Effect of sunflower-seed oil and linseed oil on tissue lipid metabolism, gene expression, and milk fatty acid secretion in Alpine goats fed maize silage–based diets

Lipid in the diet is known to enhance milk fat secretion and alter milk fatty acid composition in lactating goats. In the current experiment, the contribution of peripheral tissue and mammary gland lipid metabolism to changes in milk fat composition from plant oils was examined. Fourteen Alpine goats in midlactation were used in a 3 × 3 Latin square design with 28-d experimental periods. Treatments comprised maize silage–based diets containing no additional oil (M), sunflower-seed oil (MSO; 6.1% of diet DM), or linseed oil (MLO; 6.2% of diet DM). Compared with the control, milk yield was greater in goats fed MSO (3.37 and 3.62 kg/d, respectively), whereas MLO enhanced milk fat content (+3.9 g/kg), resulting in a 14% increase in milk fat secretion. Both MSO and MLO increased milk lactose secretion by 12 and 8%, respectively, compared with M. Relative to the control, plant oils decreased C10 to C16 secretion (32 and 24%, respectively, for MSO and MLO) and enhanced C18 output in milk (ca. 110%). Diets MSO and MLO increased cis-9 18:1 secretion in milk by 25 and 31%, respectively, compared with M. The outputs of trans-11 18:1 and cis-9, trans-11 18:2 in milk were increased 8.34- and 6.02-fold for MSO and 5.58- and 3.71-fold for MLO compared with M, and MSO increased trans-10 18:1 and trans-10, cis-12 18:2 secretion. Plant oils decreased milk fat cis-9 14:1/14:0; cis-9 16:1/16:0; cis-9 18:1/18:0; and cis-9, trans-11 18:2/trans-11 18:1 concentration ratios but had no effect on mammary stearoyl-CoA desaturase mRNA or activity. Furthermore, changes in milk fatty acid secretion were not associated with alterations in mammary acetyl-CoA carboxylase mRNA and activity, abundance of mRNA encoding for lipoprotein lipase and fatty acid synthase, or malic enzyme and glycerol-3-phosphate dehydrogenase activity in mammary tissue. Mammary lipoprotein lipase activity was increased with MSO relative to MLO. Treatments had no effect on glucose-6-phosphate dehydrogenase, malic enzyme, glycerol-3-phosphate dehydrogenase activity, or mRNA abundance and/or activity of lipoprotein lipase, acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase in liver or adipose tissue. In conclusion, inclusion of sunflower-seed oil and linseed oil in maize silage–based diets alters milk fatty acid secretion in goats via mechanisms independent of changes in mammary, hepatic, or adipose tissue lipogenic gene expression. Furthermore, data provided indications that the regulation of mammary lipogenic responses to plant oils on starch-rich diets differs between the caprine and bovine.     

Effect of a whey protein and rapeseed oil gel feed supplement on milk fatty acid composition of Holstein cows

Isoenergetic replacement of dietary saturated fatty acids (SFA) with cis-monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) can reduce cardiovascular disease risk. Supplementing dairy cow diets with plant oils lowers milk fat SFA concentrations. However, this feeding strategy can also increase milk fat trans fatty acids (FA) and negatively affect rumen fermentation. Protection of oil supplements from the rumen environment is therefore needed. In the present study a whey protein gel (WPG) of rapeseed oil (RO) was produced for feeding to dairy cows, in 2 experiments. In experiment 1, four multiparous Holstein-Friesian cows in mid-lactation were used in a change-over experiment, with 8-d treatment periods separated by a 5-d washout period. Total mixed ration diets containing 420 g of RO or WPG providing 420 g of RO were fed and the effects on milk production, composition, and FA concentration were measured. Experiment 2 involved 4 multiparous mid-lactation Holstein-Friesian cows in a 4 × 4 Latin square design experiment, with 28-d periods, to investigate the effect of incremental dietary inclusion (0, 271, 617, and 814 g/d supplemental oil) of WPG on milk production, composition, and FA concentration in the last week of each period. Whey protein gel had minimal effects on milk FA profile in experiment 1, but trans-18:1 and total trans-MUFA were higher after 8 d of supplementation with RO than with WPG. Incremental diet inclusion of WPG in experiment 2 resulted in linear increases in milk yield, cis- and trans-MUFA and PUFA, and linear decreases in SFA (from 73 to 58 g/100 g of FA) and milk fat concentration. The WPG supplement was effective at decreasing milk SFA concentration by replacement with MUFA and PUFA in experiment 2, but the increase in trans FA suggested that protection was incomplete.     

Feeding a concentrate rich in rapeseed oil improves fatty acid composition and flavor in Norwegian goat milk

Impaired quality due to a high content of free fatty acids (FFA) and off-flavors has caused challenges in the development of Norwegian goat milk products. The present study aimed to examine the effect of lipid-supplemented concentrates on milk fat content, fatty acid composition, FFA, lipoprotein lipase activity, sensory properties, and size of milk fat globules of goat milk. Thirty goats assigned to 3 experimental groups were fed different concentrates from 60 d in milk (DIM) until late lactation (230 DIM). The diets were (1) control concentrate (no added fat); (2) control concentrate with 8% (added on air-dry basis) hydrogenated palm oil enriched with palmitic acid (POFA); and (3) control concentrate with 8% (added on air-dry basis) rapeseed oil (RSO). The POFA group produced milk with the highest fat content, and fat content was positively correlated with the mean size of milk fat globules. Goats in the RSO group had a higher content of long-chain and unsaturated fatty acids, whereas milk from goats in the POFA group had a higher content of palmitic and palmitoleic acids (C16:0 and C16:1 cis). The control group produced milk with a higher content of short-, medium-, odd-, and branched-chain fatty acids compared with the 2 other groups. The content of FFA in milk was low in early and late lactation and peaked in mid lactation (90 DIM). A high content of FFA was correlated with poor sensory properties (tart/rancid flavor). The RSO group produced milk with lower content of FFA and off-flavors in mid lactation and a higher proportion of unsaturated fatty acids. Therefore, replacement of palm oil with rapeseed oil as a lipid source in dairy goat feed would be favorable.     

Effects of fat supplements containing different levels of palmitic and stearic acid on milk production and fatty acid digestibility in lactating dairy cows

Fat supplements based on palmitic acid (PA) or stearic acid (SA) are expected to have different effects on milk production and nutrient metabolism in lactating dairy cows. In this study, the effects of prilled fat supplements containing different levels of PA and SA were tested in 12 high-producing multiparous cows (pretrial milk yield = 53.4 ± 8.7 kg/d; mean ± SD) arranged in a 4 × 4 Latin square design with 21-d periods. Treatments were control (CON; no supplemental fat), an enriched PA supplement (HP; 91% C16:0), an enriched SA supplement (HS; 92.5% C18:0), and a blend of PA and SA (INT) fed at 1.95% of diet dry matter. All supplements contained oleic acid at approximately 5% of fatty acids. The HP treatment decreased dry matter intake (DMI) by 1.9 kg/d and 1.1 kg/d compared with SA and CON, respectively. Milk yield was not changed by treatment, but INT increased energy-corrected milk by 2.7 kg/d compared with HS. The HP and INT treatments increased milk fat yield by 0.11 and 0.14 kg/d compared with CON, respectively. Additionally, HP decreased yield of <16 carbon fatty acids (FA; de novo synthesized) by 44 g/d and 43 g/d compared with INT and CON, respectively. The HP treatment increased 16-carbon FA (mixed source) by 155 g/d compared with CON and 64 g/d relative to INT. No effect of treatment on apparent total-tract digestibility of dry matter, organic matter, or neutral detergent fiber was detectable. The INT and HS treatments decreased total-tract digestibility of 16-carbon FA by 10.3 and 10.5 percentage units compared with HP, respectively. Total-tract digestibility of 18-carbon FA was lowest in the HS diet and highest with HP. In conclusion, supplementing PA increased milk fat yield compared with control and SA, but supplementing a mixture of PA and SA increased energy-corrected milk without decreasing intake. The FA profile of fat supplements influences their digestibility and effects on DMI and milk and milk fat synthesis.     

Effect of feeding oilseed supplements to dairy cows on ruminal and milk fatty acid composition

The objective of this study was to compare the effects of oilseed‐based supplements, rapeseed and linseed, against a barley‐based control, on the fatty acid composition, and subsequent solid fat ratio, of the milk fat from dairy cows. In addition, as a means of understanding the digestive processes which influence the milk fat composition, ruminal extracts were collected from the cows and analysed for fatty acid composition. Four lactating dairy cows each fitted with a rumen fistula were provided with silage and one of four concentrate diets. The main constituent of the concentrate supplements was either rapeseed (ground or unground), linseed (unground) or a barley control. The diets were offered in accordance with a 4 × 4 Latin square arrangement. The oilseed‐supplemented concentrates provided the cows with 620–640 g fatty acids day^?1. Experimental treatments were provided to the cows for 2 weeks, after which ruminal extracts were collected over a 24 h period and a milk sample was taken. All extracts were analysed for fatty acid composition. The diets fed influenced the long‐chain fatty acid composition of the ruminal extracts and milk fat. The proportion of C18:1n‐9 in the ruminal extracts increased from 202–224 to 282–321 g kg^?1 of the total fatty acids when the cows were provided with the rapeseed‐based diets. The linseed‐based diet increased the C18:1n‐9 proportion of the ruminal extracts from 164 to 218 g kg^?1 of the total fatty acids. Both rapeseed‐based diets also resulted in a higher proportion of C18:0 in the ruminal extract, possibly owing to biohydrogenation of the dietary fatty acids. This proportion of C18:0 in the ruminal extract was lowest immediately after feeding, increasing to a maximum 4–6 h later. Both rapeseed‐based concentrates increased the proportion of C18:1n‐9 in the milk fat to approximately 300 g kg^?1 of the total fatty acids as compared with 214 g kg^?1 for the control. The proportion of C18:1n‐9 in the milk fat from the cows offered the linseed‐based concentrate was 246 g kg^?1 of the total fatty acids. There were also significant decreases in the proportions of C16:0 in the milk fat from the cows offered all oilseed‐based concentrates. There was no difference between the fatty acid compositions of the milk fats from the cows fed the ground or unground rapeseed‐based supplements. The oilseed‐based supplements also resulted in significant decreases in the solid fat content of the milk fat at temperatures ranging from 0 to 35 °C, which would be indicative of a softer, more spreadable butter. © 2002 Society of Chemical Industry     

Effectiveness of extruded rapeseed associated with an alfalfa protein concentrate in enhancing the bovine milk fatty acid composition

Linseed and rapeseed, good sources of 18:3 n-3 and cis9-18:1, respectively, have been shown to improve the bovine milk fatty acid (FA) profile. However, rapeseed, unlike linseed, has little effect on the concentration of 18:3 n-3 in milk fat. Alfalfa protein concentrate (APC), besides being a valuable protein source for milk production, contains lipids rich in 18:3 n-3. Therefore, this experiment aimed at (1) evaluating the transfer efficiency of unsaturated FA (UFA), especially 18:3 n-3, of APC to bovine milk fat, and (2) evaluating whether extruded rapeseed (ER) associated with APC is as effective as extruded linseed (EL) in enhancing the bovine milk fat composition. Six lactating Holstein cows were used in a replicated 2 × 2 Latin square design with 2 iso-energy, iso-nitrogen and iso-FA corn silage-based diets (EL and ER-APC) and two 21-d periods. Extruded linseed, as main UFA source, was included in the first diet, whereas ER, as main UFA source, and APC, as supplemental 18:3 n-3, were included in the second diet. Diets were distributed as a restricted total mixed ration. Compared with the EL diet, the ER-APC diet, where ER was associated with APC, increased milk concentration of 18:3 n-3 (1.18 vs. 1.31% of FA) and cis9-18:1 (18.35 vs. 20.01% of FA). The apparent transfer efficiency of 18:3 n-3 from diet to milk was almost twice as much for the ER-APC diet than for the EL diet (7.4 vs. 3.8% of intake). Extruded linseed accounted for 84% of 18:3 n-3 provided in the EL diet, whereas ER and APC accounted for 33 and 38% of 18:3 n-3 provided in the ER-APC diet, respectively. Because both EL and ER underwent extrusion in similar conditions, these results suggest that 18:3 n-3 of EL in the EL diet and ER in the ER-APC diet were subjected to more extensive ruminal biohydrogenation than 18:3 n-3 of APC in the ER-APC diet. This experiment shows that corn silage-based diets supplemented with ER as the main UFA source, associated with APC as supplemental 18:3 n-3, are as effective as corn silage-based diets supplemented with EL as the main UFA source, in increasing bovine milk UFA and 18:3 n-3 contents. Furthermore, at similar levels of dietary incorporation, this experiment shows that the ruminal bypass of 18:3 n-3 is higher for APC compared with EL.     

Effect of varying levels of fatty acids from palm oil on feed intake and milk production in Holstein cows

To determine the optimum feeding level of fatty acids of palm oil (PALM; Energizer RP10; 86.6% palmitic acid) on milk production, lactating cows (n = 18) were randomly assigned to a treatment sequence in replicated 4 × 4 Latin squares. Animals were assigned to squares by parity (3 multiparous and 1 primiparous squares with primiparous in the incomplete square). The 4 diets were designed to provide 0, 500, 1,000, and 1,500 g of PALM per day. Cows were fed individually with feed intake measured daily. Each period lasted 16 d with milk production and composition determined the final 2 d. Milk production, milk composition and feed intake data were analyzed using the MIXED procedure of SAS. Milk yields were 30.9, 34.0, 34.2, and 34.2 kg/ d (SEM = 1.9) for the 0, 500, 1,000, and 1,500 g levels, respectively. Milk yield was increased by the addition of PALM; however, there were no differences among the levels of PALM. Milk fat percentage was also increased from 3.44% for 0 g to 3.95% (SEM = 0.17) across all levels of PALM but there were no differences among the PALM treatments. Dry matter intakes were 23.3, 26.4, 24.7, and 23.8 kg/d (SEM = 1.4) for the 0, 500, 1,000 and 1,500 g levels, respectively. The addition of PALM increased milk yield and milk fat percentage, and no adverse effects on dry matter intake were observed.     

Comparison of enriched palmitic acid and calcium salts of palm fatty acids distillate fat supplements on milk production and metabolic profiles of high-producing dairy cows

A variable response to fat supplementation has been reported in dairy cows, which may be due to cow production level, environmental conditions, or diet characteristics. In the present experiment, the effect of a high palmitic acid supplement was investigated relative to a conventional Ca salts of palm fatty acids (Ca-FA) supplement in 16 high-producing Holstein cows (46.6 ± 12.4 kg of milk/d) arranged in a crossover design with 14-d periods. The experiment was conducted in a non-heat-stress season with 29.5% neutral detergent fiber diets. Treatments were (1) high palmitic acid (PA) supplement fed as free FA [1.9% of dry matter (DM); 84.8% C16:0] and (2) Ca-FA supplement (2.3% of DM; 47.7% C16:0, 35.9% C18:1, and 8.4% C18:2). The PA supplement tended to increase DM intake, and increased the yields of milk and energy-corrected milk. Additionally, PA increased the yields of milk fat, protein, and lactose, whereas milk concentrations of these components were not affected. The yields of milk de novo and 16-C FA were increased by PA compared with Ca-FA (7 and 20%, respectively), whereas the yield of preformed FA was higher in Ca-FA. A reduction in milk fat concentration of de novo and 16-C FA and a marginal elevation in trans-10 C18:1 in Ca-FA is indicative of altered ruminal biohydrogenation and increased risk of milk fat depression. No effect of treatment on plasma insulin was observed. A treatment by time interaction was detected for plasma nonesterified fatty acids (NEFA), which tended to be higher in Ca-FA than in PA before feeding. Overall, the palmitic acid supplement improved production performance in high-producing cows while posing a lower risk for milk fat depression compared with a supplement higher in unsaturated FA.     

Milk fatty acid composition of grazing dairy cows when supplemented with linseed oil

The effects of varying amounts of linseed oil (LSO) in grazing dairy cows’ diet on milk conjugated linoleic acid (cis-9, trans-11 CLA) were investigated in this study. Twelve Holstein cows in midlactation (150 ± 19 DIM) were placed on alfalfa-based pasture and assigned to 4 treatments using a 4 × 4 Latin square design with 3-wk periods. Treatments were: 1) control grain supplement; 2) control grain supplement containing 170 g of LSO (LSO1); 3) control grain supplement containing 340 g of LSO (LSO2); and 4) control grain supplement containing 510 g of LSO (LSO3). Grain supplements were offered at 7 kg/d. Additional 100 g/d of algae, divided evenly between the 2 feeding times, were added to every treatment diet. Milk samples were collected during the last 3 d of each period and analyzed for chemical and fatty acid composition. Treatments had no effect on milk production (18.9, 18.5, 19.6, and 19.1 kg/d for treatments 1 to 4, respectively). Linseed oil supplementation caused a quadratic increase in milk fat (3.23, 3.44, 3.35, and 3.27% for treatments 1 to 4, respectively) and protein (3.03, 3.19, 3.12, and 3.08%) contents. Concentrations (g/100 g of fatty acids) of milk cis-9, trans-11 CLA (1.12, 1.18, 1.39, and 1.65 for treatments 1 to 4, respectively) and VA (3.39, 3.62, 4.25, and 4.89) linearly increased with LSO supplementations. Results from this trial suggest that the increase in milk cis-9, trans-11 CLA was proportional to the amounts of LSO fed. In conclusion, adding LSO to grazing dairy cow diets can improve the nutritional value of milk without compromising milk composition or cow performance.     

Effects of dietary deoiled soy lecithin supplementation on milk production and fatty acid digestibility in Holstein dairy cows

Deoiled soy lecithin is a feed additive enriched in phospholipids. Our study evaluated the effects of dietary deoiled soy lecithin supplementation on (1) milk production and composition, (2) plasma and milk fatty acid (FA) content and yield, and (3) apparent FA digestibility and absorption in lactating dairy cows fed fractionated palm fat. In a split-plot Latin square design, 16 Holstein cows (160 ± 7 days in milk; 3.6 ± 1.2 parity) were randomly allocated to a main plot receiving a corn silage and alfalfa haylage-based diet with palm fat containing either moderate (MPA) or high palmitic acid (HPA) content at 1.75% of ration dry matter (72 or 99% palmitic acid, respectively; n = 8/palm fat diet). On each palm fat diet, deoiled soy lecithin was top-dressed at 0, 0.12, 0.24, or 0.36% of ration dry matter in a replicated 4 × 4 Latin square design. Following a 14-d covariate period, lecithin supplementation spanned 14 d, with milk and blood collected during the final 3 d. Milk composition and pooled plasma markers were measured. The statistical model included the fixed effects of palm fat type, lecithin dose, period, and the interaction between palm fat type and lecithin dose. The random effect of cow nested within palm fat group was also included. Lecithin linearly decreased dry matter intake. In cows fed HPA, lecithin feeding reduced milk fat content and tended to decrease milk fat yield. Although no changes in milk yield were observed, a quadratic reduction in 3.5% fat-corrected milk was observed with increasing lecithin dose. Lecithin linearly increased energy-corrected milk efficiency in cows fed MPA. Lecithin supplementation also decreased milk urea nitrogen, relative to unsupplemented cows. The proportion of 16-carbon FA in milk fat decreased linearly with lecithin dose, whereas 18-carbon FA increased linearly. Lecithin reduced de novo FA (<16-carbon) content and tended to increase preformed FA (>16-carbon) content in a linear manner. Compared with MPA, HPA diets reduced apparent total and 16-carbon FA digestibility and absorption. Deoiled soy lecithin feeding did not modify FA digestibility or absorption. Our observations suggest that soy lecithin feeding modifies rumen digestion to reduce dry matter intake and change milk composition.     

Mammary lipid metabolism and milk fatty acid secretion in alpine goats fed vegetable lipids

Fourteen Alpine goats at midlactation were fed a diet of hay and concentrate (55:45), without (control) or with formaldehyde-treated linseed (FLS) or oleic sunflower oil (OSO) at 11.2 or 3.5% of dry matter intake, respectively, in a 3 x 3 Latin Square design with three 3-wk periods. Milk yield was lower in goats fed FLS than control or OSO (2.13 vs. 2.32 kg/d). Milk fat content was higher with FLS or OSO than control (40.8 vs. 33.8 g/kg). Formaldehyde-treated linseed and OSO caused a significant decrease (23 and 18%, respectively) of C10 to C17 fatty acids secretion compared with control. The secretion of cis-9 C18:1 and cis-9, trans-11 C18:2 were increased 1.44- and 1.54-fold for FLS and 1.78- and 1.36-fold for OSO, compared with control. The C18:3 (n-3) secretion was increased 2.61-fold with FLS compared with control. Milk cis-9 C14:1/C14:0, cis-9 C16:1/C16:0, and cis-9 C18:1/C18:0 ratios decreased with the supplemented diets compared with control. Mammary stearoyl-CoA desaturase mRNA and activity were decreased by the lipid supplements, whereas no significant change was observed for acetyl-CoA carboxylase and fatty acid synthase. The activities of glucose-6-phosphate dehydrogenase, malic enzyme, and glycerol-3-phosphate dehydrogenase were not affected by the lipid supplements. Mammary lipoprotein lipase mRNA increased with OSO, whereas lipoprotein lipase activity tended to decrease with FLS compared with control. Milk lipoprotein lipase activity sharply decreased with lipid supplement (by 59 and 71%, for FLS and OSO, respectively). The changes in milk fatty acid profile due to FLS and OSO supplements were partly related to changes in the levels of mammary enzyme activities or mRNA.     

Effects of conjugated linoleic acid supplementation and feeding level on dairy performance,milk fatty acid composition,and body fat changes in mid-lactation goats

The objective of this trial was to study the interaction between the supplementation of lipid-encapsulated conjugated linoleic acid (CLA; 4.5 g of cis-9,trans-11 C18:2 and 4.5 g of trans-10,cis-12 C18:2) and feeding level to test if milk performance or milk fatty acid (FA) profile are affected by the interaction between CLA and feeding level. Twenty-four dairy goats were used in an 8-wk trial with a 3-wk adaptation to the experimental ration that contained corn silage, beet pulp, barley, and a commercial concentrate. During the third week, goats were assigned into blocks of 2 goats according to their dry matter intake (DMI), raw milk yield, and fat yield. Each block was randomly allocated to control (45 g of Ca salt of palm oil/d) or CLA treatment. Within each block, one goat was fed to cover 100% (FL100) of the calculated energy requirements and the other was fed 85% of the DMI of the first goat (FL85). Individual milk production and composition were recorded weekly, and milk FA composition was analyzed in wk 3, 5, and 7. Conjugated linoleic acid supplementation reduced milk fat content and fat yield by 17 and 19%, respectively, independent of the feeding level. It reduced both the secretion of milk FA synthesized de novo, and those taken up from the blood. No interaction between CLA and feeding level was observed on milk secretion of any group of FA. The CLA supplementation had no effect on DMI, milk yield, protein, and lactose yields but it improved calculated net energy for lactation balance. Goats fed the FL100 × CLA diet tended to have the highest DMI and protein yield. The interaction between CLA and feeding level was not significant for any other variables. Compared with the goats fed FL100, those fed FL85 had lower DMI, lower net energy for lactation balance, and lower digestible protein in the intestine balance. The body weight; milk yield; milk fat, protein, and lactose yields; and fat, protein, lactose, and urea contents in milk were not affected by feeding level. In conclusion, reduction in energy spared via fat yield reduction after CLA supplementation was not partitioned toward milk lactose or protein in goats at a low feeding level, possibly because of a simultaneous shortage of energy and amino acids. In goats on the high feeding level, energy spared tended to be partitioned toward milk protein yield, and at the same time to the prevention of excessive lipid mobilization.     

Effects of calcium salts differing in fatty acid composition on duodenal and milk fatty acid profiles in dairy cows

Ruminal biohydrogenation of fatty acids (FA) was studied in vivo in relation with the fermentation pattern in the rumen and milk secretion. Calcium salts (Ca salts) of palm oil (diet 1) or rapeseed oil (diet 2) were given to dairy cows (about 650 g day^?1) in a diet based on maize silage. Significant variation in propionate concentration was observed among diets. Rumen pH and total volatile fatty acids (VFA) did not change. Duodenal FA pattern was analysed throughout the day. With diets 1 and 2, linoleic acid was to a large extent biohydrogenated: calculations of ruminal biohydrogenation were equal to 63.6 and 74.0% for diets 1 and 2, respectively. No difference between diets was observed in milk production, fat and protein percentages. The percentages of stearic and octadecenoic FA in milk were higher and the percentage of palmitic acid was lower with Ca salts of rapeseed oil FA than with Ca salts of palm oil FA.     

Within-milking variation in milk composition and fatty acid profile of Holstein dairy cows

Changes in milk composition during a milking are well characterized, but variation in milk fatty acid (FA) profile is not well described and may affect the accuracy of in-line milk composition analyzers and could potentially be used for selective segregation of milk. Within-milking samples were collected from 8 multiparous high-producing Holstein cows (54.86 ± 6.8 kg of milk/d; mean ± standard deviation). A milk-sampling device was designed to allow collection of multiple samples during a milking without loss of vacuum or interruption of milk subsampling. Milk was collected during consecutive morning and afternoon milkings (12-h intervals) and was replicated 1 wk later. Each sample represented approximately 20% of the milking and was analyzed for fat, true protein, and lactose concentration and FA profile. Milk fat concentration markedly increased over the course of milk let down (4.4 and 4.2 percentage units at the a.m. and p.m. milking, respectively), whereas milk fat globule size did not change. Milk protein and lactose concentration decreased slightly during milking. Modest changes in milk FA profile were also observed, as milk de novo and 16-C FA concentrations increased approximately 10 and 8%, respectively, whereas the concentration of preformed FA decreased about 7% during the milking. In agreement, mean milk FA chain length and unsaturation modestly decreased during milking (0.59 and 0.014 U, respectively). The observed changes in milk fat concentration during a milking are consistent with previous reports and reflect the dynamic nature of milk fat secretion from the mammary gland. Changes in milk FA profile are not expected to practically affect the accuracy of spectroscopy methods for determination of milk fat concentration. Furthermore, the small variation in FA profile during a milking limits the use of within-milking milk segregation to tailor milk FA profile.     

Effect of replacing solvent-extracted canola meal with high-oil traditional canola, high-oleic acid canola, or high-erucic acid rapeseed meals on rumen fermentation, digestibility, milk production, and milk fatty acid composition in lactating dairy cows

The objective of this experiment was to investigate the effects of replacing conventional, solvent-extracted canola meal (control; CTRL) with high oil content; conventional, mechanically extracted canola meal (CMEC); high-oleic, low polyunsaturated fatty acid (FA) canola meal (HOLL); and high-erucic acid, low-glucosinolate rapeseed meal (RPS) on rumen function, digestibility, milk production, and milk FA composition in lactating dairy cows. The experimental design was a replicated 4 × 4 Latin square with 8 lactating dairy cows. Four of the cows were ruminally cannulated. All oilseed meals were included at approximately 12 to 13% of dietary dry matter (DM). Crude protein and fat concentrations (% of DM) of the meals were 43 and 3.1%, 32.8 and 16.1%, 45.2 and 13.7%, and 34.3 and 17.9% for CTRL, CMEC, HOLL, and RPS, respectively. All diets were formulated to supply net energy of lactation in excess of requirements. The CMEC and RPS diets were predicted to be about 1% deficient in metabolizable protein. Relative to the CTRL, inclusion of high-oil seed meals in the diet lowered ruminal acetate concentration and the molar acetate:propionate ratio and decreased DM intake. Milk yield generally followed DM intake and was lower for CMEC and RPS than the CTRL. Treatments had no effect on milk composition, other than an increase in milk urea nitrogen concentration for HOLL. Fat-corrected milk (3.5%) feed efficiency was increased by HOLL and RPS compared with CTRL. Urinary urea nitrogen losses were increased by HOLL, which, as a consequence, increased the ammonia-emitting potential of manure. The ratio of milk N-to-N intake was greater for CMEC and RPS. Replacing solvent-extracted canola meal with the high-oil meal decreased milk fat 12:0, 14:0, 16:0, and total saturated FA content and enhanced cis-9 18:1 and total monounsaturated FA concentrations. Relative to the CTRL, canola increased total trans FA in milk, whereas inclusion of HOLL in the diet increased trans-11 18:1 and cis-9, trans-11 CLA content. The RPS increased milk fat cis-13 22:1 content from 0.07 to 2.33 g/100 g of FA. In conclusion, HOLL or RPS, which are likely to come from small-scale biodiesel plants where oil is cold pressed without hexane extraction, fed at levels at or above 12 to 13% of dietary DM may decrease feed intake and milk production, but can be used to alter milk FA composition in lactating dairy cows.     

Effect of saturated fatty acid supplementation on production and metabolism indices in heat-stressed mid-lactation dairy cows

Experimental objectives were to determine the effects of supplemental saturated fatty acids on production, body temperature indices, and some aspects of metabolism in mid-lactation dairy cows experiencing heat stress. Forty-eight heat-stressed Holstein cows were allocated into 3 groups (n = 16/group) according to a completely randomized block design. Three treatment diets consisted of supplemental saturated fatty acids (SFA) at 0 (SFA0), 1.5 (SFA1.5), or 3.0% (SFA3) of dry matter (DM) for 10 wk. Diets were isonitrogenous (crude protein = 16.8%) and contained 1.42, 1.46, and 1.49 Mcal of net energy for lactation/kg of DM for the SFA0, SFA1.5 and SFA3 diets, respectively. The average temperature-humidity index at 0700, 1400 and 2200 h was 72.2, 84.3, and 76.6, respectively. Rectal temperatures at 1400 h were decreased with fat supplementation. Treatment did not affect dry matter intake (20.1 ± 0.02 kg/d), body condition score (2.72 ± 0.04), body weight (627 ± 16.1 kg), or calculated energy balance (1.32 ± 0.83 Mcal/d). Saturated fatty acid supplementation increased milk yield, milk fat content, and total milk solids. Increasing fat supplementation decreased plasma nonesterified fatty acids (8%) but had no effect on other energetic metabolites or hormones. In summary, supplemental SFA improved milk yield and milk fat content and yield and reduced peak rectal temperatures in mid-lactation heat-stressed dairy cows. This demonstrates the remarkable amount of metabolic heat that is “saved” by energetically replacing fermentable carbohydrates with supplemental SFA.