Blood and Milk Lipid Responses Induced by Growth Hormone Administration in Lactating Cows

Nine multiparous Holstein cows (average 5.8 yr, 63 to 132 days postpartum) were in a 28-day single reversal experiment in the Beltsville open circuit respiration chambers with two 14-day injection periods (placebo versus bovine growth hormone, 51.5 IU/day). With growth hormone treatment, milk fat percentage increased 25 to 29%, milk fat yield increased 41%, and cows averaged ?13.7 Mcal/day energy balance. There were small increases of triglycerides and 1,2-diglycerides, core lipids, and small decreases of cholesterol and phospholipids, the membrane lipids. Fat from growth hormone treatment had 6% less short (6:0, 8:0, 10:0) and medium (12:0, 14:0, 14:1, 15:0, 16:0) chain fatty acids and 6% more long chain 18:1 fatty acids. Plasma of cows treated with growth hormone had an increase of concentrations of free fatty acids, but no shifts were apparent among other lipid classes. Analysis of total plasma fatty acids did not show any net changes, but within individual plasma lipid classes, 18:1 increased and 18:2 decreased. Overall changes of blood and milk lipids are consistent with the concept that adipose tissue reserves were mobilized in response to hormone treatment and that these mobilized lipids were the major carbon source for the 41% increase of milk fat secretion. Increases of de novo synthesis of short and medium chain fatty acids also occurred but much less. Cows treated with growth hormone were in negative energy balance, and the mechanism may differ when cows are in positive energy balance.     

Infusion of long-chain fatty acids varying in saturation and chain length into the abomasum of lactating dairy cows.

Free long-chain fatty acids were infused into the abomasum of lactating dairy cows to determine postruminal effects on feed intake, production and composition of milk, nutrient digestibilities, and metabolites in blood. Four Holstein cows averaging 120 DIM and fitted with ruminal cannulas were used in a 4 x 4 Latin square design with 14-d periods. Treatments were abomasal infusions of 1) control, 168 g/d of meat solubles (carrier for fatty acids), 2) control plus 450 g/d of mostly saturated fatty acids (C16:C18 = .75), 3) control plus 450 g/d of a mixture of saturated and unsaturated fatty acids (C16:C18 = .40), and 4) control plus 450 g/d of mostly unsaturated fatty acids (C16:C18 = .11). Production of milk and milk components, DMI, and intake of digestible energy decreased linearly as unsaturation and chain length of infused fatty acids increased. Percentages of fat, CP, and SNF in milk and total tract apparent digestibilities of DM, OM, ADF, NDF, energy, and fatty acids were not affected significantly by treatments. Infusing fatty acids decreased proportions and yields of short- and medium-chain fatty acids and increased proportions and yields of unsaturated C18 fatty acids in milk fat. Increasing unsaturation and chain length of infused fatty acids linearly decreased proportion and yield of palmitic acid but increased proportions and yields of polyunsaturated C18 fatty acids in milk fat. Infusing fatty acids increased concentrations of NEFA and cholesterol in blood plasma. The profile of fatty acids reaching the intestine may be an important determinant of responses to supplemental fats fed to lactating dairy cows.     

Effects of feeding lactating dairy cows diets containing extruded soybeans and calcium salts of long-chain fatty acids.

Four multiparous Holstein cows averaging 36 DIM and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design to investigate the effects of feeding extruded whole soybeans and Ca salts of long-chain fatty acids. Treatments were diets containing 1) no added fat, 2) 16% extruded whole soybeans, 3) 16% extruded whole soybeans and 3% Ca salts of long-chain fatty acids, and 4) 16% extruded whole soybeans and 6% Ca salts of long-chain fatty acids. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (35:15:50, DM basis). Intakes of DM and energy and production of milk, 4% FCM, fat, CP, and SNF were decreased by feeding extruded whole soybeans and 6% Ca salts of long-chain fatty acids, but differences were small among the other treatments. The weight percentages and yields of C18:0, C18:1, and C18:2 in milk were increased, and most shorter chain fatty acids were decreased, by feeding supplemental fat. Digestibilities of DM, OM, ADF, soluble residue, total C18 fatty acids, and total fatty acids were decreased, but digestibility of hemicellulose was increased by feeding supplemental fat. The largest decrease in digestibilities of most dietary constituents and in energy and N utilization occurred when 16% extruded whole soybeans plus 6% Ca salts of long-chain fatty acids were fed to the cows. Calcium salts of long-chain fatty acids can supply up to 3% of the dietary DM in diets containing 16% extruded whole soybeans without having deleterious effects on most variables measured in this experiment.     

Factors affecting variations in the detailed fatty acid profile of Mediterranean buffalo milk determined by 2-dimensional gas chromatography

Buffalo milk is the world's second most widely produced milk, and increasing attention is being paid to its composition, particularly the fatty acid profile. The objectives of the present study were (1) to characterize the fatty acid composition of Mediterranean buffalo milk, and (2) to investigate potential sources of variation in the buffalo milk fatty acid profile. We determined the profile of 69 fatty acid traits in 272 individual samples of Mediterranean buffalo milk using gas chromatography. In total, 51 individual fatty acids were identified: 24 saturated fatty acids, 13 monounsaturated fatty acids, and 14 polyunsaturated fatty acids. The major individual fatty acids in buffalo milk were in the order 16:0, 18:1 cis-9, 14:0, and 18:0. Saturated fatty acids were the predominant fraction in buffalo milk fat (70.49%); monounsaturated and polyunsaturated fatty acids were at 25.95 and 3.54%, respectively. Adopting a classification based on carbon-chain length, we found that medium-chain fatty acids (11–16 carbons) represented the greater part (53.7%) of the fatty acid fraction of buffalo milk, whereas long-chain fatty acids (17–24 carbons) and short-chain fatty acids (4–10 carbons) accounted for 32.73 and 9.72%, respectively. The n-3 and n-6 fatty acids were 0.46 and 1.77%, respectively. The main conjugated linoleic acid, rumenic acid, represented 0.45% of total milk fatty acids. Herd/test date and stage of lactation were confirmed as important sources of variation in the fatty acid profile of buffalo milk. The percentages of short-chain and medium-chain fatty acids in buffalo milk increased in early lactation (+0.6 and +3.5%, respectively), whereas long-chain fatty acids decreased (?4.2%). The only exception to this pattern was butyric acid, which linearly decreased from the beginning of lactation, confirmation that its synthesis is independent of malonyl-CoA. These results seem to suggest that in early lactation the mobilization of energy reserves may have less influence on the fatty acid profile of buffalo milk than that of cow milk, probably due to a shorter and less severe period of negative energy balance. Parity affected the profiles of a few traits and had the most significant effects on branched-chain fatty acids. This work provided a detailed overview of the fatty acid profile in buffalo milk including also those fatty acids present in small concentrations, which may have beneficial effects for human health. Our results contributed also to increase the knowledge about the effects of some of the major factors affecting buffalo production traits and fatty acid concentrations in milk, and consequently its technological and nutritional properties.     

Effects of intraruminal and intra-abomasal additions of cod-liver oil on milk fat production in the cow.

Four Holstein cows were used in a modified switchback design to show the effect on milk-fat synthesis of (1) control diet, (2) 29.23, 3.92, 6.48, 30.65, 3.44 control diet plus 255 g/day of cod-liver oil in rumen, and (3) control diet plus 225 g/day of cod-liver oil in abomasum. Mean milk yield (kg/day), fat production (kg/day), and milk-fat percentage were (1) 21.87, .79, 3.63; (2) 22.99, .70, 3.05; and (3) 23.02, .75, 3.28. Compared to the post-treatment control period, only one cow decreased in milk-fat percentage on 3 while all cows decreased in milk-fat percentage on 2. Proportions of carbons 16:0, 16:1, 18:0, 18:1, 18:2, and trans-monoene fatty acids of the milk fat were (1) 30.31, 3.24, 10.15, 30.48, 2.59, 7.91; (2) 26.37; and (3) 26.30, 3.72, 10.56, 30.10, 2.96, 9.84. Proportions of rumen volatile fatty acids were not significantly affected by treatment. Proportions of carbons 16:0, 18:0, 18:1, 18:2, and 18:3 fatty acids in the rumen ingesta were (1) 17.28, 47.92, 21.71, 10.59, 2.46; (2) 19.55, 25.90, 37.21, 11.97, 5.39; and (3) 16.90, 50.80, 19.66, 9.11, and 3.23. Fatty acid composition of blood-serum phospholipids were affected by treatment.     

Genetic parameters for major milk fatty acids and milk production traits of Dutch Holstein-Friesians

The objective of this study was to estimate genetic parameters for major milk fatty acids and milk production traits. One morning milk sample was collected from 1,918 Holstein-Friesian heifers located in 398 commercial herds in the Netherlands. Each sample was analyzed for total percentages of fat and protein, and for detailed fatty acid percentages (computed as fatty acid weight as a proportion of total fat weight). Intraherd heritabilities were high for C4:0 to C16:0, ranging from 0.42 for C4:0 to 0.71 for C10:0. Saturated and unsaturated C18 fatty acids had intraherd heritability estimates of approximately 0.25, except for C18:2 cis-9, trans-11, which was 0.42. Standard errors of the heritabilities were between 0.07 and 0.12. Genetic correlations were high and positive among C4:0 to C14:0, as well as among unsaturated C18, but correlations of C4:0 to C14:0 with unsaturated C18 were generally weak. The genetic correlation of C16:0 with fat percentage was positive (0.65), implying that selection for fat percentage should result in a correlated increase of C16:0, whereas unsaturated C18 fatty acids decreased with increasing fat percentage (−0.74). Milk fat composition can be changed by means of selective breeding, which offers opportunities to meet consumer demands regarding health and technological aspects.     

Milk composition and apparent digestibilities of dietary fatty acids in lactating dairy cows abomasally infused with Cis or Trans fatty acids

Fat supplementation of diets for dairy cows produces changes in nutrient supply and milk composition. The effect of abomasal infusion of either cis-C18:1 or trans-C18:1 fatty acid isomers on the digestibility of fatty acids and milk composition was determined in lactating dairy cows. Six multiparous midlactation Holstein cows were used and fed a control diet containing 50% forage and 50% concentrate. Treatments were (per day): no infusion, infusion of a 630-g fat mixture high in cis-C18:1 isomers, and infusion of a 623-g fat mixture high in trans-C18:1 isomers using two 3 x 3 Latin squares with 4-wk experimental periods. Fat infusion did not affect total dry matter intake and increased apparent digestibilities of total fatty acids. Apparent digestibilities of C18 fatty acids were directly related to the number of double bonds within isomers, and cis-C18:1 isomers were slightly more digestible than trans-C18:1 isomers. The lower yield of C12:0, C14:0, and C16:0 fatty acids in milk fat and higher milk citrate observed when cows were infused with trans-C18:1 suggests a depressed de novo milk fatty acid synthesis. Effects of trans infusion on milk fat were independent of ruminal fermentation, fatty acid apparent absorption, and fatty acid plasma concentrations. Lower milk protein yield in cows infused with fat may have been caused by a decrease in milk protein synthesis.     

不同胎次中国荷斯坦牛鲜乳脂肪酸组成研究

对5个胎次共98头中国荷斯坦牛鲜奶乳成分及脂肪酸含量进行了测定分析。结果表明，乳脂率、乳蛋白率及体细胞数在胎次间存在显著（P＜0．05）或极显著（P＜0．01）差异；短、中链脂肪酸（C4∶0～C16∶0）中，除C6∶0在第一胎与其他4胎间含量差异显著（P＜0．05）、C12∶0在第2、5胎间含量差异显著（P＜0．05）外，其他脂肪酸含量在胎次间差异不显著（P＞0．05）；长链脂肪酸中，硬脂酸（C18：0）在第1胎含量最高。第3胎含量最低，1、3胎间差异极显著（P＜0．01）；油酸（C18∶1）和亚油酸（C18∶2）含量在胎次间变化规律相似，均表现为第1胎最低，第3胎最高，且两胎间存在极显著（P＜0．01）和显著差异（P＜0．05）。     

Duodenal rapeseed oil infusion in early and midlactation cows. 5. Milk fatty acids and adipose tissue lipogenic activities

Lipogenic activities of perirenal adipose tissue were investigated in early (wk 3) and midlactation (wk 19 to 26) cows that received a duodenal rapeseed oil infusion (1.0 to 1.1 kg/d). In midlactation, oil infusion resulted in a decreased rate of fatty acid synthesis from acetate and a decreased rate of the activities of fatty acid synthetase and glucose-6-phosphate dehydrogenase, whereas lipoprotein lipase activity tended to increase. The rate of glucose incorporation into glyceride-glycerol and the activities of glycerol-3-phosphate dehydrogenase and malic enzyme were not significantly affected. Fatty acid C14:0 content of perirenal adipose tissue was decreased, and fatty acid C18:2 and C18:3 contents were increased in oil-infused cows. In early lactation, rates of acetate incorporation into fatty acids and activities of fatty acid synthetase and lipoprotein lipase were very low. Activities of glucose-6-phosphate dehydrogenase and glycerol-3-phosphate dehydrogenase were lower in the early than in the midlactation trial. Oil infusion did not change the measured parameters. In both trials, percentages and yields of milk fatty acids C18:1, C18:2, and C18:3 were increased, whereas those of C14:0 and C16:0 were decreased by oil. Calculated transfer rates of absorbed fatty acid C18:2 from oil to milk fat were 16 to 26%. Results suggested that oil fatty acids affected adipose and mammary de novo lipogenesis in a direct way without affecting fatty acid esterification in adipose tissue or total fat secretion in mammary tissue.     

Feeding polyunsaturated vegetable oils to lactating cows

Holstein cows fed concentrate:hay diets also were fed for 14 days supplements of soybean oil plus casein, soybean oil protected from ruminal hydrogenation by encapsulation in a casein-formaldehyde matrix, cottonseed oil plus casein, or cottonseed oil protected with casein formaldehyde. The supplements were fed at rates to give a linoleic acid (18:2) intake of 225 g/day. Yields of milk and milk protein were not affected by treatment. Milk 18:2 was not increased by the unprotected soybean oil or cottonseed oil but was increased by protected soybean and cottonseed oil from a control of 2.3 to 5.7% of total milk fat. Milk 18:0 and 18:1 also increased. Compensatory declines were observed in milk 16:0 and 14:0 acids. In fecal fatty acids during the treatment periods, percentage of 18:2 of the total fat decreased and 18:0 markedly increased. These results indicate hydrogenation of the dietary oils in the alimentary tract or a differential absorption. Fecal 16:0 and 14:0 decreased.     

Milk fatty acid composition and mammary lipid metabolism in Holstein cows fed protected or unprotected canola seeds.

Six midlactation Holstein cows were fed a total mixed ration supplemented with either 4.8% canola meal, 3.3% unprotected canola seeds plus 1.5% canola meal, or 4.8% formaldehyde-protected canola seeds, according to a double 3 x 3 Latin square design. Each period lasted 3 wk; experimental analyses were restricted to the last week of each period. Mammary biopsies were taken the last day of each period for gene expression measurements. Milk production and milk protein percentage were reduced by canola seeds, whether protected or unprotected. Protected canola seeds also decreased dry matter intake. Feeding canola seeds reduced the content of C8 to C16 fatty acids in milk and increased the content of oleic acid (C18:1c9). Unprotected canola seeds elevated the concentrations of C18:0. Protected canola seeds increased the C18:2 and C18:3 content, and reduced the C18d:0/C18:1c9 ratio. Similar results were obtained for plasma fatty acids, with some specific features, such as an increased C16:0/C16:1 ratio with protected canola seeds. Canola seeds had no significant effects on insulin, triglycerides, or cholesterol present in serum, but increased the concentration of nonesterified fatty acids; a greater increase was obtained with protected canola seeds. Expression levels of acetyl-CoA carboxylase and delta 9-stearoyl-CoA desaturase genes measured in the mammary gland did not differ significantly between diets. Therefore, the reduced C18s:0/C18:1c9 ratio observed in milk with protected canola seeds was not due to an enhanced expression of the delta-9 desaturase in the mammary gland.     

Intestinal absorption of fatty acids, and blood lipid composition in sheep

Interrelationships between intestinal uptake of fatty acids and their concentrations in lipids of blood plasma of sheep were assessed by quantities of individual fatty acids that flowed through and were absorbed from the intestinal tract under different dietary conditions. Major long-chain fatty acids were approximately 90% digested, thus demonstrating that dietary fatty acids of high melting points can be absorbed efficiently by ruminants provided they are well dispersed. Relationships were linear between uptakes of 16:0, 18:0, 18:1, and 18:2 fatty acids from the gut and their concentrations in both triglycerides and triglyceride-free plasma lipids. The proportion of each transferred to triglyceride-free plasma lipids was in order 18: 2 greater than 18:1 greater than 16:0 greater than 18:0, whereas in plasma triglycerides the order was 16:0 = 18:0 = 18:2 less than 18:1. Interconversion of 18:0 to 18:1 by intestinal mucosa may explain the anomalous behavior of 18:1 triglycerides. These results are consistent with the hypothesis that the intrinsic nature of the fatty acid primarily determines the composition of triglyceride-free plasma lipids whereas the relative amount of each acid absorbed by the intestine determines that of plasma triglycerides and, hence, of milk and depot fats of ruminants.     

Lipids of bovine and human milks: a comparison

Human and bovine milks contain about 3 to 5% total lipid, existing as emulsified globules 2 to 4 microns in diameter and coated with a membrane derived from the secreting cell. About 98% or more of the lipid is triacylglycerol, which is found in the globule. Phospholipids are about .5 to 1% of total lipids and sterols are .2 to .5%; these are mostly located in the globule membrane. Cholesterol is the major sterol. The major differences are in fatty acid composition, triacylglycerol structure, and the response of fatty acids in human milk to changes in diet. Bovine milk contains substantial quantities of 4:0 to 10:0, about 2% 18:2, and almost no other long-chain polyunsaturated fatty acids. The fatty acid composition is not altered by ordinary changes in diet. Human milk contains very little 4:0 to 10:0, 10 to 14% 18:2, and small quantities of other polyunsaturates. The triacylglycerol structure differs, with much of the sn-2 position occupied by 16:0 in human milk and 4:0 to 10:0 at sn-3 in bovine milk. The effects of milk cholesterol and fatty acids on human blood cholesterol levels are discussed.     

Diet and the lipid composition of adipose tissue in the young lamb

The changes in the lipid composition of the perirenal adipose tissue obtained from groups of lambs receiving either ewes' milk or a reconstituted low-fat milk powder have been studied during the first 8 days after birth. The triglycerides were further analysed by a stereospecific analytical procedure to obtain the intramolecular distribution of the fatty acids between the hydroxyl groups of the glycerol moeity. The percentage composition of the major lipid fractions in the perirenal adipose tissue from the naturally fed lambs remained similar to that of the adipose tissue obtained from the lambs at birth, but in the lambs receiving the artificial diet the relative concentration of the triglycerides was considerably reduced and that of the unesterified fatty acid and phospholipid fractions increased. At birth 18 :1 was the major fatty acid present in the triglyceride, unesterified fatty add and phospholipid fractions. Any polyunsaturated fatty acids were confined to the phospholipid fraction. Although there were negligible concentrations of the C18 polyunsaturated fatty acids, the C20 and C22 polyunsaturated fatty acids comprised some 20% of the fatty acids of the phospholipids. In the naturally fed lambs the concentration of 18: 2ω6 increased considerably during the 8 days after birth and there was a decrease in the concentration of 20 : 3ω9. In the artificially fed lambs the concentration of 20 : 3ω9 remained similar to that found at birth and there was no accumulation of 18 : 2ω6. In the triglycerides at birth 70–80% of 18 : 1-cis was in the 2-position and the saturated fatty acids were located mainly in the 1-and 3-positions. In both groups of lambs the concentration of 18 : 1-cis decreased and the concentration of 18 : 0 increased after birth. In the naturally fed lambs the increase in 18 : 0 occurred mainly in positions 1-and 3-but in the artificially fed lambs the concentration of 18 : 0 also markedly increased in position 2. The changes in concentration of 16 : 0 paralleled that of 18 : 0. In the naturally fed lambs the concentrations of 14:0, 18: 1-trans and 18 : 2ω6 which were probably of dietary origin increased considerably. 14 : 0 and 18 : 1 trans were concentrated largely in positions 1 and 3 whilst 18 : 2ω6 was concentrated mainly in position 2.     

Effects of dietary fat and protein on fatty acid flow to the duodenum and in milk produced by dairy cows.

Four Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square with treatments in a 2 x 2 factorial arrangement. Treatments were 1) soybean meal, no fat; 2) fish meal, no fat; 3) soybean meal, fat; and 4) fish meal, fat. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (30:20:50) on a DM basis. Intake of gross energy (105 Mcal/d) was not altered by treatment comparisons. However, feeding fat decreased energy digested in the rumen (15 vs. 24%) and increased energy digested postruminally (55 vs. 43%) but resulted in similar amounts of energy (72 Mcal/d) digested in the total tract. The flow of C14:0, C16:0, C18:0, C18:1, C18:2, C18:3, and total fatty acids to the duodenum was increased by feeding fat. The average flow of C14:0, total C18, and total fatty acids to the duodenum was greater than their intake for all treatments, suggesting de novo synthesis of fatty acids by ruminal microbes. Biohydrogenation of unsaturated C18 was decreased 70, 67, 59, and 51% for treatments 1 to 4, respectively, by feeding fat and fish meal. Digestibility of total fatty acids entering the small intestine (78%) was not altered by treatment comparisons; however, feeding fat altered digestibility of individual fatty acids. The proportion of C16:0 and C18:1 was increased, and the proportion of C6:0, C8:0, C10:0, C12:0, and C14:0 was decreased in milk fat produced by cows fed fat.     

Reduced fatty acid synthesis and desaturation due to exogenous trans10,cis12-CLA in cows fed oleic or linoleic oil

To determine effects of an elevated supply of cis9,trans11-18:2 (9/11CLA) or trans10,cis12-18:2 (10/12CLA) on de novo synthesis and desaturation of long-chain fatty acids, four Holstein cows fed high-oleic sunflower (OLE) or high-linoleic safflower oil (LIN) at 2.5% of DM were infused (0.625 g/h) with 9/11CLA or 10/12CLA for 48 h via the abomasum. Treatments were assigned in a 2 x 2 factorial design. The assigned diets were fed for 11 d before each 48-h infusion period. Milk samples were obtained at 12 and 0 h before infusion and at 12-h intervals from 0 to 96 h. Concentrations of trans11-18:1 and 18:2n-6 in arterial plasma phospholipid, triglyceride, and FFA fractions were greater due to feeding LIN compared with OLE. Infused 9/11CLA and 10/12CLA were incorporated into plasma triglycerides and FFA primarily. Exogenous 10/12CLA also was found in plasma phospholipids. Milk yield and DMI were not affected by treatments. Percentages and yields of protein, lactose, and SNF in milk also were not affected by treatments. Milk fat percentage and yield, however, decreased 25% from 0 to 96 h in response to infusion of 10/12CLA compared with 9/11CLA. Yields of trans11-18:1, 9/11CLA and 18:2n-6 in milk fat before infusion were higher when LIN was fed compared with OLE. Infusion of 9/11CLA, regardless of diet, increased 9/11CLA in milk fat by 44%. Although 10/12CLA was not detectable in milk fat before infusion, it averaged 6 mg/g of total fatty acids and 2 g/d after 48 h. At 48 h, recovery in milk of infused 9/11CLA was 16% compared with 8% for 10/12CLA. Yields of saturated 6:0 to 16:0, cis9-18:1, 9/11CLA, and 20:4n-6 were reduced by 10/12CLA infusion. Due to a 40% increase in the concentration of 18:0 by 48 h of 10/12CLA infusion, however, yield of 18:0 was not affected. Ratios of cis9-18:1/18:0, 9/11CLA/trans11-18:1, and 20:4n-6/18:2n-6 in milk fat decreased in response to infusion of 10/12CLA, regardless of diet. At peak concentration of 10/12CLA, reductions in cis9-18:1 and saturated 4:0-16:0 yields accounted for 36% and 53% of the decrease in total fatty acid yield. Results indicated 10/12CLA alters lipid metabolism in the bovine mammary gland by simultaneously reducing de novo synthesis and desaturation. Furthermore, milk triglyceride synthesis may have a stringent requirement for endogenously synthesized oleic acid.     

Effect of plant oils and camelina expeller on milk fatty acid composition in lactating cows fed diets based on red clover silage

Five multiparous Finnish Ayrshire cows fed red clover silage-based diets were used in a 5 × 5 Latin square with 21-d experimental periods to evaluate the effects of various plant oils or camelina expeller on animal performance and milk fatty acid composition. Treatments consisted of 5 concentrate supplements containing no additional lipid (control), or 29 g/kg of lipid from rapeseed oil (RO), sunflower-seed oil (SFO), camelina-seed oil (CO), or camelina expeller (CE). Cows were offered red clover silage ad libitum and 12 kg/d of experimental concentrates. Treatments had no effect on silage or total dry matter intake, whole-tract digestibility coefficients, milk yield, or milk composition. Plant oils in the diet decreased short- and medium-chain saturated fatty acid (6:0-16:0) concentrations, including odd- and branched-chain fatty acids and enhanced milk fat 18:0 and 18-carbon unsaturated fatty acid content. Increases in the relative proportions of cis 18:1, trans 18:1, nonconjugated 18:2, conjugated linoleic acid (CLA), and polyunsaturated fatty acids in milk fat were dependent on the fatty acid composition of oils in the diet. Rapeseed oil in the diet was associated with the enrichment of trans 18:1 (Δ4, 6, 7, 8, and 9), cis-9 18:1, and trans-7,cis-9 CLA, SFO resulted in the highest concentrations of trans-5, trans-10, and trans-11 18:1, Δ9,11 CLA, Δ10,12 CLA, and 18:2n-6, whereas CO enhanced trans-13-16 18:1, Δ11,15 18:2, Δ12,15 18:2, cis-9,trans-13 18:2, Δ11,13 CLA, Δ12,14 CLA, Δ13,15 CLA, Δ9,11,15 18:3, and 18:3n-3. Relative to CO, CE resulted in lower 18:0 and cis-9 18:1 concentrations and higher proportions of trans-10 18:1, trans-11 18:1, cis-9,trans-11 CLA, cis-9,trans-13 18:2, and trans-11,cis-15 18:2. Comparison of milk fat composition responses to CO and CE suggest that the biohydrogenation of unsaturated 18-carbon fatty acids to 18:0 in the rumen was less complete for camelina lipid supplied as an expeller than as free oil. In conclusion, moderate amounts of plant oils in diets based on red clover silage had no adverse effects on silage dry matter intake, nutrient digestion, or milk production, but altered milk fat composition, with changes characterized as a decrease in saturated fatty acids, an increase in trans fatty acids, and enrichment of specific unsaturated fatty acids depending on the fatty acid composition of lipid supplements.     

Effects of duodenal infusions of palmitic, stearic, or oleic acids on milk composition and physical properties of butter

Four dairy cows fitted with a duodenal cannula were used in a 4 x 4 Latin square design to investigate the effects of daily duodenal infusion of 500 g of fatty acids (containing mainly C16:0, C18:0, or cis-C18:1) on fecal concentrations of fatty acids, fatty acid profiles of milk fat, and solid fat content of butter. Fecal concentrations of C16:0 and especially of C18:0 were increased by duodenal infusion. Infusion with C16:0 increased the proportion of C16:0 in milk fat and delayed softening of butter when the temperature rose. Infusion with C18:0 resulted only in a slight increase of C18:0 proportion in milk fat and did not significantly affect solid fat in butter between -10 and 30 degrees C. With the infusion of cis-C18:1, the proportion of cis-C18:1 in milk fat was more than twice that of control, to the detriment of C16:0. Butter contained low proportion of solid fat, even at low temperatures. Increasing C16:0 or cis-C18:1 in milk fatty acid via duodenal infusion can be used to study their specific effects on butter characteristics, but, because of a low transfer from infusion to milk, this method is less efficient with C18:0.     

Genetic determination of fatty acid composition in Spanish Churra sheep milk

The objective of this study was to estimate the genetic variation of ovine milk fatty acid (FA) composition. We collected 4,100 milk samples in 14 herds from 976 Churra ewes sired mostly by 15 AI rams and analyzed them by gas-liquid chromatography for milk fatty acid composition. The studied traits were 12 individual FA contents (proportion in relation to the total amount of FA), 3 groups of fatty acids [saturated fatty acids (SFA), monounsaturated FA (MUFA), and polyunsaturated FA (PUFA)], and 2 FA ratios (n-6:n-3 and C18:2 cis-9,trans-11:C18:1 trans-11). In addition, percentages of fat and protein and daily milk yield were studied. For the analysis, repeatability animal models were implemented using Bayesian methods. In an initial step, univariate methods were conducted to test the hypothesis of the traits showing additive genetic determination. Deviance information criterion and Bayes factor were employed as model choice criteria. All the studied SFA showed additive genetic variance, but the estimated heritabilities were low. Among unsaturated FA (UFA), only C18:1 trans-11 and C18:2 cis-9,cis-12 showed additive genetic variation, their estimated heritabilities being [marginal posterior mean (marginal posterior SD)] 0.02(0.01) and 0.11(0.04), respectively. For the FA groups, only PUFA showed significant additive genetic variation. None of the studied ratios of FA showed additive genetic variation. In second multitrait analyses, genetic correlations between individual FA and production traits, and between groups of FA and ratios of FA and production traits, were investigated. Positive genetic correlations were estimated among medium-chain SFA, ranging from 0 to 0.85, but this parameter was close to zero between long-chain SFA (C16:0 and C18:0). Between long- and medium-chain SFA, estimated genetic correlations were negative, around −0.6. Among those UFA showing significant additive genetic variance, genetic correlations were close to zero. The estimated genetic correlations among all the investigated FA, milk yield, and fat and protein percentages were not different from zero. Our results suggest that low additive genetic variation is involved in the determination of the FA composition of milk fat in Churra sheep under current production conditions, which results in low values of heritabilities.