented with fat than for cows fed the control diet (283 vs. 64 g/d). Incomplete biohydrogenation accounted for the increased flow of trans-C18:1 to the duodenum in cows fed diets containing high oleic and high linoleic sunflower oil. Increased flow of trans-C18:1 in cows fed the diet containing partially hydrogenated vegetable shortening most likely originated from the trans-C18:1 in the diet. Milk fat percentages were 3.48, 3.07, 3.18, and 3.38% for cows fed the control diet and diets containing high oleic sunflower oil, high linoleic sunflower oil, and vegetable shortening, respectively. Milk trans-C18:1 increased from 2.9 to 11.2% of the total fatty acids for cows fed the control diet and the diets supplemented with fat, respectively. Milk trans-C18:1 were equal across all diets supplemented with fat. Ruminal and total tract digestion of organic matter, neutral detergent fiber, and N did not change with fat supplementation. Results showed that trans-C18:1 is increased in the milk of cows with reduced milk fat; however, excessive amounts of trans-C18:1 in milk do not necessarily correspond directly to milk fat depression.     

Fatty acid composition of milk from Holstein cows fed oleamide or canola oil

Based on previous in vitro results that showed reduced biohydrogenation of oleamide by ruminal microbes, this study was conducted to determine whether the addition of oleamide to the diets of dairy cows would enhance the C18:1 concentration in milk. Nine first lactation Holstein cows were fed three diets in a 3 x 3 Latin square replicated three times. Each period lasted 3 wk. The total mixed diets consisted of 42% corn silage and 58% concentrate (dry matter basis) with either no added fat (control), 3.5% high oleic canola oil, or 3.5% oleamide. Dry matter intake was reduced when oleamide was added to the diet but not when canola oil was added. Milk yields were the same for cows fed all three diets. Canola oil reduced fat-corrected milk yield and milk fat concentration, but these were not affected by oleamide. Milk protein concentration was lower for cows fed oleamide than for cows fed canola oil. Milk C18:1 averaged 23.16% of total fatty acids for cows fed the control diet and increased to 35.13% when canola oil was fed. Oleamide further increased C18:1 to 48.16% of total fatty acids in milk. All fatty acids with > or = 16 carbon chain length were reduced by oleamide. Oleamide was more effective than was canola oil in this study at increasing the oleic acid content of bovine milk. Oleamide reduced dietary intake when added at 3.5% of the dietary dry matter but still had no effect on milk yield or milk composition.     

The pharmacokinetics of 14C-zolimidine in rats]

The effects of supplementing a basal diet, in which the low level of fatty acids limited milk production, with soya oil, a palm oil/palmitic acid mixture and tallow, on the yield of milk and of its constituents, and on the composition of the milk, are reported. The yields of milk and milk fat were greatly increased by all the oil-supplemented diets; the mean daily yield of solids-not-fat (SNF) was also increased, but supplementation with soya oil caused the yield of crude protein (CP) to decrease, whereas the other fat-rich concentrate mixtures gave the same mean yield of protein as did the low-fat, control diet. All 3 oil-supplemented diets lowered the proportion of CP in the milk, but the SNF content was unchanged by any treatment. Dietary soya oil tended to lower the proportion of fat in the milk, whilst the palm oil/palmitic acid mixture raised it, with the tallow exerting no effect. The results are discussed in relation to previous work in which these dietary oils have been used, but in which the intake of fatty acids from the control diets did not limit milk production to the extent reported here.     

Increasing polyunsaturation of milk fats by feeding formaldehyde protected sunflower-soybean supplement

A practical means of protecting fats of a feed concentrate containing high polyunsaturated fatty acids is described. A ground mixture of 30% soybeans and 70% sunflower seeds was treated with 1% formaldehyde to protect the unsaturated lipids from microbial hydrogenation in the rumen. This was fed as a supplement to two Holstein cows in amounts that were doubled weekly. These ranged from 524 to 8384 g/day and provided successively increasing intakes of 100, 200, 400, 800, and 1600 g of linoleic acid daily. Percent milk fat increased by more than one, and linoleic acid (C18:2) of milk fat increased from 2.5 to 20% with compensatory declines in myristic (C14:0) and palmitic (C16:0) acids. Cholesterol and vitamin E of plasma both doubled at the highest supplementation. Milk yield, solids-not-fat, protein and milk cholesterol were unaltered. Fat in feces doubled from about 3 to 6%. Daily linoleic acid content of feces increased from 25 g to 120 g, indicating a dietary loss of 7 to 10% of this polyunsaturated acid. These cheaper feed ingredients elevated the polyunsaturated fats in milk as effectively as the expensive purified casein and safflower oil supplements in previous experiments.     

Abomasal infusion of cis or trans fatty acid isomers and energy metabolism of lactating dairy cows

Diets for dairy cows that provide or induce formation of trans isomers of polyunsaturated fatty acids result in reduced percentages of milk fat. The effect of abomasal infusion of trans-C18:1 fatty acid isomers on energy utilization by mature cows was determined. Six multiparous Holstein cows in midlactation had ad libitum access to a basal diet containing 50% forage and 50% concentrate. Treatments were 1) no infusion, 2) infusion of 630 g/d of a fat mixture high in cis-C18:1 isomers (64% cis-C18:1; 68% high oleic sunflower oil and 32% cocoa butter), and 3) infusion of 623 g/d of a fat mixture high in trans-C18:1 isomers (42% trans-C18:1; 90% partially hydrogenated soybean oil and 10% high linoleic safflower oil). The experiment was a replicated 3 x 3 Latin square design with 4-wk periods. Measurements of energy balance were made in open circuit respiration chambers during wk 4 of each period. Fat infusion increased milk production by 2.5 kg/d; apparent digestibility of DM, OM, energy, ADF, and ash by 1 to 4 percentage units; metabolizable energy by 11%; and NEL of the diet by 15%. Milk fat percentage and yield were higher when cows were infused with cis-C18:1 than when they were infused with trans-C18:1 (4.12% and 1.41 kg/d vs. 3.15% and 1.06 kg/d, respectively). Infusion of fat increased milk production, but trans-C18:1 reduced milk fat and energy output.     

Corandomization of fats improves absorption in rats

Human milk fat is well absorbed despite its large concentration of long-chain saturated fatty acids (LCSFA), particularly palmitic acid. The superior absorption has been ascribed in part to the uncommonly high proportion of the palmitic acid in the sn-2 position of the triglycerides, 70% in human milk triglycerides compared with 10-15% in the fats and oils commonly used in infant formula blends. Colipase-dependent pancreatic lipase selectively hydrolyzes the fatty acids at the sn-1 and 3 positions, yielding free fatty acids and the 2-monoglyceride, which are absorbable. Free palmitic acid, but not monopalmitin, can be lost as calcium soaps in the feces. The present study demonstrated that mixtures of coconut oil and palm olein are better absorbed by rats if the proportion of LCSFA in the sn-2 position is increased by the process of chemical randomization, in which the fatty acids of the native oils are redistributed equally to all three positions in the rearranged triglycerides. The fecal excretion of total fatty acids, essentially LCSFA, from the mixtures in which the oils were randomized together (corandomized) was 30 to 60% less than from the mixtures of native oils.     

The composition of lipids in intestinal digesta of young pigs receiving diets containing tallow and tallow fatty acids

Three semipurified diets containing a low level of fat or 10 percent of either beef tallow or beef tallow free fatty acids were fed to young pigs. Jejunal digesta was sampled 1.5, 2.5, 3.5, and 4.5 h after feeding by aspiration through tubes leading from the jejunal lumen to the exterior. The samples were forced through Millipore filters (1 x 10(-7) m pore size) to separate aqueous phase and oil phase lipid. The total and aqueous phase lipid was separated into triglyceride, monoglyceride, and free fatty acid, and the fatty acid composition of each fraction determined. The concentration of aqueous phase lipid was not influenced by diet, although the concentration of the oil phase lipid was generally higher for the addition of fat to the diets; the increase was greater for the beef tallow free fatty acid diet than for the beef tallow diet. Free fatty acids were the predominant component of the aqueous phase lipid along with some monoglyceride and traces of triglyceride. The major component of the oil phastions of triglyceride and monoglyceride. These must have been derived from endogenously secreted lipid in the case of the tallow fatty acid diet. Thus, the lower digestibility of completely hydrolyzed beef tallow than of conventional beef tallow was not due to an absence of monoglyceride in the intestinal lumen. The proportion of stearic acid in the jejunal digesta was greater than in the dietary lipid, whereas there were lower proportions of palmitic and oleic acids in the jejunal digesta than in the diet; the effect being most pronounced for the tallow free fatty acid diet. The ratio of oleic to palmitic acid in the aqueous phase was less than in the lipid phase suggesting preferential uptake of oleic acid from the micelle by the intestinal mucosa.     

Juice-extracted grass pellets and sodium bicarbonate for cows fed timothy silage of two chop lengths

Eighteen multiparous Holstein cows in midlactation were used in a switchback design trial to evaluate the effect of chop length (3 or 30 mm) of timothy grass silage, containing less than 30% ADF and treated with formic acid, on DMI and cow performance. Within chop length, addition of NaHCO3 (2% of DMI) or the replacement of 30% of silage DM with juice-extracted grass pellets was also evaluated. Cows were fed a TMR composed of 90% silage and 10% concentrate. Silage preservation characteristics were not different between chop lengths. The DMI and apparent digestibility were similar among treatments. Yields of 4% FCM (24.9 vs. 22.7 kg/d), fat (1.03 vs. .93 kg/d), and protein (.83 vs .77 kg/d) were higher with the short chopped silage. Milk protein, milk NPN content, and serum urea were higher for cows fed long chopped silage. Yields of milk and milk constituents were not affected by the addition of juice-extracted grass pellets or NaHCO3. Fat percentage and fatty acid composition of milk remained unchanged by treatments. Reduction of particle size, from 30 to 3 mm, of timothy grass, treated with formic acid at harvest and using compaction at ensiling in bag silos, did not affect silage conservation characteristics but did improve milk, fat, and protein yields when cows were fed high silage diets.     

Effect of disease localization on the anthropometric and metabolic features of Crohn''s disease

Conjugated linoleic acid (CLA) is a potent anticarcinogen secreted in milk of ruminants, but it inhibits de novo fatty acid synthesis and desaturation in mammary cell cultures. The potential for increasing CLA content of milk fat and the effects of elevated CLA availability on milk fat secretion were investigated. Four Holstein cows were used in a single crossover design with repeated measures to determine milk fatty acid concentration in response to a 24-h infusion of 200 g linoleic acid (LA) or a mixture of 100 g LA plus 100 g CLA (LCLA). Milk and blood samples were obtained 12 h before infusion and at 12-h intervals from 0 to 72 h. Compared with LA infusion, total CLA concentration in blood plasma at 24 h in response to LCLA was elevated fivefold, whereas CLA content of plasma triglycerides was increased 10-fold. Milk fat yield from 24 to 72 h was approximately 34% lower in response to LCLA compared with LA, due primarily to reduced yield of fatty acids with six to 16 carbons. Amount of CLA in milk increased from 0.5 g/100 g total fatty acids at 0 h to 3.3 g/100 g at 36 h in response to LCLA. Concentration of stearic acid in milk fat at 36 h in response to LCLA was nearly double the stearic acid concentration in response to LA. Oleic and arachidonic acid concentrations in milk declined as stearic acid increased in response to LCLA. Results indicated CLA content of milk fat reflects the amount available for absorption from the small intestine, and CLA appeared to be a potent inhibitor of de novo fatty acid synthesis and desaturation in the mammary gland.     

Effects on nutrient digestion of wheat processing and methods of tallow addition to the diets of lactating dairy cows

Five multiparous Holstein cows in midlactation that were fitted with ruminal and duodenal cannulas were used in a 3 x 5 incomplete Latin square. The objective of this study was to examine the effects on nutrient digestion of wheat processing and method of tallow addition to the diets of lactating dairy cows. Diets consisted of 45% forage and 55% concentrate, and each diet contained 20% wheat and 2% tallow (as-fed basis). Treatments were dry-rolled wheat with tallow added to the concentrate, steam-rolled wheat with tallow added to the concentrate, and steam-rolled wheat with tallow added first to the wheat. The dry matter intake; digestion of starch, fiber, and fatty acids; ammonia N concentration; and molar proportions of volatile fatty acids in ruminal fluid were not affected by treatments. The apparent digestibility in the total tract of organic matter and nitrogenous compounds was significantly higher for the steam-rolled treatment with tallow added first to the wheat. Mean ruminal fluid pH was similar across treatments; however, cows fed the diet containing steam-rolled wheat with tallow added first to the wheat had the smallest pH change from 0 to 2 h postfeeding. Milk yield did not differ, regardless of cow diet. Method of tallow addition had marked effects on the apparent digestibility of organic matter and N in the total tract of lactating dairy cows.     

Elaboration of the messenger transport organizer pathway for localization of RNA to the vegetal cortex of Xenopus oocytes

1. Two experiments were designed to study the influence of free fatty acid content and degree of saturation of free fatty acids and neutral fat on digestibility of added fats and fatty acids. Sunflower oil and tallow were used as neutral fats, and palmitic, stearic, oleic and linoleic acids as free fatty acids. Fat inclusion was 80 g/kg and mixtures of each fat and each free fatty acid were prepared in the proportions 100:0, 70:30 and 40:60. 2. Experimental diets were evaluated for fat and fatty acid digestibilities with broiler chickens at 21 d of age. The metabolisable energy of fat was calculated from the product of digestibility and gross energy. Increasing concentrations of saturated free fatty acids decreased the ME of added fat, whereas unsaturated free fatty acids did not significantly affect the ME value of added fat. 3. Digestibilities of individual fatty acids were analysed by linear regression with rate of inclusion of free fatty acid in the fat blend: palmitic and stearic acids gave a negative slope, whereas oleic and linoleic acids gave a slope not statistically different from zero. Because slopes for saturated fatty acids did not differ between the sunflower oil and tallow treatments, synergism between unsaturated and saturated fatty acids was not detected.